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diff --git a/old/26535-0.txt b/old/26535-0.txt deleted file mode 100644 index 572b36a..0000000 --- a/old/26535-0.txt +++ /dev/null @@ -1,36293 +0,0 @@ -Project Gutenberg's The Standard Electrical Dictionary, by T. O'Conor Slone - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: The Standard Electrical Dictionary - A Popular Dictionary of Words and Terms Used in the Practice - of Electrical Engineering - -Author: T. O'Conor Slone - -Release Date: September 5, 2008 [EBook #26535] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE STANDARD ELECTRICAL DICTIONARY *** - - - - -Produced by Don Kostuch - - - - -[Transcriber's Notes] - -Obvious spelling errors have been corrected. I have not reconciled the -variety of spellings of names and other words. Obvious factual errors, -typographical errors, discoveries made after 1892, and contemporary -(2008) theories and use of words are noted in the text within square -brackets. I have not researched and checked every assertion by the -author. - -This book was published 5 years before discovery of the electron. See -the labored and completely inaccurate explanations of aurora and -"energy, atomic". The author and his contemporaries were like fifteenth -century sailors. They had a good idea of their latitude and direction -(Ampere, Kirkoff, Maxwell, Gauss, Faraday, Edison, …), but only the -vaguest notion of their longitude (nuclear structure, electrons, ions). -Altitude (special relativity, quantum theory) was not even imagined. - -Some relevant dates: -Franklin's Kite--1752 -Faraday's Law of Induction--1831 -Maxwell's Equations--1861 -Edison's Phonograph--1877 -Edison's light bulb--1879 -Edison's first DC power station--1882 -Michelson-Morley experiment disproving ether--1887 -Hertz demonstrates radio waves--1888 -Westinghouse first AC power station--1891 -This book--1892 -Discovery of the electron--1897 -Marconi radio signals cross the English Channel--1897 -First Vacuum Tube--1904 -Special Relativity, photo-electric effect explained with photons--1905 -General Relativity: space-time dilation and curvature--1915 -Confirmation of general relativity's prediction of the deflection - of starlight by the Sun--1919 -Discovery of the proton--1920 -Quantum theory--1926 -Discovery of neutron--1932 -First transistor--1947 -Soviet satellite Luna measures solar wind--1959 -Edward M. Purcell explains magnetism with special relativity--1963 - -Purcell's explanation of magnetism as a result of Lorentz contraction of -space along the direction of a current is a welcome relief from the -convoluted descriptions in this book. - -Mathematical notation is rendered using "programming" notation. -^ Power--Exponential; A^3 means "A cubed" -* Multiply -/ Divide -+ Add -- Subtract -( ) Precedence--Perform before enclosing expression -2E6 Scientific Notation (2,000,000) - - - A ---------------------- -4.452 X 10^12 X t - -is rendered as - -A / ( 4.452E12 * t ) - - -Where the rendering of a mathematical expression is in doubt, an image -of the original text is included. - - -Here are some definitions absent from the text. - -Foucault currents. - Eddy currents. - -inspissate - To thicken, as by evaporation. - -riband - Ribbon. - -sapotaceous - Order Sapotace[ae] of trees and shrubs, including the star apple, the - Lucuma, or natural marmalade tree, the gutta-percha tree (Isonandra), - and the India mahwa, as well as the sapodilla, or sapota, after which - the order is named. - - -Don Kostuch, MS, Electrical Engineering. -[End Transcriber's notes.] - - - -WORKS OF -T. O'CONOR SLOANE, A.M., E.M., Ph.D. - - -ARITHMETIC OF ELECTRICITY -A MANUAL OF ELECTRICAL CALCULATIONS -BY ARITHMETICAL METHODS. -Third Edition. Illustrated. $1.00. -It is very useful to that class of readers to whom Algebra is a -comparatively unknown quantity, and will meet its wants -admirably.--Electrical World. - - - -ELECTRICITY SIMPLIFIED. -A POPULAR TREATMENT OF THE SUBJECT. -Illustrated. $1. 00. -We especially recommend it to those who would like to acquire a popular -idea of the subject.--Electric Age. - - - -ELECTRIC TOY MAKING. -FOR AMATEURS. -INCLUDING BATTERIES, MAGNETS, MOTORS, MISCELLANEOUS TOYS, -AND DYNAMO CONSTRUCTION. -Fully Illustrated. $1.00. - -THE STANDARD ELECTRICAL DICTIONARY. - -A POPULAR DICTIONARY OF WORDS AND TERMS -USED IN THE PRACTICE OF ELECTRICAL ENGINEERING. - - -BY -T. O'CONOR SLOANE, A.M., E.M., Ph.D. - - -NEW YORK -GEORGE D. HURST -PUBLISHER - - - -Copyright 1892 -by -NORMAN W. HENLEY & CO. - - - -PREFACE - -The purpose of this work is to present the public with a concise and -practical book of reference, which it is believed will be appreciated in -this age of electricity. The science has expanded so much that the -limits of what may be termed strictly a dictionary of the present day -would a few years ago have sufficed for an encyclopedia. It follows that -an encyclopedia of electricity would be a work of great size. Yet a -dictionary with adequate definitions, and kept within the closest limits -by the statement of synonyms, and by the consigning of all the -innumerable cross-references to a concise index will be far more than a -mere dictionary in the ordinary sense of the term. - -Duplication of matter is to be avoided. This makes many definitions -appear short. Yet, by the assistance of the reader's own general -knowledge, and by referring to the very complete index, almost any -subject can be found treated in all its aspects. There are exceptions to -this statement. So much has been done in the way of mechanical detail, -so many inventions in telegraphy and other branches have sprung into -prominence only to disappear again, or to be modified out of -recognition, that to embody descriptions of many ingenious and -complicated apparatus has been absolutely impossible for want of space. - -A word as to the use of the book and the system of its construction may -be given here. Each title or subject is defined once in the text. Where -a title is synonymous with one or more others the definition is only -given under one title, and the others appear at the foot of the article -as synonyms. It may be that the reader is seeking the definition of one -of these synonyms. If so a reference to the index shows him at once what -page contains the information sought for. The use of an index in a work, -necessarily of an encyclopedic form, will be appreciated by all users of -this book. - - -vi PREFACE. - - -Where a title embraces several words, all orders of the words will be -cited in the index. To make the operation of finding references easy -this rule has been carried out very fully. - -It is customary to regard electricity as a growing science. It is -unquestionably such, but the multiplication of terms and words is now -not nearly so rapid as it has been, and the time for the compiling of a -work of this character seems most propitious. It is hoped that the -public will indulgently appreciate the labor it has entailed on all -concerned in its production. - - -SYMBOLS AND ABBREVIATIONS. - -adj. Adjective. -v. Verb. -q.v. "Which see.' -/ A mark of division, as A/B, meaning "A divided by B." -./. The same as above. - [Transcriber's note: / will be substituted for this divide symbol.] -= A mark of equality, meaning "is equal to." -X A mark of multiplication, meaning "multiplied by." - [Transcriber's note: * will be substituted for this divide symbol.] - -Fractional exponents indicate the roots expressed by their denominators -and the powers expressed by their numerators. Thus, A^1/2 means the -"square root of A;" A^1/3 means the "cube root of A;" B^3/2 means the -"square root of the cube or third power of B." - -The use of powers of ten, as 10^10, 10^11, as multipliers, will be found -explained at length in the definition "Ten, Powers of." - -vii STANDARD ELECTRICAL DICTIONARY - -A. -Abbreviation for anode, employed in text relating to -electro-therapeutics. It is sometimes written An. - - -Abscissa. -In a system of plane co-ordinates (see Co-ordinates) the -distance of any point from the axis of ordinates measured parallel to -the axis of abscissas. - -In the cut the abscissa of the point a is the line or distance a c. - - -Fig. 1. AXES OF CO-ORDINATES. - - -Absolute. adj. -In quantities it may be defined as referring to fixed units of quantity, -and it is opposed to "relative," which merely refers to the relation of -several things to each other. Thus the relative resistance of one wire -may be n times that of another; its absolute resistance might be 5 ohms, -when the absolute resistance of the second wire would be 5/n ohms. A -galvanometer gives absolute readings if it is graduated to read directly -amperes or volts; if not so graduated, it may by "calibration" q. v. be -made to do practically the same thing. - - -8 STANDARD ELECTRICAL DICTIONARY. - - -Absolute Measurement. -Measurement based upon the centimeter, gram, and second. (See -Centimeter-Gram-Second System.) - - -Absolute Temperature. -Temperature reckoned from absolute zero (see "Zero, Absolute"). It is -obtained by adding for the centigrade scale 273, and for the Fahrenheit -scale 459, to the degree readings of the regular scale. - - -Absorption, Electric. -A property of the static charge. When a Leyden jar is being charged it -dilates a little and the capacity increases, so that it can take a -little more charge for a given potential difference existing between its -two coatings. This phenomenon occurs with other static condensers, -varying in degree with the dielectric. With shellac, paraffin, sulphur -and resin, for instance, the absorption is very slight; with -gutta-percha, stearine, and glass, the absorption is relatively great. -The term is due to Faraday. Iceland spar seems almost or quite destitute -of electric absorption. - - -A. C. C. -Symbol of or abbreviation for "anodic closure contraction" q. v. - - -Acceleration. -The rate of change of velocity. If of increase of velocity it is -positive; if of decrease, it is negative. It can only be brought about -by the exercise of force and is used as the measure of or as determining -the unit of force. It is equal to velocity (L/T) imparted, divided by -time (T); its dimensions therefore are L/(T^2). The c. g. s. unit of -acceleration is one centimeter in one second. - -[Transcriber's note: The unit of acceleration is "centimeters per second -per second."] - - -Accumulator. -(a) A term sometimes applied to the secondary or storage battery. (See -Battery, Secondary.) -(b) See Accumulator, Electrostatic -(c) See Accumulator, Water Dropping. -(d) See Wheel, Barlow's - - -Accumulator, Electrostatic. -Two conducting surfaces oppositely placed, and separated by a -dielectric and arranged for the opposite charging of the two surfaces, -constitute an accumulator, sometimes termed a condenser. As this -arrangement introduces the element of a bound and of a binding charge, -the electrostatic capacity of such is greater than that of either or of -both of its component surfaces. The thinner the dielectric which -separates the conducting surfaces, and the larger the surfaces the -greater is the capacity; or the less will be the potential difference -which a given charge will establish between its two coatings. The nature -of the dielectric also determines its capacity. (See Capacity, Specific -Inductive.) - - -9 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 2. SIR WILLIAM THOMSON'S WATER-DROPPING ACCUMULATOR. - - -Accumulator, Water Dropping. -This is also known as Sir William Thomson's Water-Gravity Electric -Machine. It is an apparatus for converting the potential energy of -falling water drops, due to gravity, into electric energy. Referring to -the illustration, G represents a bifurcated water pipe whose two faucets -are adjusted to permit a series of drops to fall from each. C and F are -two metallic tubes connected by a conductor; E and D are the same. Two -Leyden jars, A and B, have their inner coatings represented by strong -sulphuric acid, connected each to its own pair of cylinders, B to D and -E, and A to F and C. The outer coatings are connected to earth, as is -also the water supply. One of the jars, say A, is charged interiorily -with positive electricity. This charge, C and F, share with it, being in -electric contact therewith. Just before the drops break off from the jet -leading into C, they are inductively charged with negative electricity, -the positive going to earth. Thus a series of negatively excited drops -fall into the metal tube D, with its interior funnel or drop arrester, -charging it, the Leyden jar B, and the tube E with negative electricity. -This excitation causes the other stream of drops to work in the converse -way, raising the positive potential of F and C and A, thus causing the -left-hand drops to acquire a higher potential. This again raises the -potential of the right-hand drops, so that a constant accumulating -action is kept up. The outer coatings of the Leyden jars are connected -to earth to make it possible to raise the potential of their inner -coatings. In each case the drops are drawn by gravity into contact with -objects similarly excited in opposition to the electric repulsion. This -overcoming of the electric repulsion is the work done by gravity, and -which results in the development of electric energy. - - -10 STANDARD ELECTRICAL DICTIONARY. - - -Acidometer. -A hydrometer or areometer used to determine the specific gravity of -acid. They are employed in running storage batteries, to determine when -the charging is completed. (See Areometer.) - - -Aclinic Line. -A terrestrial element; the locus on the earth's surface of no -inclination of the magnetic needle; the magnetic equator. (See Magnetic -Elements.) - - -Acoustic Telegraphy. -The system of sound-reading in telegraphy, universally used in the Morse -system. The direct stroke of the armature of the electro-magnet and its -"back stroke" disclose to the ear the long and short strokes, dots and -lines, and long and short spaces as produced by the dispatcher of the -message. In the Morse system a special magnet and armature is used to -produce the sound called the "sounder;" in other systems, e. g., -Steinheil's and Bright's apparatus, bells are used. (See Alphabets, -Telegraphic.) - - -Acoutemeter. -A Hughes audiometer or sonometer applied to determining the quality of a -person's hearing (See Hughes' Induction Balance,--Audiometer). The -central coil by means of a tuning fork and microphone with battery -receives a rapidly varying current tending to induce currents in the -other two coils. Telephones are put in circuit with the latter and pick -up sound from them. The telephones are applied to the ears of the person -whose hearing is to be tested. By sliding the outer coils back and forth -the intensity of induction and consequent loudness of the sounds in the -telephones is varied. The position when the sounds grow so faint as to -be no longer audible, gives the degree of delicacy of the person's -hearing. By using a single telephone the same apparatus affords a means -of testing the relative capacity of the right and left ears. - - -11 STANDARD ELECTRICAL DICTIONARY. - - -Actinic Rays. -The rays of light at the violet end of the spectrum; also the invisible -rays beyond such end, or the ether waves of short periods which most -strongly induce chemical change. - - -Actinism. -The power possessed by ether waves of inducing chemical change, either -of decomposition or of combination. The violet and ultra-violet end of -the spectrum of white light, generally speaking, represent the most -highly actinic rays. - - -Actinometer, Electric. -Properly an apparatus for measuring the intensity of light by its action -upon the resistance of selenium. A current produced by fixed -electro-motive force passing through the selenium affects a galvanometer -more or less according to the intensity of the light. It is more -properly an electric photometer. The term has also been applied to a -combination of a thermo-electric pile and galvanometer, the light -falling on the pile affecting the motions of the galvanometer. - - -Action, Local. -(a) The wasteful oxydation of the zinc in a galvanic battery due to -local impurities and variations in the composition of the zinc. These -act to constitute local galvanic couples which cause the zinc to -dissolve or oxydize, without any useful result. Amalgamation of the zinc -prevents local action. Chemically pure zinc is also exempt from local -action, and can be used in an acid battery without amalgamation. (See -Amalgamation.) - -(b) The same term has been employed to indicate the eddy or foucault -currents in dynamo electric machines. (Sec Current, Foucault.) - - -Activity. -The rate of doing work; the work done per second by any expenditure of -energy. The activity of a horse-power is 550 foot lbs. per second, or -746 volt-coulombs per second. The practical electric unit is the -volt-ampere, often called the watt. (Sec Energy, Electric.) - - -Adapter. -A screw coupling to engage with a different sized screw on each end; one -of the uses is to connect incandescent lamps to gas-fixtures. - - -A. D. C. -Abbreviation for Anodic Duration Contraction, q. v.; a term in -electro-therapeutics. - - -Adherence, Electro-magnetic. -The adherence between surfaces of iron due to elcctro-magnetic -attraction. It has been applied to the driving-wheels of an engine and -rail, whose grip is increased by such action. In one method a deep -groove was cut around the wheel which was wound with a magnetizing coil. -Thus one rim becomes a north and the other a south pole, and the rail -completing the circuit acts as the armature. Such an arrangement -prevents a wheel from sliding. Electro-magnetic adherence has also been -employed to drive friction gear wheels. In one arrangement the two -wheels are surrounded by a magnetizing coil, under whose induction each -attracts the other, developing high adherence between their peripheries. - - -12 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 3. ELECTRO-MAGNETIC CAR WHEEL. - - -Fig. 4. ELECTRO-MAGNETIC FRICTION GEAR. - - -Admiralty Rule of Heating. -The British Admiralty specifications for the permissible heating of -dynamos. It holds that at the end of a run of six hours no part of the -dynamo under trial shall show a rise of temperature greater than 11º C. -(20º F.) above the temperature of the air surrounding it. This is -thought to be a very stringent and unnecessarily high requirement. - - -Aerial Conductor. -An electric conductor carried from housetops, poles, or otherwise so as -to be suspended in the air, as distinguished from an underground or -submarine conductor. - - -Affinity. -The attraction of atoms and in some cases perhaps of molecules for each -other by the force of chemical attraction. When the affinity is allowed -to act or is carried out, a chemical change, as distinguished from a -physical or mechanical change, ensues. Thus if sulphur and iron are each -finely powdered and are mixed the change and mixture are mechanical. If -slightly heated the sulphur will melt, which is a physical change. If -heated to redness the iron will combine with the sulphur forming a new -substance, ferric sulphide, of new properties, and especially -characterized by unvarying and invariable ratios of sulphur to iron. -Such change is a chemical one, is due to chemical affinity, is due to a -combination of the atoms, and the product is a chemical compound. - - -13 STANDARD ELECTRICAL DICTIONARY. - - -Agir Motor. -The Anderson and Girdlestone motor. The term "agir" is made up from the -first portions of each name. - - -Agonic Line. -The locus of points on the earth's surface where the magnetic needle -points to the true north; an imaginary line determined by connecting -points on the earth's surface where the needle lies in the true -geographical meridian. Such a line at present, starting from the north -pole goes through the west of Hudson's Bay, leaves the east coast of -America near Philadelphia, passes along the eastern West Indies, cuts -off the eastern projection of Brazil and goes through the South Atlantic -to the south pole. Thence it passes through the west of Australia, the -Indian Ocean, Arabia, the Caspian sea, Russia and the White sea to the -North Pole. It crosses the equator at 70° W. and 55° E. approximately. -(See Magnetic Elements.) - -Synonym--Agone. - -[Transcriber's note: The file Earth_Declination_1590_1990.gif provided -by the U.S. Geological Survey (http://www.usgs.gov) is an animation of -the declination of the entire earth.] - - -Air. -Air is a dielectric whose specific inductive capacity at atmosphere -pressure is taken as 1. It is practically of exactly the same -composition in all places and hence can be taken as a standard. When dry -it has high resistance, between that of caoutchouc and dry paper. -Dampness increases its conductivity. - -It is a mixture of oxygen and nitrogen, with a little carbonic acid gas -and other impurities. Its essential composition is: - -Oxygen: (by weight) 23.14 (by volume) 21 -Nitrogen: 76.86 79 - -The specific inductive capacity varies for different pressures thus: - -Approximate vacuum (.001 mm., .0004 inch) 0.94 (Ayrton) - " " ( 5 mm. , .2 inches ) 0.9985 (Ayrton) - 0.99941 (Boltzman.) - -The specific gravity of air under standard conditions 15.5° C (60° F.) -and 760 mm. barometric pressure (30 inches) is taken as unity as a -standard for gases. - -[Transcriber's note: Argon accounts for 0.9340%. It was discovered in -1894, two years after this book.] - - -Air-Blast. -(a) In the Thomson-Houston dynamo an air-blast is used to blow away the -arc-producing spark liable to form between the brushes and commutator. -It is the invention of Prof. Elihu Thomson. The air is supplied by a -positive action rotary blower connected to the main shaft, and driven -thereby. The wearing of the commutator by destructive sparking is thus -prevented. - -A drum H H is rotated, being mounted on the axis X of the dynamo. As it -rotates the three vanes are thrown out against the irregular shaped -periphery of the outer case T T. The arrow shows the direction of -rotation. The air is thus sent out by the apertures a a. O is the -oil-cup. - -(b) The air-blast has also been used by Prof. Thomson in experiments -with high frequency currents of high potential. By directing a blast of -air against a spark discharge between ball terminals of an alternating -current, the nature of the current was changed and it became capable of -producing most extraordinary effects by induction. - - -14 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO. - - -Air Condenser. -A static condenser whose dielectric is air. The capacity of an air -condenser in farads is equal to - A / ( 4.452E12 * t ) -in which A is the area of one sheet or sum of the areas of one set of -connected sheets in square inches and t is the thickness of the layer of -air separating them. - -A convenient construction given by Ayrton consists in a pile of glass -plates P separated by little bits of glass F of known thickness, three -for each piece. Tin-foil T is pasted on both sides of each piece of -glass and the two coatings are connected. The tin-foil on each second -plate is smaller in area than that on the others. The plates are -connected in two sets, each set comprising every second plate. For A in -the formula the area of the set of smaller sheets of tin-foil is taken. -By this construction it will be seen that the glass does not act as the -dielectric, but only as a plane surface for attachment of the tin-foil. -Posts E E keep all in position. One set of sheets connects with the -binding post A, the other with B. - -The capacity of any condenser with a dielectric of specific inductive -capacity i is given by the formula: - ( i *A^1 ) / ( 4.452E12 * t1 ) - -The air condenser is used for determining the value of i for different -dielectrics. - - -Fig. 6. AIR CONDENSER. - - -15 STANDARD ELECTRICAL DICTIONARY. - - -Air Gaps. -In a dynamo or motor the space intervening between the poles of the -field magnet and the armature. They should be of as small thickness, and -of as extended area as possible. Their effect is to increase the -magnetic reluctance of the circuit, thereby exacting the expenditure of -more energy upon the field. They also, by crowding back the potential -difference of the two limbs, increase the leakage of lines of force from -limb to limb of the magnet. - - -Air Line Wire. -In telegraphy the portion of the line wire which is strung on poles and -carried through the air. - - -Air Pump, Heated. -It has been proposed to heat portions of a mercurial air pump to secure -more perfect vacua, or to hasten the action. Heating expands the air and -thus produces the above effects. - - -16 STANDARD ELECTRICAL DICTIONARY. - - -Air Pump, Mercurial. -An air pump operated by mercury. The mercury acts virtually as the -piston, and the actuating force is the weight of the column of mercury, -which must exceed thirty inches in height. There are many types. -Mercurial air pumps are largely used for exhausting incandescent lamp -chambers. (See Geissler Air Pump,--Sprengel Air Pump.) - - -Air Pumps, Short Fall. -A mercurial air pump in which the fall of mercury or the height of the -active column is comparatively small. It is effected by using several -columns, one acting after the other. A height of ten inches for each -column suffices in some forms. Enough columns must be used in succession -to make up an aggregate height exceeding 30 inches. - - -Fig. 7. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. - - -Fig. 8. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. - - -Alarm, Burglar. -A system of circuits with alarm bell extending over a house or -apartments designed to give notice of the opening of a window or door. -As adjuncts to the system the treads of the stairs are sometimes -arranged to ring the bell, by completing a circuit when trod on. Door -mats are also arranged to close circuits in like manner. - - -17 STANDARD ELECTRICAL DICTIONARY. - - -For doors and windows switches are provided which are open as long as -the door or window is closed, but which, on being released by opening -the door or windows, automatically close the circuit. The circuit -includes an alarm bell and battery, and the latter begins to ring and -continues until stopped, either by the closing of the door or by a -switch being turned. The connections are sometimes so contrived that the -reclosing of the door or window will not stop the bell from ringing. - -The cuts show various switches for attachment to doors and windows. It -will be seen that they normally keep the circuit closed, and that it is -only open when pressure, as from a closed door, is brought upon them. In -the case of a door a usual place for them is upon the jamb on the hinge -side, where they are set into the wood, with the striking pin -projecting, so that as the door is closed the pin is pressed in, thus -breaking the circuit. - -Sometimes the connections are arranged so as to switch on the electric -lights if the house is entered. Special annunciators showing where the -house has been entered are a part of the system. A clock which turns the -alarm on and off at predetermined hours is also sometimes used. - -The circuits may be carried to a central station or police station. One -form of burglar alarm device is the Yale lock switch. This is a contact -attached to a Yale lock which will be closed if the wrong key is used, -completing a circuit and ringing a bell. - - -Fig. 9. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. - - -Alarm, Electric. -An appliance for calling attention, generally by -ringing a bell. It is used to notify of water-level in boilers or tanks, -of entrance of a house, or of other things as desired. It is evident -that any number of alarms could be contrived. - - -18 STANDARD ELECTRICAL DICTIONARY. - - -Alarm, Fire and Heat. -An alarm for giving notice of the existence of a conflagration. Such are -sometimes operated by a compound bar thermostat (see Thermostat), which -on a given elevation of temperature closes a circuit and rings an -electric bell. Sometimes the expansion of a column of mercury when -heated is used. This, by coming in contact with one or two platinum -points, completes a circuit, and rings the bell. - -The identical apparatus may be used in living rooms, greenhouses. -factories and elsewhere, to give an alarm when the temperature rises or -falls beyond predetermined limits. - - -Alarm, Overflow. -An alarm to indicate an overflow of water has been suggested on the -lines of a contact completed by water, or of the elements of a battery -which would be made active by water. Thus two sheets of metal might be -separated by bibulous paper charged with salt. If these sheets were -terminals of a circuit including a bell and battery, when water reached -them the circuit would be closed and the bell would ring. It was also -proposed to use one copper and one zinc sheet so as to constitute a -battery in itself, to be thrown into action by moisture. These contacts -or inactive batteries could be distributed where water from an overflow -would be most likely to reach them. - - -Alarm, Water Level. -An alarm operated by a change of water level in a tank or boiler. By a -float a contact is made as it rises with the water. Another float may be -arranged to fall and close a contact as the level falls. The closing of -the contacts rings an electric bell to notify the attendant in charge. - - -Alcohol, Electrical Rectification of. -A current of electricity passed through impure alcohol between zinc -electrodes is found to improve its quality. This it does by decomposing -the water present. The nascent hydrogen combines with the aldehydes, -converting them into alcohols while the oxygen combines with the zinc -electrode. - - -Alignment. -The placing in or occupying of the same straight line. The bearings of a -shaft in dynamos, engines, and other machinery have to be in accurate -alignment. - - -Allotropy. -The power of existing in several modifications possessed by some -substances, notably by chemical elements. Instances of the allotropic -state are found in carbon which exists as charcoal, as graphite -(plumbago or black lead), and as the diamond. All three are the same -elemental substance, although differing in every physical and electrical -property. - - -19 STANDARD ELECTRICAL DICTIONARY. - - -Alloy. -A mixture, produced almost universally by fusion, of two or more metals. -Sometimes alloys seem to be chemical compounds, as shown by their having -generally a melting point lower than the average of those of their -constituents. An alloy of a metal with mercury is termed an amalgam. An -important application in electricity is the use of fusible alloys for -fire alarms or for safety fuses. German silver is also of importance for -resistance coils, and palladium alloys are used for unmagnetizable -watches. An alloy of wrought iron with manganese is almost -unmagnetizable, and has been proposed for use in ship building to avoid -errors of the compass. - -Alloys or what are practically such can be deposited by electrolysis in -the electro- plater's bath. We give the composition of some alloys -interesting to the electrician. - - Solder: Lead 1 part Tin 2 parts - " " " 1 " - " " " 2 " - -German Silver: Copper, 2 parts; Nickel, 1 part; - Zinc, 1 part (used for resistances). - -Platinum, Silver Alloys: Platinum, 1 part; - silver, 2 parts (used for resistances.) - -Palladium alloys for watch springs. (See Palladium.) - - -Alphabet, Telegraphic. -The combinations of sounds, of dots and dashes marked on paper, of -right-hand and left-hand deflections of a needle, of bells of different -notes, or of other symbols by which a fixed combination is expressed for -each character of the alphabet, for numerals, and for punctuation. While -the code is designed for telegraphic uses it can be used not only for -the conveyance of signals and messages by the electrical telegraphs, but -also by any semaphoric or visual system, as by flashes of light, -movements of a flag or even of the arms of the person signalling. - -In the English and continental needle telegraphy in which the message is -transmitted by the movements of an index normally vertical, but -oscillating to one side or the other under the influence of the current, -the latter being controlled by the transmitter of the message, the left -hand swings of the needle are interpreted as dots, the right hand as -dashes. - -This system enables one alphabet to be translated into the other, or -virtually one alphabet answers for both Morse and needle transmitters. - -There are two principal telegraphic alphabets, the American Morse and -the International codes. They are very similar, their essential -distinction being that spaces are used in the American code, while they -are excluded from the International code. - -In the American Morse system the message is now universally received by -sound. (See Sounder--Sound Reading.) - - -20 STANDARD ELECTRICAL DICTIONARY. - - -The two codes or telegraphic alphabets are given here. - -THE INTERNATIONAL ALPHABET. - Parenthesis, - . - - . - - Understand, ... - . - I don't understand, ..-- ....--.. - Wait, .-. . . - Erase, ... ... ... - Call signal, -.-.-.- - End of message, .-.-.-. - Cleared out all right, .-..-..-. - A .- L .-.. W .-- - B -... M -- X -..- - C -.-. N -. Y -.-- - D -.. O --- Z --.. - E . P .--. - F ..-. Q --.- Ch ---- - G --. R .-. Ä .-.- - H .... S ... Ö ---. - I .. T - Ü ..-- - J .--- U ..- É ..-.. - K -.- V ...- Ñ --.-- - -NUMERALS - 1 .---- 4 ....- 8 ---.. - 2 ..--- 5 ..... 9 ----. - 3 ...-- 6 -.... 0 ----- - 7 --... - - -[Transcriber's note: The original image of the dot/dash pattern is somewhat -ambiguous. Since there may be differences from contemporary specifications, -the original image is included.] - -[Image of page 20: THE INTERNATIONAL ALPHABET.] - - -21 STANDARD ELECTRICAL DICTIONARY. - -PUNCTUATION, ETC., - - Period (.) ... ... - Comma (,) .-.-.- - Query(?) ..--.. - Exclamation (!) --..-- - Apostrophe (') .----. - Hyphen (-) -....- - Fresh paragraph, .-.-.. - Inverted commas, -..-. - -THE AMERICAN ALPHABET. - A .- L ----(Continuous) W .-- - B -... M -- X .-.. - C ..s. N -. Y ..s.. - D -.. O .s. Z …. - E . P ..... - F .-. Q ..-. Ch ---- - G --. R .s.. Ä .-.- - H .... S ... Ö ---. - I .. T - Ü ..-- - J - . - . U ..- É ..-.. - K -.- V ...- Ñ --.-- - -NUMERALS - 1 .--. 4 ....- 8 -.... - 2 ..-.. 5 --- 9 -..- - 3 ...-. 6 ... ... 0 -----(Continuous) - 7 --.. - -[Transcriber's Note: The "s" in the American Code indicates a "space". I -leave the following to the reader's imagination. See the original -image.] - -Comma (,) -Semicolon (;) -Colon (:) -Colon Dash (:~) -Period (.) -Interrogation (?) -Exclamation (!) -Dash (-) -Hyphen (-) -Pound Sterling (£) -Shilling Mark ( ) - - -[Image of page 21: THE AMERICAN ALPHABET.] - - -22 STANDARD ELECTRICAL DICTIONARY. - - -[Transcriber's Note: I leave these to the reader's imagination. See the -following original image.] - -Dollars ($) -Decimal Point (.) -Cents (c) -Paragraph () -Pence (d.) -Fractional Mark (--) -Capitalized Letter -Italics or Underline -Colon followed by Quotation :" -Parenthesis ( ) -Brackets [ ] -Quotation Marks " " -Quotation within a Quotation " ' ' " - -[Image of page 22: THE AMERICAN ALPHABET.] - -The principal differences in the two codes are the use of spaces in the -American code, such being excluded from the International code. This -affects the letters C, R, Y, & Z. - -The following diagram, due to Commandant Perian, enables the letter -corresponding to an International code sign to be rapidly found with the -exception of R. - - <- dot start dash -> - / \ - E T - / \ / \ - I A N M - / \ / \ / \ / \ - S U R W D K G O - / \ / \ / \ / \ / \ / \ / \ / \ -H V F U L A P J B X C Y Z Q Ô CH - -Fig. 10. Diagram for translating the Morse Alphabet. - - -In order to find what letter corresponds to a given sign, starting from -the top of the diagram, each line is traced down to a bifurcation, -taking the right hand line of each bifurcation for a dash, and the left -hand line for a dot, and stopping when the dots and dashes are used up. -Thus, for example, - -the signal -.- - leads us to the letter d, - -the signal - - - - to the letter j and so on. - - -23 STANDARD ELECTRICAL DICTIONARY. - - -Alternating. adj. -Term descriptive of a current changing periodically in -direction. (See Current, Alternating.) - -Synonyms--Oscillatory--periodic--undulatory--harmonic. - - -Alternating Current Arc. -The arc produced by the alternating current. It presents several -peculiarities. With an insufficient number of alternations per second it -goes out. As the carbons wear away equally it is adopted for such lamps -as the Jablochkoff candle, (see Candle, Jablochkoff). As no crater is -formed the light is disseminated equally both up and down. For this -reason to get full downward illumination a reflector is recommended. - - -Alternating Current System. -A system of electric distribution employing the alternating current. For -transmission in the open air or in conduits a high potential circuit is -used, from 1,000 to 10,000 volts being maintained at the central -station. Two leads unconnected at the end lead from the station. Where -current is desired a converter or transformer (see Converter) is placed, -whose primary is connected to the two leads bridging the interval -between them. From the secondary the house leads are taken with an -initial potential in some cases of 50 volts. The converters are thus all -placed in parallel. By law or insurance rules the converters are -generally kept outside of buildings. Where no secondary current is taken -from the converters very little primary current passes them on account -of their counter-electromotive force. As more secondary current is taken -the primary increases and this accommodation of one to the other is one -of the interesting and valuable features. Street lamps are sometimes -connected in series. Each lamp in such case is in parallel with a small -coil with iron core. While the lamp is intact little current passes -through the coil. If the lamp is broken, then the converter impedes the -current by its spurious resistance, q. v., just enough to represent and -replace the resistance of the extinguished and broken lamp filament. -(See Meter, Alternating Current; Motor, Alternating Current.) - - -Alternation. -The change in direction of a current. The number of such changes is -expressed as number of alternations; thus a current may have a frequency -of 500 or 20,000 alternations per second. - -[Transcriber's note: One alternation per second is now called one hertz.] - - -Alternation, Complete. -A double alternation; a change from one direction -to the other and back again to the original phase. A symbol derived from -its graphic representation by a sine curve is used to indicate it. The -symbol is ~ - - -24 STANDARD ELECTRICAL DICTIONARY. - - -Alternative Path. -A second path for a current appearing as a disruptive -discharge. Where two paths are offered the discharge, as it is of -alternating or oscillatory type, selects the path of least -self-induction. Thus a thick bar of copper, with no air gap, may be -abandoned by the current in favor of a small iron wire with an air gap, -but which has less self-induction. - -The lightning arresters, q. v., for the protection of telegraph offices -are sometimes based on these principles. A path of very high resistance -but of small self-induction is offered between the line and the earth. -This the lightning discharge selects in preference to the instruments -with their iron cores, as the latter are of very high self-induction. - - -Alternator. -A dynamo electric generator supplying an alternating current. (See -Dynamo, Alternating Current.) - -Synonym--Alternating current generator or dynamo. - - -Alternator, Constant Current. -An alternating current dynamo supplying a current of unvarying virtual -amperage. Alternators of this type are constructed with an armature of -high self-induction. Sometimes fine winding contained in deep peripheral -notches in the core-discs is employed to magnify the self-induction. -Such generators are employed for series lighting, especially -arc-lighting. - - -Aluminum. -A metal; one of the elements; symbol: Al. -Atomic weight: 27.4. Equivalent: 9.13. Valency: 3. -Specific gravity: 2.6. It is a conductor of electricity. -Relative resistance annealed, (Silver = 1) 1.935 -Specific resistance at 0ºC (32°F.) 2.912 microhms - -Resistance of a wire at 0ºC (32°F.) -a) 1 foot long, weighing 1 grain, 0.1074 ohms. -b) 1 foot long, 1/1000 inch thick, 17.53 " -c) 1 meter long, weighing 1 gram, 0.0749 " -d) 1 meter long, 1 millimeter thick 0.03710 " -Resistance of a 1-inch cube at 0ºC (32°F.) 1.147 microhms -Electro-chemical equivalent. .0958 (hydrogen == .0105) - - -25 STANDARD ELECTRICAL DICTIONARY. - - -Amalgam. -(a) A combination or alloy in which one of the constituents is mercury. -Usually the term is applied to an alloy of a single metal with mercury. -Some metals readily form amalgams; such metals are: Gold, zinc, silver, -lead and others; some, such as platinum and iron, form amalgams only -under exceptional circumstances. - -(b) The word is also applied to compositions for application to the -cushions of frictional electric machine in which cases it is often a -misnomer. True amalgams used for this purpose are made as follows: - -(a) Tin, 1 part; Zinc, 1 part; Mercury, 2 parts (Kienmayer). -(b) Tin, 2 parts; Zinc, 3 parts. -(c) Tin, 3 parts; Zinc, 5 parts; Mercury, 4 parts. -(d) Zinc, 1 part: Mercury, 4 parts; Mercury, 9 parts. [sic] - -The tin, if such is used, (formula a, b and c) is first melted, the zinc -is added in successive portions. The mercury, which must be heated, is -slowly poured into the melted alloy after removal of the latter from the -fire, and the mixture, while making, is constantly stirred. It is kept -stirred or rubbed in a mortar until cold. Sometimes it is poured into -water and kept in constant agitation until cold. It is thus obtained in -a granular condition, and is pounded in a mortar until reduced to -powder. It must be dried and kept in tightly stopped bottles and is -applied to the cushions after they have been greased. It is to be -noticed that it is said that alloy (d) requires no pulverization beyond -constant rubbing in a mortar as it cools. Sometimes the amalgam is -shaken about in a wooden tray with chalk while cooling. The action of -amalgams is not very clearly understood. Some claim that there is a -chemical action, others that they simply act as conductors, others that -they are more highly negative to the glass than the leather of the -cushions. - -Graphite or sulphide of tin (mosaic gold) are sometimes used to coat the -cushions; it is these that are sometimes incorrectly called amalgams. - - -Amalgamation. -The application of mercury to a metal with which it forms an amalgam, or -with which it amalgamates. Battery zincs are amalgamated in two ways. In -the immersion method, the plate is dipped into an acid solution of -mercuric chloride or nitrate. The latter is best. In the direct -application method the plate is first wet all over with dilute acid and -a little mercury is dropped upon it and is rubbed over the surface with -a rag or, what is better, with a piece of galvanized iron. A very little -mercury answers the purpose. The whole surface of the plate should be -left as bright as silver. (See Action, Local.) - - -Amber. -Amber is a fossil resin, supposed to be a product of the extinct Pinites -Succinifer and other coniferous trees. Most of it is gathered on the -shores of the Baltic between Koenigsberg and Memel. It is also found in -small pieces at Gay Head, Mass., and in New Jersey green sand. It is -found among the prehistoric remains of the Swiss Lake dwellers. When -rubbed with a cloth it becomes excited with negative electricity. The -Greek word for it is electron, which gave the name electricity to the -modern science. Thales of Miletus, 600 B. C., and Theophrastus, about -300 B. C., both mention its electric properties or power of attracting -small objects when rubbed. - - -26 STANDARD ELECTRICAL DICTIONARY. - - -Ammeter. -The commercial name for an ampere-meter, an instrument designed -to show by direct reading the number of amperes of current which are -passing through a circuit. - -A great variety of ammeters have been invented, based on different -principles. The definitions following this one give some idea of the -lines of construction followed. - -Synonym--Ampere meter. - - -Ammeter, Ayrton's. -A direct reading instrument for measuring current intensity. - -A solenoid receives the current. In the axis of the solenoid an iron -tube is suspended by a long spiral spring that passes down within it, -and the upper end of which spring is fastened to the glass top of the -instrument. The tube is provided with proper guides so as to maintain a -vertical position, and is free to rotate. Its upper end carries an -index. - -The whole operates as a magnifying device. A slight longitudinal -displacement of the tube causes it to rotate through a considerable -angle by the action of the spring. By properly proportioning the parts, -the angle of displacement of the index is directly proportional to the -current between 15º and 270º angular displacement. - -The same instrument is wound for use as a volt-meter. - -Its principal fault is its restricted range. - - -Ammeter, Commutator. -A commutator ammeter is one whose windings consist of separate strands, -each of any desired number of turns, and provided with a commutating -attachment for throwing them into series or into parallel as desired. -The essential condition is that all the wires shall be of equal -resistance and of equal number of turns. Such an instrument can be used -for heavy or light currents. Two sets of graduations are marked on its -scale if it is a calibrated instrument. (See Calibration.) Commutator -volt-meters are constructed on the same principle. - - -Ammeter, Cunynghame's. -A modification of the Siemens' electro-dynamometer. (See -Electro-dynamometer, Siemens'.) An electro-magnet with very massive core -is excited by the current. As the core is of small reluctance the -strength of the magnet is nearly proportional to the current strength. -Between the poles of the magnet a soft iron armature or induced magnet -is pivoted. It carries a pointer so adjusted that when the axis of the -soft iron magnet is at an angle of about 30º with the line joining the -poles of the electro-magnet the pointer will indicate zero. - -The soft iron armature is so massive that the magnetism induced in it is -proportional to the strength of the electro-magnet. Hence the couple -exerted by the electro-magnet on the pivoted armature will be -proportional to the square of the current. - -The armature is retained in place by a spiral spring lying in line with -its axis of rotation. The instrument is operated as a zero reading -instrument. The current is passed through it. The needle is deflected; -it is brought back to zero by turning a milled head which twists the -spring. The current will be proportional to the square root of the angle -of displacement of the milled head. A scale with index is provided, -giving directly the square roots of the angle over which the pointer is -moved. - -The same instrument is wound for use as a volt-meter. - - -27 STANDARD ELECTRICAL DICTIONARY. - - -Ammeter, Eccentric Iron Disc. -This ammeter comprises a cylindrical electro-magnet excited by the -current to be measured. A disc of iron free to rotate is suspended on -pivots below it. A piece is cut off the disc at one part of its -periphery so as to give more metal to one side than to the other. In its -zero position this portion of the disc swings towards the magnet. As the -latter is more and more excited the other or more projecting portion of -the disc turns towards it, being attracted like an armature, and moves -against the force of gravity, the disc rotating. An index attached to -the disc swings over the face of a graduated scale. The disc is so -counterpoised that in its natural position the index points to zero. - - -Ammeter, Electro-magnetic. -An ammeter depending for its working upon the action of an -electro-magnet, which is excited by the current to be measured. - - -Ammeter, Gravity. -An ammeter whose hand or index is drawn into the zero position by -gravity, and whose displacement therefrom is produced by the action of -the current to be measured. - - -Fig. 11. GRAVITY SOLENOID AMMETER. - - -Ammeter, Magnetic Vane. -A fixed plate of soft iron is placed within a coil. Facing it is a -second disc free to move or swing on an axis. When the field is excited -the two repel each other because like polarity is induced in each, and -the motion of the movable disc indicates the strength of the current. -The same instrument is wound for high resistance and constitutes a -Magnetic Vane Voltmeter. - - -28 STANDARD ELECTRICAL DICTIONARY. - - -Ammeter, Magnifying Spring. -A solenoid ammeter in which a spiral spring is used to convert the -longitudinal motion of the armature or movable core into a rotary motion -(see Ammeter, Ayrton's) and magnify the apparent range of motion. - - -Ammeter, Permanent Magnet. -An ammeter with a magnetic field produced by a permanent magnet. - - -Ammeter, Solenoid. -An ammeter in which the attraction, when a current is passing through -it, exerted by a hollow coil of wire upon an iron bar or tube in line -with its axis, is utilized to indicate the strength of current. The bar -is drawn into the coil to different extents proportional to the -attraction. As an example see Ammeter, Ayrton's, and cut of Gravity -Ammeter. - - -Ammeter, Spring. -An ammeter in which the part moved by the current is controlled or -brought to the zero position by a spring. - - -Ammeter, Steel Yard. -A solenoid ammeter in which the solenoid core is suspended vertically -from the short end of a steel yard fitted with a sliding weight. The -current passes through the solenoid coil and attracts or draws downwards -the coil. A sliding weight is moved in and out on the long steel-yard -arm which is graduated for amperes. In use the weight is slid out until -the arm is in equipose; the divisions give the amperes. - - -Fig. 12. STEEL YARD AMMETER. - - -29 STANDARD ELECTRICAL DICTIONARY. - - -Ammunition Hoist, Electric. -An apparatus for use on ships for hoisting ammunition to the guns by an -electric elevator. The characteristic feature of it is that a constant -motion of the switch or handle is required to keep it in action. If the -operator is shot so as to be incapacitated from taking charge of the -switch, the hoist stops until another is assigned to it. - - -Amperage. -Current intensity expressed in amperes, as an amperage of ten amperes. - - -Ampere. -The practical unit of electric current strength. It is the measure of -the current produced by an electro-motive force of one volt through a -resistance of one ohm. In electric quantity it is the rate of one -coulomb per second. It is one-tenth the absolute C. G. S. unit of -current strength. Its best analogy is derived from water. Assuming the -electric current to be represented by a current of water, the pressure, -head, or descent producing such current would be the electro-motive -force. The current might be measured in gallons (or other unit) passed -per second. In the analogy these gallons would be coulombs. But it might -be measured by reference to a standard stream, as for instance, the -stream which would pass through a hole an inch square under a given -head, say six inches of water. This unit is the miner's inch, and is the -exact analogy of the ampere. A current of water may flow at the rate of -so many miner's inches, just as a current of electricity may flow at the -rate of so many amperes. In neither case it will be noted is there any -reference to time. "An ampere per second" is a redundant expression, and -means no more than "an ampere"; an "ampere-second," on the other hand, -is a coulomb. The number of coulombs passed per second gives the amperes -of current. - -For value of ampere, see Coulomb. - -[Transcriber's note: The SI definition of an ampere: A current in two -straight parallel conductors of infinite length and negligible -cross-section, 1 metre apart in vacuum, would produce a force equal to -2E-7 newton per metre of length.] - - - -Fig. 13. THE MINER'S INCH AS AN ANALOGY FOR THE AMPERE. - - -30 STANDARD ELECTRICAL DICTIONARY. - - -Ampere, Arc. -A conductor bent into the arc of a circle, and employed in measuring the -electric current by the electric balance. - - -Ampere-currents. -The currents assumed to be the cause of magnetism. (See Magnetism, -Ampere's Theory of.) - - -Ampere-feet. -The product of amperes of current by the length, in feet, of a conductor -passing such current. It may be in empiric calculations of dynamo or -motor construction, but is little used. One ampere-foot is a current of -one ampere passing through one foot length of a conductor, or one-tenth -ampere through ten feet, and so on. - - -Ampere-hour. -The quantity of electricity passed by a current of one ampere in one -hour. It is used by electric power and lighting companies as the unit of -energy supplied by them, because they maintain a constant potential -difference in their leads, so that only the amperes and hours need -measuring or recording to give the energy, viz. : volt-ampere-hours. -The same unit is applied to batteries to indicate their potential -energy, because they also are assumed to be of constant voltage or -electro-motive force. - - -Ampere-meters. -The product of amperes of current by the length, in meters, of a -conductor carrying such current. One ampere-meter is a current of one -ampere passing through one meter of a conductor. - -The term must not be confused with the identically spelled Ampere-meter, -a synonym for Ammeter. - - -Ampere-minute. -The quantity of electricity passed by a current of one ampere in one -minute; sixty coulombs. - - -Ampere Ring. -A conductor forming a ring or circle used in electric balances for -measuring currents. (See Balance, Ampere.) - - -Ampere-second. -The quantity of electricity passed by a current of one ampere in one -second; the coulomb, q. v. - - -Amperes, Lost. -In a shunt or compound-wound dynamo, part of the total amperes of -current produced in the armature coils go through the shunt, and hence, -do not appear in the outer circuit. S. P. Thompson has proposed the term -"lost amperes" for this portion of the current. - - -Ampere's Memoria Technica. -An expression of the effect of a current on a magnetic needle. If we -imagine the observer in the line of the current and facing the magnetic -needle, the current entering by his feet and leaving by his head, the -north pole is deflected to his left. - - -31 STANDARD ELECTRICAL DICTIONARY. - - -Ampere-turns. -The amperes of current supplied to a magnet coil multiplied by the -number of turns the current makes in the coil. If the coil is wound two -or three in parallel, the virtual turns by which the amperes are -multiplied are one-half or one-third the actual turns of wire. - -Synonym--Ampere Windings. - - -Ampere-turns, Primary. -The ampere-turns in the primary coil of an induction coil or -transformer. - - -Ampere-turns, Secondary. -The ampere-turns in the secondary coil of an induction coil or -transformer. - - -Amplitude of Waves. -Waves are distinguished by length and amplitude. The latter, in the case -of transverse waves, such as those of water and of the ether, correspond -with and measure the height from lowest to highest point, or from valley -to summit of the waves in question. In the case of longitudinal waves, -such as those of the air, due to sounding bodies, the ratio of degree of -rarefaction to degree of condensation existing in the system is the -amplitude. The latter can be graphically represented by a sinuous line, -such as would represent the section of a transverse wave. Ether waves -are produced by heated bodies and by electro-magnetic impulses, as in -the discharge of the Leyden jar. - -The amplitude of a wave, other things being equal, is the measure of its -intensity. Thus, the louder a sound the greater is the amplitude of the -system of waves to which it is due. The same applies to ether waves, -whether they are perceived in the electro-magnetic, light, or -heat-giving modification. As the amplitude of ether waves cannot be -accurately known, amplitude is a relative term and is not stated -generally in any absolute unit. - - -Analogous Pole. -One of the elements of a pyro-electric crystalline substance, such as -tourmaline. When heated, such bodies acquire electrical properties. If -of such crystalline form that they are differently modified at the ends -of their crystalline axis, by hemihedral modifications, the ends may be -differently affected. One end may show positive electricity when the -temperature is rising, and negative when falling. Such end is then -called the analogous pole. The opposite end presents, in such cases, the -opposite phenomena; becoming negative when the temperature is rising, -and becoming positive when it is falling; such end is called the -antilogous pole. - - -Analysis. -The determination of the elements of a case. It may be chemical, and -consist in finding what a substance consists of; it may be mathematical, -and consist in determining the unknown quantities in a problem; or it -may belong to other branches of science. The term has a very extended -application. Where the constituents are only determined in kind it is -called qualitative analysis; where their quantity or percentage is -ascertained it is called quantitative analysis. - - -32 STANDARD ELECTRICAL DICTIONARY. - - -Analysis, Electric. -Chemical analysis by electrolytic methods. (See Electrolytic Analysis.) - - -Analyzer, Electric. -An apparatus used in investigations on electric ether waves. It consists -of a series of parallel metallic wires. When the electric waves have -been polarized, the analyzer will only permit them to go through it -intact, when the plane of vibration of the waves is parallel to its -wires. - - -Anelectrics. -(a) Bodies which do not become electrified by friction; a term -introduced by Gilbert, now little used, as all bodies develop -electricity under proper conditions by contact action; the reverse of -idioelectrtics. - -(b) Also a conductor of electricity, the reverse of a dielectric, q. v. -(See Conductor.) - -It will be seen that Gilbert's anelectrics were, after all, the same as -the modern anelectrics, i.e., conductors. - - -Anelectrotonus. -A term used in medical electricity or electro-therapeutics to indicate -the deceased functional activity induced in a nerve by the proximity of -the anode of an active electric circuit completed through the nerve. The -converse of Kathelectrotonus. - - -Angle of Declination. -The angle of error of the magnetic needle or compass, measuring the -extent of its deviation from the meridian in any locality. It is the -angle between the plane of the magnetic axis of a magnetic needle free -to take its natural position, and the geographical meridian, the needle -being counterpoised if necessary, so as to hold an absolutely horizontal -position. The deviation is expressed as being east or west, referring -always to the north pole. (See Magnetic Elements.) - -Synonym--Variation of the Compass. - -[Transcriber's note: See Agonic Line.] - - -Angle of the Polar Span. -In a dynamo or motor the angle subtended by the portion of a pole piece -facing the armature, such angle being referred to the centre of the -cross-section of the armature as its centre. - - -STANDARD ELECTRICAL DICTIONARY. 33 - - -Angular Velocity. -The velocity of a body moving in a circular path, measured with -reference to the angle it passes over in one second multiplied by the -radius and divided by the time. A unit angle is taken (57°.29578 = -57° 17' 44".8 nearly) such that it is subtended by a portion of the -circumference equal in length to the radius. Hence, the circumference, -which is 360°, is equal to 2*PI*unit angle, PI being equal to 3.1416--. -"Unit angular velocity" is such as would in a circle of radius = 1 -represent a path = 1, traversed in unit time = 1 second. If the radius -is r and the angle passed over is theta, the distance is proportional to -r*theta; if this distance is traversed in t seconds the angular velocity -is theta / t. The angular velocity, if it is multiplied by r, theta -expressing a distance, will give the linear velocity. The dimensions of -angular velocity are an angle (= arc / radius) / a Time = (L/L)/T = -(T^-1). - -The velocity expressed by the rate of an arc of a circle of unit radius, -which arc subtends an angle of 57° 17' 44".8, such arc being traversed -in unit time, is unit angular velocity. - - -Animal Electricity. -Electricity, notably of high tension, generated in the animal system, in -the Torpedo, Gymnotus and Silurus. The shocks given by these fish are -sometimes very severe. The gymnotus, or electric eel, was elaborately -investigated by Faraday. It has the power of voluntarily effecting this -discharge. There is undoubtedly some electricity in all animals. The -contact of the spinal column of a recently killed frog with the lumbar -muscles produces contraction, showing electric excitement. Currents can -be obtained from nerve and muscle, or from muscle sides and muscle cut -transversely, in each case one thing representing positive and the other -negative elements of a couple. - - -Angle of Inclination or Dip. -The angle which the magnetic axis of a magnet, which magnet is free to -move in the vertical plane of the magnetic meridian, makes with a -horizontal line intersecting such axis. To observe it a special -instrument, the dipping compass, inclination compass, dipping needle, or -dipping circle, as it is called, is used. (See Elements, Magnetic, ---Dipping Needle,--Compass, Inclination.) - - -Angle of Lag. -The angle expressing the displacement of the magnetic axis of the -armature core of a dynamo in the direction of its rotation. (See Lag.) -Lag is due to the motion of the armature core. - - -Angle of Lead. -The angle expressing the displacement in the direction of rotation of -the armature of a dynamo which has to be given the brushes to compensate -for the lag. (See Lag.) This is positive lead. In a motor the brushes -are set the other way, giving a negative angle of lead or angle of -negative lead. - - -Anion. -The electro-negative element or radical of a molecule, such as oxygen, -chlorine or the radical sulphion. (See Ions.) It is the portion which -goes to the anode, q.v., in electrolytic decomposition. - - -34 STANDARD ELECTRICAL DICTIONARY. - - -Anisotropic. (adj.) -Unequal in physical properties, as in conduction and specific inductive -capacity, along various axes or directions. An anisotropic conductor is -one whose conductivity varies according to the direction of the current, -each axis of crystallization in a crystalline body marking a direction -of different conductivity. An anisotropic medium is one varying in like -manner with regard to its specific inductive capacity. In magnetism an -anisotropic substance is one having different susceptibilities to -magnetism in different directions. The term is applicable to other than -electric or magnetic subjects. - -Synonym--AEolotropic. - - -Annealing, Electric. -Annealing by the heat produced by the passage of the electric current -through the body to be annealed. The object is clamped or otherwise -brought into a circuit, and a current strong enough to heat it to -redness, or to the desired temperature is passed through it. - - -Annunciator. -An apparatus for announcing a call from any place to another, as from a -living-room to an office in a hotel, or for announcing the entering of -any given room or window in a building protected by a burglar alarm. - -A usual system comprises for each annunciator an electro-magnet. Its -armature is normally held away from its poles by a spring, and when in -that position a latch connected to the armature holds a little shutter. -When by a push-button or other device a current is sent through a -circuit which includes the electro-magnet the armature is attracted, -this releases the latch and the shutter drops. In dropping it displays a -number, letter or inscription which indicates the locality of the -push-button or other circuit-closing device. Often annunciators are -connected in circuit with a bell. - - -Fig. 14. ANNUNCIATOR. - - -35 STANDARD ELECTRICAL DICTIONARY. - - -Annunciator Clock. -A clock operating an annunciator by making contact at determined times. - -Annunciator Drop. -The little shutter which is dropped by some forms of annunciators, and -whose fall discloses a number, character or inscription, indicating -whence the call was sent. - - -Fig. 15. DROP ANNUNCIATOR. - - -Fig. 16. ANNUNCIATOR DETACHING MECHANISM. - - -Annunciator, Gravity Drop. -An annunciator whose operations release shutters which fall by gravity. - - -Annunciator, Needle. -A needle annunciator is one whose indications are given by the movements -of needles, of which there is usually a separate one for each place of -calling. - - -Annunciator, Swinging or Pendulum. -An annunciator which gives its indications by displacing from its -vertical position a pendulum or vertically suspended arm. - - -36 STANDARD ELECTRICAL DICTIONARY. - - -Anodal Diffusion. -A term in electro-therapeutics; the introduction of a medicine into the -animal system by using a sponge-anode saturated with the solution of the -drug in question. On passing a current the desired result is secured by -cataphoresis, q. v. - - -Anode. -The positive terminal in a broken metallic or true conducting circuit; -the terminal connected to the carbon plate of a galvanic battery or to -its equivalent in case of any other generator. In general practice it is -restricted to the positive terminal in a decomposition or electrolytic -cell, such as the nickel anode in a nickel-plating bath or the anode of -platinum in a gas voltameter. It is the terminal out of or from which -the current is supposed to flow through the decomposition cell. In -electro-therapeutics the term is used simply to indicate the positive -terminal. In an electrolytic cell the electro-negative substance or -anion goes to the anode. Hence, it is the one dissolved, if either are -attacked. The nickel, copper or silver anodes of the electroplater -dissolve in use and keep up the strength of the bath. The platinum anode -in a gas voltameter is unattacked because the anion cannot act upon it -chemically. - - -Anodic Closure Contraction. -A physiological change in a living subject produced by the closing of -the electric current; the muscular contraction which takes place beneath -the anode applied to the surface of the body when the circuit is closed, -the kathode being applied elsewhere; it is due, presumably, to direct -action on the motor nerve. It is a term in electro-therapeutics. It is -the converse of anodic opening contraction, q. v. An abbreviation A. C. -C. is often used to designate it. - - -Anodic Duration Contraction. -A term in electro-therapeutics. On the opening or closing of an electric -circuit, the anode of which is placed over a muscle, a contraction is -observed (see Anodic Closure Contraction--Anodic Opening Contraction). -The above term is used to designate the duration of such contraction. An -abbreviation A. D. C. is often used to designate it. - - -Anodic Opening Contraction. -The converse of Anodic Closure Contraction, q. v.; it is the contraction -of living muscle beneath or near the anode where the circuit, including -such anode and the body in its course, is closed; a physiological -phenomenon observed in electro-therapeutics to which branch of science -the term belongs. An abbreviation A. O. C. is often used to designate -it. - - -Anodic Reactions. -A term in electro-therapeutics; the diagnosis of disease by the actions -of the tissue near the anode of a circuit. - - -Anti-Induction Conductor. -A conductor constructed to avoid induction effects in the conducting -element. Many kinds have been made. A tubular metal shield or envelope -which may be grounded will protect an enclosed conductor to some extent. -Or the conductor may be a double wire twisted around itself, one branch -being used for the regular and the other for the return circuit, thus -constituting a closed metallic circuit. The inductive effects are due to -interrupted or varying currents in neighboring wires and circuits. Many -anti-induction conductors have been invented and patented. - - -37 STANDARD ELECTRICAL DICTIONARY. - - -Anti-magnetic Shield. -In general terms a hollow screen of soft iron designed to protect any -mass of steel behind or enclosed by it from magnetization by any magnet -near it, such as a dynamo field magnet. This it does by concentrating -the lines of force within its own mass, so that the space within it or -enclosed by it is comparatively free from lines of force. It is often -applied to watches, and is virtually an iron case in which they are -enclosed. - -Antimony. -A metal, one of the elements, atomic weight, 122: -equivalent, 40.6 and 24.4; valency, 3 and 5; -specific gravity, 6.8. -It is a conductor of electricity. -Relative resistance, compressed (silver = 1), 23.60 -Specific resistance, 35.50 microhms. -Resistance of a wire, -(a) 1 foot long, weighing 1 grain, 3.418 ohms. -(b) 1 foot long, 1/1000 inch thick, 213.6 " -(c) 1 meter long, weighing 1 gram, 2.384 " -(d) 1 meter long. 1 millimeter thick, 0.4521 " - -Resistance of a 1-inch cube, 13.98 microhms. - -Approximate percentage resistance per degree C. -(1.8º F. at 20º C. 88º F.) 0.389 per cent. - -Elcctro-chemical equivalent (hydrogen = .0105) .2560 -(See Thermo-Electric Series.) - - -Anvil. -An intermittent contact, or "make and break" of the current is sometimes -produced by directly pressing a key down upon a metallic surface, the -two being terminals of the circuit. The surface or stud on which such -pressure is produced is called the anvil. The ordinary telegraph key, -which makes a contact by the pressure of the operator's fingers does it -by making a contact between a contact piece upon the front end of the -key and the anvil. In the induction coil the anvil is also found. Thus -in the cut representing the end of an induction coil and its circuit -breaker in which O and O' and P and P' represent the secondary circuit -terminal connections A is the core of soft iron wires, h is the anvil; -the hammer when resting upon it so as to be in contact closes the -circuit. When the current coming from the primary to the post i, passes -through the hammer and anvil h, and emerges by m, it magnetizes the -core; this attracts the hammer, which is made of or is armed with a mass -of iron. This breaks the circuit. The hammer falls at once on the anvil, -again making the circuit, and the action is repeated with great -rapidity. Hammer and anvil or key and anvil connections should be made -of platinum. - - -Fig. 17. INDUCTION COIL CIRCUIT BREAKER. - - -38 STANDARD ELECTRICAL DICTIONARY. - - -A. O. C. -Abbreviation for Anodic Opening Contraction, q. v. - - -Aperiodic. adj. -In an oscillating apparatus, or in the oscillating member of apparatus, -the fact of having no reference to time of vibration; dead-beat. - -Synonym. Dead-beat. - - -39 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 18. ARAGO'S DISC. - - -Arago's Disc. -An apparatus consisting of a disc of copper mounted horizontally, or on -a vertical spindle, and so arranged as to be susceptible of rapid -rotation. Immediately over it, and best with a pane of glass -intervening, a magnetic needle is mounted on a pivot directly over the -axis of the disc. If the disc is rotated the lines of force of the -magnet are cut by it, and consequently currents are produced in the -copper. These currents act upon the needle and cause it to rotate, -although quite disconnected. It is advisable for the needle to be strong -and close to the disc, which should rotate rapidly. - - -Arc v. -To form a voltaic arc. - - -Arc, Compound. -A voltaic arc springing across between more than two electrodes. - - -Arc, Metallic. -The voltaic arc produced between terminals or electrodes of metal. The -characteristics of such arc as contrasted with the more usual arc -between carbon electrodes are its greater length for the same -expenditure of energy, its flaming character and characteristic colors -due to the metals employed. It is sometimes, for the latter reason, used -in spectroscopic investigations. - - -Arc Micrometer. -A micrometer for measuring the distance between the electrodes of a -voltaic arc. - - -Arc, Simple. -A voltaic arc produced, as usual, between only two electrodes. - - -40 STANDARD ELECTRICAL DICTIONARY. - - -Arc, Voltaic. -The voltaic arc is the arc between two carbon electrodes slightly -separated, which is produced by a current of sufficient strength and -involving sufficient potential difference. The pencils of carbon are -made terminals in a circuit. They are first placed in contact and after -the current is established they are separated a little. The current now -seems to jump across the interval in what sometimes appears an arch of -light. At the same time the carbon ends become incandescent. As regards -the distance of separation with a strong current and high electro-motive -force, the arc may be several inches long. - -The voltaic arc is the source of the most intense heat and brightest -light producible by man. The light is due principally to the -incandescence of the ends of the carbon pencils. These are differently -affected. The positive carbon wears away and becomes roughly cupped or -hollowed; the negative also wears away, but in some cases seems to have -additions made to it by carbon from the positive pole. All this is best -seen when the rods are slender compared to the length of the arc. - -It is undoubtedly the transferred carbon dust which has much to do with -its formation. The conductivity of the intervening air is due partly, -perhaps, to this, but undoubtedly in great measure to the intense -heating to which it is subject. But the coefficient of resistance of the -intervening air is so much higher than that of any other part of the -circuit that an intense localization of resistance occurs with -corresponding localization of heating effect. This is the cause of the -intense light. Thus if the carbons are but 1/32 of an inch apart as in a -commercial lamp the resistance may be 1.5 ohms. The poor thermal -conductivity of the carbon favors the concentration of heat also. The -apparent resistance is too great to be accounted for by the ohmic -resistance of the interposed air. A kind of thermoelectric effect is -produced. The positive carbon has a temperature of about 4,000° C. -(7,232° F.), the negative from 3,000° C. (5,432° F.) to 3,500° C. -(6,322° F.). This difference of temperature produces a -counter-electro-motive force which acts to virtually increase the -resistance of the arc. The carbon ends of an arc can be projected with -the lantern. Globules are seen upon them due to melted silica from the -arc of the carbon. - - -Fig. 19. EXPERIMENTAL APPARATUS FOR PRODUCING THE VOLTAIC ARC. - - -41 STANDARD ELECTRICAL DICTIONARY. - - -Areometer. -An instrument for determining the specific gravity of a fluid. It -consists of an elongated body ballasted so as to float vertically and -provided with a mark or a scale. It floats deeper in a light than in a -heavy liquid. If it carries but one mark weights are added until that -mark is reached, when the weights required give the specific gravity. Or -the scale may give the reading directly based upon the depth to which it -sinks. Areometers are often made of glass, ballasted with shot or -mercury enclosed in their bottom bulb as shown. They are used in -regulating battery solutions, and in watching the charging and -discharging of storage batteries. - - -Fig. 20. AREOMETER - - -Fig. 21. BEAD AREOMETER - - -Areometer, Bead. -A tube of glass containing beads of different specific gravities. It has -apertures at top and bottom. When immersed in a liquid, the same fills -it, and the specific gravity within certain limits, depending on the -factors of the beads, is shown by the beads which float and those which -sink. It is used for storage batteries and other purposes where acids -and solutions have to be tested. - - -Argyrometry. -The method of ascertaining the weight and inferentially the thickness of -an electroplater's deposit of silver. It is done by weighing the article -before and after plating. - - -Arm. -The four members of a Wheatstone bridge, q. v., are termed its arms. -Referring to the diagram of a bridge, P, Q, R, S, are the arms. - - -Fig. 22. DIAGRAM OF WHEATSTONE'S BRIDGE. - - -Armature. -(a.) A mass or piece of iron or steel, or a collection of pieces of iron -designed to be acted on by a magnet. While nickel or cobalt might be -used, they rarely or never are except in experimental apparatus. The -armature of a permanent horse shoe magnet is simply a little bar of soft -iron. When the magnet is not in use it is kept in contact with the poles -with the idea of retaining its magnetism. It is then said to be used as -a keeper. A bar magnet does not generally have an armature. The armature -is also used to exhibit the attraction of the magnet. - -Sometimes an armature is made of steel and is permanently magnetized. -Such an armature, termed a polarized armature, is repelled when its like -poles are opposed to like poles of the magnet and otherwise is attracted -with force due to the sums of the magnetism. If the magnet is -sufficiently powerful depolarization of the armature may ensue when like -poles are opposed to like poles. Polarized armatures are used in various -appliances, magneto generators, telegraphic instruments and others. - -(b) In a dynamo or Motor the mass of laminated iron or of wire which -carries the coils of insulated wires which are caused to rotate in the -field of force of the field magnets in order to establish and maintain -potential difference with its accompanying current, or which rotates -under the effects of a current in a motor. (See Dynamo Electric -Generator.) - -The work of the armature core is twofold. It acts as a portion of the -magnetic circuit, conducting the lines of force, and by virtue of its -high permeability or multiplying power concentrating a number of the -lines of force through its own substance. To enable it to act with -efficiency in this direction it should be made of iron of the highest -permeability, and should approach as closely as possible to the armature -cores consistent with leaving space for the wire winding. It next acts -as a support for the wires which are to be swept through the field of -force. Thus it acts both to establish a strong field and then acts as a -carrier for the wires which are to be cut by the wires in question. In -connection with this subject the different definitions under Armature, -Dynamo, Commutator, Induction and similar topics may be consulted. - -(c) See Armature of Influence Machine. - -(d) See Armature of Leyden Jar or Static Condenser. - - -42 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Bar. -An armature in a dynamo or motor whose winding is made up of conductors -in the form of bars, round, rectangular and of other sections. This type -of armature conductor is objectionable as Foucault currents are produced -in it. It is found best to laminate or subdivide low resistance armature -windings. - -[Transcriber's Note: Foucault currents are also called eddy currents.] - - -Armature, Bipolar. -An armature in which two poles are induced by the field. A bipolar field -magnet produces a bipolar armature. - - -Armature Bore. -The cylindrical space defined by the pole pieces of a dynamo or motor -within which the armature rotates. - -Synonym--Armature Chamber. - - -43 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Closed Coil. -An armature for a motor or dynamo, the ends of all of whose coils are -united, so as to be in one closed circuit all the way around. - - -Fig. 23. CLOSED COIL GRAMME RING ARMATURE. - - -Armature Coil, or Coils. -The insulated wire wound around the core of the armature of an electric -current generator or motor. - - -Armature Core. -The central mass of iron on which the insulated wire, to be rotated in -the field of an electric current generator or motor, is wound. (See -Dynamo-electric Machine and Motor, Electric.) - - -Armature, Cylinder. -An armature of the Gramme ring type, but longer in the axial direction, -so that its core resembles a long hollow cylinder, the wire being wound -inside and outside as in the Gramme ring. (See Gramme Ring.) - - -Armature, Disc. -(a) An armature of a dynamo electric machine or motor in which the coils -are wound so as to be flat and are carried on the face of a disc forming -the core or part of the core of the armature. S. P. Thompson treats it -as a modified drum armature extended radially, the outer periphery -corresponding to the back end of the drum. The poles of the field are -generally placed to face the side or sides of the disc. - -(b) Another type of disc armature has its wire wound on bobbins arranged -around the periphery of a disc. - -In disc armatures there is often no iron core, their thinness enabling -this to be dispensed with. - - -44 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 24. DISC ARMATURE OF FRITSCHE MACHINE. - - -Fig. 25. PLAN OF WINDING PACINOTTI'S DISC ARMATURE. - - -Armature, Discoidal Ring. -In a dynamo an armature of the shape of a ring of considerable radial -depth of section as compared to its axial depth. It is generally made of -iron ribbon or thin band wound to the proper size. - -Synonym--Flat Ring Armature. - - -45 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Drum. -An armature for a dynamo or motor, consisting of a cylinder of iron -preferably made up of discs insulated from each other by thin shellacked -paper, or simply by their oxidized surfaces, and wound with wire -parallel to the axis where it lies on the cylindrical periphery and -crossing the heads approximately parallel to the diameter. It operates -practically on the same principle as a Gramme Ring Armature. (See Gramme -Ring.) - -Synonym--Cylindrical Armature. - - -Armature Factor. -The number of conductors on an armature, counted or enumerated all -around its external periphery. - - -Armature, Hinged. -An armature pivoted to the end of one of the legs of an electro-magnet -so as to be free to swing and bring its other end down upon the other -pole. - - -Fig. 26. HINGED ARMATURES OF CLUB-FOOT ELECTRO MAGNETS. - - -Armature, Hole. -An armature whose core is perforated to secure cooling. - -Synonym--perforated Armature. - - -Armature, Intensity. -An armature wound for high electro-motive force. A term little used at -the present time. - - -Armature Interference. -A limit to the ampere turns permissible on a given armature is found in -the increase of cross magnetizing effect, q. v., the increased lead -necessitated, and the growth of the demagnetizing power. All such -perturbing effects are sometimes expressed as armature interference. - - -46 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Load of. -The circumflux, q. v., of the armature, or the ampere turns of the same. -The maximum load which can be carried by an armature without sparking is -directly proportional to the radial depth of core and to the length of -the gap, and inversely proportional to the breadth of the polar span. - - -Armature, Multipolar. -An armature in which a number of poles greater than two is determined by -the field. A multipolar field is employed for its production. - - -Armature, Neutral. -An armature of a magnet or telegraph relay which is not polarized or -magnetized. - -Synonym--Non-polarized Armature--Neutral Relay Armature. - - -Armature of Influence Machine. -Pieces of paper pasted on the stationary plate of an electric machine of -the Holtz type. - - -Armature of Leyden Jar or Static Condenser. -The inner and outer tin-foil coatings of a Leyden jar or other -condenser. - - -Armature, Open Coil. -An armature of a dynamo or motor on which the coils are not joined in -one closed circuit, but have their ends or some of them separated, and -connected each to its own commutator bar or each set to their own bar. - - -Fig. 27. OPEN COIL RING ARMATURE. - - -47 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Pivoted. -An armature for an electro-magnet mounted on a pivot, which is at right -angles to the yoke or parallel with the legs of the magnet, so as to be -free to rotate. When the magnet is excited the armature is drawn into -line or approximately so with its base or yoke. The system is used in -some telegraph apparatus. - - -Armature Pockets. -Spaces or recesses in armatures provided for the reception of the coils. - - -Armature, Polarized. -An armature made of steel or having a steel core to which permanent -magnetism has been imparted. Such are used in some forms of magneto -current generators, and in telegraphic instruments. (See Relay, -Polarized.) - - -Armature, Pole. -An armature having coils wound on separate poles projecting radially all -around the periphery of its central hub or disc, or projecting -internally from a ring-like frame, their ends facing the field magnet. - -Synonym--Radial Armature. - - -Armature, Quantity. -An armature of a dynamo or motor wound for current of large quantity. -The term is now but little used. - - -Armature-Reactions. -When an armature is running in an active dynamo a series of -reactions is established, the more important of which are: -I. A tendency to cross-magnetize the armature. -II. A tendency to spark at the brushes. -III. A tendency for the armature current to demagnetize on account of -the lead which has to be given to the brushes. -IV. Variations in the neutral points as more or less current is taken -from the machine. -V. Heating of armature, both core and conductors, and of pole pieces, -which heating is due to Foucault currents. - - -Armature, Revolving, Page's. -An early form of motor. The field is produced by a permanent magnet. -Above its poles is a soft iron armature wound with a coil of insulated -wire. A two-part commutator with contact springs conveys the current to -the coil. The whole is so arranged that the polarity of the armature, as -induced by the coil, through which a current is passed, is reversed as -its ends sweep by the poles of the magnet. Then it is repelled from the -poles and swings through 180° to have its polarity reversed and to go -through the next 180°, and so on. Thus it rotates at a very high rate of -speed. - -In the cut showing the elevation A, B, is the armature; f, g, the -springs or brushes; h, the commutator with its sections o, i. In the -section of the commutator W, W, designate the springs or brushes, A, the -vertical spindle carrying the armature and commutator, and S, S, the -commutator sections. - - -48 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 28. PAGE'S REVOLVING ARMATURE. - - -Fig. 29. SECTION OF COMMUTATOR OF PAGE'S REVOLVING ARMATURE. -W, W, Brushes; A, Spindle; S, S, Armature Segments. - - -Armature, Ring. -An armature whose core is in the shape of a ring, as the Gramme Ring -Armature. (See Figs. 23 & 27.) - - -49 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Rolling. -(a) An armature for a permanent horseshoe magnet consisting of a -straight cylinder of soft iron on which a heavy wheel is mounted. When -the legs of the magnet are inclined downward and the bar is laid across -them it rolls down to the poles, across their ends, and back up the -under side. It is merely a magnetic toy or illustrative experiment. - -Synonym--Wheel Armature. - -(b) Another form consists of little bars of iron with brass discs -attached to the ends. On placing two of these together and bringing the -poles of a magnet near them, as shown, they become magnetized with like -polarity by induction and repel each other, rolling away in opposite -directions. - - -Fig. 30. ROLLING OR WHEEL ARMATURE. - - -Fig. 31. ROLLING ARMATURES. - - -Armature, Shuttle. -The original Siemens' armature, now discarded. The core was long and -narrow, and its cross section was nearly of the section of an H. The -grooves were wound full of wire, so that the whole formed almost a -perfect cylinder, long and narrow comparatively. (See Winding Shuttle.) - -Synonym--Siemens' Old Armature--Girder Armature--H Armature. - - -Fig. 32. SHUTTLE OR H ARMATURE. - - -Armature, Spherical. -An armature of a dynamo which is wound on a spherical core, so as to be -almost a sphere. It is employed in the Thomson-Houston dynamo, being -enclosed in a cavity nearly fitting it, formed by the pole pieces. - - -Armature, Stranded Conductor. -A substitute for bar-armatures in which stranded copper wire conductors -are substituted for the solid bar conductors, to avoid Foucault -currents. (See Armature, Bar.) - - -50 STANDARD ELECTRICAL DICTIONARY. - - -Armature, Unipolar. -An armature of a unipolar dynamo. (See Dynamo Unipolar.) - - -Armor of Cable. -The metal covering, often of heavy wire, surrounding a telegraph or -electric cable subjected to severe usage, as in submarine cables. - -Synonym--Armature of Cable. - - -Arm, Rocker. -An arm extending from a rocker of a dynamo or motor, to which arm one of -the brushes is attached. (See Rocker.) Ordinarily there are two arms, -one for each brush. - - -Articulate Speech. -Speech involving the sounds of words. It is a definition which has -acquired importance in the Bell telephone litigations, one contention, -concerning the Bell telephone patent, holding that the patentee did not -intend his telephone to transmit articulations, but only sound and -music. - - -Astatic. adj. -Having no magnetic directive tendency due to the earth's magnetism. -Examples are given under Astatic Needle; Circuit, Astatic; and -Galvanometer Astatic. - - -Fig. 33. NOBILI'S PAIR. - - -FIG. 34. VERTICAL PAIR ASTATIC COMBINATION. - - -Astatic Needle. -A combination of two magnetic needles so adjusted as to -have as slight directive tendency as possible. Such a pair of needles -when poised or suspended will hardly tend to turn more to one point of -the compass than another. The combination is generally made up of two -needles arranged one above the other, with their poles in opposite -directions. This combination is usually called Nobili's pair. If of -equal strength and with parallel magnetic axes of equal length they -would be astatic. In practice this is very rarely the case. A resultant -axis is generally to be found which may even be at right angles to the -long axis of the magnets, causing them to point east and west. Such a -compound needle requires very little force to turn it one way or the -other. If one of the needles is placed within a coil of insulated wire a -feeble current will act almost as strongly to deflect the system as if -the other was absent, and the deflection will only be resisted by the -slight directive tendency of the pair of needles. This is the basis of -construction of the astatic galvanometer. Sometimes coils wound in -opposite directions and connected in series, or one following the other, -surround both needles, thus producing a still greater effect of -deflection. - -Other astatic needles are shown in the cuts below. [Figures 33 to 35.] - - -51 STANDARD ELECTRICAL DICTIONARY. - - -FIG. 35. SIMPLE ASTATIC NEEDLE. - - -Asymptote. -A line continuously approached by a curve, but which the curve, owing to -its construction or nature of curvature, can never touch, be tangent to, -or intersect. - - -Atmosphere. -(a) A term applied to the atmospheric pressure as a practical unit of -pressure equal to 15 lbs. to the square inch as generally taken. It is -really about 14.7 lbs. per square inch, or 1,033 grams per square -centimeter. - -(b) Air, q. v. - - -Atmosphere Residual. -The atmosphere left in a vessel after exhaustion. The term may be -applied to any gas. In an incandescent lamp after flashing the residual -atmosphere consists of hydro-carbons. - - -Atmospheric Electricity. -The electricity of the atmosphere, rarely absent, but often changing in -amount and sign. Benjamin Franklin, in a memoir published in 1749, -indicated the method of drawing electricity from the clouds by pointed -conductors. In June, 1752, he flew a kite and by its moistened cord drew -an electric spark from the clouds, confirming his hypothesis that -lightning was identical with the disruptive discharge of electricity. To -observe electricity in fine weather a gold-leaf or other electroscope -may be connected to the end of a long pointed insulated conductor. The -electricity during thunderstorms can be shown by a similar arrangement, -or burning alcohol or tinder gives an ascending current of warm air that -acts as a conductor. Quite elaborate apparatus for observing and -recording it have been devised. Atmospheric electricity is usually -positive, but occasionally negative. When the sky is cloudless it is -always positive, increasing with the elevation and isolation of the -place. In houses, streets, and under trees no positive electricity can -be found. In the Isle of Arran, Scotland, a rise of 24 to 48 volts per -foot of increase in elevation was found by Sir William Thomson. At -sunrise the electrification of the air is feeble, it increases towards -noon and decreases again to reach a second maximum a few hours after -sunset. It increases with the barometric pressure generally. In cloudy -weather it is sometimes negative and the sign often changes several -times in the same day. In a thunderstorm the changes in sign and -potential are very rapid. The cause of atmospheric electricity is far -from clear. Tait attributes it to a contact effect between air and water -vapor, Solmeke to friction of water vesicles against ice particles in -the upper atmosphere, he first showing that the two may coexist. The -cause of the enormous increase of potential producing lightning is -attributed to the decreased capacity due to the change of water from -cloud vesicles to drops, thus diminishing the electrostatic capacity of -the water in question. (See Lightning.) - - -52 STANDARD ELECTRICAL DICTIONARY. - - -Atom. -The ultimate particle or division of an elementary substance; the -smallest part that can exist in combination, and one which cannot exist -alone. An elementary substance is composed of molecules just as truly as -a compound one, but the atoms in the molecule of an elementary substance -are all precisely alike. Hence atoms are the units of chemistry, they -have to do with combinations, but the physical unit, the smallest -particle of matter that can have an independent existence, is the -molecule. The two are often confounded, especially by writers of a few -years ago, so that by "atom" the molecule is often meant. There is -nothing to be said of their size or mass. All such calculations refer to -the molecule, q. v., often spoken of and called the atom. - -[Transcriber's note: Yet to be discovered: electron--1897 (5 years), -proton--1920 (28 years), neutron--1932 (30 years), quark--1961 (69 years).] - - -Atomic Attraction. -The attraction of atoms for each other, in virtue of which they combine -into molecules; chemical affinity, q. v., treats principally of this, -although molecular attraction also plays a part in it. - - -Atomic Heat. -The product of the atomic weight of a substance by its specific heat. -This product is approximately the same, 6.4; this approximation is so -close that it is of use in determining the valency and atomic weights of -substances. The atomic weight of a substance therefore represents the -approximate number of gram-calories required to raise one gram-atom, q. -v., of such substance through 1° C. (1.8° F.) - - -Atomicity. -The quantivalence or valency of the atoms; the number of combination -bonds, or bonds of affinity, possessed by the atoms of any substance. -Thus two atoms of hydrogen combine with one atom of oxygen, and three of -oxygen with one of sulphur, forming saturated compounds. Therefore, -taking hydrogen as of single atomicity or a monad, oxygen is of double -atomicity or a dyad, and sulphur is of six-fold atomicity, or a hexad. -The elements are thus classified into seven orders of atomicities, thus: - - 1, Monads or Univalent elements, Hydrogen, etc. - 2, Dyads or Bivalent " Oxygen, etc. - 3, Triads or Trivalent " Nitrogen, etc. - 4, Tetrads or Quadrivalent " Lead, etc. - 5, Pentads or Quinquivalent " Phosphorous, etc. - 6, Hexads or Sexivalent " Chromium, etc. - 7, Heptads or Septivalent " Chromium, etc. - -The same element often possesses several atomicities. Barium is -generally a dyad, sometimes a tetrad; nitrogen acts as a monad, dyad, -triad, tetrad and pentad. The familiar electrolysis of water, giving two -volumes of hydrogen to one of oxygen, is one of the illustrations of the -theory indicating that two atoms of hydrogen are combined with one of -oxygen. - - -53 STANDARD ELECTRICAL DICTIONARY. - - -Atomic Weight. -The number expressing the relative weight of the atom of any substance, -that of hydrogen being generally taken as unity. This is the universal -system, although any other element might be taken as the basis of the -system. The whole theory of atomic weights is based on the -indivisibility of the atom and on the theory of atomicity, q. v. (See -Equivalents.) - -[Transcriber's note: The standard is now the isotope carbon-12 as -exactly 12.] - - -Attraction. -The tendency to approach and adhere or cohere, shown by all forms of -matter. It includes gravitation, cohesion, adhesion, chemical affinity -and other forms, and is opposed by repulsion, and is sometimes overcome -by it, although it may be assumed to be always present. See the -different kinds of attractions under their titles: Atomic Attraction, -Electro-magnetic Attraction and Repulsion, Electro Static Attraction and -Repulsion, Electro-dynamic Attraction and Repulsion; Magnetic Attraction -and Repulsion; Molar Attraction. - - -Audiometer. -An apparatus for obtaining a balance of induction from two coils acting -upon a third. The third is placed between the other two and is free to -move towards either. A scale is provided to show the extent of its -movement. A varying or interrupted current being passed through the two -outer coils, the preponderating current will produce the most induction -if the central coil is equidistant. It can always be moved to such a -point that there will be no inductive effect, one counteracting the -other. Thus its position measures the relative induction. A telephone is -in circuit with the intermediate coil and is used to determine when its -position is such that no current is induced in it. It is sometimes used -as a direct test of hearing. (See Hughes' Induction Balance.) - -Synonym--Acoutemeter. - - -Aura, Electrical. -The blast of air produced at highly electrified points. - - -Aurora. -A luminous display seen in the northern heavens in the northern -hemisphere, where it is the Aurora Borealis, and seen in the southern -heavens in the southern hemisphere, where it is called Aurora Australis, -or indifferently for either, the Aurora Polaris. It takes the form of -pale luminous bands, rays and curtains varying in color. Near the poles -they are very numerous. A French commission observed 150 auroras in 200 -days. Their height is variously estimated at from 90 to 460 miles; they -are most frequent at the equinoxes and least so at the solstices. There -is a secular variation also, they attain a maximum of occurrence every -11 years together with sun spots, with a minimum 5 or 6 years after the -maximum. There is also a period of 60 years, coincident with -disturbances in the earth's magnetism. Various attempts have been made -to account for them. They have a constant direction of arc with -reference to the magnetic meridian (q. v.) and act upon the magnetic -needle; in high latitudes they affect telegraph circuits violently. -There is a strong probability that they represent electric currents or -discharges. De la Rive considers them due to electric discharges between -the earth and atmosphere, which electricities are separated by the -action of the sun in equatorial regions. According to Balfour Stewart, -auroras and earth currents.(q. v.) may be regarded as secondary currents -due to small but rapid changes in the earth's magnetism. The subject is -very obscure. Stewart treats the earth as representing the magnetic core -of an induction coil, the lower air is the dielectric, and the upper -rarefied and therefore conducting atmosphere is the secondary coil. This -makes the aurora a phenomenon of induced currents. Then the sun may be -regarded as the instigator of the primary changes in the earth's lines -of force representing the primary of an induction coil. - -[Transcriber's note: Solar wind, streams of electrons and protons, -interacting with the earth's magnetic field causes aurora. Neither -electrons (1897) nor protons (1920) were known in 1892. The Soviet -satellite Luna first measured the solar wind in 1959. Even today -increased understanding of solar and auroral phenomenon continues.] - - -54 STANDARD ELECTRICAL DICTIONARY. - - -Austral Pole. -The north pole of the magnet is thus called sometimes in France; the -austral pole of a magnet is the one which points towards the north polar -regions As unlike magnetic poles attract each other, it is but rational -to call the north-seeking pole of the magnet the south or Austral Pole. -In the same nomenclature the south pole of a magnet, or the -south-seeking pole, is called the Boreal Pole. - - -A. W. G. -Abbreviation for American Wire Gauge, q. v. - - -Axis, Electric. -The electric axis of a pyroelectric crystal, such as a tourmaline -crystal; the line connecting the points of greatest pyroelectric -excitability. - - -Axis of Abscissa. -In a system of rectilinear, or right angle co-ordinates, the horizontal -axis. (See Co-ordinates.) - -Synonym--Axis of X. - - -Axis of Ordinates. -In a system of rectilinear right angle co-ordinates, the vertical axis. -(See Co-ordinates.) - -Synonym--Axis of Y. - - -Azimuth. -The angle between the plane of the meridian and the plane of an azimuth -circle, q. v. - - -Azimuth Circle. -A great circle, whose plane passes through the zenith or point of the -heavens directly overhead; any great circle in whose plane the vertical -at the point of observation is included. - -Each celestial body has or determines an azimuth circle. - - -55 STANDARD ELECTRICAL DICTIONARY. - - -B. -(a) Abbreviation for Baumé, a hydrometer scale. (See Baumé.) Thus 10º B. -means "ten degrees Baumé." - -(b) Symbol for the coefficient of induced magnetization, or the number -of lines per square centimeter induced in a magnetic circuit or in any -specified part of it. - - -B. A. -Abbreviation for British Association. It is prefixed to standards fixed -by the committee of the British Association for the Advancement of -Science. Thus the B. A. ohm means the British Association ohm, a measure -of resistance which is equal to the resistance of a column of mercury -104.9 centimeters long and one square millimeter area of cross-section. -(See Ohm.) - - -Back Induction. -A demagnetizing force produced in a dynamo armature when a lead is given -the brushes. The windings by such setting of the brushes are virtually -divided into two sets, one a direct magnetizing set, the other a cross -magnetizing set. The latter have a component due to the obliqueness of -the neutral line, which component is demagnetizing in its action. - - -Back Shock or Stroke of Lightning. -A lightning stroke received after the main discharge of the lightning, -and caused by a charge induced in neighboring surfaces by the main -discharge. The discharge affects the evenness of distribution of -surrounding surfaces so that a species of secondary discharge is -required to make even the distribution, or to supply charge where needed -to bind an opposite one. The effects are much lese severe as a rule than -those of the main charge, although the back stroke has caused death. The -back stroke is sometimes felt a considerable distance from the place of -the original lightning stroke. - -Synonym--Return Stroke. - - -Back Stroke. -(a) In telegraphy the return stroke of the lever in a telegraph sounder, -striking the end of the regulating screw with a sound distinct from that -which it produces on the forward stroke as it approaches the magnet -poles. It is an important factor in receiving by ear or sound reading. - -(b) See Back Shock or Stroke of Lightning. - - -Balance. -(a) Wheatstone's Bridge, q. v., is sometimes termed the Electric -Balance. - -(b) A suspension or torsion balance is one which includes a filament or -pair of filaments to whose lower end or ends are attached a horizontal -indicator often called a needle, or a magnetic needle. (See Torsion -Balance.) - -(c) See Induction Balance, Hughes'. - -(d) For Thermic Balance, see Bolometer. - -(e) See Balance, Ampere. - - -56 STANDARD ELECTRICAL DICTIONARY. - - -Balance, Ampere. -A class of electrical measuring instruments due to Sir William Thomson -may be grouped under this head. - -The instrument is a true balance or scales such as used for weighing. It -is supported by a torsional wire support in place of knife edges. At -each end it carries a circle of wire through which the current to be -tested is passed. The torsional wire support enables the current to be -carried to these wire rings. Above and below each of these rings are two -similar rings, also connected so as to receive the current. They are so -connected that the current shall go through them in opposite senses. -When a current passes, therefore, one of these rings repels and one -attracts the balanced ring. - -The extent of this action measures the intensity of the current. A -sliding weight moving along a graduated scale on the balance is used to -bring the balance beam into equilibrium when the current is passing. The -degree of displacement of this weight gives the strength of the current -in amperes. - -These balances are made for different currents. Thus there is a -centi-ampere balance, deka-ampere balance and others, as well as an -ampere balance. - - -Balata. -A gum used as an insulating material. It is the inspissated juice of a -sapotaceous tree, the bullet tree, Mimusops globosa, of tropical -America, from the Antilles to Guiana. It is intermediate in character -between caoutchouc and gutta percha. It is superior to gutta percha in -some respects, being very slightly acted on by light. - -Synonym--Chicle. - - -B. & S.. W. G. -Abbreviation for Brown & Sharpe Wire Gauge; the regular American Wire -Gauge. (See Wire Gauge, American.) - - -Barad. -An absolute or fundamental unit of pressure, equal to one dyne per -square centimeter. - - -Barometer. -An apparatus for measuring the pressure exerted by the atmosphere. It -consists, in the mercurial form, of a glass tube, over 31 inches long, -closed at one end, filled with mercury and inverted, with its open end -immersed in a cistern of mercury. The column falls to a height -proportional to the pressure of the atmosphere from 30 to 31 inches at -the sea level. The "standard barometer" is a height of the mercury or of -the "barometric column" of 30 inches or 760 centimeters, measured from -the surface of the mercury in the cistern. - -The column of mercury is termed the barometric column. Above it in the -tube is the Torricellian vacuum. - -[Transcriber's note: More accurately, 29.92 inches of mercury or 14.696 -PSI.] - - -Bars of Commutators. -The metal segments of a commutator of a dynamo or motor. They are made -of bars of copper, brass or bronze insulated from one another. (See -Commutator.) - -Synonyms--Segments, Commutator Segments, Commutator Bars. - - -57 STANDARD ELECTRICAL DICTIONARY. - - -Bath. -(a) In electro-plating the solution used for depositing metal as -contained in a vat or tank; as a silver, copper, or nickel bath used for -plating articles with silver, copper, or nickel respectively. - -(b) In electro-therapeutics a bath with suitable arrangements, -electrodes and connections for treating patients with electricity. It is -termed an electric bath or electro-therapeutic bath. - - -Bath, Bipolar Electric. -In electro-therapeutics a bath in which the electrodes are both immersed -in the water. The patient placed between them receives part of the -discharge. The electrodes are large copper plates, termed shovel -electrodes. - - -Bath, Electric Shower. -An electro-medical shower bath. The patient is placed on a metallic -stove or support connected to one of the electric terminals. Water -slightly alkaline is showered upon him. The other electrode is in -connection with the water. The rain of drops and streamlets is the -conductor of the current or discharge. - - -Bath, Multipolar Electric. -An electro-medical bath with a number of electrodes instead of two. - - -Bath, Stripping. -In electro-plating a solution used for dissolving and thus removing the -plating from any object. The stripping bath is of the same general type -as the plating bath for the same metal as the one to be dissolved. The -object to be "stripped" is made the anode of a plating circuit, and as -the current acts the old plating is attacked and dissolves, leaving the -body of the article bare. It is simply the operation of plating -reversed. The same term is applied to baths acting by simple solution. -Stripping baths are described under the different metals as Silver Bath, -Stripping--Gold Bath, Stripping. - - -Bath, Unipolar Electric. -An electro-medical bath, in which only one electrode connects with the -water of the bath. The second electrode is supported above the bath. The -patient touches this while in the water whenever electric action is -desired. - - -FIG. 36. THREE WIRE MOULDING OR BATTEN. - - -FIG. 37. TWO WIRE MOULDING OR BATTEN. - - -58 STANDARD ELECTRICAL DICTIONARY. - - -Batten. -A strip of wood grooved longitudinally for holding wires in wiring -apartments for electric light or power. In use they are fastened to the -wall, grooves inward, or else grooves outward, with the wires lying in -the grooves and covered with the covering strip. For two wire work each -batten contains two grooves; for the three wire system it contains three -grooves. - -Synonym--Moulding. - - -Battery. -A combination of parts or elements for the production of electrical -action. The term is principally applied to voltaic batteries, but there -are also magnetic batteries, batteries of Leyden jars, and other -combinations, described in their places, which come under this category. - -[Transcriber's note: A group of similar items such as questions, -machines, parts, guns, or electric cells.] - - -Battery, Acetic Acid. -A battery whose active solution or excitant is acetic acid or vinegar. -This acid has been used by Pulvermacher in his medical battery, as being -a substance found in every household in the form of vinegar. It is now -but little used. - - -Battery, Alum. -A battery using as excitant a solution of alum. This battery has had -some application for electric clocks, but only to a limited extent. - - -Fig. 38. BALLOON OR FLASK BATTERY. - - -Battery, Aluminum. -A battery in which aluminum is the negative plate and aluminum sulphate -the excitant. It is mounted like the gravity battery. Its electro-motive -force is 0.2 volt. - - -59 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Bagration. -A battery with zinc and carbon electrodes immersed in earth sprinkled -with sal ammoniac (ammonium chloride). The copper is preferably first -immersed in sal ammoniac solution and dried, until a green layer is -formed on its surface. - -The battery is highly praised for its constancy by De la Rive, but may -be regarded as obsolete. - - -Battery, Balloon. -A form of gravity battery into whose centre a globular flask, B, is -inverted, which is filled before inversion with copper sulphate, of -which 2 lbs. are used, and water, so as to remain full. This acts as a -reservoir of copper sulphate, which it constantly supplies. The glass -jar is closed with a perforated wooden cover. - - -Battery, Banked. -(a) A battery arranged to feed a number of separate circuits. - -(b) A battery connected in parallel or in multiple arc. - - -Battery, Bichromate. -A battery with amalgamated zinc and carbon plates, with an exciting -fluid composed of sulphuric acid, water, and potassium bichromate. For -formula of such solutions see Electropoion Fluid--Kookogey's -Solution--Poggendorff's Solution--Trouvé's Solution--Delaurier's -Solution, and others. (See Index.) - - -Battery, Bunsen. -A two fluid porous cell battery. The negative plate is carbon, the -positive plate, amalgamated zinc. The depolarizer is nitric acid or -electropoion fluid, q.v., in which the carbon is immersed. The last -named depolarizer or some equivalent chromic acid depolarizing mixture -is now universally used. The excitant is a dilute solution of sulphuric -acid. Originally the carbon was made cylindrical in shape and surrounded -the porous cups, in which the zinc was placed. This disposition is now -generally reversed. The electro-motive force is 1.9 volts. The -depolarizing solution is placed in the compartment with the carbon. The -excitant surrounds the zinc. - - -Fig. 39. BUNSEN'S BATTERY. - - -60 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Cadmium. -A battery in which cadmium is the negative plate, sulphate of cadmium -solution the excitant and depolarizer, and zinc the positive plate. -Electro-motive force, .31 volt or about one third of a Daniell cell. It -is mounted like a gravity battery. - - -Battery, Callan. -A modification of Grove's battery. Platinized lead is used for the -negative plate, and as a depolarizer a mixture of 4 parts concentrated -sulphuric acid, 2 parts of nitric acid, and 2 parts of a saturated -solution of potassium nitrate. (See Battery, Grove's.) - - -Battery, Camacho's. -A battery with carbon negative and amalgamated zinc positive electrodes. -The carbon is contained in a porous cup, packed with loose carbon. -Electropoion or other fluid of that type serves as excitant and -depolarizer, and is delivered as shown from cell to cell by syphons. - - -Fig. 40. CAMACHO'S BATTERY. - - -Battery, Carré's. -A Daniell battery for whose porous cup a vessel or species of sack made -of parchment paper is substituted. The battery has been used for -electric light, and has been run for 200 successive hours, by replacing -every 24 hours part of the zinc sulphate solution by water. - - -61 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Cautery. -A battery used for heating a platinum wire or other conductor used for -cauterization in electro-therapeutics. The term is descriptive, not -generic. - - -Battery, Chloric Acid. -A battery of the Bunsen type in which an acidulated solution of -potassium chlorate is used as depolarizer. - - -Battery, Chloride of Lime. -A battery in which bleaching powder is the excitant. The zinc electrode -is immersed in a strong solution of salt, the carbon in a porous vessel -is surrounded with fragments of carbon and is packed with chloride of -lime (bleaching powder). There is no action on open circuit. It has to -be hermetically sealed on account of the odor. Its electro-motive force -is--initial, 1.65 volts; regular, 1.5 volts. - -Synonym--Niaudet's Battery. - - -Battery, Chromic Acid. -Properly a battery in which chromic acid is used as a depolarizer. It -includes the bichromate battery. (See Battery, Bichromate.) - - -Battery, Closed Circuit. -A battery adapted by its construction to maintain a current on a closed -circuit for a long time without sensible polarization. The term is -merely one of degree, for any battery becomes exhausted sooner or later. -As examples the Grove, Bunsen or Daniell batteries may be cited. - - -62 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 41. COLUMN BATTERY. - - -Battery, Column. -The original Volta's pile. It consists of a series of compound circular -plates, the upper or lower half, A, copper; the other, Z, of zinc. -Between each pair of plates some flannel or cloth, u, u, is laid, which -is saturated with dilute acid. As shown in the cut, the parts are laid -up in two piles, connected at the top with a bar, c, c, and with vessels -of acidulated water, b, b, as electrodes. The great point in setting it -up is to be sure that no acid runs from one disc of flannel to the next -over the outside of the plates, as this would create a short circuit. -The plates are best compound, being made up of a zinc and a copper plate -soldered together. They may, however, be separate, and merely laid one -on the other. In such case great care must be taken to admit no acid -between them. - -Volta's pile is no longer used, except occasionally. Trouvé's blotting -paper battery (see Battery, Trouvé's) is a relic of it, and the same is -to be said for Zamboni's dry pile. - -It rapidly polarizes, the flannel retains but little acid, so that it is -soon spent, and it is very troublesome to set up. Great care must be -taken to have the cloth discs thoroughly saturated, and wrung out to -avoid short circuiting by squeezing out of the acid. - - -Battery, D'Arsonval's. -A battery of the Bunsen type, differing therefrom in the solutions. As -excitant in which the zinc electrode is immersed, the following solution -is used: - -Water, 20 volumes; -Sulphuric Acid (purified by shaking with a little olive or similar oil), -1 volume; -hydrochloric acid, 1 volume. - -As polarizer in which the carbon is immersed the following is used: - -Nitric acid, 1 volume; -hydrochloric acid, 1 volume; -water acidulated with 1/20th sulphuric acid, 2 volumes. - - -Battery, de la Rue. -A battery with zinc positive and silver negative electrode; the -depolarizer is silver chloride; the excitant common salt or ammonium -chloride. The cut shows one of its forms of construction. - -The right hand portion of the cut, Fig. 42, shows the zinc perforated at -C for the connection from the next silver plate. The next to it is the -negative electrode of silver around which a mass of silver chloride is -cast in cylindrical form. A is a parchment paper cylinder with two holes -near its top, through which the silver wire of the negative electrode is -threaded, as shown in B. A solution of 23 parts ammonium chloride in -1,000 parts of water is the approved excitant. Its electro-motive force -is 1.03 volts. - -The jars are closed with paraffin. - - -Fig. 42. DE LA RUE'S BATTERY. - - -63 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Dry. -(a) A form of open circuit battery in which the solutions by a mass of -zinc oxychloride, gypsum, or by a gelatinous mass such as gelatinous -silica, or glue jelly, are made practically solid. Numbers of such have -been patented, and have met with considerable success. - -(b) Zamboni's dry pile, q. v., is sometimes termed a dry battery. - - -Battery, Element of. -A term applied sometimes to a single plate, sometimes to the pair of -plates, positive and negative, of the single couple. - - -Battery, Faradic. -A term applied, not very correctly however, to apparatus for producing -medical faradic currents. It may be an induction coil with battery, or a -magneto-generator worked by hand. - - -Battery, Ferric Chloride. -A battery of the Bunsen type, in which a solution of perchloride of iron -(ferric chloride) is used for the depolarizing agent. A little bromine -is added with advantage. The depolarizing agent recuperates on standing, -by oxidation from the oxygen of the air. - - -Battery, Fuller's. -A battery of the Bunsen type. The zinc plate is short and conical, and -rests in the porous jar into which some mercury is poured. An insulated -copper wire connects with the zinc. A plate of carbon is in the outer -jar. The solutions are used as in the Bunsen battery. - -Synonym--Mercury Bichromate Battery. - - -Battery, Gas. -(a) A battery whose action depends on the oxidation of hydrogen as its -generating factor. It was invented by Grove. Plates of platinum are -immersed in cups of dilute acid, arranged as if they were plates of zinc -and carbon, in an ordinary battery. Each plate is surrounded by a glass -tube sealed at the top. The plates are filled with acid to the tops. -Through the top the connection is made. A current from another battery -is then passed through it, decomposing the water and surrounding the -upper part of one set of plates with an atmosphere of oxygen and of the -other with hydrogen. Considerable quantities of these gasses are also -occluded by the plates. On now connecting the terminals of the battery, -it gives a current in the reverse direction of that of the charging -current. - -This battery, which is experimental only, is interesting as being the -first of the storage batteries. - -(b) Upward's Chlorine Battery and any battery of that type (see Battery, -Upward's,) is sometimes termed a gas battery. - - -64 STANDARD ELECTRICAL DICTIONARY. - - -Battery Gauge. -A pocket or portable galvanometer for use in testing batteries and -connections. - - -Battery, Gravity. -A battery of the Daniell type, in which the porous cup is suppressed and -the separation of the fluids is secured by their difference in specific -gravity. A great many forms have been devised, varying only in details. -The copper plate, which is sometimes disc shaped, but in any case of -inconsiderable height, rests at the bottom of the jar. Near the top the -zinc plate, also flat or of slight depth, is supported. As exciting -liquid a strong solution of copper sulphate lies at the bottom of the -jar. This is overlaid by a solution of zinc sulphate, or sodium -sulphate, which must be of considerably less specific gravity than that -of the copper sulphate solution. In charging the jar one-tenth of a -saturated solution of zinc sulphate mixed with water is sometimes used -as the upper fluid. This may be first added so as to half fill the jar. -The strong solution of copper sulphate may then be added with a syphon -or syringe underneath the other so as to raise it up. From time to time -copper sulphate in crystals are dropped into the jar. They sink to the -bottom and maintain the copper sulphate solution in a state of -saturation. - - -Fig. 43. GRAVITY BATTERY OF THE TROUVÉ-CALLAUD TYPE. - - -If the battery is left on open circuit the liquids diffuse, and metallic -copper precipitates upon the zincs. This impairs its efficiency and -creates local action. As long as the battery is kept at work on closed -circuit work but little deposition, comparatively speaking, occurs. - -From time to time, in any case, the zinc plates are removed and scraped, -so as to remove the copper which inevitably forms on their surface. Care -must be taken that the zinc sulphate solution, which is constantly -increasing in strength, does not get so strong as to become of as high -specific gravity as the copper sulphate solution. From time to time some -of the upper solution is therefore removed with a syphon or syringe and -replaced with water. An areometer is useful in running this battery. - - -65 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Grenet. -A plunge battery with zinc positive and carbon negative electrodes. -Electropoion or other chromic acid or bichromate solution is used as -depolarizer and excitant. The zinc plate alone is plunged into and -withdrawn from the solution. - - -Fig. 44. GRENET'S BATTERY. - - -Fig. 45. GROVE'S BATTERY. - - -Battery, Grove's. -A two fluid galvanic battery. A porous cup has within it a riband of -platinum, which is the negative plate; amalgamated zinc in the outer jar -is the positive plate. Dilute sulphuric acid (10 per cent. solution) is -placed in the outer jar, and strong nitric acid (40° B.) as a -depolarizer in the porous cups. Its E. M. F. is 1.96 volts. - -It is objectionable, as it gives off corrosive nitrous fumes. These are -produced by the oxidation of the nascent hydrogen by the nitric acid, by -the following reaction: - -3 H + H N O3 = 2 H2 O + N O. There are other reactions, one of which -results in the formation of ammonia by the reduction of the nitric acid -radical by the hydrogen. Ammonium can be detected in the spent liquids. - - -66 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Hydrochloric Acid. -A battery in which hydrochloric acid is used as the excitant. Many -attempts have been made to use this acid in batteries, but the volatile -nature of the acid causes the production of so much odor with corrosive -fumes that it has never come into use. - - -Battery, Lead Chloride. -A battery of the lead sulphate type in which lead chloride is the -depolarizer. It has had no extended use. - - -Battery, Lead Sulphate. -A battery similar to Marié Davy's battery or the gravity battery, but -using lead sulphate as depolarizer and excitant. Lead, copper or tin is -the material of the negative plate. Becquerel used the lead sulphate as -a solid cylindrical mass surrounding a lead rod 1/5 to 1/4 inch in -diameter. One part of common salt may be mixed with 5 parts of the lead -sulphate. The electro-motive force is about 0.5 volt. The resistance is -very high. - - -Battery, Leclanché. -An open circuit battery with porous cup. In the outer jar is a zinc rod; -a carbon plate is placed in the porous cup. The latter is packed with a -mixture of clean powdered manganese binoxide as depolarizer, and -graphite in equal volumes. A strong solution of ammonium chloride (sal -ammoniac) is placed in the outer jar. It is only used on open circuit -work. Its electromotive force is 1.48 volts, when not polarized. - -The reaction is supposed to be about the following: - -2 N H4 Cl + 2 Mn O2 + Zn = Zn Cl2 + 2 N H3 + H2 0 + M2 O3 - -The battery rapidly weakens on open circuit, but quickly recuperates. -There is another form of this battery, termed the agglomerate battery. -(See Battery, Leclanché Agglomerate.) - - -Fig. 46. LECLANCHÉ BATTERY. - - -Battery, Leclanché Agglomerate. -A form of the Leclanché in which the porous jar is suppressed. Cakes -made of a mixture of carbon, 52 parts; manganese binoxide, 40 parts; gum -lac, 5 parts; potassium bisulphate, 3 parts, compressed at 300 -atmospheres, at a temperature of 100° C. (212° F.), are fastened by -India rubber bands or otherwise against the carbon plate. These -constitute the depolarizer. Various shapes are given the carbon and -depolarizing agglomerates. - - -Battery, Local. -A battery supplying a local circuit (see Circuit. Local). The current is -governed by the relay situated on the main line and operated by its -current. - - -Battery, Main. -The battery used in operating the main line. It is usually applied to -telegraphy. Its function is then to supply current for working relays, -which in turn actuate the local circuits. - -Main and local circuits and batteries are also used in the automatic -block system of railroad signalling. - - -67 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Marié Davy's. -A two fluid porous cup battery with carbon negative plate, zinc positive -plate, and mercury sulphate, a nearly insoluble salt, as depolarizer and -excitant. Mercurous or mercuric sulphates have been used in it. Its -electromotive force is 1.5 volts. The local action and waste, owing to -the slight solubility of the mercury compounds, is very slight. If used -on close circuit it becomes polarized. It is also subject under extreme -circumstances to reversal of polarity, zinc becoming deposited upon the -carbon, and there forming a positive electrode. - -In using the cells in series the level of liquid in all must be the -same, otherwise the cell in which it is lowest will become polarized and -exhausted. - -Modifications of this battery on the lines of the gravity battery have -been constructed. - -Synonym--Sulphate of Mercury Battery. - - -Battery, Maynooth's. -A battery of the Bunsen type, with cast iron negative plate. The iron -takes the passive form and is not attacked. - - -Battery, Medical. -A term applied very indiscriminately to medical current generators, and -to medical induction coils, or to any source of electricity, static or -current, for medical application. - - -68 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Meidinger's. -A variety of Daniell cell of the gravity type. The plates are -cylindrical. The zinc plate lies against the upper walls of the vessel. -The copper plate of smaller diameter rests on the bottom. A large tube, -with an aperture in its bottom, is supported in the centre and is -charged with copper sulphate crystals. The cup is filled with a dilute -solution of Epsom salts (magnesium sulphate) or with dilute sulphuric -acid. - - -Battery Mud. -A deposit of mud-like character which forms in gravity batteries and -which consists of metallic copper precipitated by the zinc. It indicates -wasteful action. - - -Battery, Multiple-connected. -A battery connected in parallel, all the positive plates being connected -to one electrode, and all the negative to another. - - -Battery, Nitric Acid. -A battery in which nitric acid is used as the excitant. Owing to its -cost and volatility this acid has been but little used in batteries, -other than as a depolarizer. In Grove's battery (see Battery, Grove's) -it has been thus used. - - -Battery of Dynamos. -A number of dynamos may be arranged to supply the same circuit. They are -then sometimes termed as above, a Dynamo Battery. They may be arranged -in series or in parallel or otherwise combined. - - -Battery of Leyden Jars. -To produce the quantity effect of a single large Leyden jar with a -number of small ones they are often connected in parallel and termed a -battery. In such case the inner coatings are all connected by regular -bar conductors, and the outside coatings are also all in connection. -They are conveniently placed in a box or deep tray whose inner surface -is lined with tinfoil, with an outside connection for grounding, etc. -The cascade, q. v., arrangement is not so generally termed a battery. - - -Battery, Open Circuit. -A battery adapted for use in open circuit work. Its main requirement is -that it shall not run down, or exhaust itself when left on open circuit. -The Leclanché battery is very extensively used for this work. Its action -is typical of that of most open circuit batteries. It is without any -action on open circuit. It is very quickly exhausted on closed circuit, -but recuperates or depolarizes quite soon when on open circuit. It is -always in condition for a momentary connection, but useless for steady -work. - - -Battery, Oxide of Copper. -A battery with zinc positive and iron negative electrodes. The excitant -is a 30 or 40 per cent. solution of sodium or potassium hydrate (caustic -soda or caustic potash). The depolarizer is copper oxide. In action the -copper is gradually reduced to the metallic state. The iron element is -often the containing vessel. The battery is practically inactive on open -circuit. - -Its electro-motive force varies from .75 to .90 volt. To prevent the -formation of sodium or potassium carbonate the cell should be closed, or -else the liquid should be covered with mineral oil. - -Synonyms--Lalande & Chaperon Battery--Lalande-Edison Battery. - - -69 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Peroxide of Lead. -A battery in which peroxide of lead (lead binoxide) is the depolarizer. -It is a sort of predecessor of the present secondary battery. - - -Battery, Platinized Carbon. -A modification of Smee's battery, in which platinized carbon is used for -the negative plates. Before polarization the E. M. F. is equal to that -of Smee's battery. Polarization reduces its electro-motive force -one-half. - - -Battery, Plunge. -A battery whose plates are mounted so as to be immersed in the battery -cups or cells, when the battery is to be used, and withdrawn and -supported out of the cups when not in use. The object is to prevent -wasting of the plates by standing in the solution. It is a construction -generally used with sulphuric acid--chromic acid solution and -amalgamated zinc and carbon plates. - - -Battery, Pneumatic. -A battery arranged to have air blown through the solution to assist -diffusion and depolarization. It is a construction applied to chromic -acid or bichromate batteries. - - -Battery, Primary. -A battery in which the current is supplied by the solution of one of the -plates by the solution. The term distinguishes it from a secondary or -storage battery. - - -Battery, Pulvermacher's Electro-Medical. -In this battery, the electrodes were zinc and copper wires wound upon -small pieces of wood. Dilute vinegar was used as the excitant, because -it could be found in every household. Formerly the battery had great -success. It is now little used. - - -Battery, Sal Ammoniac. -Batteries in which a solution of ammonium chloride is the excitant; they -are very extensively used on open circuit work. (See Battery, -Leclanché.) - -The crystals formed in these batteries have been analyzed and found to -consist of ammonium zinc chloride, 3 Zn Cl2, 8 N H3, 4 H20. - - -Battery, Salt, or Sea Salt. -Batteries in which a solution of sodium chloride or common salt is the -excitant, have been largely used, especially for telegraphic purposes. -The Swiss telegraphs use a carbon-zinc combination with salt and water -as the excitant. The batteries are sometimes mounted as plunge -batteries. They are exhausted by short circuiting after some hours, but -recuperate on standing. The zinc is not amalgamated. - - -70 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Sand. -A battery whose cells are charged with sand saturated with dilute acid. -It prevents spilling of acid. It is now practically obsolete. - - -Fig. 47. SECONDARY BATTERY. - - -Battery, Secondary. -A voltaic battery whose positive and negative electrodes are formed or -deposited by a current from a separate source of electricity by -electrolysis. On disconnection the battery is ready to yield a current, -in the reverse direction of that of the charging current. The usual type -has lead plates on one of which lead binoxide and on the other of which -spongy lead is formed. The lead binoxide seems to be the negative -element, and it also acts as the depolarizer. The spongy lead is the -positive electrode. The solution is dilute sulphuric acid of specific -gravity 1.17. The action consists first in the oxidation of the spongy -lead. The hydrogen set free by the reaction, and which by electrolytic -transfer goes to the other plate, reduces the lead binoxide to -protoxide. The sulphuric acid then attacks the oxides and converts the -oxides into sulphates. - -The charging process consists in sending a current in the reverse -direction through the battery. If there are several cells they are -arranged in series, so that each one receives the same intensity of -current. An electrolytic decomposition takes place, the lead sulphate on -one plate is reduced to metallic lead, and that on the other plate is -oxidized to lead binoxide. It is then ready for use. - - -71 STANDARD ELECTRICAL DICTIONARY. - - -The plates in a lead plate battery are of very large area per cell, and -are placed close together. Sometimes, as in Planté's battery, large flat -plates are laid together with a separating insulator between them, and -are then rolled into a spiral. Sometimes, the most usual arrangement, -the plates are in sets, the positive and negative ones alternating, and -each cell containing a number of plates. - -To secure a good quantity of active material, the plates are sometimes -perforated, and the perforations are filled with oxide of lead. This -gives a good depth of material for the charging current to act on, and -avoids the necessity for a tedious "forming," q. v. - -The electro-motive force of such a battery per cell is 2 volts. Its -resistance may only be one or two-hundredths of an ohm. An intense -current of many amperes can be supplied by it, but to avoid injuring the -cell a current far less than the maximum is taken from it. - -To charge it, a slightly greater electro-motive force, the excess being -termed spurious voltage, is required. - - -Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY. - - -72 STANDARD ELECTRICAL DICTIONARY. - -Battery, Secondary, Plante's. -Plante's secondary battery is one of the earlier forms of storage -battery, but has had much success. Two lead plates, large in area and -close together but not touching, are "formed," by exposure to an -electrolyzing current of electricity in one direction, while they are -immersed in dilute sulphuric acid. This converts the surface of one -plate into binoxide. The cell is then allowed to discharge itself almost -completely, when the charging current is again turned on. This process -is repeated over and over again, until the surfaces of the plates are -considerably attacked, one plate, however, being maintained in a state -of oxidation. After a few days of this operation a period of rest is -allowed between the reversals, which sets up a local action on the -oxidized plate, between the metallic lead of the plate, and its coating -of binoxide. This causes the lead to be attacked, under the influence of -the local couple, and sulphate of lead is formed, which, ultimately, by -the charging current is converted into peroxide. These operations -produce an exceedingly good battery. The process described is termed -forming. - -The plates separated by strips of insulating material are generally -wound into a double spiral. - - -Battery, Siemens' and Halske's. -A Daniell battery of peculiar shape. The copper, C, is at the bottom of -the glass jar, A. The inner jar, K, has the form of a bell, and supports -a mass of paper pulp, which is dampened with sulphuric acid. The zinc, -Z, rests on top of the mass of pulp. The battery is very durable, but of -high resistance. - - -Battery, Sir William Thomson's. -A form of Daniell battery, of the gravity type. The receptacles are -shallow wooden trays lined with lead. A thin plate of copper rests on -the bottom. The zinc plate is of gridiron shape, and rests on wooden -blocks which support it in a horizontal position above the copper. One -tray is placed on top of the other, the upper tray resting on the -corners of the zinc plate which rise above the level of the top of the -flat vessel. Thus connection is assured without wires or binding posts. -It is charged like a gravity battery. The density of the zinc sulphate -solution should be between 1.10 and 1.30. The circuit must be kept -closed to prevent deposition of metallic copper on the zinc. The entire -disposition of the battery is designed to reduce resistance. - - -Battery, Skrivanow. -A pocket battery of the De la Rue type, with a solution of 75 parts -caustic potash in 100 parts of water as the excitant. The silver -chloride is contained in a parchment paper receptacle. Its -electro-motive force is 1.45 to 1.5 volts. - - -Battery, Smee's. -A single fluid combination, with zinc positive plate, and a plate of -silver, coated with platinum black, for the negative plate. The finely -divided platinum affords a surface from which the hydrogen bubbles -instantly detach themselves, thus preventing polarization. The liquid is -a mixture of one part sulphuric acid to seven parts of water. For the -negative plate silver-plated copper, coated with platinum black, is -used. Electromotive force, .47 volt. - - -Fig. 49. SMEE'S BATTERY. - - -73 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 50. SPIRAL BATTERY, OR HARE'S DEFLAGRATOR. - - -Battery, Spiral. -A battery whose plates of thin zinc and copper are wound into a spiral -so as to be very close, but not touching. Dilute sulphuric acid is the -excitant. It is now practically obsolete. - -Synonyms--Calorimeter--Hare's Deflagrator. - - -Battery, Split. -A battery of a number of voltaic cells, connected in series, with their -central portion grounded or connected to earth. This gives the ends of -opposite potentials from the earth, and of difference therefrom equal to -the product of one-half of the number of cells employed, multiplied by -their individual voltage. - - -Battery Solutions, Chromic Acid. -A number of formulae have been proposed for these solutions. (See -Electropoion Fluid--Kookogey's Solution--Poggendorff's Solution-- -Trouvé's Solution--Delaurier's Solution--Chutaux's Solution--Dronier's -Salt--Tissandier's Solution.) - - -Battery, Trough. -A battery whose elements are contained in a trough, which is divided by -cross-partitions so as to represent cups. A favorite wood for the trough -is teak, which is divided by glass or slate partitions. Marine glue or -other form of cement is used to make the joints tight. For porous cup -divisions plates of porous porcelain or pottery are placed across, -alternating with the impervious slate partitions. - - -Battery, Trouvé's Blotting Paper. -A battery of the Daniell type in which the solutions are retained by -blotting paper. A considerable thickness of blotting paper lies between -the two plates. The upper half of the thickness of the blotting paper is -saturated with a solution of zinc sulphate, on which the zinc plate -rests. - -The lower half of the paper is saturated with copper sulphate solution, -and this rests upon the copper plate. - - -Fig. 51. TROUVÉ'S BLOTTING PAPER BATTERY. - - -74 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Tyer's. -A modification, as regards the positive element, of Smee's battery, q. -v. The bottom of the battery jar contains a quantity of mercury in which -pieces of zinc are thrown, and this constitutes the positive element. - -A ball of zinc at the end of an insulated copper wire affords the -connection with the zinc and mercury. Its great advantage is that the -smallest scraps of zinc can be used in it, by being dropped into the -mercury. The negative plate is platinized silver; the exciting liquid, -dilute sulphuric acid. - - -Fig. 52. TYER'S BATTERY. - - -75 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 53. SECTION OF UPWARD'S BATTERY. - - -Fig. 54. ELEVATION OF UPWARD'S BATTERY. - - -Battery, Upward's. -A primary voltaic cell, the invention of A. Renée Upward. Referring to -the cuts, the positive plate. Z, is of cast zinc; it is immersed in -water, in a porous cup, B. Outside of the porous cup and contained in -the battery jar are two carbon plates, C, C, connected together. The -rest of the space between the porous cup and battery jar is packed with -crushed carbon, and the top is cemented. Chlorine gas is led by a pipe, -D, into the outer cell. It diffuses through the fine carbon, dissolves -in the water, and so finds its way to the zinc, which it attacks, -directly combining therewith, and forming zinc chloride (Zn + 2 Cl = Zn -Cl 2). Such of the chlorine as is not absorbed finds its way by an outlet -tube, E, to the next cell. Arrangements are provided for generating -chlorine gas as required. The high specific gravity of the gas is -utilized in regulating its distribution through the cells. The -electro-motive force of the cell is 2.1 volts. A cell 11.5 by 5.5 inches -and 12.5 inches deep has a resistance of 0.2 ohm. - -An overflow pipe, F, with faucet, T, is supplied to withdraw the -solution of zinc chloride as it accumulates. - - -76 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Varley's. -A Daniell battery of the Siemens' and Halske's type (see Battery, -Siemens' and Halske's), in which zinc oxide is substituted for the paper -pulp of the other battery. It has been very little used. - - -Battery, Volta's. -The original acid battery. It has a negative electrode of copper, a -positive electrode of zinc; the excitant is sulphuric acid diluted with -sixteen times its volume of water. It rapidly polarizes, and is very -little used. - - -Battery, Voltaic or Galvanic. -An apparatus for converting chemical energy directly into electric -energy. This is as broad a definition as can well be given. The general -conception of a battery includes the action of electrolysis, a solution -in the battery acting upon one of two conducting electrodes immersed in -such fluid, which dissolves one of them only, or one more than the -other. The best way to obtain a fundamental idea of a battery is to -start with the simplest. Dilute sulphuric acid dissolves neither pure -zinc nor copper. But it has a far stronger affinity for the first named -metal. If now we immerse in dilute acid two plates, one of pure zinc, -and one of copper, no action will be discernible. But if the plates are -brought in contact with each other a stream of bubbles of hydrogen gas -will escape from the surface of the copper and the zinc will dissolve. -By applying proper tests and deductions it will be found that the copper -and zinc are being constantly charged with opposite electricities, and -that these are constantly recombining. This recombination produces what -is known as an electric current. - -To constitute a battery the zinc and copper plates must be connected -outside of the solution. This connection need not be immediate. Any -conductor which touches both plates will bring about the action, and the -current will pass through it. - -The easiest way to picture the action of a battery is to accept the -doctrine of contact action. In the battery the molecules of water are -pulled apart. The hydrogen molecules go to the copper, the oxygen -molecules go to the zinc, each one, leaving its contact with the other, -comes off charged with opposite electricity. This charges the plates, -and the continuous supply of charge and its continuous discharge -establishes the current. - -The accumulation of hydrogen acts to stop the action by polarization. -Its own affinity for oxygen acts against or in opposition to the -affinity of the zinc for the same element, and so cuts down the action. -A depolarizer of some kind is used in acid batteries for this reason. As -such depolarizer has only to act upon one plate, in most batteries it is -usual to surround such plate only, as far as it is possible, with the -depolarizer. The solution which dissolves the zinc is termed the -excitant or exciting solution. - -To this concrete notion of a voltaic battery the different modifications -described here may be referred. Zinc, it will be seen, forms the almost -universally used dissolved plate; carbon or copper forms the most usual -undissolved plate; sulphuric acid in one form or another is the most -usual excitant. - -The solution in a voltaic battery is electrolyzed (see Electrolysis). -Hence the solutions must be electrolytes. The sulphuric acid and other -ingredients play a secondary role as imparting to the battery fluids -this characteristic. - -It is not necessary to have electrodes of different substances, the same -metal maybe used for both if they are immersed in different solutions -which act differentially upon them, or which act with more energy on one -than on the other. Such are only of theoretical interest. - - -77 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Water. -A voltaic battery, whose exciting fluid is water. They are used for -charging quadrant electrometer needles and similar purposes. They -polarize very quickly and are of high resistance. Hence very small -plates in large number can be used without impairing their advantage. - -Rowland's water battery dispenses with cups and uses capillarity -instead. The zinc and platinum or copper plates of a couple are placed -very close together, while the couples are more distant. On dipping into -water each couple picks up and retains by capillarity a little water -between its plates, which forms the exciting fluid. Many hundred couples -can be mounted on a board, and the whole is charged by dipping into -water and at once removing therefrom. It then develops its full -potential difference. - - -Fig. 55. SECTION OF WOLLASTON BATTERY. - - -Fig. 56. PLATES OF WOLLASTON'S BATTERY. - - -78 STANDARD ELECTRICAL DICTIONARY. - - -Battery, Wollaston. -The original plunge battery is attributed to Wollaston. He also invented -the battery known by his name, having the disposition shown in the cut, -of zinc Z, surrounded by a thin sheet of copper C; o, o', o", are the -terminals and B, B, the battery jars. Dilute sulphuric acid is used for -exciting fluid. - - -B. A. U. -Abbreviation for British Association unit, referring generally to the B. -A. unit of resistance. - - -B. A. Unit of Resistance. -The original ohm used under that name previous to 1884. The Paris -committee of that year recommended as a practical unit what is known as -the legal ohm. (See Ohm, Legal.) - 1 Legal Ohm = 1.0112 B. A. Units of Resistance. - 1 B. A. Unit of Resistance = .9889 Legal Ohms. - 1 B. A. Unit of Resistance = .98651E9 C. G. S. units. - - -B. E. adj. -British Engineering, a qualification of a set of units, the B. E. units, -having for base the foot and pound. The term is but little used. - - -Beaumé Hydrometer. -A hydrometer graduated on the following principle: - -The zero point corresponds to the specific gravity of water for liquids -heavier than water. A solution of 15 parts of salt in 85 parts of water -corresponds in specific gravity to 15° B., and between that and zero -fifteen equal degrees are laid out. The degrees are carried down below -this point. - -The zero points for liquids lighter than water correspond to the -specific gravity of a solution of 10 parts of salt in 90 parts of water. -The specific gravity of water is taken as 10° B. This gives ten degrees -which are continued up the scale. - - -Becquerel's Laws of Thermoelectricity. -These are stated under the heads, Law of Intermediate Metals and Law of -Successive Temperatures, q. v. - - -Bed Piece. -In a dynamo or motor the frame carrying it, including often the -standards in which the armature shaft is journaled, and often the yoke -or even entire field magnet core. - - -Bell, Automatic Electric. -A bell which rings as long as the circuit is closed, having a circuit -breaker operated by its own motion. (See Bell, Electric.) - -Synonyms--Trembling Bell--Vibrating Bell. - - -Bell, Call. -A bell operated by electricity, designed to call attention, as to a -telephone or telegraphic receiver. (See Bell, Electric.) - - -79 STANDARD ELECTRICAL DICTIONARY. - - -Bell Call. -A calling device for attracting the attention of any one, consisting of -some type of electric bell. - - -Bell, Circular. -A gong-shaped bell, whose clapper and general mechanism is within its -cavity or behind it. - - -Bell, Differentially Wound. -An electric bell, whose magnet is wound differentially so as to prevent -sparking. - - -Fig 57. AUTOMATIC ELECTRIC BELL. - - -Bell, Electric. -A bell rung by electricity. Generally it is worked by a current exciting -an electro-magnet, attracting or releasing an armature which is attached -to the vibrating or pivoted tongue of the bell. It may be worked by a -distant switch or press-button, q. v., ringing once for each movement of -the distant switch, etc., or it may be of the vibrating bell type as -shown in the cut. When the current is turned on in this case it attracts -the armature. As this moves towards the poles of the magnet it breaks -the circuit by drawing the contact spring, q. v., away from the contact -point, q. v. This opens the circuit, to whose continuity the contact of -these two parts is essential. The hammer, however, by its momentum -strikes the bell and at once springs back. This again makes the contact -and the hammer is reattracted. This action continues as long as the -circuit is closed at any distant point to which it may be carried. The -ordinary vibrating bell is a typical automatic circuit breaker, q. v., -this type keeping up the ringing as long as the circuit is closed. Other -bells have no electric contact and simply ring once every time the -circuit is closed. Others worked by an alternating current ring once for -each change of direction of current. - - -80 STANDARD ELECTRICAL DICTIONARY. - - -Bell, Electro-mechanical. -A bell which has its striking train operated by a spring or descending -weight, and which train is thrown into action by the release of a detent -or equivalent action by the closing of an electric circuit. It rings for -any given time after being started. - - -Bell, Indicating. -A bell which by drop-shutter or other indicator connected in circuit -with it, indicates its number or other designation of its call. - - -Bell, Magneto. -An electric bell operated by the alternating current from a magneto -generator. It has a polarized armature and no circuit breaker. The -armature is attracted first in one direction and then in the other, as -the current alternates and reverses the polarity of the electro-magnet. - - -Bell, Relay. -A bell operated by a relay circuit. - - -Bias. -In polarized relay the adjustment of the tongue to lie normally against -one or the other contact. (See Relay, Polarized.) - - -81 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 58. RESISTANCE COILS SHOWING BIFILAR WINDING. - - -Bifilar Winding. -The method followed in winding resistance coils to prevent them from -creating fields of force. The wire is doubled, and the doubled wire -starting with the bend or bight is wound into a coil. The current going -in opposite senses in the two lays of the winding produces no field of -force. - - -Binary Compound. -A chemical compound whose molecule contains only two elements, such as -water (H2 0), lead oxide (Pb 0), and many others. - - -Binding. -In a dynamo or motor armature the wire wound around the coils to secure -them in place and prevent their disturbance by centrifugal action. - - -Fig. 59. DOUBLE BINDING POST. - - -Fig. 60. BINDING POST, ENGLISH PATTERN. - - -FIG. 61. WOOD SCREW BINDING POST. - - -Binding Posts or Screws. -Arrangements for receiving the loose end of a wire of an electric -circuit, and securing such end by a screw. Several constructions are -used, as shown here. Sometimes the wire is passed through a hole, and a -screw tapped in at right angles to the hole is screwed down upon the -wire. Sometimes the wire is clamped between two shoulders, one on the -screw, the other on the post. The screw is often a flat-headed thumb -screw or has a milled edge. Sometimes the screw has a slot and is turned -by a screw-driver. - -Several openings are often provided in the same post for different -wires. - - -Binnacle. -The case containing a mariner's compass on shipboard. It is enclosed -completely; it has a glass side or window through which the compass can -be seen, and is provided with one or two lamps arranged to light the -card, while showing as little light as possible outside. - - -82 STANDARD ELECTRICAL DICTIONARY. - - -Bioscopy, Electric. -The diagnosis of life and death by the action of the animal system when -subjected to an electric current or electrification. - - -Bismuth. -A metal, one of the elements, atomic weight, 210 ; equivalent, 70; -valency, 3; specific gravity, 9.9. It is a conductor of electricity. -Relative Resistance, compressed, (silver = 1) 87.23 -Specific Resistance, 131.2 microhms -Resistance of a wire - (a) 1 foot long, weighing 1 grain, 18.44 ohms - (b) 1 foot long, 1/1000 inch thick, 789.3 " - (c) 1 meter long, weighing 1 gram, 12.88 " - (d) 1 meter long, 1 millimeter thick, 1.670 " -Resistance of a 1-inch cube 51.65 microhms -Electro chemical equivalent, .7350 -(Hydrogen = .0105) -(See Thermo-electric Series.) - - -FIGS. 62, 63. INCANDESCENT WIRE FUSE. ABEL'S PATENT. - - -FIG 64. VON EBNER'S FRICTIONAL ELECTRIC MACHINE FOR -EXPLODING ELECTRIC FUSES OR DETONATORS. - - -Bi-telephone. -A pair of telephones arranged with a curved connecting arm or spring, so -that they can be simultaneously applied to both ears. They are -self-retaining, staying in position without the use of the hands. - - -83 STANDARD ELECTRICAL DICTIONARY. - - -Blasting, Electric. -The ignition of blasting charges of powder or high explosives by the -electric spark, or by the ignition to incandescence (red or white heat) -of a thin wire immersed in or surrounded by powder. Special influence or -frictional electric machines or induction coils are used to produce -sparks, if that method of ignition is employed. For the incandescent -wire a hand magneto is very generally employed. (See Fuse, Electric.) - -The cuts, Figs. 62 and 63, show one form of incandescent wire fuse. The -large wires are secured to the capsule, so that no strand can come upon -the small wire within the cavity. - -The cut, Fig. 64, shows a frictional electric machine for igniting spark -fuses. - - -Bleaching, Electric. -Bleaching by agents produced or made available by the direct action of -electricity. Thus if a current under proper conditions is sent through a -solution of common salt (sodium chloride), the electrodes being close -together, the salt is decomposed, chlorine going to one pole and sodium -hydrate to the other. The two substances react upon each other and -combine, forming sodium hypochlorite, which bleaches the tissue immersed -in its solution. - - -Block System. -A system of signalling on railroads. The essence of the system consists -in having signal posts or stations all along the road at distances -depending on the traffic. The space between each two signal posts is -termed a block. From the signal posts the trains in day time are -signalled by wooden arms termed semaphores, and at night by lanterns. -The arms may be moved by hand or by automatic mechanism depending in -part on electricity for carrying out its functions. Thus in the -Westinghouse system the semaphores are moved by pneumatic cylinders and -pistons, whose air valves are opened and shut by the action of solenoid -magnets, q. v. The current of these magnets is short circuited by -passing trains, so as to let the valves close as the train passes the -signal post. The block system causes the semaphore to be set at "danger" -or "caution," as the train enters the next block. Then the following -train is not allowed to enter the block until the safety signal is -shown. The Westinghouse system provides for two semaphores on a post, -one indicating "danger" as long as the train is on the next block; the -other indicating "caution" as long as the train is on the next two -blocks. The rails form part of the circuit, their joints being bridged -by copper wire throughout the block, and being insulated where the -blocks meet. - - -Block Wire. -In the block system a wire connecting adjacent block-signal towers or -semaphore poles. - - -Blow-pipe. -A name sometimes given to an electric experiment illustrating the -repulsion of electrified air particles from a point held at high -relative potential. A metallic point, placed on the prime conductor of -an electric friction or influence machine, becomes highly electrified, -and the air becoming excited is repelled and acts upon the candle flame. -If the candle is placed on the conductor and a point held towards it the -repulsion is still away from the point. - - -84 STANDARD ELECTRICAL DICTIONARY. - - -Blow-pipe, Electric Arc. -A name sometimes given to devices for using the voltaic arc to produce -local heating effects. The directive action of the magnet may be used to -force out the arc like a blow-pipe flame, or a blast of air may be -directly applied for the same purpose. - - -Blue-stone. -A trade name for crystallized copper sulphate, used in Daniell's and -gravity batteries. - - -Boat, Electric. -A boat propelled by electricity. The electricity drives a motor which -actuates a screw propeller. The current is generally supplied by a -storage battery. When used on rivers charging stations are established -at proper places. When the boat is used as a tender or launch for a -steam ship, such as a war-vessel, the battery is charged by a plant on -board the ship. From their noiselessness electric boats are peculiarly -available for nocturnal torpedo operations, and the universal equipment -of modern war-ships with electric lightning and power plants makes their -use possible at all points. This type is often termed an electric -launch, and most or all electric boats fall under this category. - - -Bobbins. -A spool of wood or other material wound with insulated wire. In a -tangent galvanometer the bobbin becomes a ring, with a channel to -receive the winding. As the ring is not infinitely large compared to the -needle the tangent law is not absolutely fulfilled. It is most -accurately fulfilled (S. P. Thomson) when the depth of the groove or -channel in the radial direction bears to the breadth in the axial -direction the ratio of square root of 3 to the square root of 2 or -approximately 11 : 9 - - -Body Protector. -A metallic short circuit connected with the wrists and lower legs of the -human body, so that if by accident an active circuit is grounded by the -hands and body of the workman wearing it, most of the current will pass -through the wire conductors, thus avoiding the vital organs of the body. - - -Boiler Feed, Electric. -An apparatus by which an electric current acting on an electro-magnet, -or other equivalent device, opens the water supply when the water level -in a boiler sinks too low, and cuts off the water supply as the water -level rises. - - -Boiling. -In secondary batteries the escape of hydrogen and oxygen gas when the -battery is charged. The bubbling of the escaping gases produces the -effect of boiling. - - -85 STANDARD ELECTRICAL DICTIONARY. - - -Boll. -An absolute, or c. g. s., unit of momentum; a gram moving at the rate of -one centimeter per second; a gram-kine (see Kine); a unit proposed by -the British Association. - - -Bolometer. -An apparatus for detecting small amounts of radiant energy (radiant -heat, so called). A coil suspended by a fine wire or filament so as to -be free to rotate under the effect of force is made up of two parallel -and equal wires, insulated from each other, but connected so that -parallel currents sent through them go in opposite direction through -each. This coil is hung in a strong electro-magnetic field produced by a -large coil surrounding it. When a current passes through the suspended -coil no effect will follow, because the oppositely wound portions -counteract each other exactly. In the circuit with one half of the -suspended coil is an exceedingly thin strip of platinum wire. The other -half of the coil has no strips. Both halves unite after leaving the -coil. If now the strip of platinum is heated its conductivity is -affected and its half of the coil receives less current than the other -half. This disturbs the balance and the coil swings through a small arc. -This apparatus may be made very sensitive, so that an increase of -temperature of 1/1400º F., 9/70000°C. (1/14000º F.) will be perceptible. -Another construction takes the form of a Wheatstone Bridge, q. v., in -whose arms are introduced resistances consisting of bands of iron, .5 -Millimeter wide (.02 inches), .004 millimeter (.00016 inch) thick, and -folded on themselves 14 times so as to make a rectangular grating, 17 x -12 millimeters (.68 x .48 inch). The least difference of heat applied to -the grating affects the galvanometer. - -Synonym-Thermic Balance. - - -Boreal Pole. -The south pointing pole of the magnet. (See Austral Pole.) - - -Bot. -A colloquial expression for the English Board of Trade unit of -Electrical Supply. It is formed of the initials of the words "Board of -Trade." (See Unit, Board of Trade.) - - -Box Bridge. -A constriction of Wheatstone's Bridge in which the necessary resistance -coils are contained in a single box with plugs for throwing the coils in -and out of circuit, and connections to bring the coils into the -different arms of the system. The cut shows a box bridge. Connections -for the galvanometer, battery wires, and terminals of the unknown -resistance are provided, by which its resistances and the connections -are brought into the exact relations indicated in the conventional -diagram of Wheatstone's bridge. (See Wheatstone's Bridge.) - -Referring to the cut, the battery wire, say from the zinc plate, -connects at A1, thereby reaching A, its true connecting point. To B1 one -end of the galvanometer circuit or lead is attached, thereby reaching B, -its true connecting point. To C are connected the other end from the -galvanometer and one end of the unknown resistance. The other end of the -unknown resistance, and the other end of the battery wire, in this case -from the carbon plate, connect to D. At G is an infinity plug, as it is -called. When out it breaks the circuit. - -In use after the connections are made the key is depressed and the -galvanometer observed. The resistance is changed until no action of the -galvanometer is produced by closing the circuit when the ratio of the -resistances of the arms gives the proportion for calculating the unknown -resistances. - -Synonym--Commercial Wheatstone Bridge, or commercial form of same. - - -Fig. 65. TOP OF BOX BRIDGE. - - -86 STANDARD ELECTRICAL DICTIONARY. - - -Boxing the Compass. -Naming the thirty-two points of the compass in order, and in sequence to -any point called out at random. There are many exercises in the relative -sailing points and bearings that come under the same head. Thus the -direction of two given points being given by names of the compass -points, it may be required to state the number of points intervening. - - -Brake, Electro-magnetic. -A brake to stop a wheel from rotating. It comprises a shoe, or sometimes -a ring, which by electro-magnetic attraction is drawn against the -rotating wheel, thus preventing it from turning, or tending to bring it -to rest. (See Electro-magnet, Annular.) - - -Fig. 66. ELECTRIC BRAKE. - - -87 STANDARD ELECTRICAL DICTIONARY. - - -Branch. -A conductor branching from a main line. Sometimes the term is restricted -to a principal conductor, from which current is distributed. - - -Branch Block. -In electric wiring of buildings, a block of porcelain or other material -with grooves, holes and screws for the connection of branch wires to a -main wire. Its functions are not only to afford a basis for connecting -the wires, but also to contain safety fuses. As when a branch wire is -taken off, fuses have to be put in its line, the branch block carries -these also. One end of each fuse connects with a main wire, the other -end connects with one of the wires of the branch leader or wire. - -Porcelain is a favorite material for them, as the fusing or "blowing -out" of the safety fuses cannot set it on fire. - - -Branch Conductor. -A parallel or shunt conductor. - - -Brazing, Electric. -Brazing in which the spelter is melted by means of electricity; either -current incandescence or the voltaic arc may be used. It is identical in -general with electric welding. (See Welding, Electric.) - - -Branding, Electric. -A system of branding in which the heat of electrically ignited or -incandescent conductors is used to produce or burn in the marks upon the -surface. For the alternating current a small transformer is connected to -or forms part of the tool. - - -88 STANDARD ELECTRICAL DICTIONARY. - - -Brassing. -The deposition of a coating of brass by electrolysis. The plating bath -contains both copper and zinc. As anode a plate of brass is used. The -operation must be constantly watched. The deposition of both metals goes -on simultaneously, so that a virtual alloy is deposited. By changing -the depth of immersion of the anode the color of the deposit is varied. - -As a formula for a brassing bath the following are typical. They are -expressed in parts by weight. - -(a) For iron and steel. -I. - Sodium Bisulphate, 200 - Potassium Cyanide, 70 per cent., 500 - Sodium Carbonate, 1,000 - Water, 8,000 -II. - Copper Acetate, 125 - Zinc Chloride, 100 - Water, 2,000 -Add the second solution to the first. - -(b) For zinc. -I. - Sodium Bisulphate, 700 - Potassium Cyanide, 70 per cent., 1,000 - Water, 20,000 -II. - Copper Acetate, 350 - Zinc Chloride, 350 - Aqua Ammoniae, 400 - Water, 5,000 -Add the second solution to the first. - -Use a brass anode; add more zinc to produce a greenish color; more -copper for a red color. A weak current gives a red color; a strong -current lightens the color. The battery power can be altered, a larger -or smaller anode can be used, or a copper or zinc anode can be used to -change the color of the deposit. The bath may vary from 1.036 to 1.100 -sp. gr., without harm. - - -Break. -A point where an electric conductor is cut, broken, or opened by a -switch or other device, or simply by discontinuity of the wires. - - -Break-down Switch. -A switch used in the three-wire system to provide for the discontinuance -of the running of one of the dynamos. - -By connecting the positive and negative bus wires to one terminal of the -active dynamo, and the neutral bus wire to the other terminal, one -dynamo will supply the current and the system operates like a two-wire -system, but can only be used for half its normal capacity. - - -Breaking Weight. -The weight which, applied in tension, will break a prism or cylinder, as -an electric current conductor. - - -89 STANDARD ELECTRICAL DICTIONARY. - - -Breath Figures, Electric. -If a conductor is electrified and placed upon a piece of glass, it will -electrify the glass in contact with it by conduction or discharge. On -removing the conductor the glass remains electrified. The localized -electrification is shown by breathing gently on the glass, when a -species of image of the conductor is produced by the condensed moisture. -A coin is often used for conductor. - - -Breeze, Electric. -A term in medical electricity, used to designate the silent or brush -discharge of high tension electricity. As an instance of its employment, -the electric head bath (see Bath, Electric Head,) may be cited. The -patient forming one electrode, being insulated and connected to one of -the conductors, the other conductor, on being brought near his person, -discharges into his body. - - -Bridge. -(a) A special bar of copper connecting the dynamos to the bus wire, q. v., -in electric lighting or power stations. - -(b) Wheatstone's bridge, q. v., and its many modifications, all of which -may be consulted throughout these pages. - - -British Association Bridge. -The type of Wheatstone bridge used by the committee of the association -in determining the B. A. ohm; the meter bridge, q. v. - - -Broadside Method. -A method of determining the magnetic moment of a magnet. The magnet, n, -s, under examination is fixed so that it is at right angles to the -magnetic meridian, M, R, which passes through its own center and that of -a compass needle. From the deflection of the latter the moment is -calculated. - - -FIG 67. BROADSIDE METHOD. - - -Bronzing. -In electro-plating the deposition of a mixture or virtual alloy of -copper and tin. In general manipulation it resembles the operation of -depositing gold and silver alloy, or of brassing. - -For bronzing the following bath is recommended: - -Prepare each by itself (a) a solution of copper phosphate and (b) a -solution of stannous chloride in a solution of sodium pyrophosphate. For -a, dissolve recently precipitated copper phosphate in concentrated -solution of sodium pyrophosphate. For b, add to a saturated solution of -sodium pyrophosphate solution of stannous chloride as long as the -precipitate which is formed dissolves. Of these two solutions add to a -solution of sodium pyrophosphate which contains about 1.75 oz. of the -salt to the quart, until the precipitate appears quickly and of the -desired color. For anodes use cast bronze plates. Sodium phosphate must -be added from time to time; if the deposit is too light add copper -solution, if too dark add tin solution. (W. T. Brannt.) - - -90 STANDARD ELECTRICAL DICTIONARY. - - -Brush. -In electric current generators and motors, the pieces of copper or other -material that bear against the cylindrical surface of the commutator are -thus termed. Many different constructions have been employed. Some have -employed little wheels or discs bearing against and rotating on the -surface of the commutator. A bundle of copper strips is often employed, -placed flatwise. Sometimes the same are used, but are placed edgewise. -Wire in bundles, soldered together at their distant ends have been -employed. Carbon brushes, which are simply rods or slabs of carbon, are -used with much success. - -Synonym--Collecting Brush. - - -Brush, Carbon. -A brush for a dynamo or motor, which consists of a plate or rod of -carbon, held in a brush holder and pressed against the commutator -surface. - - -Brushes, Adjustment of. -In electric current generators and motors, the brushes which bear upon -the commutator when the machine is in action need occasional adjustment. -This is effected by shifting them until sparking between them and the -commutator is nearly or quite suppressed. - - -Fig. 68. BRUSH HOLDER. - - -Brushes, Lead of. -In a dynamo electric generator, the lead or displacement in advance of -or beyond the position at right angles to the line connecting the poles -of the field magnet, which is given the brushes. In a motor the brushes -are set back of the right angle position, or are given a negative lead. -(See Lag.) - - -91 STANDARD ELECTRICAL DICTIONARY. - - -Brush Holders. -The adjustable (generally) clutch or clamps for holding the commutator -brushes of a dynamo, which keep them in contact with the commutator, and -admit of adjustment by shifting backward and forward of the brushes to -compensate for wear. They are connected to and form part of the rocker, -q. v. By rotating the latter the brush-holders and brushes are carried -in one direction or other around the commutator, so as to vary the lead -as required. - - -Brush, Pilot. -A third brush, used for application to different parts of a revolving -armature commutator to determine the distribution of potential -difference between its different members. (See Curve of Distribution of -Potential in Armature.) One terminal of a volt-meter is connected to one -of the regular brushes, A, of a dynamo; the other to a third brush, p, -which is pressed against different portions of the commutator of the -dynamo. The readings of the volt-meter are plotted in a curve of -distribution of potential. - - -Fig. 69. PILOT BRUSH. - - -Brush, Rotating. -Brushes for taking off the current from dynamo commutators, or giving -current connection to motors, whose ends are in the form of rollers -which rotate like little wheels, and press against the commutator -surface. - - -Brush, Third. -A third brush is sometimes provided in a dynamo for regulating purposes. -Applied to a series machine it adjoins one of the regular brushes and -delivers its current to a resistance, to whose further end the regular -circuit is connected. By a sliding connection the resistance is divided -between the third brush circuit and the regular circuit, and by varying -the position of this contact regulation is obtained. - -It is to be distinguished from the pilot brush used for determining the -characteristic of the commutator, although based on the same general -principles. - - -Fig. 70. THIRD BRUSH REGULATION. - - -92 STANDARD ELECTRICAL DICTIONARY. - - -Brush, Wire Gauze. -A collecting or commutator brush for a dynamo or motor, which brush is -made of wire gauze rolled up and compressed into shape. - - -Buckling. -The bending up and distortion of secondary battery plates. It is largely -due to over-exhausting the batteries. Where the E. M. F. is never -allowed to fall below 1.90 volt it is far less liable to occur. - - -Bug. -Any fault or trouble in the connections or working of electric -apparatus. - - -Bug Trap. -A connection or arrangement for overcoming a "bug." It is said that the -terms "bug" and "bug trap" originated in quadruplex telegraphy. - - -Bunsen Disc. -In photometry, the Bunsen Disc is a piece of paper upon whose centre a -spot is saturated with melted paraffin, or a ring of paraffined surface -surrounds an untouched central spot. If placed in such a position that -it receives an equal illumination on each side, the spot almost -disappears. It is used on the bar photometer. (See Photometer, Bar.) - -Synonym--Grease Spot. - - -93 STANDARD ELECTRICAL DICTIONARY. - - -Buoy, Electric. -A buoy for use to indicate channels or dangers in harbors and elsewhere, -which carries an electric light, whose current is supplied by cable from -shore. It has been proposed to use glass tubes exhausted of air and -containing mercury, which, as moved by the waves, would produce a -luminous effect. A fifty-candle power incandescent lamp is an approved -source of light. - - -Burner, Electric Gas. -A gas burner arranged for the flame to be lighted by electricity. It -takes a great variety of forms. In some cases a pair of terminals are -arranged near the flame or a single terminal is placed near the metal -tip, the latter forming one of the terminals. The spark is generally -produced by an induction coil, or a spark coil. The gas may first be -turned on and the spark then passed. Sometimes the turning of the gas -cock of an individual burner makes and breaks a contact as it turns, and -thereby produces simultaneously with the turning on of the gas a spark -which lights it. - -Another form is wholly automatic. A pair of electro-magnets are attached -below the base of the burner, one of which, when excited, turns on the -gas, and the other one when it is excited turns it off. At the same time -a spark is produced with the turning on of the gas so that it is -lighted. Thus, by use of a automatic burner, a distant gas burner can be -lighted by turning an electric switch. An out-door lamp may be lighted -from within a house. - -The increasing use of electric incandescent lamps, lighted by the -turning of a switch, tends to displace electric gas burners. The latter -have been classified into a number of types depending on their -construction. - -Burners are sometimes connected in series with leads from an induction -coil. Then the gas is turned on all at once, and a succession of sparks -passed until the gas is all lighted. The ignition is practically -instantaneous. - - -Button, Push. -A species of switch which is actuated by the pressure of a button. In -its normal position the button is pressed outwards by a spring, and the -circuit is open. When pressed inwards, it closes the circuit. When -released it springs backward and opens the circuit again. - -They are principally used for ringing bells. If the latter are of the -automatic type, they ring as long as the button is pressed. - -For door-bells and room-bells, the button often occupies the center of a -rosette of wood or bronze or other ornamental piece. Sometimes, as shown -in the cut, they are constructed for use on floors to be pressed by the -foot. The general principle of their construction is shown, although the -method of making the contact varies. - -Synonym--Press Button. - - -Fig. 71. FLOOR PUSH BUTTON. - - -94 STANDARD ELECTRICAL DICTIONARY. - - -Burning. -(a) In a dynamo, the production of shifting and temporary arcs between -the commutator and brushes, which arcs produce heat enough to injure the -parts in question. - -(b) In electro-plating, a defect due to too strong a current in -proportion to the strength of solution and area of electrodes. This -gives a black or badly-colored deposit. - - -Bus Rod. -A copper conductor used in electric lighting or power stations, to -receive the current from all the dynamos. The distributing leads are -connected to the bus wires. - -In the three-wire system there are three; in the two-wire system there -are two bus wires. - -The name is undoubtedly derived from "omnibus." - -The bus wires may be divided into positive, negative, and, in the -three-wire system, neutral bus wires. - -Synonyms--Omnibus Rod, Wire, or Bar--Bus Bar, or Wire. - - -Buzzer. -An electric alarm or call produced by a rapid vibration of electric make -and break mechanism, which is often magnified by enclosure in a -resonating chamber, resembling a bell, but which is not struck or -touched by the vibrating parts. Sometimes a square wooden box is used as -resonator. - - -Fig. 72. BUZZER. - - -95 STANDARD ELECTRICAL DICTIONARY. - - -B. W. G. -Abbreviation for Birmingham Wire Gauge. (See Wire Gauge, Birmingham.) - - -C. -(a) Abbreviation for Centigrade, as 100 C., meaning 100 Centigrade. (See -Centigrade Scale.) - -(b) A symbol of current or of current strength. Thus in the expression -of Ohm's law C = E/R. C indicates current strength or intensity, not in -any fixed unit, but only in a unit of the same order in which E and R -are expressed; E Indicating electro-motive force and R resistance. - - -Cable. -(a) Abbreviation for Cablegram, q. v. - -(b) v. It is also used as a verb, meaning to transmit a message by -submarine cable. - -(c). An insulated electric conductor, of large diameter. It often is -protected by armor or metallic sheathing and may be designed for use as -an aerial, submarine, subterranean or conduit cable. A cable often -contains a large number of separately insulated conductors, so as to -supply a large number of circuits. - - -Cable, Aerial. -A cable usually containing a large number of separately insulated wires, -and itself insulated. It is suspended in the air. As its weight is -sometimes so great that it could not well sustain it, a suspending wire -is in such cases carried along with it, to which it is suspended by -cable hangers, q. v. - - -Cable Box. -A box for receiving underground cable ends and connecting the separate -wires of the cable to air-line wires. It is often mounted on a pole, -which forms the starting point of the air-line portion of the system. - - -Cable, Bunched. -A cable containing a number of separate and individual conductors. In -some forms it consists virtually of two or more small cables laid -tangent to each other and there secured. Thus each in section represents -two or more tangent circles with the interstice solidly filled with the -metal sheathing. - - -Cable, Capacity of. -The electrostatic capacity of a cable. A cable represents a Leyden jar -or static condenser. The outer sheathing or armor, or even the more or -less moist coating, if it is unarmored, represents one coating. The wire -conductors represent the other coating, and the insulator is the -dielectric. - -The capacity of a cable interferes with its efficiency as a conductor of -broken or interrupted currents, such as are used in telegraphy or -telephoning. As each impulse or momentary current is sent into the line, -it has to charge the cable to at least a certain extent before the -effects of the current are perceptible at the other end. Then the cable -has to discharge itself. All this creates a drag or retardation. - -The capacity of a cable is used to determine the locality of breaks in -the continuity of the conductors. The capacity per unit of length being -accurately known, it is obvious that, if the conductor breaks without -disturbance of the insulator, the distance of the break from the end can -be ascertained by determining the capacity of the cable from one end. -This capacity will be in proportion to the capacity of a mile, a knot or -any fixed unit, as the distance to the break is to the length used as -standard. - - -96 STANDARD ELECTRICAL DICTIONARY. - - -Cable Core. -The conductors of a cable. They are generally copper wire. In a -telephone cable they may be very numerous and insulated from each other. -In ocean cables they may be a group of bare wires twisted or laid -together. Sometimes the conductors are arranged for metallic circuits, -each pair being distinguished by special colored windings. - - -Cable, Duplex. -A cable containing two wires, each with separate insulation, so as to be -virtually two cables, laid and secured parallel and side by side. - - -Cable, Flat. -A cable, flat in shape, so as to lie closely against a wall or ceiling. - - -Cablegram. -A message which has been transmitted or is to be transmitted by a -submarine cable. It is sometimes called a cable. - - -Cable Grip. -A grip for holding the end of a cable, when the cable is to be drawn -into a conduit in a subway. It is an attachment to provide the cable -with an eye or loop. Its end is a split socket and embraces the end of -the cable, and is secured thereto by bolts driven through the cable end. -In drawing a cable into a conduit a capstan and rope are often used, and -the rope is secured to the cable end by the grip. - - -Fig. 73. CABLE HANGER, CABLE, AND SUSPENDING WIRE. - - -Fig. 74. CABLE HANGER, OPEN. - - -Cable Hanger. -When a heavy electric cable is suspended from poles it often would be -unsafe to trust to its longitudinal strength to support or sustain its -own weight unless the poles were very near together. In such case an -auxiliary or sustaining wire is run along with it, and by clips or -hangers the cable is connected thereto at as frequent intervals as seem -desirable. The contrivance may take the form of a strip of metal -surrounding the cable and carrying a hook or eye through which the -supporting wire passes. - -Synonym--Cable Clip. - - -97 STANDARD ELECTRICAL DICTIONARY - - -Cable Hanger Tongs. -Tongs for attaching cable hangers, q.v. They have long handles so as to -be worked from the ground at the middle of a span. - - -Cable, Suspending Wire of. -A wire by which an aerial cable is in part or entirely suspended. The -cable, being incapable of sustaining its own weight, is secured by clips -or hangers to a wire, strong from pole to pole immediately above it. -(See Cable Hanger.) - - -Cable Tank. -A tank in which a submarine cable is coiled away on board a cable-laying -ship, or in the factory on shore for the purpose of testing or -watching its insulation. Sometimes, in order to test it under pressures -approximating to those it will be subjected to in practice, the tank is -closed and the portion of cable within it is subjected to hydraulic -pressure. This represents the pressure it will be exposed to in deep -water. - - -Calamine. -A mineral; zinc silicate; formula Zn2 Si 03, crystalline system, -Orthorhombic; specific gravity, 3.16-3.9. - -The crystals often show strong pyroelectric properties. - - -Calibration. -The determination by experiment or calculation of the value of the -readings of an instrument, such as a galvanometer or eudiometer. Thus if -a tangent galvanometer has its circle graduated in degrees, a table of -the value of tangents corresponding to every reading occurring in -practice would represent a calibration by calculation. A determination -of the current required to produce each deflection would be a -calibration in the more usual sense. Calibration is generally absolute, -as referring to some fixed unit, but it may be relative, as between two -things both of unknown absolute value. - - -Calibration, Absolute. -The determination of the absolute value of currents producing given -deflections in a galvanometer, or in other instruments the determination -of corresponding values, as the instrument may be a magnetometer, -quadrant electrometer, or other apparatus. - - -Calibration, Invariable. -Calibration applicable to specially constructed galvanometers, which is -unaffected by the proximity of masses of iron or field magnets. Such -galvanometers must have a constant controlling field. Such is given by a -powerful permanent magnet, whose field is practically unaffected by the -causes named. Or else, in place of a controlling field, a spring maybe -used to which the needle is attached, and which tends to hold it in one -position. - - -98 STANDARD ELECTRICAL DICTIONARY. - - -Calibration, Relative. -The determination of the law connecting the various indications of an -instrument, such as the deflections of the needle of a galvanometer, -with the relative causes; in the case of a galvanometer, the strength of -the currents or the electro-motive forces producing them directly or -indirectly. - - -Call Bell. -A bell rung by pressing a button or otherwise to call the attention of a -person in a distant place. They can be classified into a great variety -of types according to their uses or construction. - - -Call Button. -A push button used for ringing a call bell, sounding a buzzer, working -an annunciator and for similar purposes. (See Push Button.) - -Synonym--Push Button. - - -Calling Drop. -In a telephone exchange or telegraph office a drop shutter annunciator, -which falls to call the attention of the operator, notifying him that -the line connected to such drop is to be connected to some other -circuit. - - -Calorie or Calory. -A practical unit of heat. There are two calories, respectively called -the great and the small calorie, or the kilogram and the gram calorie. -The first is the quantity of heat required to raise the temperature of -one kilogram of water one degree centigrade. The second is the quantity -of heat required to raise the temperature of one gram of water one -degree centigrade. - - -Calorimeter. -An apparatus for measuring the quantity of heat evolved or produced by -or under different conditions. Dulong's water calorimeter consists of a -water jacket, and by the increase of temperature of the water and -enclosing vessels the amount of heat produced by anything in the inner -vessels is determined. The amount of ice a heated body will melt is -sometimes made the basis of a calorimeter. The expansion of a fluid, as -water, may be used. In the calorimeter shown in the cut the heat -produced in a conductor by the passage of an electric current is caused -to heat water whose temperature is shown by a thermometer immersed -therein. The increase of temperature and the weight of the water give -the basis for a determination of the heat produced by the current. -Knowing the resistance of the conductor immersed, the watts can be -calculated. This gives the bases for the determination of the -heat-equivalent of electric energy. This is but an imperfect -calorimeter, as it constantly would lose heat by the surrounding -atmosphere, and would cease to operate as a calorimeter when the water -was as hot as the wire normally would be, for then it would not absorb -all the heat. - - -Fig. 75. CALORIMETER. - - -99 STANDARD ELECTRICAL DICTIONARY. - - -Candle. -The generally accepted unit of illuminating power; there are -three kinds in use as standards. (See Candle, Decimal--Candle, German -Standard--Candle, Standard.) - - -Candle, Concentric. -An electric candle of the Jablochkoff type, having a small solid carbon -inside of an outside tubular carbon, the space between being filled with -refractory material corresponding to the colombin, q. v., of the -ordinary type. The arc springs across from one carbon to the other. - - -Candle, Debrun. -An arc lamp with approximately parallel carbons. A transverse priming -connects their bases, and the arc starting there at once flies out to -the end. - - -Candle, Decimal. -A standard of illuminating power, proposed to the Congress of -Electricians of 1889 by Picou. It is one-twentieth of a Viole, or almost -exactly one standard candle. (See Viole's Standard of Illuminating -Power.) - -Candle, Electric. -An arc lamp regulated by simple gravity, or without any feed of the -carbons or special feeding apparatus, generally for the production of an -arc light of low intensity. This definition may be considered too -elastic, and the word may be restricted to parallel carbon lamps in -which the arc springs across from carbon to carbon. For the latter class -an alternating current is used to keep the carbons of equal length. They -are but little used now. Various kinds have been invented, some of which -are given here. - - -Candle, German Standard. -A standard of illuminating power used in Germany. It is a paraffin -candle, 6 to the pound, 20 millimeters diameter; flame, 56 millimeters -high; rate of consumption, 7.7 grams per hour. Its value is about two -per cent. lower than the English standard candle. - - -100 STANDARD ELECTRICAL DICTIONARY. - - -Candle Holder. -A clamp for holding electric candles of the Jablochkoff type. The ones -shown in the cut designed for Jablochkoff candles comprise a pair of -metallic clamps, each member insulated from the other, and connected as -terminals of the circuit. When the candle is placed in position the -metal pieces press against the carbons of the candle and thus convey the -current. Below each member of the clamps is a binding screw for the line -wire terminals. - - -Fig. 76. JABLOCHKOFF CANDLE HOLDERS. - - -Fig. 77. JABLOCHKOFF CANDLE. - - -Candle, Jablochkoff. -An arc lamp without regulating mechanism, producing an arc between the -ends of parallel carbons. It consists of two parallel rods of carbon, -between which is an insulating layer of non-combustible material called -the colombin. Kaolin was originally employed for this part; later, as -the fusion of this material was found to short- circuit the arc, a -mixture of two parts of calcium sulphate and one of barium sulphate was -used. The carbons are 4 millimeters (.16 inch) thick, and the colombin -is 3 millimeters (.12 inch) wide and two-thirds as thick. A little slip -of carbon is placed across the top, touching both carbons to start the -arc. Once started the candle burns to the end, and cannot be restarted -after ignition, except by placing a short conductor across the ends, as -at first. The Jablochkoff candle may now be considered as virtually -extinct in this country. In France at one time a great number were in -use. - -To keep the carbons of equal length an alternating current must always -be used with them. Special alternating combinations were employed in -some cases where a direct current had to be drawn upon. - - -Candle, Jamin. -An arc lamp with approximately parallel carbons, one of which oscillates -and is controlled by an electro-magnet and armature. A coil of wire is -carried around the carbons to keep the arc steady and in place. The -frame and wire coils have been found unsatisfactory, as causing a -shadow. - - -Candle Power. -The amount of light given by the standard candle. The legal English and -standard American candle is a sperm candle burning two grains a minute. -It should have burned some ten minutes before use, and the wick should -be bent over and have a red tip. Otherwise its readings or indications -are useless. A sixteen candle power lamp means a lamp giving the light -of sixteen candles. The candle power is a universal unit of illuminating -power. - - -101 STANDARD ELECTRICAL DICTIONARY. - - -Candle Power, Rated. -The candle power of arc lamps is always stated in excess of the truth, -and this may be termed as above. A 2000 candle power lamp really gives -about 800 candles illumination. - -Synonym--Nominal Candle Power. - - -Candle Power, Spherical. -The average candle power of a source of light in all directions. An arc -lamp and an incandescent lamp vary greatly in the intensity of light -emitted by them in different directions. The average of a number of -determinations at various angles, the lamp being moved about into -different positions, is taken for the spherical candle power. - - -Candle, Standard. -A standard of illuminating power. Unless otherwise expressed the English -standard sperm candle is indicated by this term. (See Candle Power.) - - -Candle, Wilde. -An arc lamp with approximately parallel carbons. One of the carbons can -rotate through a small arc being pivoted at its base. This oscillation -is regulated by an electro-magnet at its base, and the carbons touch -when no current is passing. They separate a little when the current -passes, establishing an arc. The regulation is comparable to that of a -regular arc lamp. - - -Fig. 78. WILDE CANDLE. - - -Caoutchouc. -India rubber; a substance existing in an emulsion or solution in the -juice of certain trees and vines of the tropics, whence it is obtained -by coagulation and drying. The name "rubber" is due to the fact that one -of its earliest uses was for erasing pencil marks by rubbing. It has a -very high value as an insulator. The unworked crude rubber is called -virgin gum; after working over by kneading, it is termed masticated or -pure gum rubber; after mixture with sulphur and heating, it is termed -vulcanized rubber. If enough sulphur is added it becomes hard, and if -black, is termed ebonite; if vermilion or other pigment is also added to -produce a reddish color, it is termed vulcanite. The masticated gum -dissolves more or less completely in naphtha (sp. gr., .850) benzole, -turpentine, chloroform, ether and other similar liquids.. The resistance -per centimeter cube of "Hooper's" vulcanized India rubber, such as is -used in submarine cables is 1.5E16 ohms. The specific inductive capacity -of pure India rubber is 2.34--of vulcanized 2.94 (Schiller). - -Synonyms--India Rubber--Rubber. - - -102 STANDARD ELECTRICAL DICTIONARY. - - -Capacity, Dielectric. -The capacity of a dielectric in retaining an electrostatic charge; the -same as Specific Inductive Capacity. 'The number expressing it is -sometimes called the dielectric constant. (See Capacity, Specific -Inductive.) - - -Capacity, Electric, or Electrostatic. -The relative capacity of a conductor or system to retain a charge of -electricity with the production of a given difference of potential. The -greater the charge for a given change of potential, or the less the -change of potential for a given charge the greater the capacity. The -measure of its capacity is the amount of electricity required to raise -the potential to a stated amount. The unit of capacity is the farad, q. -v. Electric capacity is comparable to the capacity of a bottle for air. -A given amount of air will raise the pressure more or less, and the -amount required to raise its pressure a stated amount might be taken as -the measure of capacity, and would be strictly comparable to -electrostatic charge and potential change. The capacity, K, is obviously -proportional to the quantity, Q, of the charge at a given potential, E, -and inversely proportional to the potential, E, for a given quantity, Q, -or, - (1) K == Q/E - and - (2) Q = K * E, -or, the quantity required to raise a conductor by a given potential is -equal to the capacity of the conductor or system multiplied by the rise -of potential. The capacity of a conductor depends upon its environments, -such as the nature of the dielectric surrounding it, the proximity of -oppositely charged bodies and other similar factors. (See -Dielectric-Condenser-Leyden jar.) - -The dimensions of capacity are found by dividing a quantity of -electricity by the potential produced in the conductor by such -quantity. - -Quantity ( ((M^.5)*(L^1.5)) / T ) / potential ( ((M^.5)*(L^.5)) / T ) = L. - - -Capacity, Instantaneous. -The capacity of a condenser when connected only for an instant to a -source of electricity. This is in contrast to electric absorption (see -Absorption, Electric), and is capacity without such absorption taking -part in the action. - - -103 STANDARD ELECTRICAL DICTIONARY. - - -Capacity of a Telegraph Conductor. -The electric capacity of a telegraphic conductor is identical in quality -with that of any other conductor. It varies in quantity, not only for -different wires, but for the same wire under different environments, as -the wire reacting through the surrounding air or other dielectric upon -the earth, represents one element of a condenser, the earth, in general, -representing the other. Hence, a wire placed near the earth has greater -capacity than one strung upon high poles, although the wires may be -identical in length, material and diameter. The effect of high capacity -is to retard the transmission of intermitting signals. Thus, when--as in -the Morse system--a key is depressed, closing a long telegraph current -and sending a signal into a line, it is at least very probable that a -portion of the electricity travels to the end of the wire with the -velocity of light. But as the wire has to be charged, enough current to -move the relay may not reach the end for some seconds. - - -Capacity of Polarization of a Voltaic Cell. -The relative resistance to polarization of a voltaic cell, measured by -the quantity of electricity it can supply before polarization. A -counter-electromotive force may be developed, or the acid or other -solution may become exhausted. The quantity of electricity delivered -before this happens depends on the size and type of cell and other -factors. - - -Capacity, Residual. -When two insulated conductors are separated by a dielectric, and are -discharged disruptively by being connected or nearly connected -electrically, on removing the discharger it is found that a slight -charge is present after a short interval. This is the residual charge. -(See Charge, Residual.) Shaking or jarring the dielectric facilitates -the complete discharge. This retaining of a charge is a phenomenon of -the dielectric, and as such, is termed residual capacity. It varies -greatly in different substances. In quartz it is one-ninth what it is in -air. Iceland spar (crystalline calcite) seems to have no residual -capacity. The action of shaking and jarring in facilitating a discharge -indicates a mechanical stress into which the electrostatic polarization -of the conductor has thrown the intervening dielectric. - - -Capacity, Specific Inductive. -The ratio of the capacity of a condenser when its plates are separated -by any substance to the capacity of the same condenser when its plates -are separated by air. - -A static accumulator consists of two conducting surfaces separated by an -insulator. It is found that the capacity of an accumulator for an -electric charge, which varies with or may be rated by the potential -difference to which its conductors will be brought by the given charge, -varies with the nature of the interposed dielectric, and is proportional -to a constant special to each substance. This constant is the specific -inductive capacity of the dielectric. - -The same condenser will have a higher capacity as the dielectric is -thinner, other things being equal. But different dielectrics having -different specific inductive capacities, the constant may be determined -by ascertaining the relative thicknesses of layers having the same total -inductive capacity. The thicker the layer, the higher is its specific -inductive capacity. - -Thus it is found that 3.2 units thickness of sulphur have the same total -inductive capacity as 1 unit thickness of air. In other words, if -sulphur is interposed between two conducting plates, they may be -separated to over three times the distance that would be requisite to -retain the same capacity in air. Hence, sulphur is the better -dielectric, and air being taken as unity, the specific inductive -capacity of sulphur is 3.2. - - -104 STANDARD ELECTRICAL DICTIONARY. - - -The specific inductive capacity of a dielectric varies with the time and -temperature. That of glass rises 2.5 per cent. between 12° C. (53.6° F.) -and 83° C. (181.4° F.). If a condenser is discharged disruptively, it -retains a small residual charge which it can part with later. If a -metallic connection is made between the plates, the discharge is not -instantaneous. Vibration shaking and jarring facilitate the complete -discharge. All this shows that the charge is a phase of the dielectric -itself, and indicates a strained state into which it is brought. - -The following table gives the specific inductive capacity of various -substances: - - Specific Inductive Capacity. -Substance Specific - Inductive Authority - Capacity. -Vacuum, air at about 0.001 millimeters pressure 0.94 about Ayrton -Vacuum, air at about 5 millimeters 0.9985 Ayrton - 0.99941 Boltzmann -Hydrogen at about 760 millimeters pressure 0.9997 Boltzmann - 0.9998 Ayrton -Air at about 760 millimeters pressure 1.0 Taken as the - standard -Carbon Dioxide at about 760 millimeters pressure 1.000356 Boltzmann - 1.0008 Ayrton -Olefiant Gas at about 760 millimeters pressure 1.000722 Boltzmann -Sulphur Dioxide at about 760 millimeters pressure 1.0037 Ayrton -Paraffin Wax, Clear 1.92 Schiller - 1.96 Wüllner - 1.977 Gibson and Barclay - 2.32 Boltzmann -Paraffin Wax, Milky 2.47 Schiller -India Rubber, Pure 2.34 Schiller -India Rubber, Vulcanized 2.94 Schiller -Resin 2.55 Boltzmann -Ebonite 2.56 Wüllner - 2.76 Schiller - 3.15 Boltzmann -Sulphur 2.88 to 3.21 Wüllner - 3.84 Boltzmann -Shellac 2.95 to 3.73 Wüllner -Gutta percha 4.2 -Mica 5 -Flint Glass, Very light 6.57 J. Hopkinson -Flint Glass, Light 6.85 J. Hopkinson -Flint Glass, Dense 7.4 J. Hopkinson -Flint Glass, Double extra dense 10.1 J. Hopkinson - - -105 STANDARD ELECTRICAL DICTIONARY. - - -Capacity, Unit of. -The unit of capacity is the capacity of a surface which a unit quantity -will raise to a unit potential. The practical unit is the surface which -a coulomb will raise to one volt, and is called the farad, q. v. - - -Capacity, Storage. -In secondary batteries the quantity of electrical current which they can -supply when charged, without undue exhaustion. It is expressed in -ampere-hours. The potential varies so little during the discharge that -it is assumed to be constant. - - -Capillarity. -The reaction between liquid surfaces of different kinds or between -liquid and solid surfaces due to surface tension. Its phenomena are -greatly modified by electric charging, which alters the surface tension. -Capillarity is the cause of solutions "creeping," as it is termed. Thus -in gravity batteries a crust of zinc sulphate often formed over the edge -of the jar due to the solution creeping and evaporating. As a liquid -withdraws from a surface which it does not wet, creeping as above is -prevented by coating the edge with paraffin wax, something which water -does not moisten. It also causes the liquids of a battery cell to reach -the connections and injure them by oxidation. The solutions creep up in -the pores of the carbons of a battery and oxidize the clamps. To give -good connections a disc of platinum or of lead is used for the contact -as not being attacked. Another way is to dip the upper ends of the dry -and warm carbons into melted paraffin wax, or to apply the wax to the -hot carbons at the top, and melt it in with a hot iron. - - -106 STANDARD ELECTRICAL DICTIONARY. - - -Carbon. -(a) One of the elements; atomic weight, 12. It exists in three -allotropic modifications, charcoal, graphite and diamond. In the -graphitic form it is used as an electric current conductor, as in -batteries and for arc lamp, electrodes and incandescent lamp filaments. -It is the only substance which conducts electricity and which cannot be -melted with comparative ease by increase of current. (See Resistance.) - -(b) The carbon plate of a battery or rod of an arc lamp. To secure -greater conductivity in lamp carbons, they are sometimes plated with -nickel or with copper. - -(c) v. To place carbons in arc lamps. This has generally to be done once -in twenty-four hours, unless the period of burning is very short. - - -Carbon, Artificial. -For lamps, carbons and battery plates carbons are made by igniting, -while protected from the action of the air, a mixture of carbon dust and -a cementing and carbonizable substance. Lamp black may be added also. -Powdered coke or gas carbon is mixed with molasses, coal tar, syrup, or -some similar carbonaceous liquid. It is moulded into shape. For lamp -carbons the mixture is forced from a vessel through a round aperture or -die, by heavy pressure, and is cut into suitable lengths. For battery -plates it may be simply pressed into moulds. The carbons are ignited in -covered vessels and also covered with charcoal dust, lamp black or its -equivalent. They are heated to full redness for some hours. After -removal and cooling they are sometimes dipped again into the liquid used -for cementing and reignited. Great care in securing pure carbon is -sometimes necessary, especially for lamps. Fine bituminous coal is -sometimes used, originally by Robert Bunsen, in 1838 or 1840; -purification by different processes has since been applied; carbon from -destructive distillation of coal tar has been used. The famous Carré -carbons are made, it is said, from 15 parts very pure coke dust, five -parts calcined lamp-black, and seven or eight parts sugar--syrup mixed -with a little gum. Five hours heating, with subsequent treatment with -boiling caramel and reignition are applied. The latter treatment is -termed "nourishing." Napoli used three parts of coke to one of tar. -Sometimes a core of different carbon than the surrounding tube is -employed. - - -107 STANDARD ELECTRICAL DICTIONARY. - - -The following are the resistances of Carré's carbons per meter (39.37 -inches): - -Diameter in Diameter in Resistance in Ohms. -Millimeters. Inches. @ 20° C. (98° F.) - 1 .039 50.000 - 2 .078 12.5 - 3 .117 5.55 - 4 .156 3.125 - 5 .195 2.000 - 6 .234 1.390 - 8 .312 .781 - 10 .390 .5 - 12 .468 .348 - 15 .585 .222 - 18 .702 .154 - 20 .780 .125 - -At high temperatures the resistance is about one-third these amounts. A -layer of copper may increase the conductivity one hundred times and -prolong the duration 14 per cent. Thus a layer of copper 1/695 -millimeter (1/17300 inch) thick increases the conductivity 4.5 times; a -coating 1/60 millimeter (1/1500 inch) thick increases the conductivity -one hundred and eleven times. - - -Carbon, Cored. -A carbon for arc lamps with a central core of softer carbon than the -exterior zone. It fixes the position of the arc, and is supposed to give -a steadier light. - -Synonym--Concentric Carbon. - - -Carbon Holders. -In arc lamps, the fixed clamps for holding the ends of the carbons. - - -Carbonization. -The igniting in a closed vessel, protected from air, of an organic -substance so as to expel from it all the constituents except part of -the carbon; destructive distillation. (See Carbonized Cloth.) - - -Carbonized Cloth. -Cloth cut in discs and heated in vessels protected from the air, until -reduced to carbon. The heating is sometimes conducted in vacuo. They are -placed in a pile in a glass or other insulating tube, and offer a -resistance which can be varied by pressure. The greater the pressure the -less will be the resistance, and vice versa. - -Carbon Dioxide. -A compound gas, CO2. It is composed of - Carbon, 12 parts by weight. - Oxygen. 32 " - Specific gravity, 1.524 (Dulong and Berzelins). - Molecular weight, 44. - -It is a dielectric of about the resistance of air. Its specific -inductive capacity at atmospheric pressures is - 1.000356 (Boltzmann). - 1.0008 (Ayrton). - -Synonyms--Carbonic Acid--Carbonic Acid Gas. - - -108 STANDARD ELECTRICAL DICTIONARY - - -Carbon, Volatilization of. -In arc lamps the heat is so intense that it is believed that part of the -carbon is volatilized as vapor before being burned or oxidized by the -oxygen of the air. The same volatilization may take place in -incandescent lamps which are overheated. - - -Carcel. -The standard of artificial illumination used in France. It is the light -yielded by a standard lamp burning 42 grams (648 grains) of colza oil -per hour, with a flame 40 millimeters (1.57 inch) in height. One carcel -is equal to 9.5 to 9.6 candles. - - -Carcel Lamp. -The lamp giving the standard of illuminating power. The wick is -cylindrical, giving an Argand or central draft flame. It is woven with -75 strands, and weighs 3.6 grams (55.5 grains) per decimeter (3.9 -inches) of length. The chimney is 29 centimeters (11.3 inches) high, 47 -millimeters (1.88 inch) in diameter at the bottom, contracting just -above the wick to 34 millimeters (1.36 inch). - - -Carcel Gas Jet. -A standard Argand gas burner, made with proper rating to give the light -of a definite number of carcels illuminating power. Cognizance must be -taken of the quality of the gas as well as of the burner used. - - -Carrying Capacity. -In a current conductor, its capacity for carrying a current without -becoming unduly heated. It is expressed in amperes. (See Wire Gauge, -American.) - - -Cascade. -The arrangement of Leyden jars in series on insulating supports, as -described below. - - -Cascade, Charging and Discharging Leyden Jars In. -An arrangement of Leyden jars in series for the purpose of charging and -discharging. They are placed on insulating supports, the inner coating -of one connected with the outer coating of the next one all through the -series. The actual charge received by such a series, the outer coating -of one end jar being grounded, and the inner coating of the other being -connected to a source of high potential, or else the same being -connected to electrodes of opposite potentials is no greater than that -of a single jar, but a much higher potential difference can be developed -without risk of perforating the glass of a jar. The difference of -potential in each jar of the series is equal to the total potential -difference divided by the number of jars. The energy of discharge is -equal to the same fraction of the energy of a single jar charged with -the same quantity. - -[Transcriber's note: The equal distribution of potential assumes all the -jars have the same capacity. The charge on all jars is the same since -they are in series.] - - -109 STANDARD ELECTRICAL DICTIONARY. - - -Case-hardening, Electric. -The conversion of the surface of iron into steel by applying a proper -carbonaceous material to it while it is heated by an electric current. -It is a superficial cementation process. - - -Cataphoresis. -Electric osmore; the transfer of substances in solution through porous -membranes under the influence probably of electrolysis, but without -themselves being decomposed. - - -Cautery, Electric. -An electro-surgical appliance for removing diseased parts, or arresting -hemorrhages, taking the place of the knife or other cutting instrument. -The cautery is a platinum wire heated to whiteness by an electric -current, and when in that condition used to cut off tumors, stop the -flow of blood and parallel operations. The application is painful, but -by the use of anaesthetics pain is avoided, and the healing after the -operation is greatly accelerated. - -The heated wire of the cautery can be used for cutting operations in -many cases where excision by a knife would be almost impracticable. - -Synonyms--Galvano-cautery--Galvano-caustry--Galvano-electric, -do.--Galvano-thermal, do. - - -C. C. -A contraction of cubic centimeter. It is often written in small letters, -as 100 c.c., meaning 100 cubic centimeters. - - -Cell, Constant. -A cell which yields a constant and uniform current under unvarying -conditions. This implies that neither the electro-motive force or the -resistance of the cell shall vary, or else that as the electro-motive -forces run down the resistance shall diminish in proper proportion to -maintain a constant current. There is really no constant cell. The -constancy is greatest when the external resistance is high in proportion -to the internal resistance. - - -Cell, Electrolytic. -A vessel containing the electrolyte, a liquid decomposable by the -current, and electrodes, arranged for the passage of a decomposing -current. The voltameter, q. v., is an example. - - -Cell, Standard Voltaic. -A cell designed to be a standard of electro-motive force; one in which -the same elements shall always be present under the same conditions, so -as to develop the same electro-motive force. In use the circuit is -closed only for a very short time, so that it shall not become altered -by polarization or exhaustion. - - -Cell, Standard Voltaic, Daniell's. -A zinc-copper-copper sulphate couple. Many forms are used. Sometimes a -number of pieces of blotting paper are interposed between two plates, -one of copper--the other of zinc. The paper next the copper is soaked in -copper sulphate solution, and those next the zinc in zinc sulphate -solution, of course before being put together. Sometimes the ordinary -porous cup combination is employed. The cut shows a modification due to -Dr. Fleming (Phil. Mag. S. 5, vol. xx, p. 126), which explains itself. -The U tube is 3/4-inch diameter, and 8 inches long. Starting with it -empty the tap A is opened, and the whole U tube filled with zinc -sulphate solution, and the tap A is closed. The zinc rod usually kept in -the tube L is put in place, tightly corking up its end of the U tube. -The cock C is opened, which lowers the level of the solution in the -right-hand limb of the U tube only. The tap B is opened and the copper -sulphate solution is run in, preserving the line of separation of the -two solutions. The copper rod is taken out of its tube M, and is put in -place. India rubber corks are used for both rods. As the liquids begin -to mix the mixture can be drawn off at C and the sharp line of -demarcation re-established. In Dr. Sloane's standard cell two test tubes -are employed for the solutions and a syphon is used to connect them. - -Oxidation of the zinc lowers the E. M. F.; oxidation of the copper -raises it. With solutions of equal sp. gr. the E. M. F. is 1.104 volts. -If the copper sulphate solution is 1.100 sp. gr. and the zinc sulphate -solution 1.400 sp. gr., both at 15° C. (59°F.), the E. M. F. will be -1.074 volt. Clean pure zinc and freshly electrolyzed copper should be -used. - - -Fig. 79 STANDARD DANIELL CELL--FLEMING'S FORM. - - -110 STANDARD ELECTRICAL DICTIONARY. - - -Cell, Standard Voltaic, Latimer Clark's. -A mercury and zinc electrode couple with mercurous sulphate as excitant -and depolarizer. The positive element is an amalgam of zinc, the -negative is pure mercury. Each element, in a representative form, the H -form, is contained in a separate vessel which communicate by a tube. -Over the pure mercury some mercurous sulphate is placed. Both vessels -are filled to above the level of the connecting tube with zinc sulphate -solution, and kept saturated. It is tightly closed or corked. The E. M. -F. at 15° C (59° F.) is 1.438. -Temperature correction - -(1 - (.00077 *(t - 15° C) ) ) - -t being expressed in degrees centigrade (Rayleigh). A diminution in -specific gravity of the zinc solution increases the E. M. F. The cell -polarizes rapidly and the temperature coefficient is considered too -high. - - -Fig. 80. LATIMER CLARK'S STANDARD CELL. - - -111 STANDARD ELECTRICAL DICTIONARY. - - -Cements, Electrical. -A few cements find their use in electrical work. Marine glue, -Chatterton's compound, and sealing wax may be cited. - - -Centi-. -Employed as a prefix to indicate one-hundredth, as centimeter, the -one-hundredth of a meter; centi-ampere, the one-hundredth of an ampere. - - -Centigrade-scale. -A thermometer scale in use by scientists of all countries and in general -use in many. The temperature of melting ice is 0º; the temperature of -condensing steam is 100° ; the degrees are all of equal length. To -reduce to Fahrenheit degrees multiply by 9 and divide by 5, and add 32 -algebraically, treating all readings below 0º as minus quantities. For -its relations to the Reamur scale, see Reamur Scale. Its abbreviation is -C., as 10º C., meaning ten degrees centigrade. - - -Centimeter. -A metric system unit of length; one-hundredth of a meter; 0.3937 inch. -The absolute or c. g. s. unit of length. - - -Centimeter-gram-second System. -The accepted fundamental or absolute system of units, called the C. G. -S. system. It embraces units of size, weight, time, in mechanics, -physics, electricity and other branches. It is also called the absolute -system of units. It admits of the formation of new units as required by -increased scope or classification. The following are basic units of the -system : - -Of length, centimeter; -of mass, gram; -of time, second: -of force, dyne: -of work or energy, erg. - -See Dyne, Erg., and other units in general. - - -112 STANDARD ELECTRICAL DICTIONARY. - - -Central Station Distribution or Supply. -The system of supplying electric energy in current form from a main -generating plant to a district of a number of houses, factories, etc. It -is in contrast with the isolated plant system in which each house or -factory has its own separate generating installment, batteries or -dynamos. - - -Centre of Gravity. -A point so situated with respect to any particular body, that the -resultant of the parallel attracting forces between the earth and the -several molecules of the body always passes through it. These are -resultants of the relative moments of the molecules. If a body is -suspended, as by a string, the centre of gravity always lies vertically -under its point of suspension. By two trials the point of intersection -of plumb lines from the point of suspension being determined the centre -of gravity is known. The vertical from the point of support coincides -with the line of direction. - - -Centre of Gyration. -The centre of gyration with respect to the axis of a rotating body is a -point at which if the entire mass of the body were concentrated its -moment of inertia would remain unchanged. The distance of this point -from the axis is the radius of gyration. - - -Centre of Oscillation. -The point referred to in a body, suspended or mounted to swing like a -pendulum, at which if all the mass were concentrated, 1t would complete -its oscillations in the same time. The distance from the axis of support -to this point gives the virtual length of the pendulum which the body -represents. - - -Centre of Percussion. -The point in a suspended body, one free to swing like a pendulum, at -which an impulse may be applied, perpendicular to the plane through the -axis of the body and through the axis of support without shock to the -axis. It is identical with the centre of oscillation, q. v., when such -lies within the body. - - -Centrifugal Force. -The force which draws a body constrained to move in a curved path away -from the centre of rotation. It is really due to a tangential impulse -and by some physicists is called the centrifugal component of tangential -velocity. It has to be provided against in generator and motor -armatures, by winding them with wire or bands to prevent the coils of -wire from spreading or leaving their bed upon the core. - - -113 STANDARD ELECTRICAL DICTIONARY. - - -Centrifugal Governor. -The usual type of steam-engine governor. The motion of the engine -rotates a system of weights, which are forced outward by centrifugal -force, and are drawn inwards by gravity or by springs. Moving outwards -they shut off steam, and moving inwards they admit it, thus keeping the -engine at approximately a constant speed. The connections between them -and the steam supply and the general construction vary widely in -different governors. - - -C. G. S. -Abbreviation or symbol for Centimeter-gram-second, as the C. G. S. -system. (See Centimeter-gram-second System.) It is sometimes expressed -in capitals, as above, and sometimes in small letters, as the c. g. s. -unit of resistance. - - -Chamber of Incandescent Lamp. -The interior of the bulb of an incandescent lamp. (See Lamp, -Incandescent.) - - -Fig. 81. CHARACTERISTIC CURVE OF A DYNAMO. - - -FIG. 82. DROOPING CHARACTERISTIC. - - -Characteristic Curve. -A curve indicating the variations in electro-motive force developed -during the rotations of the armature of a dynamo or other generator of -E. M. F. The term as used in the electrical sense is thus applied, -although the indicator diagram of a steam engine may be termed its -characteristic curve, and so in many other cases. As the amperes taken -from a series generator are increased in number, the E. M. F. rises, it -may be very rapidly up to a certain point, and thereafter more slowly. -To construct the curve coordinates, q. v., are employed. The resistance -of the dynamo and of the outer circuit being known, the current -intensity is measured. To obtain variations in electro-motive force the -external resistance is changed. Thus a number of ampere readings with -varying known resistance are obtained, and for each one an -electro-motive force is calculated by Ohm's law. From these data a curve -is plotted, usually with volts laid off on the ordinate and amperes on -the abscissa. - -By other methods other characteristic curves may be obtained, for which -the titles under Curve may be consulted. - - -114 STANDARD ELECTRICAL DICTIONARY. - - -Characteristic, Drooping. -A characteristic curve of a dynamo which indicates a fall in voltage -when an excessive current is taken from the dynamo in question. It is -shown strongly in some Brush machines, and is partly due to the -arrangements for cutting out two of the coils as they approach the -neutral line. It is an advantage, as it protects from overheating on -short circuit. - - -Characteristic, External. -In a dynamo the characteristic curve in which the relations of volts -between terminals to amperes in the outer circuit are plotted. (See -Curve, External Characteristic.) - - -Characteristic, Internal. -A characteristic curve of a shunt dynamo, in which the relations of -volts to amperes in the shunt circuit is plotted. - - -Characteristics of Sound. -Of interest, electrically, as affecting the telephone, they comprise: - -(1) Pitch, due to frequency of vibrations. - -(2) Intensity or loudness, due to amplitude of waves of sound. - -(3) Quality or timbre, the distinguishing characteristics of any -specific sound due to overtones, discords, etc., by which the sound is -recognizable from others. The telephone is held by the U. S. courts to -be capable of reproducing the voice by means of the undulatory current. -(See Current, Undulatory.) - - -Charge. -The quantity of electricity that is present on the surface of a body or -conductor. If no electricity is supplied, and the conductor is connected -to the earth, it is quickly discharged. A charge is measured by the -units of quantity, such as the coulomb. The charge that a conductor can -retain at a given rise of potential gives its capacity, expressible in -units of capacity, such as the farad. A charge implies the stretching or -straining between the surface of the charged body, and some -complimentary charged surface or surfaces, near or far, of large or -small area, of even or uneven distribution. - - -Charge. v. -(a) To introduce an electrostatic charge, as to charge a condenser. - -(b) To decompose the elements of a secondary battery, q. v., so as to -render it capable of producing a current. Thus, a spent battery is -charged or recharged to enable it to do more work. - -Synonyms--Renovate--Revivify--Recharge. - - -115 STANDARD ELECTRICAL DICTIONARY. - - -Charge, Bound. -A charge of electricity borne by the surface of a body so situated with -reference to another oppositely charged body, that the charge is -imperceptible to ordinary test, will not affect an electroscope nor -leave the surface if the latter is connected to the earth. To discharge -such a body it must be connected to its complimentarily charged body. -The bound charge was formerly called dissimulated or latent electricity. -(See Charge, Free.) - -The charge or portion of a charge of a surface which is neutralized -inductively by a neighboring charge of opposite kind. The degree of -neutralization or of binding will depend on the distance of the two -charged surfaces from one another and on the electro-static nature of -the medium intervening, which must of necessity be a dielectric. A -charge not so held or neutralized is termed a free charge. Thus a -surface may be charged and by the approach of a surface less highly -charged may have part of its charge bound. Then if connected to earth. -it will part with its unbound or free charge, but will retain the other -until the binding surface is removed, or until the electricity of such -surface is itself bound, or discharged, or until connection is made -between the two surfaces. Thus a body may have both a bound and a free -charge at the same time. - - -Charge, Density of. -The relative quantity of electricity upon a given surface. Thus a -charged surface may have an evenly distributed charge or one of even -density, or an unevenly distributed charge or one of uneven density. In -a thunderstorm the earth has a denser charge under the clouds than -elsewhere. - -Synonym--Electrical Density. - - -Charge, Dissipation of. -As every body known conducts electricity, it is impossible so to -insulate a surface that it will not lose its charge by leakage. An -absolute vacuum might answer, and Crookes in a high vacuum has retained -a charge against dissipation for years. The gradual loss is termed as -above. - - -Charge, Distribution of. -The relation of densities of charge on different parts of a charged -body. On a spherical conductor the charge is normally of even -distribution; on other conductors it is unevenly distributed, being of -greatest density at points, edges, and parts of smallest radius of -curvature. Even distribution can also be disturbed by local induction, -due to the presence of oppositely charged bodies. - - -116 STANDARD ELECTRICAL DICTIONARY. - - -Charge, Free. -The charge borne by an insulated body, independent of surrounding -objects. Theoretically it is an impossibility. A charge always has its -compliment somewhere in surrounding objects. As a matter of convenience -and convention, where the complimentary charge is so distributed that -its influence is not perceptible the charge is called a free charge. If -connected to earth the free charge will leave the body. If the body is -connected with an electroscope the free charge will affect the same. -(See Charge, Bound.) - - -Charge, Residual. -When a Leyden jar or other condenser is discharged by the ordinary -method, after a few minutes standing a second discharge of less amount -can be obtained from it. This is due to what is known as the residual -charge. It seems to be connected in some way with the mechanical or -molecular distortion of the dielectric. The jarring of the dielectric -after discharge favors the rapidity of the action, diminishing the time -required for the appearance of the residual charge. The phenomenon, it -will be seen, is analogous to residual magnetism. This charge is the -reciprocal of electric absorption and depends for its amount upon the -nature of the dielectric. (See Absorption, Electric, and Capacity, -Residual.) - -Synonym--Electric Residue. - - -Chatterton's Compound. -A cement used for cementing together layers or sheets of gutta percha, -and for similar purposes in splicing telegraph cables. Its formula is: - Stockholm Tar, 1 part. - Resin, 1 part. - Gutta Percha, 3 parts. -All parts by weight. - - -Chemical Change. -When bodies unite in the ratio of their chemical equivalents, so as to -represent the satisfying of affinity or the setting free of thermal or -other energy, which uniting is generally accompanied by sensible heat -and often by light, as in the ignition of a match, burning of a candle, -and, when the new compound exhibits new properties distinct from those -of its components, a chemical combination is indicated. More definitely -it is a change of relation of the atoms. Another form of chemical change -is decomposition, the reverse of combination, and requiring or absorbing -energy and producing several bodies of properties distinct from those of -the original compound. Thus in a voltaic battery chemical combination -and decomposition take place, with evolution of electric instead of -thermal energy. - - -Chemical Equivalent. -The quotient obtained by dividing the atomic weight, q. v., of an -element by its valency, q. v. Thus the atomic weight of oxygen is 16, -its valency is 2. its chemical equivalent is 8. It is the weight of the -element corresponding to a unit weight of hydrogen, either as replacing -it, or combining with it. In electro-chemical calculations the chemical -equivalent is often conveniently used to avoid the necessity of dividing -by the valency when atomic weights are used. The latter is really the -better practice. The atomic weights in the old system of chemical -nomenclature were chemical equivalents. - - -117 STANDARD ELECTRICAL DICTIONARY. - - -Chemical Recorder. -A form of telegraphic recorder in which the characters, often of the -Morse alphabet or some similar one, are inscribed on chemically prepared -paper by decomposition affecting the compound with which the paper is -charged. In the original chemical recorder of Bain, the instrument was -somewhat similar to the Morse recorder, except that the motionless -stylus, S, always pressing against the paper was incapable of making any -mark, but being of iron, and the paper strip being impregnated with -potassium ferrocyanide, on the passage of a current a stain of Prussian -blue was produced where the stylus touched the paper. The current passes -from the line by way of the iron stylus, through the paper, and by way -of a brass surface, M, against which the paper is held and is pressed by -the stylus, to the earth. This recorder is extremely simple and has no -part to be moved by the current. The solution in which the paper is -dipped contains a mixture of potassium ferrocyanide and ammonium -nitrate. The object of the latter is to keep the paper moist. In recent -recorders a solution of potassium iodide has been used, which gives a -brown stain of free iodine, when the current passes. This stain -disappears in a few days. - - -Fig. 83. BAIN'S TELEGRAPH EMPLOYING CHEMICAL RECORDER. - - -In the cut, R is the roll of paper, B is a tank of solution with roll, -W1, for moistening the paper; M is the brass surface against which the -stylus, S, presses the paper, P P; W, W are feed rollers; T is the -transmitting key, and zk the battery; Pl, Pl are earth plates. The -apparatus is shown duplicated for each end. - - -118 STANDARD ELECTRICAL DICTIONARY. - - -Chemistry. -The science treating of atomic and molecular relations of the elements -and of chemical compounds of the same. - - -Chimes, Electric. -An apparatus employed to illustrate the principles of the electrostatic -charge, involving the ringing of bells by electrostatic attraction and -repulsion. It is used in connection with a frictional, or influence -electric machine. Two bells are employed with a button or clapper -suspended between them. One bell is connected to one of the prime -conductors, q. v., of the machine. The other insulated therefrom is -connected to earth, or if an influence machine is used, to the other -prime conductor. The clappers are hung by a silk thread, so as to be -entirely insulated. On working the machine the bells become oppositely -excited. A clapper is attracted to one, then when charged is repelled -and attracted to the other, it gives up its charge and becoming charged -with similar electricity to that of the bell it touches, is repelled and -attracted to the other, and this action is kept up as long as the -excitement continues, the bells ringing continuously. - - -Fig. 84. ELECTRIC CHIMES. - - -Chronograph, Electric. -An apparatus for indicating electrically, and thereby measuring, the -lapse of time. The periods measured may be exceedingly short, such as -the time a photographic shutter takes to close, the time required by a -projectile to go a certain distance, and similar periods. - -A drum rotated with even and known velocity may be marked by a stylus -pressed upon it by the action of an electro-magnet when a key is -touched, or other disturbance. Then the space between two marks would -give the period elapsing between the two disturbances of the circuit. As -it is practically impossible to secure even rotation of a drum, it is -necessary to constantly measure its rate of rotation. This is effected -by causing a tuning-fork of known rate of vibration to be maintained in -vibration electrically. A fine point or bristle attached to one of its -arms, marks a sinuous line upon the smoked surface of the cylinder. This -gives the basis for most accurately determining the smallest intervals. -Each wave drawn by the fork corresponds to a known fraction of a second. - -For projectiles, the cutting of a wire opens a circuit, and the opening -is recorded instead of the closing. By firing so as to cut two wires at -a known distance apart the rate is obtained by the chronograph. - -Synonym--Chronoscope. - - -119 STANDARD ELECTRICAL DICTIONARY. - - -Chutaux's Solution. -A solution for bichromate batteries. It is composed as follows: - Water, 1,500 parts - Potassium bichromate, 100 parts - mercury bisulphate, 100 parts - 66° sulphuric acid, 50 parts. - -Circle, Galvanic or Voltaic. -A term for the voltaic circuit; obsolete. - - -Fig. 85. MAGIC CIRCLE. - - -Circle, Magic. -A form of electro-magnet. It is a thick circle of round iron and is used -in connection with a magnetizing coil, as shown, to illustrate -electro-magnetic attraction. - - -120 STANDARD ELECTRICAL DICTIONARY. - - -Circuit. -A conducting path for electric currents properly forming a complete path -with ends joined and including generally a generating device of some -kind. Part of the conduction may be true and part electrolytic. (See -Electrolytic Conduction.) The term has become extended, so that the term -is often applied to any portion of a circuit conveniently considered by -itself. The simplest example of a complete circuit would be a circular -conductor. If rotated in the earth's field so as to cut its lines of -force a current would go through it, and it would be an electric -circuit. Another example is a galvanic battery with its ends connected -by a wire. Here the battery generates the current which, by electrolytic -conduction, goes through the battery and by true conduction through the -wire. For an example of a portion of a circuit spoken of as "a circuit" -see Circuit, Astatic. - - -Circuit, Astatic. -A circuit so wound with reference to the direction of the currents -passing through it that the terrestrial or other lines of force have no -directive effect upon it, one member counteracting the other. It may be -produced by making the wire lie in two closed curves, A and B, each -enclosing an equal area, one of identical shape and disposition with the -other, and with the current circulating in opposite directions in each -one. Thus each circuit represents a magnetizing turn of opposite -polarity and counteracting each other's directive tendency exhibited in -a field of force with reference to an axis a c. Another form of astatic -circuit is shown in Fig. 86. The portions C, D, lying on opposite sides -of the axis of rotation a c, are oppositely acted on by the earth's -directive force as regards the direction of their rotation. - - -Figs. 86 and 87. ASTATIC CIRCUITS. - - -Circuit, Branch. -A circuit dividing into two or more parts in parallel with each other. - - -121 STANDARD ELECTRICAL DICTIONARY. - - -Circuit Breaker. -Any apparatus for opening and closing a circuit is thus termed, but it -is generally applied to automatic apparatus. A typical circuit breaker -is the hammer and anvil of the induction coil. (See Induction Coil; -Anvil.) Again a pendulum connected to one terminal of a circuit may -swing so as to carry a point on its lower end through a globule of -mercury as it swings, which globule is connected to the other terminal. -A great many arrangements of this character have been devised. - -Synonym.--Contact Breaker. - - -Circuit Breaker, Automatic. -A circuit breaker worked by the apparatus to which it is attached, or -otherwise automatically. (See Induction Coil; Anvil; Bell, Electric.) - - -Circuit Breaker, File. -A coarsely cut file, forms one terminal of an electric circuit, with a -straight piece of copper or steel for the other terminal. The latter -terminal drawn along the teeth makes and breaks the contact once for -every tooth. The movable piece should have an insulated handle. - - -Circuit Breaker, Mercury. -A circuit breaker which may be identical in principle, with the -automatic circuit breaker of an induction coil, but in which in place of -the anvil, q. v., a mercury cup is used, into which the end of a wire -dips and emerges as it is actuated by the impulses of the current. Each -dip makes the contact, which is broken as the wire springs back. The -mercury should be covered with alcohol to protect it from oxidation. - - -Circuit Breaker, Pendulum. -A circuit breaker in which a pendulum in its swing makes and breaks a -contact. It may be kept in motion by clockwork, or by an electro-magnet, -attracting intermittently an armature attached to its rod, the -magnet circuit being opened and closed by the pendulum or circuit -breaker itself. A mercury contact may be used with it. - - -Fig. 88. PENDULUM CIRCUIT BREAKER. - - -122 STANDARD ELECTRICAL DICTIONARY. - - -Circuit Breaker, Tuning Fork. -A circuit breaker in which a tuning fork makes and breaks the circuit. -Each vibration of one of the prongs in one direction makes a contact, -and the reverse vibration breaks a contact. The adjustment is -necessarily delicate, owing to the limited amplitude of the motion of -the fork. The fork is kept in vibration sometimes by an electro-magnet, -which is excited as the circuit is closed by the fork. One leg of the -fork acts as the armature of the magnet, and is attracted according to -its own natural period. - - -Circuit Breaker, Wheel. -A toothed wheel with a spring bearing against its teeth. One terminal of -a circuit connects with the wheel through its axle, the other connects -with the spring. When the wheel is turned the circuit is opened and -closed once for each tooth. The interstices between teeth on such a -wheel may be filled with insulating material, giving a cylindrical -surface for the contact spring to rub on. - - -Fig. 89--TOOTHED WHEEL CIRCUIT BREAKER. - - -Circuit, Closed. -A circuit whose electric continuity is complete; to make an open circuit -complete by closing a switch or otherwise is to close, complete, or make -a circuit. - -Synonyms--Completed Circuit--Made Circuit. - - -Circuit, Compound. -A circuit characterized by compounding of generating or receiving -devices, as including several separate batteries, or several motors, or -other receiving devices. It is sometimes used to indicate a circuit -having its battery arranged in series. It should be restricted to the -first definition. - - -123 STANDARD ELECTRICAL DICTIONARY. - - -Circuit, Derived. -A partial circuit connected to two points of another circuit, so as to -be in parallel with the portion thereof between such two points; a shunt -circuit. - -Synonyms--Shunt Circuit--Derivative Circuit--Parallel Circuit. - - -Circuit, Electric, Active. -A circuit through which a current passes. The circuit itself need only -be a conducting ring, or endless wire. Generally it includes, as part of -the circuit, a generator of electro-motive force, and through which -generator by conduction, ordinary or electrolytic, the same current goes -that passes through the rest of the circuit. One and the same current -passes through all parts of a series circuit when such current is -constant. - -A current being produced by electro-motive force, and electromotive -force disappearing in its production in an active circuit, there must be -some source of energy which will maintain electromotive force against -the drain made upon it by the current. - -The simplest conception of an active electric circuit is a ring or -endless conductor swept through a field of force so as to cut lines of -force. A simple ring dropped over a magnet pole represents the -simplification of this process. In such a ring a current, exceedingly -slight, of course, will be produced. In this case there is no generator -in the circuit. An earth coil (see Coil, Earth,) represents such a -circuit, with the addition, when experimented with, of a galvanometer in -the circuit. - -In practice, a circuit includes a generator such as a battery or dynamo, -and by conductors is led through a continuous path. Electric lamps, -electrolytic cells, motors and the like may be included in it. - -The term "circuit" is also applied to portions of a true circuit, as the -internal circuit, or external circuit. A certain amount of elasticity is -allowed in its use. It by no means necessarily indicates a complete -through circuit. - - -Circuit, Electrostatic. -(a) A circuit through which an electrostatic or high tension discharge -takes place. It is virtually an electric circuit. - -(b) The term is applied also to the closed paths of electrostatic lines -of force. - - -Circuit, External. -The portion of a circuit not included within the generator. - - -Circuit, Grounded. -A circuit, one of whose members, the return circuit, is represented by -the earth, so that the earth completes the circuit. In telegraphy each -end of the line is grounded or connected to an earth-plate, q. v., or to -the water or gas-pipes, and the current is assumed to go through the -earth on its return. It really amounts to a discharging at one end, and -charging at the other end of the line. The resistance of the earth is -zero, but the resistance of the grounding or connection with the earth -may be considerable. - -Synonyms--Ground Circuit--Earth Circuit--Single Wire Circuit. - -[Transcriber's note: The resistance of the earth is high enough that -large power system return currents may produce dangerous voltage -gradients when a power line is shorted to the ground. Don't walk near -downed lines!] - - -124 STANDARD ELECTRICAL DICTIONARY. - - -Circuit Indicator. -A pocket compass, decomposition apparatus, galvanometer or other device -for indicating the condition of a wire, whether carrying a current or -not, and, if carrying one, its direction, and sometimes roughly -indicating its strength. - - -Circuit, Internal. -The portion of an electric circuit included within the generator. - - -Circuit, Line. -The portion of a circuit embracing the main line or conductor, as in a -telegraph circuit the line carried on the poles; distinguished from the -local circuit (see Circuit, Local,) in telegraphy. - - -Circuit, Local. -In telegraphy, a short circuit with local generator or battery included, -contained within the limits of the office or station and operated by a -relay, q. v. This was the original local circuit; the term is applicable -to any similar arrangement in other systems. Referring to the cut, the -main line circuit includes the main battery, E, Key, P, Relay, R, ground -plates, G, G1. The relay magnet opens and closes the local circuit with -its local battery, L, and sounder magnet, H, with its armature, B. The -minor parts, such as switches, are omitted. - - -Fig. 90. LOCAL CIRCUIT OF TELEGRAPH SYSTEM. - - -Circuit, Local Battery. -A local circuit worked by and including a local battery in its course. - - -125 STANDARD ELECTRICAL DICTIONARY. - - -Circuit, Loop. -A minor circuit introduced in series into another circuit by a cut-out, -or other device, so as to become a portion of the main circuit. - - -Circuit Loop Break. -A supporter or bracket with two arms for carrying insulators. Its use is -to enable a loop connection to be introduced into a line which is cut, -so as to enable the connection of the ends of the loop to be made, one -to each end of the through wire, which ends are attached, one to each of -the two insulators. - - -Circuit, Main. -The circuit including the main line and apparatus supplied by the main -battery, as distinguished from the local circuit. (See Circuit, Local.) - - -Circuit, Main Battery. -The main circuit, including the main or principal battery in its course. - - -Circuit, Metallic. -A circuit in which the current outside the generator, or similar parts, -is carried on a metallic conductor; a circuit without any ground -circuit. The including of a galvanic battery or electro plating bath -would not prevent the application of the term; its essential meaning is -the omission of the earth as the return circuit. - - -Circuit, Negative Side of. -The side of a circuit opposite to the positive side. (See Circuit, -Positive Side of) It is defined as the half of a circuit leading to the -positive terminal of the generator. - - -Circuit, Open. -A circuit with its continuity broken, as by disconnecting a wire from -the battery, or opening a switch; a broken circuit is its synonym. To -open a switch or disconnect or cut the wire is termed opening or -breaking the circuit. - -Synonyms--Incomplete Circuit--Broken Circuit. - - -Circuit, Positive Side of. -This side is such that an observer standing girdled by the current with -his head in the positive side or region, would see the current pass -around him from his right toward his left hand. It is also defined as -the half of the circuit leading to the negative terminal of the -generator. - - -Circuit, Recoil. -The portion of a parallel circuit presenting an alternative path, q. v., -for a disruptive discharge. - - -Circuit, Return. -(a) The part of a circuit extending from the generator to the extreme -point in general, upon which no apparatus is placed. In telegraph -systems the ground generally forms the return circuit. The distinction -of return and working circuit cannot always be made. - -(b) It may also be defined as the portion of a circuit leading to the -negative terminal of the generator. - - -126 STANDARD ELECTRICAL DICTIONARY - - -Circuits, Forked. -Circuits starting in different paths or directions from one and the same -point. - - -Circuit, Simple. -A circuit containing a single generator, and single receiver of any -kind, such as a motor or sounder, with a single connecting conductor. It -is also used to indicate arrangement in multiple arc, but not generally, -or with approval. - - -Circuits, Parallel. -Two or more conductors starting from a common point and ending at -another common point are termed, parallel circuits, although really but -parts of circuits. If of equal resistance their joint resistance is -obtained by dividing the resistance of one by the number of parallel -circuits. If of unequal resistance r, r', r" , etc., the formula for -joint resistance, R, of two is - -R = ( r * r' ) / ( r + r' ) - -This resistance may then be combined with a third one by the same -formula, and thus any number may be calculated. - -Synonym--Shunt Circuit. - - -Circuit, Voltaic. -Properly a circuit including a conductor and voltaic couple. - -It is also applied to the electric circuit, q. v., or to any circuit -considered as a bearer of current electricity. - - -Circular Units. -Units of area, usually applied to cross sectional area of conductors, by -whose use area is expressed in terms of circle of unit diameter, -usually a circular mil, which is the area of a circle of one-thousandth -of an inch diameter, or a circular millimeter, which is the area of a -circle of one millimeter diameter. Thus a wire one-quarter of an inch -in diameter has an area of 250 circular mils; a bar one centimeter in -diameter has an area of ten circular millimeters. - -[Transcriber's Note: Area is the diameter squared. A 1/4 inch wire has -62500 circular mils of area. A one centimeter (10 millimeter) wire has -100 circular millimeters of area. Actual area = circular mils * (PI/4).] - - -Circumflux. -The product of the total number of conductor turns on the armature of a -dynamo or motor, into the current carried thereby. For two pole machines -it is equal to twice the armature ampere-turns; for four pole machines -to four times such quantity, and so on. - - -Clamp. -The appliance for grasping and retaining the end of the rod that holds a -carbon in the arc lamp. - -Clark's Compound. -A cement used for the outside of the sheath of telegraph cables. -Its formula is: - Mineral Pitch, 65 parts. - Silica, 30 parts. - Tar, 5 parts. -All parts by weight. - - -127 STANDARD ELECTRICAL DICTIONARY. - - -Cleats. -A support; a short block of wood, grooved transversely, for holding -electric wires against a wall. For the three wire system three grooves -are used. The entire wiring of apartments is sometimes done by the -"cleat system," using cleats instead of battens, q. v., or mouldings. -The cleats are secured against the wall with the grooves facing it, and -the wires are introduced therein. - - -Fig. 91. TWO WIRE CLEAT. - - -Fig. 92. THREE WIRE CLEAT. - - -Cleat, Crossing. -A cleat with grooves or apertures to support wires which cross each -other. Two or three grooves are transverse, and on the under side, as -above; one groove is longitudinal and on the upper side. - - -Cleavage, Electrification by. -If a mass of mica is rapidly split in the dark a slight flash is -perceived. Becquerel found that in such separation the two pieces came -away oppositely charged with electricity. The splitting of mica is its -cleavage. - - -Clock, Controlled. -In a system of electric clocks, the clocks whose movements are -controlled by the current, regulated by the master or controlling clock. - -Synonym--Secondary Clock. - - -Clock, Controlling. -In a system of electric clocks the master clock which controls the -movements of the others, by regulating the current. - -Synonym--Master Clock. - - -Clock, Electric Annunciator. -A clock operating any form of electric annunciator, as dropping -shutters, ringing bells, and the like. It operates by the machinery -closing circuits as required at any desired hour or intervals. - - -128 STANDARD ELECTRICAL DICTIONARY. - - -Clock, Electrolytic. -A clock worked by the electrolytic deposition and resolution of a -deposit of metal upon a disc. It is the invention of Nikola Tesla. A -metallic disc is mounted on a transverse axis, so as to readily rotate. -It is immersed in a vessel of copper sulphate. A current is passed -through the bath, the terminals or electrodes being near to and facing -the opposite edges of the disc, so that the line connecting the -electrodes lies in the plane of the disc. If a current is passed through -the solution by the electrodes, copper is deposited on one side of the -disc, and as it rotates under the influence of the weight thus -accumulated on one side, the same metal as it is brought to the other -side of the disc is redissolved. Thus a continuous rotation is -maintained. The cause of the deposition and solution is the position of -the disc; one-half becomes negative and the other positive in their -mutual relations. - - -Clock, Self-winding Electric. -A clock which is wound periodically by an electric motor and battery. - - -Clockwork, Feed. -In arc-lamps the system of feeding the carbon or carbons by clockwork -whose movements are controlled by the resistance of the arc. This system -is employed in the Serrin, and in the Gramme regulators, among others. -The carbons, if they approach, move clockwork. The movement of this is -stopped or freed by an electro-magnet placed in shunt around the arc -and carbons. - - -Cloisons. -Partitions or divisions; applied to the winding of electro-magnets and -coils where the winding is put on to the full depth, over single -sections of the core, one section at a time, until the whole core is -filled up. - - -Closure. -The closing or completion of a circuit by depressing a key or moving a -switch. - - -Clutch. -In arc lamps a device for the feed of the upper carbons. In its simplest -form it is simply a plate or bar pierced with a hole through which the -carbon passes loosely. The action of the mechanism raises or lowers one -end of the plate or bar. As it rises it binds and clutches the carbon, -and if the action continues it lifts it a little. When the same end is -lowered the carbon and clutch descend together until the opposite end of -the clutch being prevented from further descent, the clutch approaches -the horizontal position and the rod drops bodily through the aperture. -The cut shows the clutches of the Brush double carbon lamp. In practice -the lifting and releasing as regulated by an electro-magnet are so very -slight that practically an almost absolutely steady feed is secured. A -similar clutch is used in the Weston lamp. - - -129 STANDARD ELECTRICAL DICTIONARY. - - -Clutch, Electro-magnetic. -A clutch or appliance for connecting a shaft to a source of rotary -motion while the latter is in action. In one form a disc, in whose face -a groove has been formed, which groove is filled with a coil of wire, is -attached to the loose wheel, while the shaft carries a flat plate to act -as armature. On turning on the current the flat plate is attached, -adheres, and causes its wheel to partake of the motion of the shaft. -Contact is made by brushes and collecting rings. - -In the cut, A A is the attracted disc; the brushes, B B, take current to -the collecting rings, C. The magnetizing coil is embedded in the body of -the pulley, as shown. - - -Fig. 93. CLUTCH OF BRUSH LAMP. - - -Fig. 94. ELECTRO-MAGNETIC CLUTCH. - - -130 STANDARD ELECTRICAL DICTIONARY. - - -Coatings of a Condenser or Prime Conductor. -The thin conducting coatings of tinfoil, gold leaf or other conducting -substance, enabling the surface to receive and part with the electric -charge readily. Without such a coating the charge and discharge would be -very slow, and would operate by degrees only, as one part of a -non-conducting surface might be densely charged and another part be -quite devoid of sensible charge. - - -Code, Cipher. -A code of arbitrary words to designate prearranged or predetermined -words, figures or sentences. The systems used in commerce have single -words to represent whole sentences or a number of words of a sentence. -This not only imparts a degree of secrecy, but makes the messages much -shorter. Codes are used a great deal in cable transmission. - - -Code, Telegraphic. -A telegraphic alphabet. (See Alphabets, Telegraphic.) - - -Coefficient. -In algebra, the numerical multiplier of a symbol, as in the expression -"5x," 5 is the coefficient. In physics, generally a number expressing -the ratio or relation between quantities, one of which is often unity, -as a standard or base of the set of coefficients. Thus the coefficient -of expansion by heat of any substance is obtained by dividing its volume -for a given degree of temperature by its volume at the standard -temperature as 0º C., or 32º F. This gives a fraction by which if any -volume of a substance, taken at 0º C., or at whatever may be taken as -the basic temperature, is multiplied, the expanded volume for the given -change of temperature will be obtained as the product. A coefficient -always in some form implies the idea of a multiplier. Thus the -coefficient of an inch referred to a foot would be 1/12 or .833+, -because any number of inches multiplied by that fraction would give the -corresponding number of feet. - -[Transcriber's note: 1/12 is 0.0833+] - - -Coefficient, Economic. -In machinery, electric generators, prime motors and similar structures, -the number expressing the ratio between energy absorbed by the device, -and useful, not necessarily available, work obtained from it. It is -equal to work obtained divided by energy absorbed, and is necessarily a -fraction. If it exceeded unity the doctrine of the conservation of -energy would not be true. The economic coefficient expresses the -efficiency, q. v., of any machine, and of efficiencies there are several -kinds, to express any one of which the economic coefficient may be used. -Thus, let W--energy absorbed, and w = work produced ; then w/W is the -economic coefficient, and for each case would be expressed numerically. -(See Efficiency, Commercial--Efficiency, Electrical--Efficiency of -Conversion.) - -The distinction between useful and available work in a dynamo is as -follows: The useful work would include the work expended by the field, -and the work taken from the armature by the belt or other mechanical -connection. Only the latter would be the available work. - - -131 STANDARD ELECTRICAL DICTIONARY. - - -Coercive or Coercitive Force. -The property of steel or hard iron, in virtue of which it slowly takes -up or parts with magnetic force, is thus termed ("traditionally"; -Daniell). It seems to have to do with the positions of the molecules, as -jarring a bar of steel facilitates its magnetization or accelerates its -parting, when not in a magnetic field, with its permanent or residual -magnetism. For this reason a permanent magnet should never be jarred, -and permitting the armature to be suddenly attracted and to strike -against it with a jar injures its attracting power. - -Coercive force is defined also as the amount of negative magnetizing -force required to reduce remnant magnetism to zero. - -By some authorities the term is entirely rejected, as the phenomenon -does not seem directly a manifestation of force. - - -Coil and Coil Plunger. -A device resembling the coil and plunge, q. v., except that for the -plunger of iron there is substituted a coil of wire of such diameter as -to enter the axial aperture of the other, and wound or excited in the -same or in the opposite sense, according to whether attraction or -repulsion is desired. - - -Coil and Plunger. -A coil provided with a core which is free to enter or leave the central -aperture. When the coil is excited, the core is drawn into it. Various -forms of this device have been used in arc lamp regulators. - -Synonym--Sucking coil. - - -Fig. 95. COIL AND COIL PLUNGER OF MENGIES ARC LAMP. - - -Fig. 96. COIL AND PLUNGER EXPERIMENT. - - -132 STANDARD ELECTRICAL DICTIONARY. - - -Coil and Plunger, Differential. -An arrangement of coil and plunger in which two plungers or one plunger -are acted on by two coils, wound so as to act oppositely or -differentially on the plunger or plungers. Thus one coil may be in -parallel with the other, and the action on the plunger will then depend -on the relative currents passing through the coils. - - -Coil, Choking. -A coil of high self-induction, used to resist the intensity of or -"choke" alternating currents. Any coil of insulated wire wound around -upon a laminated or divided iron core forms a choking coil. The iron -coil is usually so shaped as to afford a closed magnetic circuit. - -A converter or transformer acts as a choking coil as long as its -secondary is left open. In alternating current work special choking -coils are used. Thus for theatrical work, a choking coil with a movable -iron core is used to change the intensity of the lights. It is in -circuit with the lamp leads. By thrusting in the core the self-induction -is increased and the current diminishes, lowering the lamps; by -withdrawing it the self-induction diminishes, and the current increases. -Thus the lamps can be made to gradually vary in illuminating power like -gas lights, when turned up or down. - -Synonyms--Kicking Coil--Reaction Coil. - - -Fig. 97. DIFFERENTIAL COILS AND PLUNGERS. - - -Fig. 98. BISECTED COILS. - - -133 STANDARD ELECTRICAL DICTIONARY. - - -Coils, Bisected. -Resistance coils with connections at their centers, as shown in the -diagram. They are used for comparing the resistances of two conductors. -The connections are arranged as shown in the coil, each coil being -bisected. For the wires, movable knife-edge contacts are employed. The -principle of the Wheatstone bridge is used in the method and -calculations. - - -Coil, Earth. -A coil of wire mounted with commutator to be rotated so as to cut the -lines of force of the earth's magnetic field, thereby generating -potential difference. The axis of rotation may be horizontal, when the -potential will be due to the vertical component of the earth's field, or -the axis may be horizontal, when the potential will be due to the -vertical component, or it may be set at an intermediate angle. - -Synonym--Delezenne's Circle. - - -Fig. 99. DELEZENNE'S CIRCLE OR EARTH COIL. - - -Coil, Electric. -A coil of wire used to establish a magnetic field by passing a current -through it. The wire is either insulated, or so spaced that its -convolutions do not touch. - - -Coil, Flat. -A coil whose windings all lie in one plane, making a sort of disc, or an -incomplete or perforated disc. - - -Coil, Induction. -A coil in which by mutual induction the electromotive force of a portion -of a circuit is made to produce higher or lower electro-motive force, in -an adjoining circuit, or in a circuit, part of which adjoins the -original circuit, or adjoins part of it. - -An induction coil comprises three principal parts, the core, the primary -coil and the secondary coil. If it is to be operated by a steady -current, means must be provided for varying it or opening and closing -the primary circuit. A typical coil will be described. - - -134 STANDARD ELECTRICAL DICTIONARY. - - -The core is a mass of soft iron preferably divided to prevent extensive -Foucault currents. A cylindrical bundle of soft iron wires is generally -used. Upon this the primary coil of reasonably heavy wire, and of one or -two layers in depth, is wrapped, all being carefully insulated with -shellac and paper where necessary. The secondary coil is wrapped upon or -over the primary. It consists of very fine wire; No. 30 to 36 is about -the ordinary range. A great many turns of this are made. In general -terms the electro-motive force developed by the secondary stands to that -of the primary terminals in the ratio of the windings. This is only -approximate. - -The greatest care is required in the insulating. The secondary is -sometimes wound in sections so as to keep those parts differing greatly -in potential far from each other. This prevents sparking, which would -destroy the insulation. - -A make and break, often of the hammer and anvil type, is operated by the -coil. (See Circuit Breaker, Automatic.) As the current passes through -the primary it magnetizes the core. This attracts a little hammer which -normally resting on an anvil completes the circuit. The hammer as -attracted is lifted from the anvil and breaks the circuit. The soft iron -core at once parts with its magnetism and the hammer falls upon the -anvil again completing the circuit. This operation goes on rapidly, the -circuit being opened and closed in quick succession. - -Every closing of the primary circuit tends to produce a reverse current -in the secondary, and every opening of the primary circuit tends to -produce a direct current in the secondary. Both are of extremely short -duration, and the potential difference of the two terminals of the -secondary may be very high if there are many times more turns in the -secondary than in the primary. - -The extra currents interfere with the action of an induction coil. To -avoid their interference a condenser is used. This consists of two -series of sheets of tin foil. Leaves of paper alternate with the sheets -of tin-foil, the whole being built up into a little book. Each sheet of -tin-foil connects electrically with the sheet next but one to it. Thus -each leaf of a set is in connection with all others of the same set, but -is insulated from the others. One set of leaves of tin-foil connects -with the hammer, the other with the anvil. In large coils there may be -75 square feet of tin-foil in the condenser. - -The action of the condenser is to dispose of the direct extra current. -When the primary circuit is opened this current passes into the -condenser, which at once discharges itself in the other direction -through the coil. This demagnetizes the core, and the action intensifies -and shortens the induced current. The condenser prevents sparking, and -in general improves the action of the coil. - -Many details enter into the construction of coils, and many variations -in their construction obtain. Thus a mercury cup into which a plunger -dips often replaces the anvil and hammer. - - -135 STANDARD ELECTRICAL DICTIONARY. - - -The induction coil produces a rapid succession of sparks, which may -spring across an interval of forty inches. The secondary generally ends -in special terminals or electrodes between which the sparking takes -place. A plate of glass, two inches in thickness, can be pierced by -them. In the great Spottiswoode coil there are 280 miles of wire in the -secondary, and the wire is about No. 36 A.W.G. - - -Fig. 100. VERTICAL SECTION OF INDUCTION COIL. - - -Fig. l01. PLAN OF INDUCTION COIL CONNECTIONS. - - -Induction coils have quite extended use in electrical work. They are -used in telephone transmitters, their primary being in circuit with the -microphone, and their secondary with the line and receiving telephone. -In electric welding, and in the alternating current system they have -extended application. In all these cases they have no automatic circuit -breaker, the actuating current being of intermittent or alternating -type. - - -136 STANDARD ELECTRICAL DICTIONARY. - - -In the cuts the general construction of an induction coil is shown. In -the sectional elevation, Fig. 100, A, is the iron core; B is the primary -of coarse wire; C is a separating tube, which may be of pasteboard; D is -the secondary of fine wire; E, E are the binding posts connected to the -secondary; H, H are the heads or standards; K, K are the terminals of -the primary; F is the vibrating contact spring; G, a standard carrying -the contact screw; J is the condenser with wires, L, M, leading to it. - -Referring to the plan, Fig. 101, H represents the primary coil; B and A -are two of the separate sheets of the condenser, each sheet with -projecting ears; G, G are the heads of the coil; the dark lines are -connections to the condenser. One set of sheets connects with the -primary coil at C, and also with the vibrating spring shown in plan and -in the elevation at F. The other set of sheets connects with the post, -carrying the contact screw. The other terminal of the primary runs to a -binding post E. F, in the plan is a binding post in connection with the -standard and contact screw. - - -Coil, Induction, Inverted. -An induction coil arranged to have a lower electro-motive force in the -secondary than in the primary. This is effected by having more -convolutions in the primary wire than in the secondary. Such coils in -practice are used with the alternating current and then do not include a -circuit breaker or condenser. They are employed in alternating current -system and in electric welding. (See Welding, Electric--Converter.) - -In the cut an inverted coil, as constructed for electric welding is -shown. In it the primary coil is marked P; the secondary, merely a bar -of metal, is marked E, with terminals S, S; the heavy coils, I, of iron -wire are the core; K is a screw for regulating the clamps; J, Z is a -second one for the same purpose, while between D and D' the heat is -produced for welding the bars, B, B', held in the clamps, C, C'. It will -be seen how great may be the difference in turns between the single -circle of heavy copper rod or bar which is the secondary of the coil, -and the long coil of wire forming the primary. - - -Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING. - - -137 STANDARD ELECTRICAL DICTIONARY. - - -Coil, Induction, Telephone. -An induction coil used in telephone circuits. It is placed in the box or -case near the transmitter. The primary is in circuit with the -microphone. The secondary is in circuit with the line and receiving -telephone. In the Bell telephone apparatus the primary of the induction -coil is wound with No. 18 to 24 A. W. G. wire to a resistance of 1/2 -ohm; the secondary, with No. 36 wire to a resistance of 80 ohms. The -Edison telephone induction coil was wound with similar wires to a -resistance of 3 to 4 ohms and of 250 ohms respectively. - - -Coil, Magnetizing. -A coil of insulated wire for making magnets; and for experimental uses; -it has a short axis and central aperture of as small size as consistent -with the diameter of the bar to be magnetized, which has to pass through -it readily. The wire may be quite heavy, 2 or 3 millimeters (.08--.12 -inch) thick, and is cemented together with carpenter's glue, or with -shellac or ethereal solution of gum copal. In use it is passed over the -bar a few times while a heavy current is going through it. It is used -for magic circles also. (See Circle, Magic.) - - -Fig. 103. MAGNETIZING COIL. - - -Coil, Resistance. -A coil constructed for the purpose of offering a certain resistance to a -steady current. This resistance may be for the purpose of carrying out -quantitative tests, as in Wheatstone bridge work (see Wheatstone's -Bridge), or simply to reduce the intensity of a current. For the first -class of work the coils are wound so as to prevent the creation of a -magnetic field. This is effected by first doubling the wire without -breaking it, and then starting at the bend the doubled wire, which is -insulated, is wound on a bobbin or otherwise until a proper resistance -is shown by actual measurement. The coils are generally contained or set -in closed boxes with ebonite tops. Blocks of brass are placed on the -top, and one end from one coil and one end from the next connect with -the same block. By inserting a plug, P, so as to connect any two blocks, -which have grooves reamed out for the purpose, the coil beneath will be -short circuited. German silver, platinoid or other alloy, q. v., is -generally the material of the wire. A great object is to have a wire -whose resistance will be unaffected by heat. - - -138 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 104. RESISTANCE COILS AND CONNECTIONS, SHOWING PLUG. - - -Coil, Rhumkorff. -The ordinary induction coil with circuit breaker, for use with original -direct and constant current, is thus termed. (See Coil, Induction.) - -Synonym--Inductorium. - - -Coil, Ribbon. -A coil made of copper ribbon wound flatwise, often into a disc-like -shape, and insulated by tape or strips of other material intervening -between the successive turns. - - -Coils, Compensating. -Extra coils on the field magnets of dynamos or motors, which coils are -in series with the armature windings for the purpose of keeping the -voltage constant. In compound wound machines the regular series-wound -coil is thus termed. In a separately excited dynamo a coil of the same -kind in circuit with the armature may be used as a compensator. - - -Coils, Henry's. -An apparatus used in repeating a classic experiment in electro-magnetic -induction, due to Prof. Henry. It consists in a number of coils, the -first and last ones single, the intermediate ones connected in pairs, -and one of one pair placed on the top of one of the next pair. On -opening or closing the circuit of an end coil the induced effect goes -through the series and is felt in the circuit of the other end coil. -Prof. Henry extended the series so as to include seven successive -inductions, sometimes called inductions of the first, second, third and -other orders. Frequently ribbon coils (see Coil, Ribbon,) are used in -these experiments. - - -Coils, Sectioned. -A device for prolonging the range of magnetic attraction. It consists of -a series of magnetizing coils traversed by an iron plunger. As it passes -through them, the current is turned off the one in the rear or passing -to the rear and turned into the next one in advance. The principle was -utilized in one of Page's electric motors about 1850, and later by -others. The port-electric railroad, q. v., utilizes the same principle. - - -139 STANDARD ELECTRICAL DICTIONARY. - - -Collecting Ring. -In some kinds of generators instead of the commutator a pair of -collecting rings of metal, insulated from the machine and from each -other, are carried on the armature shaft. A brush, q. v., presses on -each, and the circuit terminals connect to these two brushes. Such rings -are employed often on alternating current generators, where the current -does not have to be changed or commuted. Collecting rings with their -brushes are used also where a current has to be communicated to a -revolving coil or circuit as in the magnetic car wheel, the cut of which -is repeated here. The coil of wire surrounding the wheel and rotating -with it has to receive current. This it receives through the two -stationary brushes which press upon two insulated metallic rings, -surrounding the shaft. The terminals of the coil connect one to each -ring. Thus while the coil rotates it constantly receives current, the -brushes being connected to the actuating circuit. - - -Fig. 105. MAGNETIC CAR WHEEL SHOWING COLLECTING RINGS AND BRUSHES. - - -Collector. -(a) A name for the brush, q. v., in mechanical electric generators, such -as dynamos, a pair of which collectors or brushes press on the -commutator or collecting rings, and take off the current. - -(b) The pointed connections leading to the prime conductor on a static -machine for collecting the electricity; often called combs. The points -of the combs or collectors face the statically charged rotating glass -plate or cylinder of the machine. - - -Colombin. -The insulating material between the carbons in a Jablochkoff candle or -other candle of that type. Kaolin was originally used. Later a mixture -of two parts calcium sulphate (plaster of Paris) and one part barium -sulphate (barytes) was substituted. - -The colombin was three millimeters (.12 inch) wide, and two millimeters -(.08 inch) thick. (See Candle, Jablochkoff.) - - -Column, Electric. -An old name for the voltaic pile, made up of a pile of discs of copper -and zinc, with flannel discs, wet with salt solution or dilute acid, -between each pair of plates. - - -140 STANDARD ELECTRICAL DICTIONARY. - - -Comb. -A bar from which a number of teeth project, like the teeth of a comb. It -is used as a collector of electricity from the plate of a frictional or -influence electric machine; it is also used in a lightning arrester to -define a path of very high resistance but of low self-induction, for the -lightning to follow to earth. - - -Communicator. -The instrument by which telegraph signals are transmitted is sometimes -thus termed. - - -Commutator. -In general an apparatus for changing. It is used on electric current -generators, and motors, and on induction coils, and elsewhere, for -changing the direction of currents, and is of a great variety of types. - -Synonym--Commuter (but little used). - - -Fig. 106. DYNAMO OR MOTOR COMMUTATOR. - - -Commutator Bars. -The metallic segments of a dynamo or motor commutator. - - -Commutator, Flats in. -A wearing away or lowering in level of one or more metallic segments of -a commutator. They are probably due in many cases to sparking, set up by -periodic springing in the armature mounting, or by defective commutator -connections. - - -Commutator of Current Generators and Motors. -In general a cylinder, formed of alternate sections of conducting and -non-conducting material, running longitudinally or parallel with the -axis. Its place is on the shaft of the machine, so that it rotates -therewith. Two brushes, q. v., or pieces of conducting material, press -upon its surface. - - -141 STANDARD ELECTRICAL DICTIONARY. - - -As a part of electric motors and generators, its function is to collect -the currents produced by the cutting of lines of force so as to cause -them all to concur to a desired result. The cut shows the simplest form -of commutator, one with but two divisions. Its object may be to enable a -current of constant direction to be taken from a rotating armature, in -which the currents alternate or change direction once in each rotation. -It is carried by the shaft A of the armature and rotates with it. It -consists of two leaves, S S, to which the terminals of the armature are -connected. Two springs, W W, the terminals of the outer circuit, press -against the leaves. The springs which do this take off the current. It -is so placed, with reference to the springs and armature, that just as -the current changes in direction, each leaf changes from one spring to -the other. Thus the springs receive constant direction currents. The -changing action of this commutator appears in its changing the character -of the current from alternating to constant. Were two insulated -collecting rings used instead of a commutator, the current in the outer -circuit would be an alternating one. On some dynamos the commutator has -a very large number of leaves. - -Taking the Gramme ring armature, there must be as many divisions of the -commutator as there are connections to the coils. In this case the -function of the commutator is simply to lessen friction, for the brushes -could be made to take current from the coils directly outside of the -periphery of the ring. - - -Commutator, Split Ring. -A two-division commutator for a motor; it consists of two segments of -brass or copper plate, bent to arcs of a circle, and attached to an -insulating cylinder. They are mounted on the revolving spindle, which -carries the armature, and acts as a two part commutator. For an example -of its application, see Armature, Revolving, Page's. (See also Fig. -107.) - - -Fig. 107. SECTION OF SPLIT RING COMMUTATOR, WITH BRUSHES. - - -Compass. -An apparatus for utilizing the directive force of the earth upon the -magnetic needle. It consists of a circular case, within which is poised -a magnetized bar of steel. This points approximately to the north, and -is used on ships and elsewhere to constantly show the direction of the -magnetic meridian. Two general types are used. In one the needle is -mounted above a fixed "card" or dial, on which degrees or points of the -compass, q. v., are inscribed. In the other the card is attached to the -needle and rotates with it. The latter represents especially the type -known as the mariner's compass. (See Compass, Mariner's--Compass, -Spirit, and other titles under compass, also Magnetic Axis--Magnetic -Elements.) The needle in good compasses carries for a bearing at its -centre, a little agate cup, and a sharp brass pin is the point of -support. - - -Compass, Azimuth. -A compass with sights on one of its diameters; used in determining the -magnetic bearing of objects. - - -142 STANDARD ELECTRICAL DICTIONARY. - - -Compass Card. -The card in a compass; it is circular in shape, and its centre coincides -with the axis of rotation of the magnetic needle; on it are marked the -points of the compass, at the ends generally of star points. (See -Compass, Points of the.) It may be fixed, and the needle may be poised -above it, or it may be attached to the needle and rotate with it. - - -Compass, Declination. -An instrument by which the magnetic declination of any place may be -determined. It is virtually a transit instrument and compass combined, -the telescope surmounting the latter. In the instrument shown in the -cut, L is a telescope mounted by its axis, X, in raised journals with -vernier, K, and arc x, for reading its vertical angle, with level n. The -azimuth circle, Q, R, is fixed. A vernier, V is carried by the box, A, -E, and both turn with the telescope. A very light lozenge-shaped -magnetic needle, a, b, is pivoted in the exact centre of the graduated -circles, Q R, and M. The true meridian is determined by any convenient -astronomical method, and the telescope is used for the purpose. The -variation of the needle from the meridian thus determined gives the -magnetic declination. - - -FIG. 108. DECLINATION COMPASS. - - -Compass, Inclination. -A magnetic needle mounted on a horizontal axis at its centre of gravity, -so as to be free to assume the dip, or magnetic inclination, when placed -in the magnetic meridian. It moves over the face of a vertical graduated -circle, and the frame also carries a spirit level and graduated -horizontal circle. In use the frame is turned until the needle is -vertical. Then the axis of suspension of the needle is in the magnetic -meridian. The vertical circle is then turned through 90° of the horizon, -which brings the plane of rotation of the needle into the magnetic -meridian, when it assumes the inclination of the place. - - -143 STANDARD ELECTRICAL DICTIONARY. - - -Compass, Mariner's. -A compass distinguished by the card being attached to and rotating with -the needle. A mark, the "lubber's mark" of the sailors is made upon the -case. This is placed so that the line connecting it, and the axis of -rotation of the card is exactly in a plane, passing through the keel of -the ship. Thus however the ship may be going, the point of the card -under or in line with the "lubber's mark," shows how the ship is -pointing. The case of the mariner's compass is often bowl-shaped and -mounted in gimbals, a species of universal joint, so as to bc always -horizontal. (See Compass, Spirit-Gimbals.) - - -FIG. 109. MARINER'S COMPASS. - - -Compass, Points of the. -The circle of the horizon may bc and is best referred to angular -degrees. It has also been divided into thirty-two equiangular and named -points. A point is 11.25°. The names of the points are as follows: -North, North by East, North North-east, North-east by North, North-east, -North-east by East, East North-east, East by North, East, East by South, -East South-east, South-east by East, South-east, South-east by South, -South South-east, South by East, South, South by West, South South-west, -South-west by South, South-west, South-west by West, West South-west, -West by South, West, West by North, West North-west, North-west by West, -North-west, North West by North, North North-west, North by West. They -are indicated by their initials as N. N. W., North North-west, N. by W., -North by West. - - -Compass, Spirit. -A form of mariner's compass. The bowl or case is hermetically sealed and -filled with alcohol or other nonfreezing liquid. The compass card is -made with hollow compartments so as nearly to float. In this way the -friction of the pivot or point of support is greatly diminished, and the -compass is far more sensitive. - - -Compass, Surveyor's. -A species of theodolite; a telescope with collimation lines, mounted -above a compass, so as to be applicable for magnetic surveys. Its use is -to be discouraged on account of the inaccuracy and changes in -declination of the magnetic needle. - - -144 STANDARD ELECTRICAL DICTIONARY. - - -Compensating Resistances. -In using a galvanometer shunt the total resistance of the circuit is -diminished so that in some cases too much current flows through it; in -such case additional resistance, termed as above, is sometimes -introduced in series. The shunt in parallel with the galvanometer is -thus compensated for, and the experimental or trial circuit does not -take too much current. - - -Complementary Distribution. -Every distribution of electricity has somewhere a corresponding -distribution, exactly equal to it of opposite electricity; the latter is -the complimentary distribution to the first, and the first distribution -is also complimentary to it. - - -Component. -A force may always be represented diagrammatically by a straight line, -terminating in an arrow-head to indicate the direction, and of length to -represent the intensity of the force. The line may always be assumed to -represent the diagonal of a parallelogram, two of whose sides are -represented by lines starting from the base of the arrow, and of length -fixed by the condition that the original force shall be the diagonal of -the parallelogram of which they are two contiguous sides; such lines are -called components, and actually represent forces into which the original -force may always be resolved. The components can have any direction. -Thus the vertical component of a horizontal force is zero; its -horizontal component is equal to itself. Its 450 component is equal to -the square root of one-half of its square. - - -Condenser. -An appliance for storing up electrostatic charges: it is also called a -static accumulator. The telegraphic condenser consists of a box packed -full of sheets of tinfoil. Between every two sheets is a sheet of -paraffined paper, or of mica. The alternate sheets of tinfoil are -connected together, and each set has its own binding post. (See -Accumulator, Electrostatic.) - - -Condenser, Sliding. -An apparatus representing a Leyden jar whose coatings can be slid past -each other. This diminishes or increases the facing area, and -consequently in almost exactly similar ratio diminishes or increases the -capacity of the condenser. - - -Conductance. -The conducting power of a given mass of specified material of specified -shape and connections. Conductance varies in cylindrical or prismatic -conductors, inversely as the length, directly as the cross-section, and -with the conductivity of the material. Conductance is an attribute of -any specified conductor, and refers to its shape, length and other -factors. Conductivity is an attribute of any specified material without -direct reference to its shape, or other factors. - - -Conduction. -The process or act of conducting a current. - - -145 STANDARD ELECTRICAL DICTIONARY. - - -Conductivity. -The relative power of conducting the electric current possessed by -different substances. A path for the current through the ether is opened -by the presence of a body of proper quality, and this quality, probably -correlated to opacity, is termed conductivity. There is no perfect -conductor, all offer some resistance, q. v., and there is hardly any -perfect non-conductor. It is the reverse and reciprocal of resistance. - - -Conductivity, Specific. -The reciprocal of specific resistance. (See Resistance--Specific.) - - -Conductivity, Unit of. -The reciprocal of the ohm; it is a more logical unit, but has never been -generally adopted; as a name the title mho (or ohm written backwards) -has been suggested by Sir William Thomson, and provisionally adopted. - - -Conductivity, Variable. -The conductivity for electric currents of conductors varies with their -temperature, with varying magnetization, tension, torsion and -compression. - - -Conductor. -In electricity, anything that permits the passage of an electric -current. Any disturbance in the ether takes the form of waves because -the ether has restitutive force or elasticity. In a conductor, on the -other hand, this force is wanting; it opens a path through the ether and -a disturbance advances through it from end to end with a wave front, but -with no succession of waves. This advance is the beginning of what is -termed a current. It is, by some theorists, attributed to impulses given -at all points along the conductor through the surrounding ether, so that -a current is not merely due to an end thrust. If ether waves preclude a -current on account of their restitutive force, ether waves cannot be -maintained in a conductor, hence conductors should be opaque to light, -for the latter is due to ether waves. This is one of the more practical -every day facts brought out in Clerk Maxwell's electromagnetic theory of -light. The term conductor is a relative one, as except a vacuum there is -probably no substance that has not some conducting power. For relative -conducting power, tables of conductivity, q. v., should be consulted. -The metals beginning with silver are the best conductors, glass is one -of the worst. - -[Transcriber's note: See "ether" for contemporary comments on this now -discarded concept.] - - -Conductor, Anti-Induction. -A current conductor arranged to avoid induction from other lines. Many -kinds have been invented and made the subject of patents. A fair -approximation may be attained by using a through metallic circuit and -twisting the wires composing it around each other. Sometimes concentric -conductors, one a wire and the other a tube, are used, insulated, one -acting as return circuit for the other. - - -Conductor, Conical. -A prime conductor of approximately conical shape, but rounded on all -points and angles. Its potential is highest at the point. - - -146 STANDARD ELECTRICAL DICTIONARY. - - -Conductor, Imbricated. -A conductor used in dynamo armatures for avoiding eddy currents, made by -twisting together two or more strips of copper. - - -Conductor, Prime. -A body often cylindrical or spherical in shape, in any case with no -points or angles, but rounded everywhere, whose surface, if the -conductor itself is not metallic, is made conducting by tinfoil or gold -leaf pasted over it. It is supported on an insulating stand and is used -to collect or receive and retain static charges of electricity. - - -Conductors, Equivalent. -Conductors of identical resistance. The quotient of the length divided -by the product of the conductivity and cross-section must be the same in -each, if each is of uniform diameter. - - -Conjugate. adj. -Conjugate coils or conductors are coils placed in such relation that the -lines of force established by one do not pass through the coils of the -other. Hence variations of current in one produce no induced currents in -the other. - - -Connect. v. -To bring two ends of a conductor together, or to bring one end of a -conductor in connection with another, or in any way to bring about an -electrical connection. - - -Connector. -A sleeve with screws or other equivalent device for securing the ends of -wires in electrical contact. A binding-post, q. v., is an example. -Sometimes wire spring-catches are used, the general idea being a device -that enables wires to be connected or released at will without breaking -off or marring their ends. The latter troubles result from twisting -wires together. - - -Consequent Poles. -A bar magnet is often purposely or accidentally magnetized so as to have -both ends of the same polarity, and the center of opposite polarity. The -center is said to comprise two consequent poles. (See Magnet, -Anomalous.) - - -Conservation of Electricity. -As every charge of electricity has its equal and opposite charge -somewhere, near or far, more or less distributed, the sum of negative is -equal always to the sum of positive electrical charges. For this -doctrine the above title was proposed by Lippman. - - -Contact Breaker. -Any contrivance for closing a circuit, and generally for opening and -closing in quick succession. An old and primitive form consisted of a -very coarsely cut file. This was connected to one terminal, and the -other terminal was drawn over its face, making and breaking contact as -it jumped from tooth to tooth. (See Circuit Breaker--do. Automatic, -etc.--do. Wheel-do. Pendulum.) - - -147 STANDARD ELECTRICAL DICTIONARY. - - -Contact, Electric. -A contact between two conductors, such that a current can flow through -it. It may be brought about by simple touch or impact between the ends -or terminals of a circuit, sometimes called a dotting contact, or by a -sliding or rubbing of one terminal on another, or by a wheel rolling on -a surface, the wheel and surface representing the two terminals. - -There are various descriptions of contact, whose names are -self-explanatory. The term is applied to telegraph line faults also, and -under this, includes different descriptions of contact with neighboring -lines, or with the earth. - - -Contact Electricity. -When two dissimilar substances are touched they assume different -electric potentials. If conductors, their entire surfaces are affected; -if dielectrics, only the surfaces which touch each other. (See Contact -Theory.) - - -Contact Faults. -A class of faults often called contacts, due to contact of the conductor -of a circuit with another conductor. A full or metallic contact is where -practically perfect contact is established; a partial contact and -intermittent contact are self-explanatory. - - -Contact Point. -A point, pin or stud, often of platinum, arranged to come in contact -with a contact spring, q. v., or another contact point or surface, under -any determined conditions. - - -Contact Potential Difference. -The potential difference established by the contact of two dissimilar -substances according to the contact theory, q. v. - - -Contact Series. -An arrangement or tabulation of substances in pairs, each intermediate -substance appearing in two pairs, as the last member of the first, and -first member of the succeeding pair, with the statement of the potential -difference due to their contact, the positively electrified substance -coming first. The following table of some contact potentials is due to -Ayrton and Perry: -CONTACT SERIES. -Difference of Potential in Volts. -Zinc--Lead .210 -Lead--Tin .069 -Tin--Iron .313 -Iron--Copper .146 -Copper--Platinum .238 -Platinum-Carbon .113 - -The sum of these differences is 1.089, which is the contact potential -between zinc and carbon. - -Volta's Law refers to this and states that-- - The difference of potential produced by the contact of any two - substances is equal to the sum of the differences of potentials - between the intervening substances in the contact series. - -It is to be remarked that the law should no longer be restricted to or -stated only for metals. - - -148 STANDARD ELECTRICAL DICTIONARY. - - -Contact-spring. -A spring connected to one lead of an electric circuit, arranged to press -against another spring, or contact point, q. v., under any conditions -determined by the construction of the apparatus. (See Bell, -Electric--Coil, Induction.) - - -Contact Theory. -A theory devised to explain electrification, the charging of bodies by -friction, or rubbing, and the production of current by the voltaic -battery. It holds that two bodies, by mere contact become oppositely -electrified. If such contact is increased in extent by rubbing together, -the intensity of their electrification is increased. This -electrification is accounted for by the assumption of different kinetic -energy, or energy of molecular motion, possessed by the two bodies; -there being a loss and gain of energy, on the two sides respectively, -the opposite electrifications are the result. Then when separated, the -two bodies come apart oppositely electrified. - -The above accounts for the frictional production of electricity. In the -voltaic battery, a separation of the atoms of hydrogen and oxygen, and -their consolidation into molecules occurs, and to such separation and -the opposite electrification of the electrodes by the oxygen and -hydrogen, the current is attributed, because the hydrogen goes to one -electrode, and the oxygen to the other, each giving up or sharing its -own charge with the electrodes to which it goes. If zinc is touched to -copper, the zinc is positively and the copper negatively electrified. In -the separation of hydrogen and oxygen, the hydrogen is positively and -the oxygen negatively electrified. In the battery, the current is due to -the higher contact difference of oxygen and hydrogen compared to that -between zinc and copper. It will be seen that the two contact actions in -a battery work against each other, and that the current is due to a -differential contact action. The zinc in a battery is electrified -negatively because the negative electrification of the oxygen is greater -in amount than its own positive electrification due to contact with the -copper. - - -Contractures. -A muscular spasm or tetanus due to the passage of a current of -electricity; a term in electro-therapeutics. - - -Controlling Field. -The magnetic or electro-magnetic field, which is used in galvanometers -to control the magnetic needle, tending to restore it to a definite -position whenever it is turned therefrom. It may be the earth's field or -one artificially produced. - - -Controlling Force. -In galvanometers and similar instruments, the force used to bring the -needle or indicator back to zero. (See Controlling -Field--Electro-Magnetic Control--Gravity Control--Magnetic -Control--Spring Control.) - - -149 STANDARD ELECTRICAL DICTIONARY. - - -Convection, Electric. -The production of blasts or currents of air (convection streams) from -points connected to statically charged conductors. The term is sometimes -applied to electric convection of heat. (See Convection of Heat, -Electric.) - - -Convection, Electrolytic. -The resistance of acidulated water as a true conductor is known to be -very, almost immeasurably, high. As an electrolytic, its resistance is -very much lower. Hence the current produced between immersed electrodes -is theoretically almost null, unless the difference of potential between -them is high enough to decompose the liquid. Yet a feeble current too -great for a true conduction current is sometimes observed when two -electrodes with potential difference too low to cause decomposition are -immersed in it. Such a current is termed an electrolytic convection -current. It is supposed to be due to various causes. Some attribute it -to the presence of free oxygen from the air, dissolved in the water with -which the hydrogen combines. Others attribute it to the diffusion of the -gases of decomposition in the solution; others assume a partial -polarization of the molecules without decomposition. Other theories are -given, all of which are unsatisfactory. The term is due to Helmholtz. - - -Convection of Heat, Electric. -The effect of a current upon the distribution of heat in an unevenly -heated conductor. In some, such as copper, the current tends to equalize -the varying temperatures; the convection is then said to be positive, as -comparable to that of water flowing through an unequally heated tube. In -others, such as platinum or iron, it is negative, making the heated -parts hotter, and the cooler parts relatively cooler. - -The effect of the electric current in affecting the distribution of heat -in unequally heated metal (Thomson's effect. q. v.), is sometimes so -termed. If a current passes through unequally heated iron it tends to -increase the difference of temperature, and the convection is negative; -in copper it tends to equalize the temperature, and the convection is -positive. - - -Converter. -An induction coil used with the alternating current for changing -potential difference and inversely therewith the available current. They -generally lower the potential, and increase the current, and are placed -between the primary high potential system that connects the houses with -the central station, and the secondary low potential system within the -houses. A converter consists of a core of thin iron sheets, wound with a -fine primary coil of many convolutions, and a coarse secondary coil of -few convolutions. The ratio of convolutions gives the ratio of maximum -potential differences of their terminals between the primary and -secondary coils. The coil may be jacketed with iron to increase the -permeance. (See Alternating Current System.) - - -Fig. 110. FERRANTI'S CONVERTER OR TRANSFORMER. - - -Fig. 111. SWINBURNE'S HEDGEHOG TRANSFORMER. - - -150 STANDARD ELECTRICAL DICTIONARY. - - -Co-ordinates, System of. -A system for indicating the position of points in space by reference to -fixed lines, intersecting at a determined and arbitrary point 0, termed -the origin of co-ordinates. In plane rectangular co-ordinates two lines -are drawn through the origin, one horizontal, termed the axis of -abscissas, or axis of X. All distances measured parallel to it, if -unknown, are indicated by x, and are termed abscissas. The other axis is -vertical, and is termed the axis of ordinates, or axis of Y. All -distances measured parallel to it, if unknown, are indicated by y and -are termed ordinates. Thus by naming its abscissa and ordinate a point -has its position with reference to the axes determined, and by -indicating the relation between a point, line or curve, and a system of -abscissas and ordinates, the properties of a line or curve can be -expressed algebraically. Co-ordinates may also be inclined to each other -at any other angles, forming oblique co-ordinates; relations may be -expressed partly in angles referred to the origin as a centre, giving -polar co-ordinates. For solid geometry or calculations in three -dimensions, a third axis, or axis of Z, is used, distances parallel to -which if unknown are indicated by z. - - -Fig. 112. AXES OF CO-ORDINATES. - - -151 STANDARD ELECTRICAL DICTIONARY. - - -Cooling Box. -In a hydroelectric machine, q. v., a conduit or chest through which the -steam passes on its way to the nozzles. Its object is to partially -condense the steam so as to charge it with water vesicles whose friction -against the sides of the nozzles produces the electrification . - - -152 STANDARD ELECTRICAL DICTIONARY. - - -Copper. -A metal; one of the elements. Symbol, Cu; atomic weight, 63.5; -equivalent, 63.5 and 31.75; valency, 1 and 2; specific gravity, 8.96. -It is a conductor of electricity, whose conductivity is liable to -vary greatly on account of impurities. - - Annealed. Hard drawn. -Relative resistance (Silver = 1), 1.063 1.086 -Specific resistance, 1.598 1.634 microhms. - -Resistance of a wire at 0° C. (32° F.), - Annealed. Hard Drawn. -(a) 1 foot long, weighing 1 grain, .2041 ohms .2083 ohms. -(b) 1 foot long, 1/1000 inch thick, 9.612 " 9.831 " -(c) 1 meter long, weighing 1 gram, .1424 " .1453 " -(d) 1 meter long, 1 millimeter thick, .02034 " .02081 " - - microhm. microhm. -Resistance of 1 inch cube at 0°C. (32° F.) .6292 .6433 - -Percentage of resistance change, -per 1° C. (1.8° F.) at about 20° C. (68° F.) = 0.388 per cent. - -Electro-chemical Equivalent (Hydrogen = .0105) Cuprous .6667 - Cupric .3334 - -In electricity it has been very extensively used as the negative plate -of voltaic batteries. It has its most extensive application as -conductors for all classes of electrical leads. - - -Copper Bath. -A solution of copper used for depositing the metal in the electroplating -process. For some metals, such as zinc or iron, which decompose copper -sulphate solution, special baths have to be used. - -The regular bath for copper plating is the following: - -To water acidulated with 8 to 10 percent. of sulphuric acid as much -copper sulphate is added as it will take up at the ordinary temperature. -The saturated bath should have a density of 1.21. It is used cold and is -kept in condition by the use of copper anodes, or fresh crystals may be -added from time to time. - -For deposition on zinc, iron, tin and other metals more electropositive -than copper, the following baths may be used, expressed in parts by -weight: - - Tin - Iron and Steel. Cast Iron - Cold Hot. and Zinc. Zinc. -Sodium Bisulphate, 500 200 300 100 -Potassium Cyanide, 500 700 500 700 -Sodium Carbonate, 1000 500 --- --- -Copper Acetate, 475 500 350 450 -Aqua Ammoniae, 350 300 200 150 -Water, 2500 2500 2500 2500 - -These are due to Roseleur. - - -153 STANDARD ELECTRICAL DICTIONARY. - - -Copper Stripping Bath. -There is generally no object in stripping copper from objects. It can be -done with any of the regular copper baths using the objects to be -stripped as anode. The danger of dissolving the base itself and thereby -injuring the article and spoiling the bath is obvious. - - -Cord Adjuster. -A device for shortening or lengthening the flexible cord, or flexible -wire supplying the current, and by which an incandescent lamp is -suspended. It often is merely a little block of wood perforated with two -holes through which the wires pass, and in which they are retained in -any desired position by friction and their own stiffness. - - -Fig. 113. FLEXIBLE CORD ADJUSTER. - - -Cord, Flexible. -A pair of flexible wire conductors, insulated lightly, twisted together -and forming apparently a cord. They are used for minor services, such as -single lamps and the like, and are designated according to the service -they perform, such as battery cords, dental cords (for supplying dental -apparatus) and other titles. - - -Core. -(a) The conductor or conductors of an electric cable. (See Cable Core.) - -(b) The iron mass, generally central in an electro-magnet or armature, -around which the wire is coiled. It acts by its high permeance to -concentrate or multiply the lines of force, thus maintaining a more -intense field. (See Armature--Magnet, Electro--Magnet, Field--Core, -Laminated). In converters or transformers (See Converter) it often -surrounds the wire coils. - - -Core-discs. -Discs of thin wire, for building up armature cores. (See Laminated -Core.) The usual form of core is a cylinder. A number of thin discs of -iron are strung upon the central shaft and pressed firmly together by -end nuts or keys. This arrangement, it will be seen, gives a cylinder as -basis for winding the wire on. - - -Core-discs, Pierced. -Core-discs for an armature of dynamo or motor, which are pierced around -the periphery. Tubes of insulating material pass through the peripheral -holes, and through these the conductors or windings are carried. The -conductors are thus embedded in a mass of iron and are protected from -eddy currents, and they act to reduce the reluctance of the air gaps. -From a mechanical point of view they are very good. For voltages over -100 they are not advised. - -Synonym--Perforated Core-discs. - - -154 STANDARD ELECTRICAL DICTIONARY. - - -Core-discs, Segmental. -Core-discs made in segments, which are bolted together to form a -complete disc or section of the core. The plan is adopted principally on -large cores. The discs thus made up are placed together to form the core -exactly as in the case of ordinary one piece discs. - - -Fig. 114. PIERCED OR PERFORATED CORE-DISC. - - -Core-discs, Toothed. -Core-discs of an armature of a dynamo or motor, which discs are cut into -notches on the periphery. These are put together to form the armature -core, with the notches corresponding so as to form a series of grooves -in which the wire winding is laid. This construction reduces the actual -air-gaps, and keeps the wires evenly spaced. Distance-pieces of -box-wood, m, m, are sometimes used to lead the wires at the ends of the -armature. - - -Fig. 115. TOOTHED CORE-DISC. - - -Core, Laminated. -A core of an armature, induction coil or converter or other similar -construction, which is made up of plates insulated more or less -perfectly from each other. The object of lamination is to prevent the -formation of Foucault currents. (See Currents, Foucault.) As insulation, -thin shellacked paper may be used, or sometimes the superficial -oxidation of the plates alone is relied on. The plates, in general, are -laid perpendicular to the principal convolutions of the wire, or -parallel to the lines of force. The object is to break up currents, and -such currents are induced by the variation in intensity of the field of -force, and their direction is perpendicular to the lines of force, or -parallel to the inducing conductors. - -A core built up of core discs is sometimes termed a tangentially -laminated core. Made up of ribbon or wire wound coil fashion, it is -termed a radially laminated core. - - -155 STANDARD ELECTRICAL DICTIONARY. - - -Core Ratio. -In a telegraph cable the ratio existing between the diameter of the -conducting core and the insulator. To get a ratio approximately accurate -in practical calculations, the diameter of the core is taken at 5 per -cent. less than its actual diameter. The calculations are those -referring to the electric constants of the cable, such as its static -capacity and insulation resistance. - - -Core, Ribbon. -For discoidal ring-shaped cores of armatures, iron ribbon is often used -to secure lamination and prevent Foucault currents. - -Synonym--Tangentially Laminated Core. - - -Core, Ring. -A core for a dynamo or motor armature, which core forms a complete ring. - - -Core, Stranded. -In an electric light cable, a conducting core made up of a group of -wires laid or twisted together. - - -Core, Tubular. -Tubes used as cores for electro-magnets. For very small magnetizing -power, tubular cores are nearly as efficient as solid ones in straight -magnets, because the principal reluctance is due to the air-path. On -increasing the magnetization the tubular core becomes less efficient -than the solid core, as the reluctance of the air-path becomes -proportionately of less importance in the circuit. - - -Corpusants. -The sailors' name for St. Elmo's Fire, q. v. - - -Coulomb. -The practical unit of quantity of electricity. It is the quantity passed -by a current of one ampere intensity in one second. It is equal to 1/10 -the C. G. S. electro-magnetic unit of quantity, and to 3,000,000,000 C. -G. S. electrostatic units of quantity. It corresponds to the -decomposition of .0935 milligrams of water, or to the deposition of -1.11815 milligrams of silver. - -[Transcriber's note: A coulomb is approximately 6.241E18 electrons. Two -point charges of one coulomb each, one meter apart, exerts a force of -900,000 metric tons.] - - -Coulomb's Laws of Electrostatic Attraction and Repulsion. -1. The repulsions or attractions between two electrified bodies are in -the inverse ratio of the squares of their distance. - -2. The distance remaining the same, the force of attraction or repulsion -between two electrified bodies is directly as the product of the -quantities of electricity with which they are charged. - - -156 STANDARD ELECTRICAL DICTIONARY. - - -Counter, Electric. -A device for registering electrically, or by electro-magnetic machinery, -the revolutions of shafts, or any other data or factors. - - -Counter-electro-motive Force. -A potential difference in a circuit opposed to the main potential -difference, and hence, resisting the operation of the latter, and -diminishing the current which would be produced without it. It appears -in electric motors, which, to a certain extent, operate as dynamos and -reduce the effective electro-motive force that operates them. It -appears in the primary coils of induction coils, and when the secondary -circuit is open, is almost equal to the main electro-motive force, so -that hardly any current can go through them under such conditions. It -appears in galvanic batteries, when hydrogen accumulates on the copper -plate, and in other chemical reactions. A secondary battery is charged -by a current in the reverse direction to that which it would normally -produce. Its own potential difference then appears as a -counter-electro-motive force. - -Synonym--Back Electro-motive Force. - - -Counter-electro-motive Force of Polarization. -To decompose a solution by electrolysis, enough electro-motive force is -required to overcome the energy of composition of the molecule -decomposed. A part of this takes the form of a counter-electromotive -force, one which, for a greater or less time would maintain a current in -the opposite direction if the original source of current were removed. -Thus in the decomposition of water, the electrodes become covered, one -with bubbles of oxygen, the others with bubbles of hydrogen; this -creates a counter E. M. F. of polarization. In a secondary battery, the -working current may be defined as due to this cause. - -Synonym--Back Electro-motive Force of Polarization. - - -Couple. -Two forces applied to different points of a straight line, when opposed -in direction or unequal in amount, tend to cause rotation about a point -intermediate between their points of application and lying on the -straight line. Such a pair constitute a couple. - - -Couple, Voltaic or Galvanic. -The combination of two electrodes, and a liquid or liquids, the -electrodes being immersed therein, and being acted on differentially by -the liquid or liquids. The combination constitutes a source of -electro-motive force and consequently of current. It is the galvanic or -voltaic cell or battery. (See Battery, Voltaic--Contact -Theory--Electro-motive Force--Electro-motive Series.) - - -Coupling. -The joining of cells of a galvanic battery, of dynamos or of other -devices, so as to produce different effects as desired. - - -157 STANDARD ELECTRICAL DICTIONARY - - -Couple, Astatic. -An astatic couple is a term sometimes applied to astatic needles, q.v. - - -C. P. -(a) An abbreviation of or symbol for candle power, q. v. - -(b) An abbreviation of chemically pure. It is used to indicate a high -degree of purity of chemicals. Thus, in a standard Daniell battery, the -use of C. P. chemicals may be prescribed or advised. - - -Crater. -The depression that forms in the positive carbon of a voltaic arc. (See -Arc, Voltaic.) - - -Creeping. -A phenomenon of capillarity, often annoying in battery jars. The -solution, by capillarity, rises a little distance up the sides, -evaporates, and as it dries more creeps up through it, and to a point a -little above it. This action is repeated until a layer of the salts may -form over the top of the vessel. To avoid it, paraffine is often applied -to the edges of the cup, or a layer of oil, often linseed oil, is poured -on the battery solution, - - -Crith. -The weight of a litre of hydrogen at 0º C. (32º F.), and 760 mm. (30 -inches) barometric pressure. It is .0896 grams. The molecular weight of -any gas divided by 2 and multiplied by the value of the crith, gives the -weight of a litre of the gas in question. Thus a litre of electrolytic -gas, a mixture of two molecules of hydrogen for one of oxygen, with a -mean molecular weight of 12, weighs (12/2) * .0896 or .5376 gram. - - -Critical Speed. -(a) The speed of rotation at which a series dynamo begins to excite its -own field. - -(b) In a compound wound dynamo, the speed at which the same potential is -generated with the full load being taken from the machine, as would be -generated on open circuit, in which case the shunt coil is the only -exciter. The speed at which the dynamo is self-regulating. - -(c) In a dynamo the rate of speed when a small change in the speed of -rotation produces a comparatively great change in the electro-motive -force. It corresponds to the same current (the critical current) in any -given series dynamo. - - -Cross. -(a) A contact between two electric conductors; qualified to express -conditions as a weather cross, due to rain, a swinging cross when a wire -swings against another, etc. - -(b) vb. To make such contact. - - -Cross-Connecting Board. -A special switch board used in telephone exchanges and central telegraph -offices. Its function is, by plugs and wires, to connect the line wires -with any desired section of the main switchboard. The terminals of the -lines as they enter the building are connected directly to the -cross-connecting board. - - -158 STANDARD ELECTRICAL DICTIONARY. - - -Cross Connection. -A method of disposing of the effects of induction from neighboring -circuits by alternately crossing the two wires of a metallic telephone -circuit, so that for equal intervals they lie to right and left, or one -above, and one below. - -[Transcriber's note: Also used to cancel the effect of variations in the -ambient magnetic field, such as solar activity.] - - -Crossing Wires. -The cutting out of a defective section in a telegraph line, by carrying -two wires from each side of the defective section across to a -neighboring conductor, pressing it for the time into service and cutting -the other wire if necessary. - - -Cross-magnetizing Effect. -A phase of armature interference. The current in an armature of a dynamo -or motor is such as to develop lines of force approximately at right -angles to those of the field. The net cross-magnetizing effect is such -component of these lines, as is at right angles to the lines produced by -the field alone. - - -Cross-over Block. -A piece of porcelain or other material shaped to receive two wires which -are to cross each other, and hold them so that they cannot come in -contact. It is used in wiring buildings, and similar purposes. (See -Cleat, Crossing.) - -Cross Talk. -On telephone circuits by induction or by contact with other wires sound -effects of talking are sometimes received from other circuits; such -effects are termed cross talk. - - -Crucible, Electric. -A crucible for melting difficultly fusible substances, or for reducing -ores, etc., by the electric arc produced within it. Sometimes the -heating is due more to current incandescence than to the action of an -arc. - - -Fig. 116. ELECTRIC FURNACE OR CRUCIBLE. - - -Crystallization, Electric. -Many substances under proper conditions take a crystalline form. The -great condition is the passage from the fluid into the solid state. When -such is brought about by electricity in any way, the term electric -crystallization may be applied to the phenomenon. A solution of silver -nitrate for instance, decomposed by a current, may give crystals of -metallic silver. - - -159 STANDARD ELECTRICAL DICTIONARY. - - -Cup, Porous. -A cup used in two-fluid voltaic batteries to keep the solutions separate -to some extent. It forms a diaphragm through which diffusion inevitably -takes place, but which is considerably retarded, while electrolysis and -electrolytic convection take place freely through its walls. As -material, unglazed pottery is very generally used. - -In some batteries the cup is merely a receptacle for the solid -depolarizer. Thus, in the Leclanché battery, the cup contains the -manganese dioxide and graphite in which the carbon electrode is -embedded, but does not separate two solutions, as the battery only uses -one. Nevertheless, the composition of the solution outside and inside -may vary, but such variation is incidental only, and not an essential of -the operation. - - -Current. -The adjustment, or effects of a continuous attempt at readjustment of -potential difference by a conductor, q. v., connecting two points of -different potential. A charged particle or body placed in a field of -force tends to move toward the oppositely charged end or portion of the -field. If a series of conducting particles or a conducting body are held -so as to be unable to move, then the charge of the field tends, as it -were, to move through it, and a current results. It is really a -redistribution of the field and as long as such redistribution continues -a current exists. A current is assumed to flow from a positive to a -negative terminal; as in the case of a battery, the current in the outer -circuit is assumed to flow from the carbon to the zinc plate, and in the -solution to continue from zinc to carbon. As a memoria technica the zinc -may be thought of as generating the current delivering it through the -solution to the carbon, whence it flows through the wire connecting -them. (See Ohm's Law--Maxwell's Theory of Light--Conductor-Intensity.) - -[Transcriber's note: Supposing electric current to be the motion of -positive charge causes no practical difficulty, but the current is -actually the (slight) motion of negative electrons.] - - -Current, After. -A current produced by the animal tissue after it has been subjected to a -current in the opposite direction for some time. The tissue acts like a -secondary battery. The term is used in electro-therapeutics. - - -Current, Alternating. -Usually defined and spoken of as a current flowing alternately in -opposite directions. It may be considered as a succession of currents, -each of short duration and of direction opposite to that of its -predecessor. It is graphically represented by such a curve as shown in -the cut. The horizontal line may denote a zero current, that is no -current at all, or may be taken to indicate zero electro-motive force. -The curve represents the current, or the corresponding electro-motive -forces. The further from the horizontal line the greater is either, and -if above the line the direction is opposite to that corresponding to the -positions below the line. Thus the current is alternately in opposite -directions, has periods of maximum intensity, first in one and then in -the opposite sense, and between these, passing from one direction to the -other, is of zero intensity. It is obvious that the current may rise -quickly in intensity and fall slowly, or the reverse, or may rise and -fall irregularly. All such phases may be shown by the curve, and a curve -drawn to correctly represent these variations is called the -characteristic curve of such current. It is immaterial whether the -ordinates of the curve be taken as representing current strength or -electromotive force. If interpreted as representing electro-motive -force, the usual interpretation and best, the ordinates above the line -are taken as positive and those below as negative. - -Synonyms--Reversed Current--Periodic Currents. - - -Fig. 117. CHARACTERISTIC CURVE OF ALTERNATING CURRENT. - - -160 STANDARD ELECTRICAL DICTIONARY. - - -Current, Atomic. -A unit of current strength used in Germany; the strength of a current -which will liberate in 24 hours (86,400 seconds) one gram of hydrogen -gas, in a water voltameter. The atomic current is equal to 1.111 -amperes. In telegraphic work the milliatom is used as a unit, comparable -to the milliampere. The latter is now displacing it. - - -Current, Charge. -If the external coatings of a charged and uncharged jar are placed in -connection, and if the inner coatings are now connected, after -separating them they are both found to be charged in the same manner. In -this process a current has been produced between the outside coatings -and one between the inner ones, to which Dove has given the name Charge -Current, and which has all the properties of the ordinary discharge -current. (Ganot.) - - -Current, Circular. -A current passing through a circular conductor; a current whose path is -in the shape of a circle. - - -Current, Commuted. -A current changed, as regards direction or directions, by a commutator, -q. v., or its equivalent. - - -Current, Constant. -An unvarying current. A constant current system is one maintaining such -a current. In electric series, incandescent lighting, a constant current -is employed, and the system is termed as above. In arc lighting systems, -the constant current series arrangement is almost universal. - - -161 STANDARD ELECTRICAL DICTIONARY. - - -Current, Continuous. -A current of one direction only; the reverse of an alternating current. -(See Current, Alternating.) - - -Current, Critical. -The current produced by a dynamo at its critical speed; at that speed -when a slight difference in speed produces a great difference in -electro-motive force. On the characteristic curve it corresponds to the -point where the curve bends sharply, and where the electro-motive force -is about two-thirds its maximum. - - -Current, Daniell/U.S. , Daniell/Siemens' Unit. -A unit of current strength used in Germany. It is the strength of a -current produced by one Daniell cell in a circuit of the resistance of -one Siemens' unit. The current deposits 1.38 grams of copper per hour. -It is equal to 1.16 amperes. - - -Current, Demarcation. -In electro-therapeutics, a current which can be taken from an injured -muscle, the injured portion acting electro-negatively toward the -uninjured portion. - - -Current Density. -The current intensity per unit of cross-sectional area of the conductor. -The expression is more generally used for electrolytic conduction, where -the current-density is referred to the mean facing areas of the -electrodes, or else to the facing area of the cathode only. - -The quality of the deposited metal is intimately related to the current -density. (See Burning.) - - Proper Current Density for Electroplating - Amperes Per Square Foot of Cathode.--(Urquhart.) -Copper, Acid Bath. 5.0 to 10.0 -" Cyanide Bath, 3.0 " 5.0 -Silver, Double Cyanide, 2.0 " 5.0 -Gold, Chloride dissolved in Potassium Cyanide, 1.0 " 2.0 -Nickel, Double Sulphate, 6.6 " 8.0 -Brass, Cyanide, 2.0 " 3.0 - - -Current, Diacritical. -A current, which, passing through a helix surrounding an iron core, -brings it to one-half its magnetic saturation, q. v. - - -Current, Diaphragm. -If a liquid is forced through a diaphragm, a potential difference -between the liquid on opposite sides of the diaphragm is maintained. -Electrodes or terminals of platinum may be immersed in the liquid, and a -continuous current, termed a diaphragm current, may be taken as long as -the liquid is forced through the diaphragm. The potential difference is -proportional to the pressure, and also depends on the nature of the -diaphragm and on the liquid. - - -162 STANDARD ELECTRICAL DICTIONARY. - - -Current, Direct. -A current of unvarying direction, as distinguished from an alternating -current. It may be pulsatory or intermittent in character, but must be -of constant direction. - - -Current, Direct Induced. -On breaking a circuit, if it is susceptible of exercising -self-induction, q. v., an extra current, in the direction of the -original is induced, which is called "direct" because in the same -direction as the original. The same is produced by a current in one -circuit upon a parallel one altogether separated from it. (See -Induction, Electro-Magnetic-Current, Extra.) - -Synonym--Break Induced Current. - - -Current, Direction of. -The assumed direction of a current is from positively charged electrode -to negatively charged one; in a galvanic battery from the carbon or -copper plate through the outer circuit to the zinc plate and back -through the electrolyte to the carbon or copper plate. (See Current.) - -[Transcriber's note: Current is caused by the motion of negative -electrons, from the negative pole to the positive. The electron was -discovered five years after this publication.] - - -Current, Displacement. -The movement or current of electricity taking place in a dielectric -during displacement. It is theoretical only and can only be assumed to -be of infinitely short duration. (See Displacement, Electric.) - - -Currents, Eddy Displacement. -The analogues of Foucault currents, hypothetically produced in the mass -of a dielectric by the separation of the electricity or by its -electrification. (See Displacement.) - - -Current, Extra. -When a circuit is suddenly opened or closed a current of very brief -duration, in the first case in the same direction, in the other case in -the opposite direction, is produced, which exceeds the ordinary current -in intensity. A high potential difference is produced for an instant -only. These are called extra currents. As they are produced by -electro-magnetic induction, anything which strengthens the field of -force increases the potential difference to which they are due. Thus the -wire may be wound in a coil around an iron core, in which case the extra -currents may be very strong. (See Induction, Self-Coil, Spark.) - - -Current, Faradic. -A term in medical electricity for the induced or secondary alternating -current, produced by comparatively high electro-motive force, such as -given by an induction coil or magneto-generator, as distinguished from -the regular battery current. - - -163 STANDARD ELECTRICAL DICTIONARY. - - -Current, Foucault. -A current produced in solid conductors, and which is converted into heat -(Ganot). These currents are produced by moving the conductors through a -field, or by altering the strength of a field in which they are -contained. They are the source of much loss of energy and other -derangement in dynamos and motors, and to avoid them the armature cores -are laminated, the plane of the laminations being parallel to the lines -of force. (See Core, Laminated.) - -The presence of Foucault currents, if of long duration, is shown by the -heating of the metal in which they are produced. In dynamo armatures -they are produced sometimes in the metal of the windings, especially if -the latter are of large diameter. - -Synonyms--Eddy Currents--Local Currents--Parasitical Currents. - - -Current, Franklinic. -In electro-therapeutics the current produced by a frictional electric -machine. - - -Current, Induced. -The current produced in a conductor by varying the conditions of a field -of force in which it is placed; a current produced by induction. - - -Current Induction. -Induction by one current on another or by a portion of a current on -another portion of itself. (See Induction.) - - -Current Intensity. -Current strength, dependent on or defined by the quantity of electricity -passed by such current in a given time. The practical unit of current -intensity is the ampere, equal to one coulomb of quantity per second of -time. - - -Current, Inverse Induced. -The current induced in a conductor, when in a parallel conductor or in -one having a parallel component a current is started, or is increased in -strength. It is opposite in direction to the inducing current and hence -is termed inverse. (See Induction, Electro-magnetic.) The parallel -conductors may be in one circuit or in two separate circuits. - -Synonyms--Make-induced Current--Reverse-induced Current. - - -Current, Jacobi's Unit of. -A current which will liberate one cubic centimeter of mixed gases -(hydrogen and oxygen) in a water voltameter per minute, the gases being -measured at 0º C. (32º F.) and 760 mm. (29.92 inches) barometric -pressure. It is equal to .0961 ampere. - - -Current, Joint. -The current given by several sources acting together. Properly, it -should be restricted to sources connected in series, thus if two battery -cells are connected in series the current they maintain is their joint -current. - - -Current, Linear. -A current passing through a straight conductor; a current whose path -follows a straight line. - - -164 STANDARD ELECTRICAL DICTIONARY. - - -Current, Make and Break. -A succession of currents of short duration, separated by absolute -cessation of current. Such current is produced by a telegraph key, or by -a microphone badly adjusted, so that the circuit is broken at intervals. -The U. S. Courts have virtually decided that the telephone operates by -the undulatory currents, and not by a make and break current. Many -attempts have been made to produce a telephone operating by a -demonstrable make and break current, on account of the above -distinction, in hopes of producing a telephone outside of the scope of -the Bell telephone patent. - -[Transcriber's note: Contemporary long distance telephone service is -digital, as this item describes.] - - -Current-meter. -An apparatus for indicating the strength of current. (See Ammeter.) - - -Current, Negative. -In the single needle telegraph system the current which deflects the -needle to the left. - - -Current, Nerve and Muscle. -A current of electricity yielded by nerves or muscles. Under proper -conditions feeble currents can be taken from nerves, as the same can be -taken from muscles. - - -Current, Opposed. -The current given by two or more sources connected in opposition to each -other. Thus a two volt and a one volt battery may be connected in -opposition, giving a net voltage of only one volt, and a current due to -such net voltage. - - -Current, Partial. -A divided or branch current. A current which goes through a single -conductor to a point where one or more other conductors join it in -parallel, and then divides itself between the several conductors, which -must join further on, produces partial currents. It produces as many -partial currents as the conductors among which it divides. The point of -division is termed the point of derivation. - -Synonym--Derived Current. - - -Current, Polarizing. -In electro-therapeutics, a constant current. - - -Current, Positive. -In the single needle telegraph system the current which deflects the -needle to the right. - - -Current, Pulsatory. -A current of constant direction, but whose strength is constantly -varying, so that it is a series of pulsations of current instead of a -steady flow. - -Current, Rectified. -A typical alternating current is represented by a sine curve, whose -undulations extend above and below the zero line. If by a simple two -member commutator the currents are caused to go in one direction, in -place of the sine curve a series of short convex curves following one -another and all the same side of the zero line results. The currents all -in the same direction, become what is known as a pulsating current. - -Synonym--Redressed Current. - - -165 STANDARD ELECTRICAL DICTIONARY. - - -Current, Rectilinear. -A current flowing through a rectilinear conductor. The action of -currents depending on their distance from the points where they act, -their contour is a controlling factor. This contour is determined by the -conductors through which they flow. - - -Current Reverser. -A switch or other contrivance for reversing the direction of a -current in a conductor. - - -Currents, Ampérian. -The currents of electricity assumed by Ampere's theory to circulate -around a magnet. As they represent the maintenance of a current or of -currents without the expenditure of energy they are often assumed to be -of molecular dimensions. As they all go in the same sense of rotation -and are parallel to each other the result is the same as if a single set -of currents circulated around the body of the magnet. More will be found -on this subject under Magnetism. The Ampérian currents are purely -hypothetical and are predicated on the existence of a field of force -about a permanent magnet. (See Magnetism, Ampére's Theory of.) - -If the observer faces the north pole of a magnet the Ampérian currents -are assumed to go in the direction opposite to that of a watch, and the -reverse for the south pole. - - -Figs. 118-119 DIRECTION OF AMPÉRIAN CURRENTS. - - -Currents, Angular. -Currents passing through conductors which form an angle with each other. - - -Currents, Angular, Laws of. -1. Two rectilinear currents, the directions of which form an angle with -each other, attract one another when both approach to or recede from the -apex of the angle. - -2. They repel one another, if one approaches and the other recedes from -the apex of the angle. - - -166 STANDARD ELECTRICAL DICTIONARY - - -Currents, Earth. -In long telegraph lines having terminal grounds or connected to earth -only at their ends, potential differences are sometimes observed that -are sufficient to interfere with their working and which, of course, can -produce currents. These are termed earth-currents. It will be noted that -they exist in the wire, not in the earth. They may be of 40 milliamperes -strength, quite enough to work a telegraph line without any battery. -Lines running N. E. and S. W. are most affected; those running N.W. and -S. E. very much less so. These currents only exist in lines grounded at -both ends, and appear in underground wires. Hence they are not -attributable to atmospheric electricity. According to Wilde they are the -primary cause of magnetic storms, q. v., but not of the periodical -changes in the magnetic elements. (See Magnetic Elements.) - -Synonym--Natural Currents. - - -Current, Secondary. -(a) A current induced in one conductor by a variation in the current in -a neighboring one; the current produced in the secondary circuit of an -induction coil or alternating current converter. - -(b) The current given by a secondary battery. This terminology is not to -be recommended. - - -Current, Secretion. -In electro-therapeutics, a current due to stimulation of the secretory -nerves. - - -Current Sheet. -(a) If two terminals of an active circuit are connected to two points of -a thin metallic plate the current spreads over or occupies practically a -considerable area of such plate, and this portion of the current is a -current sheet. - -The general contour of the current sheet can be laid out in lines of -flux. Such lines resemble lines of force. Like the latter, they are -purely an assumption, as the current is not in any sense composed of -lines. - -(b) A condition of current theoretically brought about by the Ampérian -currents in a magnet. Each molecule having its own current, the -contiguous portions of the molecules counteract each other and give a -resultant zero current. All that remains is the outer sheet of electric -current that surrounds the whole. - - -Current, Sinuous. -A current passing through a sinuous conductor. - - -Currents, Multiphase. -A term applied to groups of currents of alternating type which -constantly differ from each other by a constant proportion of periods of -alternation. They are produced on a single dynamo, the winding being so -contrived that two, three or more currents differing a constant amount -in phase are collected from corresponding contact rings. There are -virtually as many windings on the armature as there are currents to be -produced. Separate conductors for the currents must be used throughout. - -Synonyms--Polyphase Currents--Rotatory Currents. - - -167 STANDARD ELECTRICAL DICTIONARY. - - -Currents of Motion. -In electro-therapeutics, the currents produced in living muscle or -nerves after sudden contraction or relaxation. - - -Currents of Rest. -In electro-therapeutics, the currents traversing muscular or nervous -tissue when at rest. Their existence is disputed. - - -Currents, Orders of. -An intermittent current passing through a conductor will induce -secondary alternating currents in a closed circuit near it. This -secondary current will induce a tertiary current in a third closed -circuit near it, and so on. The induced currents are termed as of the -first, second, third and other orders. The experiment is carried out by -Henry's coils. (See Coils, Henry's.) - - -Currents, Thermo-electric. -These currents, as produced from existing thermo-electric batteries, -are generated by low potential, and are of great constancy. The opposite -junctions of the plates can be kept at constant temperatures, as by -melting ice and condensing steam, so that an identical current can be -reproduced at will from a thermopile. - -Thermo-electric currents were used by Ohm in establishing his law. (See -Ohm's Law.) - - -Current, Swelling. -In electro-therapeutics, a current gradually increasing in strength. - - -Current, Undulatory. -A current varying in strength without any abrupt transition from action -to inaction, as in the make and break current. The current may be -continually changing in direction (see Current, Alternating), and hence, -of necessity, may pass through stages of zero intensity, but such -transition must be by a graduation, not by an abrupt transition. Such -current may be represented by a curve, such as the curve of sines. It is -evident that the current may pass through the zero point as it crosses -the line or changes direction without being a make and break current. -When such a current does alternate in direction it is sometimes called a -"shuttle current." The ordinary commercial telephone current and the -alternating current is of this type. (See Current, Make and Break.) - - -Current, Unit. -Unit current is one which in a wire of unit length, bent so as to form -an arc of a circle of unit length of radius, would act upon a unit pole -(see Magnetic Pole, Unit,) at the center of the circle with unit force. -Unit length is the centimeter; unit force is the dyne. - -[Transcriber's note: The SI definition of an ampere: A current in two -straight parallel conductors of infinite length and negligible -cross-section, 1 metre apart in vacuum, would produce a force equal to -2E-7 newton per metre of length.] - - -168 STANDARD ELECTRICAL DICTIONARY. - - -Current, Wattless. -Whenever there is a great difference in phase in an alternating current -dynamo between volts and current, the true watts are much less than the -product of the virtual volts and amperes, because the the watts are -obtained by multiplying the product of the virtual volts and amperes by -the cosine of the angle of lag (or lead). Any alternating current may be -resolved into two components in quadrature with each other, one in phase -with the volts, the other in quadrature therewith, the former is termed -by S. P. Thompson the Working Current, the latter the Wattless Current. -The greater the angle of lag the greater will be the wattless current. - - -Curve, Arrival. -A curve representing the rate of rise of intensity of current at the end -of a long conductor when the circuit has been closed at the other end. -In the Atlantic cable, for instance, it would require about 108 seconds -for the current at the distant end to attain 9/10 of its full value. The -curve is drawn with its abscissa representing time and its ordinates -current strength. - - -Curve, Characteristic. -A curve indicating, graphically, the relations between any two factors, -which are interdependent, or which vary simultaneously. Thus in a -dynamo, the voltage increases with the speed of rotation, and a -characteristic curve may be based on the relations between the speed of -rotation and voltage developed. The current produced by a dynamo varies -with the electro-motive force, and a curve can express the relations -between the electro-motive force and the current produced. - -A characteristic curve is usually laid out by rectangular co-ordinates -(see Co-ordinates). Two lines are drawn at right angles to each other, -one vertical, and the other horizontal. One set of data are marked off -on the horizontal line, say one ampere, two amperes, and so on, in the -case of a dynamo's characteristic curve. - -For each amperage of current there is a corresponding voltage in the -circuit. Therefore on each ampere mark a vertical is erected, and on -that the voltage corresponding to such amperage is laid off. This gives -a series of points, and these points may be connected by a curve. Such -curve will be a characteristic curve. - -The more usual way of laying out a curve is to work directly upon the -two axes. On one is laid off the series of values of one set of data; on -the other the corresponding series of values of the other dependent -data. Vertical lines or ordinates, q. v., are erected on the horizontal -line or axis of abscissas at the points laid off; horizontal lines or -abscissas, q. v., are drawn from the points laid off on the vertical -line or axis of ordinates. The characteristic curve is determined by the -intersections of each corresponding pair of abscissa and ordinate. - - -169 STANDARD ELECTRICAL DICTIONARY. - - -Variations exist in characteristic curve methods. Thus to get the -characteristic of a commutator, radial lines may be drawn from a circle -representing its perimeter. Such lines may be of length proportional to -the voltage developed on the commutator at the points whence the lines -start. A cut giving an example of such a curve is given in Fig. 125. -(See Curve of Distribution of Potential in Armature.) - -There is nothing absolute in the use of ordinates or abscissas. They may -be interchanged. Ordinarily voltages are laid off as ordinates, but the -practise may be reversed. The same liberty holds good for all -characteristic curves. Custom, however, should be followed. - -Synonym--Characteristic. - - -Fig. 120. CHARACTERISTIC CURVE OF A DYNAMO WITH HORSE POWER CURVES. - - -Curve, Characteristic, of Converter. -The characteristic curve of the secondary circuit of an alternating -current converter. It gives by the usual methods (see Curve, -Characteristic,) the relations between the electro-motive force and the -current in the secondary circuit at a fixed resistance. If connected in -parallel a constant electro-motive force is maintained, and the curve is -virtually a straight line. If connected in series an elliptical curve is -produced. - - -170 STANDARD ELECTRICAL DICTIONARY. - - -Curve, Charging. -In secondary battery manipulation, a curve indicating the increase of -voltage as the charging is prolonged. The rise in voltage with the -duration of the charging current is not uniform. In one case, shown in -the cut, there was a brief rapid rise of about 0.1 volt; then a long -slow rise for 0.15 volt; then a more rapid rise for nearly 0.40 volt, -and then the curve became a horizontal line indicating a cessation of -increase of voltage. The charging rate should be constant. - -The horizontal line is laid off in hours, the vertical in volts, so that -the time is represented by abscissas and the voltage by ordinates of the -curve. - - -Fig. 121. CHARGING CURVE OF A SECONDARY BATTERY. - - -Curve, Discharging. -A characteristic curve of a storage battery, indicating the fall in -voltage with hours of discharge. The volts may be laid off on the axis -of ordinates, and the hours of discharging on the axis of abscissas. To -give it meaning the rate of discharge must be constant. - - -Curve, Electro-motive Force. -A characteristic curve of a dynamo. It expresses the relation between -its entire electromotive force, as calculated by Ohm's Law, and the -current intensities corresponding thereto. To obtain the data the dynamo -is driven with different resistances in the external circuit and the -current is measured for each resistance. This gives the amperes. The -total resistance of the circuit, including that of the dynamo, is known. -By Ohm's Law the electro-motive force in volts is obtained for each case -by multiplying the total resistance of the circuit in ohms by the -amperes of current forced through such resistance. Taking the voltages -thus calculated for ordinates and the corresponding amperages for -abscissas the curve is plotted. An example is shown in the cut. - - -171 STANDARD ELECTRICAL DICTIONARY. - - -Curve, External Characteristic. -A characteristic curve of a dynamo, corresponding to the electro-motive -force curve, except that the ordinates represent the voltages of the -external circuit, the voltages as taken directly from the terminals of -the machine, instead of the total electro-motive force of the circuit. -The dynamo is run at constant speed. The resistance of the external -circuit is varied. The voltages at the terminals of the machine and the -amperages of current corresponding thereto are determined. Using the -voltages thus determined as ordinates and the corresponding amperages as -abscissas the external characteristic curve is plotted. - -This curve can be mechanically produced. A pencil may be moved against a -constant force by two electro-magnets pulling at right angles to each -other. One must be excited by the main current of the machine, the other -by a shunt current from the terminals of the machine. The point of the -pencil will describe the curve. - - -Fig. 122. CHARACTERISTIC CURVE OF A DYNAMO. - - -Curve, Horse Power. -Curves indicating electric horse power. They are laid out with -co-ordinates, volts being laid off on the axis of ordinates, and amperes -on the axis of abscissas generally. The curves are drawn through points -where the product of amperes by volts equals 746. On the same diagram 1, -2, 3 .... and any other horse powers can be plotted if within the -limits. See Fig. 120. - - -Curve, Isochasmen. -A line drawn on the map of the earth's surface indicating the locus of -equal frequency of auroras. - - -172 STANDARD ELECTRICAL DICTIONARY. - - -Curve, Life. -A characteristic curve showing the relations between the durability and -conditions affecting the same in any appliance. It is used most for -incandescent lamps. The hours of burning before failure give ordinates, -and the rates of burning, expressed indirectly in volts or in -candle-power, give abscissas. For each voltage or for each candle-power -an average duration is deducible from experience, so that two dependent -sets of data are obtained for the construction of the curve. - - -Curve, Load. -A characteristic curve of a dynamo, expressing the relation between its -voltage and the amount of excitation under a definite condition of -ampere load, at a constant speed. The ordinates represent voltage, the -abscissas ampere turns in the field, and the curves may be constructed -for a flow of 0, 50, 100, or .. , or any other number of amperes. - - -Fig. 123. LOAD CURVES. - - -Curve, Magnetization. -A characteristic curve of an electromagnet, indicating the relation of -magnetization to exciting current. Laying off on the axis of ordinates -the quantities of magnetism evoked, and the corresponding strengths of -the exciting current on the axis of abscissas, the curve can be plotted. -It first rises rapidly, indicating a rapid increase of magnetization, -but grows nearly horizontal as the iron becomes more saturated. The -effect due to the coils alone, or the effect produced in the absence of -iron is a straight line, because air does not change in permeability. - - -Curve of Distribution of Potential in Armature. -A characteristic curve indicating the distribution of potential -difference between adjoining sections of the commutator of an armature -in different positions all around it. The potential differences are -taken by a volt-meter or potential galvanometer, connection with the -armature being made by two small metal brushes, held at a distance apart -equal to the distance from centre to centre of two adjoining commutator -bars. The curve is laid out as if by polar co-ordinates extending around -the cross-section of the commutator, with the distances from the -commutator surface to the curve proportional to the potential -differences as determined by shifting the pair of brushes all around the -commutator. - -The above is S. P. Thompson's method. Another method of W. M. Mordey -involves the use of a pilot brush. (See Brush, Pilot.) Otherwise the -method is in general terms identical with the above. - - -173 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 124. MAGNETIZATION CURVE. - - -Fig. 125. ARMATURE: CURVE. - - -Fig. 126. DEVELOPMENT OF ARMATURE CURVE. - - -Curve of Dynamo. -The characteristic curve of a dynamo. (See Curve, Characteristic.) - - -Curve of Sines. -An undulating curve representing wave motion. It is produced by -compounding a simple harmonic motion, or a two and fro motion like that -of an infinitely long pendulum with a rectilinear motion. Along a -horizontal line points may be laid off to represent equal periods of -time. Then on each point a perpendicular must be erected. The length of -each must be equal to the length of path traversed by the point up to -the expiration of each one of the given intervals of time. The abscissas -are proportional to the times and the ordinates to the sines of angles -proportional to the times. Thus if a circle be drawn upon the line and -divided into thirty-two parts of equal angular value, the sines of these -angles may be taken as the ordinates and the absolute distance or length -of arc of the angle will give the abscissas. - -Synonyms--Sine Curve--Sinusoidal Curve--Harmonic Curve. - - -Fig. 127. CURVE OF SINES. - - -174 STANDARD ELECTRICAL DICTIONARY. - - -Curve of Saturation of the Magnetic Circuit. -A characteristic curve whose ordinates may represent the number of -magnetic lines of force induced in a magnetic circuit, and whose -abscissas may represent the ampere turns of excitation or other -representative of the inducing force. - -Curve of Torque. -A characteristic curve showing the relations between torque, q. v., and -current in a dynamo or motor. - - -Curve, Permeability Temperature. -A characteristic curve expressing the changes in permeability of a -paramagnetic substance as the temperature changes. The degrees of -temperature may be abscissas, and the permeabilities corresponding -thereto ordinates of the curve. - - -Cut In. v. -To connect any electric appliance, mechanism or conductor, into a -circuit. - - -Cut Out. v. -The reverse of to cut in; to remove from a circuit any conducting -device, and sometimes so arranged as to leave the circuit completed in -some other way. - - -Cut Out. -An appliance for removing any apparatus from an electric circuit, so -that no more current shall pass through such apparatus, and sometimes -providing means for closing the circuit so as to leave it complete after -the removal of the apparatus. - - -175 STANDARD ELECTRICAL DICTIONARY. - - -Cut Out, Automatic. -(a) A mechanism for automatically shunting an arc or other lamp when it -ceases to work properly. It is generally worked by an electro-magnet of -high resistance placed in parallel with the arc. If the arc grows too -long the magnet attracts its armature, thereby completing a shunt of -approximately the resistance of the arc, and which replaces it until the -carbons approach again to within a proper distance. Sometimes a strip or -wire of fusible metal is arranged in shunt with the arc. When the arc -lengthens the current through the wire increases, melts it and a spring -is released which acts to complete or close a shunt circuit of -approximately arc-resistance. - -(b) See Safety Device--Safety Fuse. - -(c) See below. - - -Cut-out, Magnetic. -A magnetic cut-out is essentially a coil of wire with attracted core or -armature. When the coil is not excited the core, by pressing down a -strip of metal or by some analogous arrangement, completes the circuit. -When the current exceeds a certain strength the core rises as it is -attracted and the circuit is opened. - - -Cut-out, Safety. -A block of porcelain or other base carrying a safety fuse, which melts -and breaks the circuit before the wire connected to it is dangerously -heated. - -Synonyms--Fuse Block--Safety Catch--Safety Fuse. - - -Cut Out, Wedge. -A cut out operated by a wedge. The line terminals consist of a spring -bearing against a plate, the circuit being completed through their point -of contact. A plug or wedge composed of two metallic faces insulated -from each other is adapted to wedge the contact open. Terminals of a -loop circuit are connected to the faces of the wedge. Thus on sliding it -into place, the loop circuit is brought into series in the main circuit. - -Synonym--Plug Cut Out--Spring Jack. - - -Cutting of Lines of Force. -A field of force is pictured as made up of lines of force; a conductor -swept through the field is pictured as cutting these lines. By so doing -it produces potential difference or electro-motive force in itself with -a current, if the conductor is part of a closed circuit. - - -Cycle of Alternation. -A full period of alternation of an alternating current. It begins -properly at the zero line, goes to a maximum value in one sense and -returns to zero, goes to maximum in the other sense and returns to zero. - - -Cystoscopy. -Examination of the human bladder by the introduction of a special -incandescent electric lamp. The method is due to Hitze. - - -176 STANDARD ELECTRICAL DICTIONARY. - - -Damper. -(a) A copper frame on which the wire in a galvanometer is sometimes -coiled, which acts to damp the oscillations of the needle. - -(b) A tube of brass or copper placed between the primary and secondary -coils of an induction coil. It cuts off induction and diminishes the -current and potential of the secondary circuit. On pulling it out, the -latter increases. It is used on medical coils to adjust their strength -of action. - - -Damping. -Preventing the indicator of an instrument from oscillating in virtue of -its own inertia or elasticity. In a galvanometer it is defined as -resistance to quick vibrations of the needle, in consequence of which it -is rapidly brought to rest when deflected (Ayrton). In dead-beat -galvanometers (see Galvanometer, Dead-Beat,) damping is desirable in -order to bring the needle to rest quickly; in ballistic galvanometers -(see Galvanometer, Ballistic,) damping is avoided in order to maintain -the principle of the instrument. Damping may be mechanical, the -frictional resistance of air to an air-vane, or of a liquid to an -immersed diaphragm or loosely fitting piston, being employed. A -dash-pot, q. v., is an example of the latter. It may be -electro-magnetic. A mass of metal near a swinging magnetic needle tends -by induced currents to arrest the oscillations thereof, and is used for -this purpose in dead-beat galvanometers. This is termed, sometimes, -magnetic friction. The essence of damping is to develop resistance to -movement in some ratio proportional to velocity, so that no resistance -is offered to the indicator slowly taking its true position. (See -Galvanometer, Dead-Beat.) - - -Dash-Pot. -A cylinder and piston, the latter loosely fitting or perforated, or some -equivalent means being provided to permit movement. The cylinder may -contain a liquid such as glycerine, or air only. Thus the piston is -perfectly free to move, but any oscillations are damped (see Damping). -In some arc lamps the carbon holder is connected to a dash-pot to check -too sudden movements of the carbon. The attachment may be either to the -piston or to the cylinder. In the Brush lamp the top of the carbon -holder forms a cylinder containing glycerine, and in it a loosely -fitting piston works. This acts as a dash-pot. - - -Dead Beat. adj. -Reaching its reading quickly; applied to instruments having a moving -indicator, which normally would oscillate back and forth a number of -times before reaching its reading were it not prevented by damping. (See -Galvanometer, Aperiodic--Damping.) - - -Dead Earth. -A fault in a telegraph line which consists in the wire being thoroughly -grounded or connected to the earth. - - -177 STANDARD ELECTRICAL DICTIONARY. - - -Dead Point of an Alternator. -A two-phase alternator of the ordinary type connected as a motor to -another alternator cannot start itself, as it has dead points where the -relations and polarity of field and armature are such that there is no -torque or turning power. - - -Dead-Turns. -In the winding of an armature, a given percentage of the turns, it may -be 80 per cent., more or less, is assumed to be active; the other 20 per -cent. or thereabouts, is called dead-turns. This portion represents the -wire on such portions of the armature as comes virtually outside of the -magnetic field. They are termed dead, as not concurring to the -production of electro-motive force. - - -Dead Wire. -(a) The percentage or portion of wire on a dynamo or motor armature that -does not concur in the production of electromotive force. The -dead-turns, q. v., of a drum armature or the inside wire in a Gramme -ring armature are dead wire. - -(b) A disused and abandoned electric conductor, such as a telegraph -wire. - -(c) A wire in use, but through which, at the time of speaking, no -current is passing. - - -Death, Electrical. -Death resulting from electricity discharged through the animal system. -The exact conditions requisite for fatal results have not been -determined. High electro-motive force is absolutely essential; a -changing current, pulsatory or alternating, is most fatal, possibly -because of the high electro-motive force of a portion of each period. -Amperage probably has something to do with it, although the total -quantity in coulombs may be very small. As applied to the execution of -criminals, the victim is seated in a chair and strapped thereto. One -electrode with wet padded surface is placed against his head or some -adjacent part. Another electrode is placed against some of the lower -parts, and a current from an alternating dynamo passed for 15 seconds or -more. The potential difference of the electrodes is given at 1,500 to -2,000 volts, but of course the maximum may be two or three times the -measured amount, owing to the character of the current. - - -Decalescence. -The converse of recalescence, q. v. When a mass of steel is being heated -as it reaches the temperature of recalescence it suddenly absorbs a -large amount of heat, apparently growing cooler. - - -Deci. -Prefix originally used in the metric system to signify one-tenth of, now -extended to general scientific units. Thus decimeter means one-tenth of -a meter; decigram, one-tenth of a gram. - - -Declination, Angle of. -The angle intercepted between the true meridian and the axis of a -magnetic needle at any place. The angle is measured to east or west, -starting from the true meridian as zero. - - -178 STANDARD ELECTRICAL DICTIONARY. - - -Declination of the Magnetic Needle. -The deviation of the magnetic needle from the plane of the earth's -meridian. It is also called the variation of the compass. (See Magnetic -Elements.) - - -Decomposition. -The reduction of a compound substance into its constituents, as in -chemical analysis. The constituents may themselves be compounds or -proximate constituents, or may be elemental or ultimate constituents. - - -Decomposition, Electrolytic. -The decomposition or separation of a compound liquid into its -constituents by electrolysis. The liquid must be an electrolyte, q. v., -and the decomposition proceeds subject to the laws of electrolysis, q. -v. See also Electrolytic Analysis. - - -Decrement. -When a suspension needle which has been disturbed is oscillating the -swings gradually decrease in amplitude if there is any damping, as there -always is. The decrement is the ratio of the amplitude of one -oscillation to the succeeding one. This ratio is the same for any -successive swings. - - -De-energize. -To cut off its supply of electric energy from an electric motor, or any -device absorbing and worked by electric energy. - - -Deflagration. -The explosive or violent volatilizing and dissipating of a substance by -heat, violent oxidation and similar means. It may be applied among other -things to the destroying of a conductor by an intense current, or the -volatilization of any material by the electric arc. - - -Deflecting Field. -The field produced in a galvanometer by the current which is being -tested, and which field deflects the needle, such deflection being the -measure of the current strength. - - -Deflection. -In magnetism the movement out of the plane of the magnetic meridian of a -magnetic needle, due to disturbance by or attraction towards a mass of -iron or another magnet. - - -Deflection Method. -The method of electrical measurements in which the deflection of the -index of the measuring instrument is used as the measure of the current -or other element under examination. It is the opposite of and is to be -distinguished from the zero or null method, q. v. In the latter -conditions are established which make the index point to zero and from -the conditions necessary for this the measurement is deduced. The -Wheatstone Bridge, q. v., illustrates a zero method, the sine or the -tangent compass, illustrates a deflection method. The use of deflection -methods involves calibration, q. v., and the commercial measuring -instruments, such as ammeters and volt meters, which are frequently -calibrated galvanometers, are also examples of deflection instruments. - - -179 STANDARD ELECTRICAL DICTIONARY. - - -Degeneration, Reaction of. -The diminished sensibility to electro-therapeutic treatment exhibited by -the human system with continuance of the treatment in question. The -general lines of variation are stated in works on the subject. - - -Deka. -Prefix originally used in the metric system to signify multiplying by -ten, as dekameter, ten meters, dekagram, ten grams; now extended to many -scientific terms. - - -De la Rive's Floating Battery. -A small galvanic couple, immersed in a little floating cell and -connected through a coil of wire immediately above them. When the -exciting battery solution is placed in the cell the whole, as it floats -in a larger vessel, turns until the coil lies at right angles to the -magnetic needle. Sometimes the two plates are thrust through a cork and -floated thus in a vessel of dilute sulphuric acid. - -A magnet acts to attract or repel the coil in obedience to Ampére's -Theory, (See Magnetism, Ampere's Theory of.) - - -Delaurier's Solution. -A solution for batteries of the Bunsen and Grenet type. It is of the -following composition: - Water, 2,000 parts; - potassium bichromate, 184 parts; - sulphuric acid, 428 parts. - - -Demagnetization. -Removal of magnetism from a paramagnetic substance. It is principally -used for watches which have become magnetized by exposure to the -magnetic field surrounding dynamos or motors. - -The general principles of most methods are to rotate the object, as a -watch, in a strong field, and while it is rotating to gradually remove -it from the field, or to gradually reduce the intensity of the field -itself to zero. A conical coil of wire within which the field is -produced in which the watch is placed is sometimes used, the idea being -that the field within such a coil is strongest at its base. Such a coil -supplied by an alternating current is found effectual (J. J. Wright). - -If a magnetized watch is made to turn rapidly at the end of a twisted -string and is gradually brought near to and withdrawn from the poles of -a powerful dynamo it may be considerably improved. - -A hollow coil of wire connected with a pole changer and dip-battery has -been used. The battery creates a strong field within the coil. The watch -is placed there and the pole changer is worked so as to reverse the -polarity of the field very frequently. By the same action of the pole -changer the plates of the battery are gradually withdrawn from the -solution so as to gradually reduce the magnetic field to zero while -constantly reversing its polarity. (G. M. Hopkins.) - -Steel may be demagnetized by jarring when held out of the magnetic -meridian, or by heating to redness. - - -180 STANDARD ELECTRICAL DICTIONARY. - - -Density, Electric Superficial. -The relative quantity of electricity residing as an electric charge upon -a unit area of surface. It may be positive or negative. - -Synonyms--Density of Charge--Surface Density. - - -Dental Mallet, Electric. -A dentist's instrument for hammering the fillings as inserted into -teeth. It is a little hammer held in a suitable handle, and which is -made to strike a rapid succession of blows by electro-magnetic motor -mechanism. - - -Depolarization. -(a) The removal of permanent magnetism. (See Demagnetization.) - -(b) The prevention of the polarization of a galvanic cell. It is -effected in the Grove battery by the reduction of nitric acid; in the -Bunsen, by the reduction of chromic acid; in the Smee battery, -mechanically, by the platinum coated or rather platinized negative -plate. Other examples will be found under the description of various -cells and batteries. A fluid which depolarizes is termed a depolarizer -or depolarizing fluid or solution. (See Electropoion Fluid.) - - -Deposit, Electrolytic. -The metal or other substance precipitated by the action of a battery or -other current generator. - - -Derivation, Point of. -A point where a circuit branches or divides into two or more leads. The -separate branches then receive derived or partial currents. - - -Desk Push. -A press or push button, with small flush rim, for setting into the -woodwork of a desk. - - -Detector. -A portable galvanometer, often of simple construction, used for rough or -approximate work. - - -Detector, Lineman's. -A portable galvanometer with a high and a low resistance actuating coil, -constructed for the use of linemen and telegraph constructors when in -the field, and actually putting up, repairing or testing lines. - - -Deviation, Quadrantal. -Deviation of the compass in iron or steel ships due to the magnetization -of horizontal beams by the earth's induction. The effect of this -deviation disappears when the ship is in the plane of the electric -meridian, or at right angles thereto; its name is taken from the fact -that a swing of the ship through a quadrant brings the needle from zero -deviation to a maximum and back to zero. - - -181 STANDARD ELECTRICAL DICTIONARY. - - -Deviation, Semicircular. -Deviation of the compass in iron or steel ships due to vertical -induction. (See Induction, Vertical.) The effect of this induction -disappears when the ship is in the electric meridian. Its name is -derived from the fact that a swing of the ship through half the circle -brings the needle from zero deviation to a maximum and back to zero. - - -Dextrotorsal. adj. -Wound in the direction or sense of a right-handed screw; the reverse of -sinistrotorsal, q. v. - - -Fig. 128. DEXTROTORSAL HELIX. - - -Diacritical. adj. -(a) The number of ampere turns, q. v., required to bring an iron core to -one half its magnetic saturation, q. v., is termed the diacritical -number. - -(b) The diacritical point of magnetic saturation is proposed by Sylvanus -P. Thompson as a term for the coefficient of magnetic saturation which -gives a magnet core one-half its maximum magnetization. - - -Diagnosis, Electro. -A medical diagnosis of a patient's condition based on the action of -different parts of the body under electric excitement. - - -Diamagnetic. adj. -Possessing a negative coefficient of magnetic susceptibility; having -permeability inferior to that of air. Such substances placed between the -poles of a magnet are repelled; if in the form of bars, they tend to -turn so as to have their long axis at right angles to the line joining -the poles. The reason is that the lines of force always seek the easiest -path, and these bodies having higher reluctance than air, impede the -lines of force, and hence are as far as possible pushed out of the way. -The above is the simplest explanation of a not well understood set of -phenomena. According to Tyndall, "the diamagnetic force is a polar -force, the polarity of diamagnetic bodies being opposed to that of -paramagnetic ones under the same conditions of excitement." Bismuth is -the most strongly diamagnetic body known; phosphorus, antimony, zinc, -and many others are diamagnetic. (See Paramagnetic.) - - -182 STANDARD ELECTRICAL DICTIONARY. - - -Diagometer. -An apparatus for use in chemical analysis for testing the purity of -substances by the time required for a charged surface to be discharged -through them to earth. It is the invention of Rousseau. - -An electrometer is charged with a dry pile. One of its terminals is -connected with one surface of the solution or substance to be tested, -and the other with the other surface. The time of discharge gives the -index of the purity of the substance. - - -Diamagnetic Polarity. -Treating diamagnetism as due to a polar force, the polarity of a -diamagnetic body is the reverse of the polarity of iron or other -paramagnetic bodies. A bar-shaped diamagnetic body in a field of force -tends to place itself at right angles to the lines of force. - - -Diamagnetism. -(a) The science or study of diamagnetic substances and phenomena. - -(b) The magnetic property of a diamagnetic substance. - - -Diameter of Commutation. -The points on the commutator of a closed circuit ring--or -drum--armature, which the brushes touch, and whence they take the -current, mark the extremities of the diameter of commutation. Were it -not for the lag this would be the diameter at right angles to the line -connecting the centers of the opposite faces of the field. It is always -a little to one side of this position, being displaced in the direction -of rotation. In open circuit armatures the brushes are placed on the -diameter at right angles to this one, and sometimes the term diameter of -commutation is applied to it. All that has been said is on the -supposition that the armature divisions correspond not only in -connection but in position with those of the armature coils. Of course, -the commutator could be twisted so as to bring the diameter of -commutation into any position desired. - - -Diapason, Electric. -A tuning-fork or diapason kept in vibration by electricity. In general -principle the ends of the fork act as armatures for an electro-magnet, -and in their motion by a mercury cup or other form of contact they make -and break the circuit as they vibrate. Thus the magnet alternately -attracts and releases the leg, in exact harmony with its natural period -of vibration. - - -Diaphragm. -(a) In telephones and microphones a disc of iron thrown into motion by -sound waves or by electric impulses, according to whether it acts as the -diaphragm of a transmitter or receiver. It is generally a plate of -japanned iron such as used in making ferrotype photographs. (See -Telephone and Microphone.) - -(b) A porous diaphragm is often used in electric decomposition cells and -in batteries. The porous cup represents the latter use. - -[Transcriber's note: Japanned--covered with heavy black lacquer, like -enamel paint.] - - -183 STANDARD ELECTRICAL DICTIONARY. - - -Dielectric. -A non-conductor; a substance, the different parts of which may, after an -electric disturbance, remain, without any process of readjustment, and -for an indefinite period of time, at potentials differing to any extent -(Daniell). There is no perfect dielectric. The term dielectric is -generally only used when an insulator acts to permit induction to take -place through it, like the glass of a Leyden jar. - - -Dielectric Constant. -The number or coefficient expressing the relative dielectric capacity of -a medium or substance. (See Capacity, Specific Inductive.) - - -Dielectric, Energy of. -In a condenser, the conducting coatings are merely to conduct the -current all over the surface they cover; the keeping the electricities -separated is the work of the dielectric, and represents potential energy -which appears in the discharge. The amount of energy is proportional to -the charge, and to the potential difference. As any electrified body -implies an opposite electrification somewhere, and a separating -dielectric, the existence of a condenser is always implied. - -[Transcriber's note: The energy stored in a capacitor (condenser) is -(Q*Q)/2C = (Q*V)/2 = (C*V*V)/2 -The energy is proportional to the voltage SQUARED or the charge SQUARED.] - - -Dielectric Polarization. -A term due to Faraday. It expresses what he conceived to be the -condition of a dielectric when its opposite faces are oppositely -electrified. The molecules are supposed to be arranged by the -electrification in a series of polar chains, possibly being originally -in themselves seats of opposite polarities, or having such imparted to -them by the electricities. The action is analogous to that of a magnet -pole on a mass of soft iron, or on a pile of iron filings. - - -Dielectric Strain. -The strain a solid dielectric is subjected to, when its opposite -surfaces are electrified. A Leyden jar dilates under the strain, and -when discharged gives a dull sound. The original condition is not -immediately recovered. Jarring, shaking, etc., assist the recovery from -strain. The cause of the strain is termed Electric Stress. (See Stress, -Electric.) This is identical with the phenomenon of residual charge. -(See Charge, Residual.) Each loss of charge is accompanied with a -proportional return of the dielectric towards its normal condition. - - -Dielectric Resistance. -The mechanical resistance a body offers to perforation or destruction by -the electric discharge. - - -Dielectric Strength. -The resistance to the disruptive discharge and depending on its -mechanical resistance largely or entirely. It is expressible in volts -per centimeter thickness. Dry air requires 40,000 volts per centimeter -for a discharge. - - -184 STANDARD ELECTRICAL DICTIONARY. - - -Differential Winding Working. -A method of working an electro-magnet intermittently, so as to avoid -sparking. The magnet is wound with two coils. One is connected straight -into the circuit, the other is connected in parallel therewith with a -switch inserted. The coils are so connected that when the switch is -closed the two are in opposition, the current going through them in -opposite senses. Thus one overcomes the effect of the other and the -magnet core shows no magnetism, provided the two coils are of equal -resistance and equal number of convolutions or turns. - - -Fig. 129. DIFFERENTIAL WINDING WORKING OF ELECTRO-MAGNETIC APPARATUS. - - -Diffusion. -A term properly applied to the varying current density found in -conductors of unequal cross sectional area. In electro-therapeutics it -is applied to the distribution of current as it passes through the human -body. Its density per cross-sectional area varies with the area and -with the other factors. - - -Diffusion Creep. -When electrodes of an active circuit are immersed in a solution of an -electrolyte, a current passes electrolytically if there is a sufficient -potential difference. The current passes through all parts of the -solution, spreading out of the direct prism connecting or defined by the -electrodes. To this portion of the current the above term is applied. If -the electrodes are small enough in proportion to the distance between -them the current transmission or creep outside of the line becomes the -principal conveyor of the current so that the resistance remains the -same for all distances. - - -Dimensions and Theory of Dimensions. -The expression of the unitary value of a physical quantity in one or -more of the units of length (L), time (T) and mass (M) is termed the -dimensions of such quantity. Thus the dimension or dimensions of a -distance is simply L; of an angle, expressible by dividing the arc by -the radius is L/L; of a velocity, expressible by distance divided by -time--L/T; of acceleration, which is velocity acquired in a unit of -time, and is therefore expressible by velocity divided by time--L/T/T or -L/T2; of momentum, which is the product of mass into velocity--M*L/T; of -kinetic energy taken as the product of mass into the square of -velocity--M*(L2/T2); of potential energy taken as the product of mass -into acceleration into space-M*(L/T2)*L reducing to M*(L2/T2). The -theory is based on three fundamental units and embraces all electric -quantities. The simple units generally taken are the gram, centimeter -and second and the dimensions of the fundamental compound units are -expressed in terms of these three, forming the centimeter-gram-second or -C. G. S. system of units. Unless otherwise expressed or implied the -letters L, M and T, may be taken to indicate centimeter, gram and second -respectively. It is obvious that very complicated expressions of -dimensions may be built up, and that a mathematical expression of -unnamed quantities may be arrived at. Dimensions in their application by -these symbols are subject to the laws of algebra. They were invented by -Fourier and were brought into prominence by J. Clerk Maxwell. Another -excellent definition reads as follows: "By the dimensions of a physical -quantity we mean the quantities and powers of quantities, involved in -the measurement of it." (W. T. A. Emtage.) - - -185 STANDARD ELECTRICAL DICTIONARY. - - -Dimmer. -An adjustable choking coil used for regulating the intensity of electric -incandescent lights. Some operate by the introduction and withdrawal of -an iron core as described for the choking coil (see Coil, Choking), -others by a damper of copper, often a copper ring surrounding the coil -and which by moving on or off the coil changes the potential of the -secondary circuit. - - -Dip of Magnetic Needle. -The inclination of the magnetic needle. (See Elements, Magnetic.) - - -Dipping. -(a) Acid or other cleaning processes applied by dipping metals in -cleaning or pickling solutions before plating in the electroplater's -bath. - -(b) Plating by dipping applies to electroplating without a battery by -simple immersion. Copper is deposited on iron from a solution of copper -sulphate in this way. - -Synonym--Simple Immersion. - - -Dipping Needle. -A magnet mounted in horizontal bearings at its centre of gravity. Placed -in the magnetic meridian it takes the direction of the magnetic lines of -force of the earth at that point. It is acted on by the vertical -component of the earth's magnetism, as it has no freedom of horizontal -movement. (See Magnetic Elements, and Compass, Inclination.) - -Directing Magnet. -In a reflecting galvanometer the magnet used for controlling the -magnetic needle by establishing a field. It is mounted on the spindle of -the instrument above the coil and needle. - -Synonym--Controlling Magnet. - - -186 STANDARD ELECTRICAL DICTIONARY. - - -Direction. -(a) The direction of an electric current is assumed to be from a -positively charged electrode or terminal to a negatively charged one in -the outer circuit. (See Current.) - -(b) The direction of magnetic and electro-magnetic lines of force is -assumed to be from north to south pole of a magnet in the outer circuit. -It is sometimes called the positive direction. Their general course is -shown in the cuts diagrammatically. The circles indicate a compass used -in tracing their course. The magnetic needle tends to place itself in -the direction of or tangential to the lines of force passing nearest it. - -(c) The direction of electrostatic lines of force is assumed to be out -of a positively charged and to a negatively charged surface. - - -Fig. 130. DIRECTION OF LINES OF FORCE OF A PERMANENT MAGNET. - - -Fig. 131, DIRECTION OF LINES OF FORCE OF AN ELECTRO-MAGNET. - - -187 STANDARD ELECTRICAL DICTIONARY. - - -Directive Power. -In magnetism the power of maintaining itself in the plane of the -magnetic meridian, possessed by the magnetic needle. - - -Discharge, Brush. -The static discharge of electricity into or through the air may be of -the brush or spark form. The brush indicates the escape of electricity -in continuous flow; the spark indicates discontinuity. The conditions -necessary to the production of one or the other refer to the nature of -the conductor, and of other conductors in its vicinity and to the -electro-motive force or potential difference; small alterations may -transform one into the other. The brush resembles a luminous core whose -apex touches the conductor. It is accompanied by a slight hissing noise. -Its luminosity is very feeble. The negative conductor gives a smaller -brush than that of the positive conductor and discharges it more -readily. When electricity issues from a conductor, remote from an -oppositely excited one, it gives an absolutely silent discharge, showing -at the point of escape a pale blue luminosity called electric glow, or -if it escapes from points it shows a star-like centre of light. It can -be seen in the dark by placing a point on the excited conductor of a -static-electric machine. - -Synonyms--Silent Discharge--Glow Discharge. - - -Discharge, Conductive. -A discharge of a static charge by conduction through a conductor. - - -Discharge, Convective. -The discharge of static electricity from an excited conductor through -air or rarefied gas; it is also called the quiet or silent discharge. -The luminous effect in air or gas at atmospheric pressures takes the -form of a little brush from a small positive electrode; the negative -shows a star. The phenomena of Gassiot's cascade, the philosopher's egg -and Geissler tubes, all of which may be referred to, are instances of -convective discharge. - - -Discharge, Dead Beat. -A discharge that is not oscillatory in character. - - -Discharge, Disruptive. -A discharge of a static charge through a dielectric. It involves -mechanical perforation of the dielectric, and hence the mere mechanical -strength of the latter has much to do with preventing it. A disruptive -discharge is often oscillatory in character; this is always the case -with the discharge of a Leyden jar. - - -188 STANDARD ELECTRICAL DICTIONARY. - - -Discharge, Duration of. -The problem of determining this factor has been attacked by various -observers. Wheatstone with his revolving mirror found it to be 1/24000 -second. Fedderson, by interposing resistance, prolonged it to 14/10000 -and again to 138/10000 second. Lucas & Cazin made it from 26 to 47 -millionths of a second. All these experiments were performed with Leyden -jars. - - -Discharge, Impulsive. -A disruptive discharge produced between conductors by suddenly produced -potential differences. The self-induction of the conductor plays an -especially important part in discharges thus produced. - - -Discharge, Lateral. -(a) A lightning discharge, which sometimes takes place between a -lightning rod and the building on which it is. - -(b) In the discharge of a Leyden jar or condenser the discharge which -takes the alternative path, q. v. - - -Discharge, Oscillatory. -The sudden or disruptive discharge of a static condenser, such as a -Leyden jar, or of many other charged conductors, is oscillatory in -character. The direction of the currents rapidly changes, so that the -discharge is really an alternating current of excessively short total -duration. The discharge sends electro-magnetic waves through the ether, -which are exactly analogous to those of light but of too long period to -affect the eye. - -Synonym--Surging Discharge. - -[Transcriber's note: Marconi's transmission across the English channel -occurs in 1897, five years after the publication of this book.] - - -Fig. 132. DISCHARGER. - - -Discharger. -An apparatus for discharging Leyden jars. It consists of a conductor -terminating in balls, and either jointed like a tongs or bent with a -spring-action, so that the balls can be set at distances adapted to -different sized jars. It has an insulating handle or a pair of such. In -use one ball is brought near to the coating and the other to the spindle -ball of the jar. When nearly or quite in contact the jar discharges. - -Synonyms--Discharging Rod--Discharging Tongs. - - -189 STANDARD ELECTRICAL DICTIONARY. - - -Discharger, Universal. -An apparatus for exposing substances to the static discharge spark. It -consists of a base with three insulating posts. The central post carries -an ivory table to support the object. The two side posts carry -conducting rods, terminating in metal balls, and mounted with universal -joints. A violent shock can be given to any object placed on the table. - -Synonym--Henley's Universal Discharger. - - -Discharge, Silent. -This term is sometimes applied to the glow or brush discharge and -sometimes to the condition of electric effluvium. (See Discharge, -Brush--Effluvium, Electric.) - - -Discharge, Spark. -The discontinuous discharge of high tension electricity through a -dielectric or into the air produces electric sparks. These are quite -strongly luminous, of branching sinuous shape, and in long sparks the -luminosity varies in different parts of the same spark. A sharp noise -accompanies each spark. High density of charge is requisite for the -formation of long sparks. - - -Disconnection. -The separation of two parts of, or opening a circuit, as by turning a -switch, unscrewing a binding screw, or the like. The term is sometimes -used to indicate a class of faults in telegraph circuits. Disconnections -may be total, partial or intermittent, and due to many causes, such as -open or partially replaced switches, oxidized or dirty contact points, -or loose joints. - - -Displacement, Electric. -A conception of the action of charging a dielectric. The charge is all -on the surface. This fact being granted, the theory of displacement -holds that charging a body is the displacing of electricity, forcing it -from the interior on to the surface, or vice versa, producing a positive -or negative charge by displacement of electricity. While displacement is -taking place in a dielectric there is assumed to be a movement or -current of electricity called a displacement current. - - -Disruptive Tension. -When the surface of a body is electrified, it tends to expand, all -portions of the surface repelling each other. The film of air -surrounding such a body is electrified too, and is subjected to a -disruptive tension, varying in intensity with the square of the density. - - -Dissimulated Electricity. -The electricity of a bound charge. (See Charge, Bound.) - - -Dissociation. -The separation of a chemical compound into its elements by a -sufficiently high degree of heat. All compounds are susceptible of -dissociation, so that it follows that combustion is impossible at high -temperatures. - - -190 STANDARD ELECTRICAL DICTIONARY. - - -Distance, Critical, of Alternative Path. -The length of air gap in an alternative path whose resistance joined to -the impedance of the rest of the conductors of the path just balances -the impedance of the other path. - - -Distance, Sparking. -The distance between electrodes, which a spark from a given Leyden jar -or other source will pass across. - -Synonym--Explosive Distance. - - -Distillation. -The evaporation of a liquid by heat, and sometimes in a vacuum, followed -by condensation of the vapors, which distil or drop from the end of the -condenser. It is claimed that the process is accelerated by the liquid -being electrified. - - -Distributing Box. -In an electric conduit system, a small iron box provided for giving -access to the cable for the purpose of making house and minor -connections. - -Synonym--Hand Hole. - - -Distributing Switches. -Switch systems for enabling different dynamos to supply different lines -of a system as required. Spring jacks, q. v., are used for the lines, -and plug switches for the dynamo leads. Thus, dynamos can be thrown in -or out as desired, without putting out the lights. - - -Distribution of Electric Energy, Systems of. -The systems of electric current distribution from central stations or -from private generating plants, mechanical or battery, the latter -primary or secondary. They include in general the alternating current -system and direct current systems. Again, these may be subdivided into -series and multiple arc, multiple-series and series-multiple -distribution, and the three, four, or five wire system may be applied to -multiple arc or multiple series systems. (See Alternating -Current--Current System--Multiple Arc--Multiple Series--Series -Multiple--Three Wire System.) - - -Door Opener, Electric. -An apparatus for opening a door by pushing back the latch. A spring then -draws the door open, and it is closed against the force of the spring by -the person entering. Electro-magnetic mechanism actuates the latch, and -is operated by a switch or press-button. Thus a person on the upper -floor can open the hall door without descending. - - -Dosage, Galvanic. -In electro-therapeutics the amount of electric current or discharge, and -duration of treatment given to patients. - - -Double Carbon Arc Lamp. -An arc lamp designed to burn all night, usually constructed with two -parallel sets of carbons, one set replacing the other automatically, the -current being switched from the burnt out pair to the other by the -action of the mechanism of the lamp. - - -191 STANDARD ELECTRICAL DICTIONARY. - - -Double Fluid Theory. -A theory of electricity. Electricity is conveniently treated as a fluid -or fluids. According to the double fluid hypothesis negative electricity -is due to a preponderance of negative fluid and vice versa. Like fluid -repels like, and unlike attracts unlike; either fluid is attracted by -matter; the presence in a body of one or the other induces -electrification; united in equal proportions they neutralize each other, -and friction, chemical decomposition and other causes effect their -separation. The hypothesis, while convenient, is overshadowed by the -certainty that electricity is not really a fluid at all. (See Single -Fluid Theory--Fluid, Electric.) - -Synonym--Symmer's Theory. - -[Transcriber's note: Current is the motion of negative electrons in a -conductor or plasma. Unequal distribution of electrons is static -electricity. The relatively immobile nuclei of atoms are positive when -one or more of its electrons is absent and accounts for part of the -current in electrolysis and plasmas.] - - -Double Fluid Voltaic Cell. -A cell in which two fluids are used, one generally as depolarizer -surrounding the negative plate, the other as excitant surrounding the -positive plate. A porous diaphragm or difference in specific gravities -is used to keep the solutions separate and yet permit the essential -electrolytic diffusion. Grove's Cell, Bunsen's Cell, and Daniell's Cell, -all of which may be referred to, are of this type, as are many others. - - -Double Wedge. -A plug for use with a spring-jack. It has connection strips at its end -and another pair a little distance back therefrom, so that it can make -two loop connections at once. - -Synonym--Double Plug. - - -Doubler. -A continuously acting electrophorous, q.v.; an early predecessor of the -modern electric machines. It is now no longer used. - - -D. P. -Abbreviation for Potential Difference. - - -Drag. -The pull exercised by a magnetic field upon a conductor moving through -it or upon the motion of an armature in it. - - -Dreh-strom. (German) -Rotatory currents; a system of currents alternating in periodic -succession of phases and producing a rotatory field. (See Field, -Rotatory--Multiphase Currents.) - - -Drill Electric. -A drill for metals or rock worked by an electro-magnetic motor. For -metals a rotary motion, for rocks a reciprocating or percussion action -is imparted. It is used by shipbuilders for drilling holes in plates -which are in place in ships, as its flexible conductors enable it to be -placed anywhere. For rock-drilling a solenoid type of construction is -adopted, producing rapid percussion. - - -192 STANDARD ELECTRICAL DICTIONARY. - - -Drip Loop. -A looping downward of wires entering a building, so that rain water, as -it runs along the wire, will drip from the lowest part of the loop -instead of following the wire into or against the side of the building. - - -Driving Horns. -Projections on the periphery of an armature of a dynamo for holding the -winding in place and preventing its displacement. Various arrangements -have been adopted. They are sometimes wedges or pins and are sometimes -driven into spaces left in the drum core. The toothed disc armature -cores make up an armature in which the ridges formed by the teeth form -practically driving horns. - - -Dronier's Salt. -A substance for solution for use in bichromate batteries. It is a -mixture of one-third potassium bichromate and two-thirds potassium -bisulphate. It is dissolved in water to make the exciting fluid. - - -Drop, Automatic. -A switch or circuit breaker, operating to close a circuit by dropping -under the influence of gravity. It is held up by a latch, the circuit -remaining open, until the latch is released by a current passing through -an electro-magnet. This attracting an armature lets the drop fall. As it -falls it closes a local or second circuit, and thus may keep a bell -ringing until it is replaced by hand. It is used in burglar alarms, its -function being to keep a bell ringing even though the windows or door by -which entrance was made is reclosed. - - -193 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 133. THE MAGIC DRUM. - - -Drum, Electric. -A drum with a mechanism within for striking the head with a hammer or -some equivalent method so as to be used as a piece of magical apparatus. -In the one shown in the cut a sort of telephone action is used to -produce the sound, the electro-magnet D and armature being quite -screened from observation through the hole. (See Fig. 133) A ring, C, -shown in Fig. 133, with two terminals, the latter shown by the unshaded -portions a a, and a suspending hook E, also with two terminals, and two -suspending conductors A, B, carry the current to the magnet. A sudden -opening or closing of the circuit produces a sound. - - -Dub's Laws. -1. The magnetism excited at any transverse section of a magnet is -proportional to the square root of the distance between the given -section and the end. - -2. The free magnetism at any given transverse section of a magnet is -proportional to the difference between the square root of half the -length of the magnet and the square root of the distance between the -given section and the nearest end. - - -Duct. -The tube or compartment in an electric subway for the reception of a -cable. (See Conduit, Electric Subway.) - - -Dyad. -A chemical term; an element which in combination replaces two monovalent -elements; one which has two bonds or is bivalent. - - -Dyeing, Electric. -The producing mordanting or other dyeing effects on goods in dyeing by -the passage of an electric current. - - -Dynamic Electricity. -Electricity of relatively low potential and large quantity; current -electricity as distinguished from static electricity; electricity in -motion. - - -194 STANDARD ELECTRICAL DICTIONARY. - - -Dynamo, Alternating Current. -A dynamo-electric machine for producing an alternating current; an -alternator. They are classified by S. P. Thompson into three classes--I. -Those with stationary field-magnet and rotating armature. II. Those with -rotating field magnet and stationary armature. III. Those with both -field magnet part and armature part stationary, the amount of magnetic -induction from the latter through the former being caused to vary or -alternate in direction by the revolution of appropriate pieces of iron, -called inductors. Another division rests on whether they give one simple -alternating current, a two phase current, or whether they give multi -phase currents. (See Current, Alternating--Currents, Multiphase.) - -A great many kinds of alternators have been constructed. Only an outline -of the general theory can be given here. They are generally multipolar, -with north and south poles alternating around the field. The armature -coils, equal in number in simple current machines, to the poles, are -wound in opposite senses, so that the current shall be in one direction, -though in opposite senses, in all of them at anyone time. As the -armature rotates the coils are all approaching their poles at one time -and a current in one sense is induced in every second coil, and one in -the other sense in the other coils. They are all in continuous circuit -with two open terminals, each connected to its own insulated connecting -ring on the shaft. As the coils pass the poles and begin to recede from -them the direction changes, and the current goes in the other direction -until the next poles are reached and passed. Thus there are as many -changes of direction of current per rotation as there are coils in the -armature or poles in the field. - - -Fig. 134. ALTERNATING CURRENT DYNAMO WITH -SEPARATE EXCITER MOUNTED ON MAIN SHAFT. - - -195 STANDARD ELECTRICAL DICTIONARY. - - -The field-magnets whose windings may be in series are often excited by a -separate direct current generation. Some are self-exciting, one or more -of the armature coils being separated from the rest, and connected to a -special commutator, which rectifies its current. - -By properly spacing the coils with respect to the poles of the field, -and connecting each set of coils by itself to separate connecting rings, -several currents can be taken from the same machine, which currents -shall have a constant difference in phase. It would seem at first sight -that the same result could be attained by using as many separate -alternators as there were currents to be produced. But it would be -almost impossible to preserve the exact relation of currents and current -phase where each was produced by its own machine. The currents would -overrun each other or would lag behind. In a single machine with -separate sets of coils the relation is fixed and invariable. - - -Fig. I35. DIAGRAM OF ARRANGEMENT OF ARMATURE COILS AND -COLLECTING RINGS IN AN ALTERNATING CURRENT DYNAMO. - - -Dynamo, Alternating Current, Regulation of. -Transformers, converters, or induction coils are used to regulate -alternating current dynamos, somewhat as compound winding is applied in -the case of direct-current dynamos. The arrangement consists in -connecting the primary of an induction coil or transformer into the -external circuit with its secondary connected to the field circuit. Thus -the transformer conveys current to the field picked up from the main -circuit, and represents to some extent the shunt of a direct-current -machine. - -Dynamo, Commercial Efficiency of. -The coefficient, q. v., obtained by dividing the mechanically useful or -available work of a dynamo by the mechanical energy absorbed by it. This -only includes the energy available in the outer circuit, for doing -useful work. - - -196 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 136. COMPOUND WOUND DYNAMO. - - -Dynamo. Compound. -A compound wound dynamo; one which has two coils on its field magnet; -one winding is in series with the external circuit and armature; the -other winding is in parallel with the armature winding, or else with the -armature winding and field winding, both in series. (See Winding, Long -Shunt--Winding, Short Shunt.) - -Such a dynamo is, to a certain extent, self-regulating, the two coils -counteracting each other, and bringing about a more regular action for -varying currents than that of the ordinary shunt or series dynamo. - -The extent of the regulation of such a machine depends on the -proportions given its different parts. However good the self-regulating -may be in a compound wound machine, it can only be perfect at one -particular speed. - -To illustrate the principle on which the approximate regulation is -obtained the characteristic curve diagram may be consulted. - - -Fig. 137. CURVES OF SERIES AND SHUNT WINDINGS SUPERIMPOSED. - - -One curve is the curve of a series winding, the other that of a shunt -winding, and shows the variation of voltage in each with resistance in -the external or working circuit. The variation is opposite in each case. -It is evident that the two windings could be so proportioned on a -compound machine that the resultant of the two curves would be a -straight line. This regulation would then be perfect and automatic, but -only for the one speed. - - -197 STANDARD ELECTRICAL DICTIONARY. - - -Dynamo, Direct Current. -A dynamo giving a current of unvarying direction, as distinguished from -an alternator or alternating current dynamo. - - -Dynamo, Disc. -A dynamo with a disc armature, such as Pacinotti's disc, q. v. (See also -Disc, Armature.) The field magnets are disposed so that the disc rotates -close to their poles, and the poles face or are opposite to the side or -sides of the disc. The active leads of wire are those situated on the -face or faces of the disc. - - -Fig. 138. POLECHKO'S DISC DYNAMO. - - -Dynamo-electric Machine. -A machine driven by power, generally steam power, and converting the -mechanical energy expended on driving it into electrical energy of the -current form. The parts of the ordinary dynamo may be summarized as -follows: First, A circuit as complete as possible of iron. Such circuit -is composed partly of the cores of an electro-magnet or of several -electro-magnets, and partly of the cylindrical or ring-shaped core of an -armature which fits as closely as practicable between the magnet ends or -poles which are shaped so as to partly embrace it. Second, of coils of -insulated wire wound upon the field-magnet cores. When these coils are -excited the field-magnets develop polarity and the circuit just spoken -of becomes a magnetic circuit, interrupted only by the air gaps between -the poles and armatures. Thirdly, of coils of insulated wire upon the -armature core. These coils when rotated in the magnetic field cut -magnetic lines of force and develop electro-motive force. - - -198 STANDARD ELECTRICAL DICTIONARY. - - -Fourthly, of collecting mechanism, the commutator in direct current -dynamos, attached to the armature shaft and rotating with it. This -consists of insulated rings, or segments of rings to which the wire -coils of the armature are connected, and on which two springs of copper -or plates of carbon or some other conductor presses. The electro-motive -force developed by the cutting of lines of force, by the wires of the -armature, shows itself as potential difference between the two springs. -If the ends of a conductor are attached, one to each of these brushes, -the potential difference will establish a current through the wire. By -using properly divided and connected segments on the commutator the -potential difference and consequent direction of the current may be kept -always in the same sense or direction. It is now clear that the external -wire may be connected with the windings of the field-magnet. In such -case the excitement of the field-magnets is derived from the armature -and the machine is self-excited and entirely self-contained. - -The above is a general description of a dynamo. Sometimes the coils of -the field-magnets are not connected with the armature, but derive their -current from an outside source. Such are termed separately excited -dynamos. - -Some general features of dynamo generators may be seen in the -definitions under this head and elsewhere. The general conception is to -cut lines of force with a conductor and thus generate electromotive -force, or in some way to change the number of lines of force within a -loop or circuit with the same effect. - - -Dynamo, Electroplating. -A dynamo designed for low potential and high current intensity. They are -wound for low resistance, frequently several wires being used in -parallel, or ribbon, bar or rectangular conductors being employed. They -are of the direct current type. They should be shunt wound or they are -liable to reverse. They are sometimes provided with resistance in the -shunt, which is changed as desired to alter the electro-motive force. - - -Dynamo, Equalizing. -A combination for three and five-wire systems. A number of armatures or -of windings on the same shaft are connected across the leads. If the -potential drops at any pair of mains, the armature will begin to be -driven by the other mains, acting to an extent as an element of a motor, -and will raise the potential in the first pair. - - -Dynamo, Far Leading. -A motor dynamo, used to compensate the drop of potential in long mains. -Into the mains at a distant point a series motor is connected, driving a -dynamo placed in shunt across the mains. The dynamo thus driven raises -the potential difference between the two mains. - - -199 STANDARD ELECTRICAL DICTIONARY. - - -Dynamograph. -A printing telegraph in which the message is printed at both -transmitting and receiving ends. - - -Dynamo, Inductor. -A generator in which the armature or current-generating windings are all -comprised upon the poles of the field magnets. Masses of iron, which -should be laminated and are the inductors, are carried past the field -magnet poles concentrating in their passage the lines of force, thus -inducing currents in the coils. In one construction shown in the cut the -field magnets a, a .. are U shaped and are arranged in a circle, their -poles pointing inwards. A single exciting coil c, c ... is wound around -the circle in the bend of the V-shaped segments. The poles carry the -armature coils e, e ... The laminated inductors i, i ... are mounted on -a shaft S, by spiders h, to be rotated inside the circle of magnets, -thus generating an alternating current. - -Synonym--Inductor Generator. - - -Fig. 139. INDUCTOR DYNAMO. - - -Dynamo, Interior Pole. -A dynamo with a ring armature, with field magnet pole pieces which -extend within the ring. - - -200 STANDARD ELECTRICAL DICTIONARY. - - -Dynamo, Iron Clad. -A dynamo in which the iron of the field magnet is of such shape as to -enclose the field magnet coils as well as the armature. - - -Dynamometer. -A device or apparatus for measuring force applied, or rate of -expenditure of energy by, or work done in a given time by a machine. A -common spring balance can be used as a force dynamometer, viz: to -determine how hard a man is pulling and the like. The steam engine -indicator represents an energy-dynamometer of the graphic type, the -instrument marking an area whence, with the aid of the fixed factors of -the engine, the work done may be determined. Prony's Brake, q. v., is a -type of the friction dynamometer, also of the energy type. In the latter -type during the experiment the whole power must be turned on or be -expended on the dynamometer. - - -Dynamo, Motor. -A motor dynamo is a machine for (a) converting a continuous current at -any voltage to a continuous current of different strength at a different -voltage or for (b) transforming a continuous current into an alternating -one, and vice versa. - -For the first type see Transformer, Continuous Current; for the second -type see Transformer, Alternating Current. - - -Dynamo, Multipolar. -A dynamo having a number of field magnet poles, not merely a single -north and a single south pole. The field magnet is sometimes of a -generally circular shape with the poles arranged radially within it, the -armature revolving between the ends. - - -Dynamo, Non-polar. -A name given by Prof. George Forbes to a dynamo invented by him. In it a -cylinder of iron rotates within a perfectly self-contained iron-clad -field magnet. The current is taken off by brushes bearing near the -periphery, at two extremities of a diameter. A machine with a disc 18 -inches in diameter was said to give 3,117 amperes, with 5.8 volts E. M. -F. running at 1,500 revolutions per second. The E. M. F. of such -machines varies with the square of the diameter of the disc or cylinder. - - -Dynamo, Open Coil. -A dynamo the windings of whose armatures may be grouped in coils, which -are not connected in series, but which have independent terminals. These -terminals are separate divisions of the commutator and so spaced that -the collecting brushes touch each pair belonging to the same coil -simultaneously. As the brushes come in contact with the sections forming -the terminals they take current from the coil in question. This coil is -next succeeded by another one, and so on according to the number of -coils employed. - - -Dynamo, Ring. -A dynamo the base of whose field magnets is a ring in general shape, or -perhaps an octagon, and with poles projecting inwardly therefrom. - - -201 STANDARD ELECTRICAL DICTIONARY. - - -Dynamo, Coupling of. -Dynamos can be coupled exactly like batteries and with about the same -general results. An instance of series coupling would be given by the -dynamos in the three wire system when no current is passing through the -neutral wire, and when the lamps on each side of it are lighted in equal -number. - - -Dynamo, Self-exciting. -A dynamo which excites its own field. The majority of dynamos are of -this construction. Others, especially alternating current machines, are -separately excited, the field magnets being supplied with current from a -separate dynamo or current generator. - - -Dynamo, Separate Circuit. -A dynamo in which the field magnet coils are entirely disconnected from -the main circuit, and in which current for the field is supplied by -special coils carried for the purpose by the same armature, or by a -special one, in either case a special commutator being provided to -collect the current. - - -Dynamo, Separately Excited. -A dynamo whose field magnets are excited by a separate current -generator, such as a dynamo or even a battery. Alternating current -dynamos are often of this construction. Direct current dynamos are not -generally so. The term is the opposite of self-exciting. - - -Fig. 140. SERIES DYNAMO. - - -Dynamo, Series. -A dynamo whose armature, field winding, and external circuit are all in -series. - -In such a dynamo short circuiting or lowering the resistance of the -external circuit strengthens the field, increases the electro-motive -force and current strength and may injure the winding by heating the -wire, and melting the insulation. - - -202 STANDARD ELECTRICAL DICTIONARY. - - -Dynamo, Shunt. -A dynamo whose field is wound in shunt with the external circuit. Two -leads are taken from the brushes; one goes around the field magnets to -excite them; the other is the external circuit. - -In such a dynamo the lowering of resistance on the outer circuit takes -current from the field and lowers the electro-motive force of the -machine. Short circuiting has no heating effect. - - -Fig. 141. SHUNT DYNAMO. - - -Dynamo, Single Coil. -A dynamo whose field magnet is excited by a single coil. Several such -have been constructed, with different shapes of field magnet cores, in -order to obtain a proper distribution of poles. - - -Dynamo, Tuning Fork. -A dynamo in which the inductive or armature coils were carried at the -ends of the prongs of a gigantic tuning fork, and were there maintained -in vibration opposite the field magnets. It was invented by T. A. -Edison, but never was used. - - -Dynamo, Uni-polar. -A dynamo in which the rotation of a conductor effects a continuous -increase in the number of lines cut, by the device of arranging one part -of the conductor to slide on or around the magnet. (S. P. Thomson.) -Faraday's disc is the earliest machine of this type. - - -203 STANDARD ELECTRICAL DICTIONARY. - - -Dyne. -The C. G. S. or fundamental unit of force. It is the force which can -impart an acceleration of one centimeter per second to a mass of one -gram in one second. It is equal to about 1/981 the weight of a gram, -this weight varying with the latitude. - - -Earth. -(a) The earth is arbitrarily taken as of zero electrostatic potential. -Surfaces in such condition that their potential is unchanged when -connected to the earth are said to be of zero potential. All other -surfaces are discharged when connected to the earth, whose potential, -for the purposes of man at least, never changes. - -(b) As a magnetic field of force the intensity of the earth's field is -about one-half a line of force per square centimeter. - -(c) The accidental grounding of a telegraph line is termed an earth, as -a dead, total, partial, or intermittent earth, describing the extent and -character of the trouble. - -[Transcriber's note: Fallen power lines can produce voltage gradients on -the earth's surface that make walking in the area dangerous, as in -hundreds of volts per foot. Lightning may be associated with substantial -changes in the static ground potential.] - - -Earth, Dead. -A fault, when a telegraph or other conductor is fully connected to earth -or grounded at some intermediate point. - -Synonyms--Solid Earth--Total Earth. - - -Earth, Partial. -A fault, when a telegraph or other conductor is imperfectly connected to -earth or grounded at some intermediate point. - - -Earth Plate. -A plate buried in the earth to receive the ends of telegraph lines or -other circuits to give a ground, q. v. A copper plate is often used. A -connection to a water or gas main gives an excellent ground, far better -than any plate. When the plate oxidizes it is apt to introduce -resistance. - - -Earth Return. -The grounding of a wire of a circuit at both ends gives the circuit an -earth return. - - -Earth, Swinging. -A fault, when a telegraph or other conductor makes intermittent -connection with the earth. It is generally attributable to wind action -swinging the wire, whence the name. - - -Ebonite. -Hard vulcanized India rubber, black in color. Specific resistance in -ohms per cubic centimeter at 46º C. (115º F.): 34E15 (Ayrton); specific -inductive capacity, (air = 1): 2.56 (Wüllner); 2.76 (Schiller); 3.15 -(Boltzmann). It is used in electrical apparatus for supporting members -such as pillars, and is an excellent material for frictional generation -of potential. Its black color gives it its name, and is sometimes made a -point of distinction from Vulcanite, q. v. - - -204 STANDARD ELECTRICAL DICTIONARY. - - -Economic Coefficient. -The coefficient of electric efficiency. (See Efficiency, Electric.) - - -Edison Effect. -A continuous discharge resulting in a true current which takes place -between a terminal of an incandescent lamp filament and a plate placed -near it. The lamp must be run at a definitely high voltage to obtain it. - - -Ediswan. -An abbreviation for Edison-Swan; the trade name of the incandescent lamp -used in Great Britain, and of other incandescent system apparatus. - - -Fig. 142. GYMNOTUS ELECTRICUS. - - -Eel, Electric (Gymnotus Electricus). -An eel capable of effecting the discharge of very high potential -electricity, giving painful or dangerous shocks. Its habitat is the -fresh water, in South America. Faraday investigated it and estimated its -shock as equal to that from fifteen Leyden jars, each of 1.66 square -feet of coating. (See Animal Electricity and Ray, Electric.) - - -Effect, Counter-inductive. -A counter-electro-motive force due to induction, and opposing a current. - - -Efficiency. -The relation of work done to energy absorbed. A theoretically perfect -machine would have the maximum efficiency in which the two qualities -named would be equal to each other. Expressed by a coefficient, q. v., -the efficiency in such case would be equal to 1. If a machine produced -but half the work represented by the energy it absorbed, the rest -disappearing in wasteful expenditure, in heating the bearings, in -overcoming the resistance of the air and in other ways, its efficiency -would be expressed by the coefficient 1/2 or .5, or if one hundred was -the basis, by fifty per centum. There are a number of kinds of -efficiencies of an electric generator which are given below. - - -Efficiency, Commercial. -Practical efficiency of a machine, obtained by dividing the available -output of work or energy of a machine by the energy absorbed by the same -machine. Thus in a dynamo part of the energy is usefully expended in -exciting the field magnet, but this energy is not available for use in -the outer circuit, is not a part of the output, and is not part of the -dividend. - -If M represents the energy absorbed, and W the useful or available -energy, the coefficient of commercial efficiency is equal to W/M. M is -made up of available, unavailable and wasted (by Foucault currents, -etc.,) energy. Calling available energy W, unavailable but utilized -energy w, and wasted energy m, the expression for the coefficient of -commercial efficiency becomes - - W / ( W + w + m ) - when M = W + w + m - -Synonym--Net efficiency. - - -205 STANDARD ELECTRICAL DICTIONARY. - - -Efficiency, Electrical. -In a dynamo or generator the relation of total electric energy produced, -both wasted and useful or available to the useful or available -electrical energy. If we call W the useful electric and w the wasted -electric energy, the coefficient of electrical efficiency is equal to - - W / ( W + w ) - -Synonyms--Intrinsic Efficiency--Economic Coefficient--Coefficient of -Electrical Efficiency. - - -Efficiency of Conversion. -In a dynamo or generator the relation of energy absorbed to total -electric energy produced. Part of the electric energy is expended in -producing the field and in other ways. Thus a generator with high -efficiency of conversion may be a very poor one, owing to the -unavailable electric energy which it produces. The coefficient of -Efficiency of Conversion is obtained by dividing the total electric -energy produced by the energy absorbed in working the dynamo. If M -represents the energy absorbed, or work done in driving the dynamo or -generator, W the useful electric, and w the wasted electrical energy, -then the coefficient of efficiency of conversion is equal to - -(W + w ) / M - -In the quantity M are included besides available (W) and unavailable (w) -electric energy, the totally wasted energy due to Foucault currents, -etc., calling the latter m, the above formula may be given - -( W+ w ) / (W + w + m ) - -This coefficient may refer to the action of a converter, q. v., in the -alternating system. Synonym--Gross Efficiency. - - -Efficiency of Secondary Battery, Quantity. -The coefficient obtained by dividing the ampere-hours obtainable from a -secondary battery by the ampere hours required to charge it. - - -Efficiency of Secondary Battery, Real. -The coefficient obtained by dividing the energy obtainable from a -secondary battery by the energy absorbed in charging it. The energy is -conveniently taken in watt-hours and includes the consideration of the -spurious voltage. (See Battery, Secondary.) - - -206 STANDARD ELECTRICAL DICTIONARY. - - -Efflorescence. -The appearance of a dry salt upon the walls of a vessel containing a -solution above the normal water-line from evaporation of a liquid. It -appears in battery jars and in battery carbons, in the latter -interfering with the electrical connections, and oxidizing or rusting -them. (See Creeping.) - - -Effluvium, Electric. -When a gas is made to occupy the position of dielectric between two -oppositely electrified surfaces a peculiar strain or condition of the -dielectric is produced, which promotes chemical change. The condition is -termed electrical effluvium or the silent discharge. By an apparatus -specially constructed to utilize the condition large amounts of ozone -are produced. - -Synonym--Silent Discharge. - - -Elastic Curve. -A crude expression for a curve without projections or sudden -sinuosities; such a curve as can be obtained by bending an elastic strip -of wood. - - -Electrepeter. -An obsolete name for a key, switch or pole changer of any kind. - - -Elasticity, Electric. -The phenomenon of the dielectric is described under this term. When a -potential difference is established between two parts of the dielectric, -a flow of electricity displacement current starts through the -dielectric, which current is due to the electric stress, but is -instantly arrested by what has been termed the electric elasticity of -the dielectric. This is expressed by - ( electric stress ) / ( electric strain ) -and in any substance is inversely proportional to the specific inductive -capacity. - - -Electricity. -It is impossible in the existing state of human knowledge to give a -satisfactory definition of electricity. The views of various authorities -are given here to afford a basis for arriving at the general consensus -of electricians. - -We have as yet no conception of electricity apart from the electrified -body; we have no experience of its independent existence. (J. E. H. -Gordon.) - -What is Electricity? We do not know, and for practical purposes it is -not necessary that we should know. (Sydney F. Walker.) - -Electricity … is one of those hidden and mysterious powers of nature -which has thus become known to us through the medium of effects. -(Weale's Dictionary of Terms.) - -This word Electricity is used to express more particularly the cause, -which even today remains unknown, of the phenomena that we are about to -explain. (Amédée Guillemin.) - - -207 STANDARD ELECTRICAL DICTIONARY. - - -Electricity is a powerful physical agent which manifests itself mainly -by attractions and repulsions, but also by luminous and heating effects, -by violent commotions, by chemical decompositions, and many other -phenomena. Unlike gravity, it is not inherent in bodies, but it is -evoked in them by a variety of causes … (Ganot's Physics.) - -Electricity and magnetism are not forms of energy; neither are they -forms of matter. They may, perhaps, be provisionally defined as -properties or conditions of matter; but whether this matter be the -ordinary matter, or whether it be, on the other hand, that -all-pervading ether by which ordinary matter is surrounded, is a question -which has been under discussion, and which now may be fairly held to be -settled in favor of the latter view. (Daniell's Physics.) - -The name used in connection with an extensive and important class of -phenomena, and usually denoting the unknown cause of the phenomena or -the science that treats of them. (Imperial Dictionary.) - -Electricity. . . is the imponderable physical agent, cause, force or the -molecular movement, by which, under certain conditions, certain -phenomena, chiefly those of attraction and repulsion, . . . are -produced. (John Angell.) - -It has been suggested that if anything can rightly be called -"electricity," this must be the ether itself; and that all electrical -and magnetic phenomena are simply due to changes, strains and motions in -the ether. Perhaps negative electrification. . .means an excess of -ether, and positive electrification a defect of ether, as compared with -the normal density. (W. Larden.) - -Electricity is the name given to the supposed agent producing the -described condition (i. e. electrification) of bodies. (Fleeming -Jenkin.) - -There are certain bodies which, when warm and dry, acquire by friction, -the property of attracting feathers, filaments of silk or indeed any -light body towards them. This property is called Electricity, and bodies -which possess it are said to be electrified. (Linnaeus Cumming.) - -What electricity is it is impossible to say, but for the present it is -convenient to look upon it as a kind of invisible something which -pervades all bodies. (W. Perren Maycock.) - -What is electricity? No one knows. It seems to be one manifestation of -the energy which fills the universe and which appears in a variety of -other forms, such as heat, light, magnetism, chemical affinity, -mechanical motion, etc. (Park Benjamin.) - - -208 STANDARD ELECTRICAL DICTIONARY. - - -The theory of electricity adopted throughout these lessons is, that -electricity, whatever its true nature, is one, not two; that this -Electricity, whatever it may prove to be, is not matter, and is not -energy; that it resembles both matter and energy in one respect, -however, in that it can neither be created nor destroyed. (Sylvanus P. -Thomson.) - -In Physics a name denoting the cause of an important class of phenomena -of attraction and repulsion, chemical decomposition, etc., or, -collectively, these phenomena themselves. (Century Dictionary.) - -A power in nature, often styled the electric fluid, exhibiting itself, -when in disturbed equilibrium or in activity, by a circuit movement, the -fact of direction in which involves polarity, or opposition of -properties in opposite directions; also, by attraction for many -substances, by a law involving attraction between substances of unlike -polarity, and repulsion between those of like; by exhibiting accumulated -polar tension when the circuit is broken; and by producing heat, light, -concussion, and often chemical changes when the circuit passes between -the poles, or through any imperfectly conducting substance or space. It -is evolved in any disturbance of molecular equilibrium, whether from a -chemical, physical, or mechanical cause. (Webster's Dictionary.) - -In point of fact electricity is not a fluid at all, and only in a few of -its attributes is it at all comparable to a fluid. Let us rather -consider electricity to be a condition into which material substances -are thrown. . .(Slingo & Brooker.) - -[Transcriber's note: 2008 Dictionary: Phenomena arising from the -behavior of electrons and protons caused by the attraction of particles -with opposite charges and the repulsion of particles with the same -charge.] - - -Electricity, Cal. -The electricity produced in the secondary of a transformer by changes of -temperature in the core. This is in addition to the regularly induced -current. - -Synonym--Acheson Effect. - - -Electrics. -Substances developing electrification by rubbing or friction; as -Gilbert, the originator of the term, applied it, it would indicate -dielectrics. He did not know that, if insulated, any substance was one -of his "electrics." A piece of copper held by a glass handle becomes -electrified by friction. - - -Electrification. -The receiving or imparting an electric charge to a surface; a term -usually applied to electrostatic phenomena. - - -Electrization. -A term in electro-therapeutics; the subjection of the human system to -electric treatment for curative, tonic or diagnostic purposes. - - -Electro-biology. -The science of electricity in its relation to the living organism, -whether as electricity is developed by the organism, or as it affects -the same when applied from an external source. - - -209 STANDARD ELECTRICAL DICTIONARY. - - -Electro-capillarity. -The relations between surface tension, the potential difference and the -electrostatic capacity of fluids in contact. Although nominally in -contact such surfaces are separated by about one-twenty-millionth of a -centimeter (1/50000000 inch) ; thus a globule of mercury and water in -which it is immersed constitute an electrostatic accumulator of definite -electrostatic capacity. Again the mercury and water being in electric -connection differ in potential by contact (see Contact Theory). A -definite surface tension is also established. Any change in one of these -factors changes the other also. A current passed through the contact -surfaces will change the surface tension and hence the shape of the -mercury globule. Shaking the globule will change its shape and capacity -and produce a current. Heating will do the same. (See Electrometer, -Capillary; and Telephone, Capillary.) Mercury and water are named as -liquids in which the phenomena are most conveniently observed. They are -observable in other parallel cases. - - -Electro-chemical Equivalent. -The quantity of an element or compound liberated from or brought into -combination, electrolytically, by one coulomb of electricity. The -electro-chemical equivalent of hydrogen is found by experiment to be -.0000105 gram. That of any other substance is found by multiplying this -weight by its chemical equivalent referred to hydrogen, which is its -atomic or molecular weight divided by its valency. Thus the atomic -weight of oxygen is 16, its valency is 2, its equivalent is 16/2 = 8; -its electro-chemical equivalent is equal to .0000105 X 8 = .000840 gram. - - -Electro-chemical Series. -An arrangement of the elements in the order of their relative electrical -affinities so that each element is electro-negative to all the elements -following it, and electro-positive to the elements preceding it. The -usual series begins with oxygen as the most electro-negative and ends -with potassium as the most electro-positive element. There is, of -course, no reason why other series of compound radicals, such as -sulphion (SO4), etc., should not also be constructed. For each liquid -acting on substances a separate series of the substances acted on may be -constructed. Thus for dilute sulphuric acid the series beginning with -the negatively charged or most attacked one is zinc, amalgamated or -pure, cadmium, iron, tin, lead, aluminum, nickel, antimony, bismuth, -copper, silver, platinum. In other liquids the series is altogether -different. - - -Electro--chemistry. -The branch of electricity or of chemistry treating of the relations -between electric and chemical force in different compounds and -reactions. (See Electrolysis--Electrochemical series--Electro-chemical -Equivalent .) - - - -210 STANDARD ELECTRICAL DICTIONARY. - - -Electro-culture. -The application of electricity to the cultivation of plants. In one -system wires are stretched or carried across the bed under the surface, -and some are connected to one pole and others to the other pole of a -galvanic battery of two or more elements. In some experiments improved -results have thus been obtained. - -Another branch refers to the action of the electric arc light on -vegetation. This has an effect on vegetation varying in results. - - -Electrode. -(a) The terminal of an open electric circuit. - -(b) The terminals of the metallic or solid conductors of an electric -circuit, immersed in an electrolytic solution. - -(c) The terminals between which a voltaic arc is formed, always in -practice made of carbon, are termed electrodes. - -(d) In electro-therapeutics many different electrodes are used whose -names are generally descriptive of their shape, character, or uses to -which they are to be applied. Such are aural electrodes for the ears, -and many others. - -(e) The plates of a voltaic battery. - - -Electrode, Indifferent. -A term in electro-therapeutics. An electrode to which no therapeutic -action is attributed but which merely provides a second contact with the -body to complete the circuit through the same. The other electrode is -termed the therapeutic electrode. - - -Electrodes, Erb's Standards of. -Proposed standard sizes for medical electrodes as follows: - Name. Diameter. - Fine Electrode, 1/2 centimeter .2 inch - Small " 2 " .8 " - Medium " 7.5 " 3.0 " - Large " 6X2 " 2.4 X .8 " - Very large " 16x8 " 6.4 x 3.2 " - - -Electrodes, Non-polarizable. -In electro-therapeutics electrodes whose contact surface is virtually -porous clay saturated with zinc chloride solution. The series terminate -in amalgamated zinc ends, enclosed each in a glass tube, and closed with -clay. Contact of metal with the tissues is thus avoided. - - -Electrode, Therapeutic. -A term in electro-therapeutics. An electrode applied to the body for the -purpose of inducing therapeutic action, or for giving the basis for an -electric diagnosis of the case. The other electrode is applied to -complete the circuit only; it is termed the indifferent electrode. - - -Electro-diagnosis. -The study of the condition of a patient by the reactions which occur at -the terminals or kathode and anode of an electric circuit applied to the -person. The reactions are divided into kathodic and anodic reactions. - - -211 STANDARD ELECTRICAL DICTIONARY. - - -Electro-dynamic. adj. -The opposite of electrostatic; a qualification of phenomena due to -current electricity. - -Synonym--Electro-kinetic. - - -Electro-dynamic Attraction and Repulsion. -The mutual attraction and repulsion exercised by currents of electricity -upon each other. The theory of the cause is based upon stress of the -luminiferous ether and upon the reaction of lines of force upon each -other. For a resumé of the theory see Induction, Electro-magnetic. - - -Electro-dynamics. -The laws of electricity in a state of motion; the inter-reaction of -electric currents. It is distinguished from electro-magnetic induction -as the latter refers to the production of currents by induction. The -general laws of electro-dynamics are stated under Induction, -Electro-magnetic, q. v. - -Synonym--Electro-kinetics. - - -Fig. 143. DIAGRAM OF CONNECTIONS OF SIEMENS' ELECTRO-DYNAMOMETER. - - -212 STANDARD ELECTRICAL DICTIONARY. - - -Electro-dynamometer, Siemens'. -An apparatus for measuring currents by the reaction between two coils, -one fixed and one movable, through which the current to be measured -passes. It is one of the oldest commercial ammeters or current -measurers. It comprises a fixed coil of a number of convolutions and a -movable coil often of only one convolution surrounding the other. The -movable coil is suspended by a filament or thread from a spiral spring. -The spring is the controlling factor. Connection is established through -mercury cups so as to bring the two coils in series. In use the spring -and filament are adjusted by turning a milled head to which they are -connected until the coils are at right angles. Then the current is -turned on and deflects the movable coil. The milled head is turned until -the deflection is overcome. The angle through which the head is turned -is proportional to the square of the current. The movable coil must in -its position at right angles to the fixed one lie at right angles to the -magnetic meridian. - -Thus in the diagram, Fig. 143 A B C D is the fixed coil; E F G H is the -movable coil; S is the spiral spring attached at K to the movable coil. -The arrows show the course of the current as it goes through the coils. - - -Electrolier. -A fixture for supporting electric lamps; the analogue in electric -lighting of the gasolier or gas chandelier. Often both are combined, the -same fixture being piped and carrying gas burners, as well as being -wired and carrying electric lamps. - - -Electrolysis. -The separation of a chemical compound into its constituent parts or -elements by the action of the electric current. The compound may be -decomposed into its elements, as water into hydrogen and oxygen, or into -constituent radicals, as sodium sulphate into sodium and sulphion, which -by secondary reactions at once give sodium hydrate and sulphuric acid. -The decomposition proceeds subject to the laws of electrolysis. (See -Electrolysis, Laws of.) For decomposition to be produced there is for -each compound a minimum electro-motive force or potential difference -required. The current passes through the electrolyte or substance -undergoing decomposition entirely by Electrolytic Conduction, q. v. in -accordance with Grothüss' Hypothesis, q. v. The electrolyte therefore -must be susceptible of diffusion and must be a fluid. - -The general theory holds that under the influence of a potential -difference between electrodes immersed in an electrolyte, the molecules -touching the electrodes are polarized, in the opposite sense for each -electrode. If the potential difference is sufficient the molecules will -give up one of their binary constituents to the electrode, and the other -constituent will decompose the adjoining molecule, and that one being -separated into the same two constituents will decompose its neighbor, -and so on through the mass until the other electrode is reached. This -one separates definitely the second binary constituent from the -molecules touching it. - - -213 STANDARD ELECTRICAL DICTIONARY. - - -Thus there is an exact balance preserved. Just as many molecules are -decomposed at one electrode as at the other, and the exact chain of -decomposition runs through the mass. Each compound electrolyzed develops -a binary or two-fold composition, and gives up one constituent to one -electrode and the other to the other. - - -Fig. 144. ACTION OF MOLECULES IN A SOLUTION -BEFORE AND DURING ELECTROLYSIS. - - -The cut shows the assumed polarization of an electrolyte. The upper row -shows the molecules in irregular order before any potential difference -has been produced, in other words, before the circuit is closed. The -next row shows the first effects of closing the circuit, and also -indicates the polarization of the mass, when the potential difference is -insufficient for decomposition. The third row indicates the -decomposition of a chain of molecules, one constituent separating at -each pole. - - -214 STANDARD ELECTRICAL DICTIONARY. - - -Electrolysis, Laws of. -The following are the principal laws, originally discovered by -Faraday, and sometimes called Faraday's Laws of Electrolysis: - -1. Electrolysis cannot take place unless the electrolyte is a conductor. -Conductor here means an electrolytic conductor, one that conducts by its -own molecules traveling, and being decomposed. (See Grothüss' -Hypothesis.) - -II. The energy of the electrolytic action of the current is the same -wherever exercised in different parts of the circuit. - -III. The same quantity of electricity--that is the same current for the -same period----- decomposes chemically equivalent quantities of the -bodies it decomposes, or the weights of elements separated in -electrolytes by the same quantity of electricity (in coulombs or some -equivalent unit) are to each other as their chemical equivalent. - -IV. The quantity of a body decomposed in a given time is proportional to -the strength of the current. - -To these may be added the following: - -V. A definite and fixed electro-motive force is required for the -decomposition of each compound, greater for some and less for others. -Without sufficient electro-motive force expended on the molecule no -decomposition will take place. (See Current, Convective.) - - -Electrolyte. -A body susceptible of decomposition by the electric current, and capable -of electrolytic conduction. It must be a fluid body and therefore -capable of diffusion, and composite in composition. An elemental body -cannot be an electrolyte. - - -Electrolytic Analysis. -Chemical analysis by electrolysis. The quantitative separation of a -number of metals can be very effectively executed. Thus, suppose that a -solution of copper sulphate was to be analyzed. A measured portion of -the solution would be introduced into a weighed platinum vessel. The -vessel would be connected to the zinc plate terminal of a battery. From -the other terminal of the battery a wire would be brought and would -terminate in a plate of platinum. This would be immersed in the solution -in the vessel. As the current would pass the copper sulphate would be -decomposed and eventually all the copper would be deposited in a firm -coating on the platinum. The next operations would be to wash the metal -with distilled water, and eventually with alcohol, to dry and to weigh -the dish with the adherent copper. On subtracting the weight of the dish -alone from the weight of the dish and copper, the weight of the metallic -copper in the solution would be obtained. - -In similar ways many other determinations are effected. The processes of -analysis include solution of the ores or other substances to be analyzed -and their conversion into proper form for electrolysis. Copper as just -described can be precipitated from the solution of its sulphate. For -iron and many other metals solutions of their double alkaline oxalates -are especially available forms for analysis. - -The entire subject has been worked out in considerable detail by -Classen, to whose works reference should be made for details of -processes. - - -Electrolytic Convection. -It is sometimes observed that a single cell of Daniell battery, for -instance, or other source of electric current establishing too low a -potential difference for the decomposition of water seems to produce a -feeble but continuous decomposition. This is very unsatisfactorily -accounted for by the hydrogen as liberated combining with dissolved -oxygen. (Ganot.) The whole matter is obscure. (See Current, Convection.) - - -215 STANDARD ELECTRICAL DICTIONARY. - - -Electrolytic Conduction. -Conduction by the travel of atoms or radicals from molecule to molecule -of a substance with eventual setting free at the electrodes of the atoms -or radicals as elementary molecules or constituent radicals. A substance -to be capable of acting as an electrolytic conductor must be capable of -diffusion, and must also have electrolytic conductivity. Such a body is -called an electrolyte. (See Grothüss' Hypothesis--Electrolysis-- -Electrolysis, Laws of--Electro-chemical Equivalent.) - - -Electro-magnet. -A mass, in practice always of iron, around which an electric circuit is -carried, insulated from the iron. When a current is passed through the -circuit the iron presents the characteristics of a magnet. (See -Magnetism, Ampére's Theory of--Solenoid--Lines of Force.) In general -terms the action of a circular current is to establish lines of force -that run through the axis of the circuit approximately parallel thereto, -and curving out of and over the circuit, return into themselves outside -of the circuit. If a mass of iron is inserted in the axis or elsewhere -near such current, it multiplies within itself the lines of force, q. v. -(See also Magnetic Permeability--Permeance--Magnetic Induction, -Coefficient of Magnetic Susceptibility--Magnetization, Coefficient of -Induced.) These lines of force make it a magnet. On their direction, -which again depends on the direction of the magnetizing current, depends -the polarity of the iron. The strength of an electro-magnet, below -saturation of the core (see Magnetic Saturation), is proportional nearly -to the ampere-turns, q. v. More turns for the same current or more -current for the same turns increase its strength. - -In the cut is shown the general relation of current, coils, core and -line of force. Assume that the magnet is looked at endwise, the observer -facing one of the poles; then if the current goes around the core in the -direction opposite to that of the hands of a clock, such pole will be -the north pole. If the current is in the direction of the hands of a -clock the pole facing the observer will be the south pole. The whole -relation is exactly that of the theoretical Ampérian currents, already -explained. The direction and course of the lines of force created are -shown in the cut. - -The shapes of electro-magnets vary greatly. The cuts show several forms -of electro-magnets. A more usual form is the horseshoe or double limb -magnet, consisting generally of two straight cores, wound with wire and -connected and held parallel to each other by a bar across one end, which -bar is called the yoke. - -In winding such a magnet the wire coils must conform, as regards -direction of the current in them to the rule for polarity already cited. -If both poles are north or both are south poles, then the magnet cannot -be termed a horseshoe magnet, but is merely an anomalous magnet. In the -field magnets of dynamos the most varied types of electro-magnets have -been used. Consequent poles are often produced in them by the direction -of the windings and connections. - -To obtain the most powerful magnet the iron core should be as short and -thick as possible in order to diminish the reluctance of the magnetic -circuit. To obtain a greater range of action a long thin shape is -better, although it involves waste of energy in its excitation. - - -216 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 145 DIAGRAM OF AN ELECTRO-MAGNET SHOWING RELATION OF -CURRENT AND WINDING TO ITS POLARITY AND LINES OF FORCE. - - -Fig. 146. ANNULAR ELECTRO-MAGNET - - -Electro-magnet, Annular. -An electro-magnet consisting of a cylinder with a circular groove cut in -its face, in which groove a coil of insulated wire is placed. On the -passage of a current the iron becomes polarized and attracts an armature -towards or against its grooved face. The cut shows the construction of -an experimental one. It is in practice applied to brakes and clutches. -In the cut of the electro-magnetic brake (see Brake, Electro-magnetic), -C is the annular magnet receiving its current through the brushes, and -pressed when braking action is required against the face of the moving -wheel. The same arrangement, it can be seen, may apply to a clutch. - - -217 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 147. BAR ELECTRO-MAGNET. - - -Electro-magnet, Bar. -A straight bar of iron surrounded with a magnetizing coil of wire. Bar -electromagnets are not much used, the horseshoe type being by far the -more usual. - - -Electro-magnet, Club-foot. -An electro-magnet, one of whose legs only is wound with wire, the other -being bare. - - -Fig. 148. CLUB-FOOT ELECTRO-MAGNETS WITH HINGED ARMATURES. - - -Electro-magnet, Hinged. -An electro-magnet whose limbs are hinged at the yoke. On excitation by a -current the poles tend to approach each other. - - -Fig. 149. ELECTRO-MAGNET, HINGED - - -Electro-magnetic Attraction and Repulsion. -The attraction and repulsion due to electromagnetic lines of force, -which lines always tend to take as short a course as possible and also -seek the medium of the highest permeance. This causes them to -concentrate in iron and steel or other paramagnetic substance and to -draw them towards a magnet by shortening the lines of force connecting -the two. It is exactly the same attraction as that of the permanent -magnet for its armature, Ampére's theory bringing the latter under the -same title. In the case of two magnets like poles repel and unlike -attract. In the case of simple currents, those in the same direction -attract and those in opposite directions repel each other. This refers -to constant current reactions. Thus the attraction of unlike poles of -two magnets is, by the Ampérian theory, the attraction of two sets of -currents of similar direction, as is evident from the diagram. The -repulsion of like poles is the repulsion of unlike currents and the same -applies to solenoids, q. v. (See Magnetism and do. Ampére's Theory -of--Induction, Electro-dynamic--Electro-magnetic Induction.) - - -218 STANDARD ELECTRICAL DICTIONARY. - - -Electro-magnetic Control. -Control of a magnet, iron armature, or magnetic needle in a -galvanometer, ammeter, voltmeter or similar instrument by an -electro-magnetic field, the restitutive force being derived from an -electro-magnet. The restitutive force is the force tending to bring the -index to zero. - - -Electro-magnetic Field of Force. -A field of electro-magnetic lines of force, q. v., established through -the agency of an electric current. A wire carrying a current is -surrounded by circular concentric lines of force which have the axis of -the wire as the locus of their centres. Electro-magnets produce lines of -force identical with those produced by permanent magnets. (See Field of -Force--Magnetic Field of Force--Controlling Field--Deflecting Field.) - - -Electro-magnetic Induction. -When two currents of unlike direction are brought towards each other, -against their natural repulsive tendency work is done, and the -consequent energy takes the form of a temporary increase in both -currents. When withdrawn, in compliance with the natural tendency of -repulsion, the currents are diminished in intensity, because energy is -not expended on the withdrawal, but the withdrawal is at the expense of -the energy of the system. The variations thus temporarily produced in -the currents are examples of electro-magnetic induction. The currents -have only the duration in each case of the motion of the circuits. One -circuit is considered as carrying the inducer current and is termed the -primary circuit and its current the primary current, the others are -termed the secondary circuit and current respectively. We may assume a -secondary circuit in which there is no current. It is probable that -there is always an infinitely small current at least, in every closed -circuit. Then an approach of the circuits will induce in the secondary -an instantaneous current in the reverse direction. On separating the two -circuits a temporary current in the same direction is produced in the -secondary. - - -219 STANDARD ELECTRICAL DICTIONARY. - - -A current is surrounded by lines of force. The approach of two circuits, -one active, involves a change in the lines of force about the secondary -circuit. Lines of force and current are so intimately connected that a -change in one compels a change in the other. Therefore the induced -current in the secondary may be attributed to the change in the field of -force in which it lies, a field maintained by the primary circuit and -current. Any change in a field of force induces a current or change of -current in any closed circuit in such field, lasting as long as the -change is taking place. The new current will be of such direction as to -oppose the change. (See Lenz's Law.) - -The action as referred to lines of force may be figured as the cutting -of such lines by the secondary circuit, and such cutting may be brought -about by moving the secondary in the field. (See Lines of Force--Field -of Force.) The cutting of 1E8 lines of force per second by a closed -circuit induces an electro-motive force of one volt. (See Induction, -Mutual, Coefficient of.) - - -Electro-magnet, Iron Clad. -A magnet whose coil and core are encased in a iron jacket, generally -connected to one end of the core. This gives at one end two poles, one -tubular, the other solid, and concentric with each other. It is -sometimes called a tubular magnet. - - -Electro-magnet, One Coil. -An electro-magnet excited by one coil. In some dynamos the field magnets -are of this construction, a single coil, situated about midway between -the poles, producing the excitation. - - -Electro-magnetic Leakage. -The leakage of lines of force in an electro-magnet; the same as magnetic -leakage. (See Magnetic Leakage.) - - -Electro-magnetic Lines of Force. -The lines of force produced in an electro-magnetic field. They are -identical with Magnetic Lines of Force, q. v. (See also Field of -Force-Line of Force.) - - -Electro-magnetic Stress. -The stress in an electro-magnetic field of force, showing itself in the -polarization of light passing through a transparent medium in such a -field. (See Magnetic Rotary Polarization.) - - -Electro-magnetic Theory of Light. -This theory is due to J. Clark Maxwell, and the recent Hertz experiments -have gone far to prove it. It holds that the phenomena of light are due -to ether waves, identical in general factors with those produced by -electro-magnetic induction of alternating currents acting on the ether. -In a non-conductor any disturbance sets an ether wave in motion owing to -its restitutive force; electricity does not travel through such a -medium, but can create ether waves in it. Therefore a non-conductor of -electricity is permeable to waves of ether or should transmit light, or -should be transparent. A conductor on the other hand transmits -electrical disturbances because it has no restitutive force and cannot -support an ether wave. Hence a conductor should not transmit light, or -should be opaque. With few exceptions dielectrics or non-conductors are -transparent, and conductors are opaque. - - -220 STANDARD ELECTRICAL DICTIONARY. - - -Again, the relation between the electrostatic and electro-magnet units -of quantity is expressed by 1 : 30,000,000,000; the latter figure in -centimeters gives approximately the velocity of light. The -electro-magnetic unit depending on electricity in motion should have -this precise relation if an electro-magnetic disturbance was propagated -with the velocity of light. If an electrically charged body were whirled -around a magnetic needle with the velocity of light, it should act in -the same way as a current circulating around it. This effect to some -extent has been shown experimentally by Rowland. - -A consequence of these conclusions is (Maxwell) that the specific -inductive capacity of a non-conductor or dielectric should be equal to -the square of its index of refraction for waves of infinite length. This -is true for some substances--sulphur, turpentine, petroleum and benzole. -In others the specific inductive capacity is too high, e. g., vegetable -and animal oils, glass, Iceland spar, fluor spar, and quartz. - - -Electro-magnetic Unit of Energy. -A rate of transference of energy equal to ten meg-ergs per second. - - -Electro-magnetism. -The branch of electrical science treating of the magnetic relations of a -field of force produced by a current, of the reactions of -electro-magnetic lines of force, of the electromagnetic field of force, -of the susceptibility, permeability, and reluctance of diamagnetic and -paramagnetic substances, and of electro-magnets in general. - - -Electro-magnet, Long Range. -An electro-magnet so constructed with extended pole pieces or otherwise, -as to attract its armature with reasonably constant force over a -considerable distance. The coil and plunger, q. v., mechanisms -illustrate one method of getting an extended range of action. When a -true electro-magnet is used, one with an iron core, only a very limited -range is attainable at the best. (See Electro-magnet, Stopped Coil--do. -Plunger.) - - -Electro-magnet, Plunger. -An electro-magnet with hollow coils, into which the armature enters as a -plunger. To make it a true electro-magnet it must have either a yoke, -incomplete core, or some polarized mass of iron. - - -Electro-magnet, Polarized. -An electro-magnet consisting of a polarized or permanently magnetized -core wound with magnetizing coils, or with such coils on soft iron cores -mounted on its ends. The coils may be wound and connected so as to -cooperate with or work against the permanent magnet on which it is -mounted. In Hughes' magnet shown in the cut it is mounted in opposition, -so that an exceedingly feeble current will act to displace the armature, -a, which is pulled away from the magnet by a spring, s. - - -221 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 150 HUGHES' POLARIZED ELECTRO-MAGNET - - -Electro-magnets, Interlocking. -Electro-magnets so arranged that their armatures interlock. Thus two -magnets, A A and B B, may be placed with their armatures, M and N, at -right angles and both normally pulled away from the poles. When the -armature M is attracted a catch on its end is retained by a hole in the -end of the other armature N, and when the latter armature N is attracted -by its magnet the armature M is released. In the mechanism shown in the -cut the movements of the wheel R are controlled. Normally it is held -motionless by the catch upon the bottom of the armature M, coming -against the tooth projecting from its periphery. A momentary current -through the coils of the magnet A A releases it, by attracting M, which -is caught and retained by N, and leaves it free to rotate. A momentary -current through the coils of the magnet B B again releases M, which -drops down and engages the tooth upon R and arrests its motion. - - -Fig. 151. INTERLOCKING ELECTRO-MAGNETS. - - -222 STANDARD ELECTRICAL DICTIONARY. - - -Electro-magnet, Stopped Coil. -An electro-magnet consisting of a tubular coil, in which a short fixed -core is contained, stopping up the aperture to a certain distance, while -the armature is a plunger entering the aperture. This gives a longer -range of action than usual. - - -Electro-magnet, Surgical. -An electro-magnet, generally of straight or bar form, fitted with -different shaped pole pieces, used for the extraction of fragments of -iron or steel from the eyes. Some very curious cases of successful -operations on the eyes of workmen, into whose eyes fragments of steel or -iron had penetrated, are on record. - - -Electro-medical Baths. -A bath for the person provided with connections and electrodes for -causing a current of electricity of any desired type to pass through the -body of the bather. Like all electro-therapeutical treatment, it should -be administered under the direction of a physician only. - - -Electro-metallurgy. -(a) In the reduction of ores the electric current has been proposed but -never extensively used, except in the reduction of aluminum and its -alloys. (See Reduction of Ores, Electric.) - -(b) Electro-plating and deposition of metal from solutions is another -branch. (See Electroplating and Electrotyping.) - -(c) The concentration of iron ores by magnetic attraction may come under -this head. (See Magnetic Concentration of Ores.) - - -Electrometer. -An instrument for use in the measurement of potential difference, by the -attraction or repulsion of statically charged bodies. They are -distinguished from galvanometers as the latter are really current -measurers, even if wound for use as voltmeters, depending for their -action upon the action of the current circulating in their coils. - - -Electrometer, Absolute. -An electrometer designed to give directly the value of a charge in -absolute units. In one form a plate, a b, of conducting surface is -supported or poised horizontally below a second larger plate C, also of -conducting surface. The poised plate is surrounded by a detached guard -ring--an annular or perforated plate, r g r' g'--exactly level and even -with it as regards the upper surface. The inner plate is carried by a -delicate balance. In use it is connected to one of the conductors and -the lower plate to earth or to the other. The attraction between them is -determined by weighing. By calculation the results can be made absolute, -as they depend on actual size of the plates and their distance, outside -of the potential difference of which of course nothing can be said. If S -is the area of the disc, d the distance of the plates, V-V1 the -difference of their potential, which is to be measured, and F the force -required to balance their attraction, we have: - -F = ( ( V - V1 )^2 * S ) / ( 8 * PI * d^2 ) - - -223 STANDARD ELECTRICAL DICTIONARY. - - -If V = 0 this reduces to - - F = ( V^2 * S ) / ( 8 * PI * d^2 ) (2) - or - V = d * SquareRoot( (8 * PI * F ) / S ) (3) - -As F is expressed as a weight, and S and a as measures of area and -length, this gives a means of directly obtaining potential values in -absolute measure. (See Idiostatic Method--Heterostatic Method.) - -Synonyms--Attracted Disc Electrometer--Weight Electrometer. - - -Fig. 152. SECTION OF BASE OF PORTABLE ELECTROMETER. - - -In some forms the movable disc is above the other, and supported at the -end of a balance beam. In others a spring support, arranged so as to -enable the attraction to be determined in weight units, is adopted. The -cuts, Figs. 152 and 154, show one of the latter type, the portable -electrometer. The disc portion is contained within a cylindrical vessel. - - -Fig. 153. DIAGRAM ILLUSTRATING THEORY OF ABSOLUTE ELECTROMETER. - - -Referring to Fig. 152 g is the stationary disc, charged through the -wire connection r; f is the movable disc, carried by a balance beam -poised at i on a horizontal and transverse stretched platinum wire, -acting as a torsional spring. The position of the end k of the balance -beam shows when the disc f is in the plane of the guard ring h h. The -end k is forked horizontally and a horizontal sighting wire or hair is -fastened across the opening of the fork. When the hair is midway between -two dots on a vertical scale the lever is in the sighted position, as it -is called, and the disc is in the plane of the guard ring. - - -224 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 154. PORTABLE ELECTROMETER. - - -The general construction is seen in Fig. 154. There the fixed disc D is -carried by insulating stem g1. The charging electrode is supported by an -insulating stem g2, and without contact with the box passes out of its -cover through a guard tube E, with cover, sometimes called umbrella, V. -The umbrella is to protect the apparatus from air currents. At m is the -sighting lens. H is a lead box packed with pumice stone, moistened with -oil of vitriol or concentrated sulphuric acid, to preserve the -atmosphere dry. Before use the acid is boiled with some ammonium -sulphate to expel any corrosive nitrogen oxides, which might corrode the -brass. - -In use the upper disc is charged by its insulated electrode within the -tube E; the movable disc is charged if desired directly through the case -of the instrument. The upper disc is screwed up or down by the -micrometer head M, until the sighted position is reached. The readings -of the micrometer on the top of the case give the data for calculation. - - -225 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 155. LIPPMAN'S CAPILLARY ELECTROMETER. - - -Electrometer, Capillary. -An electrometer for measuring potential difference by capillary action, -which latter is affected by electrostatic excitement. A tube A contains -mercury; its end drawn out to a fine aperture dips into a vessel B which -contains dilute sulphuric acid with mercury under it, as shown. Wires -running from the binding-posts a and b connect one with the mercury in -A, the other with that in B. The upper end of the tube A connects with a -thick rubber mercury reservoir T, and manometer H. The surface tension -of the mercury-acid film at the lower end of the tube A keeps all in -equilibrium. If now a potential difference is established between a and -b, as by connecting a battery thereto, the surface tension is increased -and the mercury rises in the tube B. By screwing down the compressing -clamp E, the mercury is brought back to its original position. The -microscope M is used to determine this position with accuracy. The -change in reading of the manometer gives the relation of change of -surface tension and therefore of potential. Each electrometer needs -special graduation or calibration, but is exceedingly sensitive and -accurate. It cannot be used for greater potential differences than .6 -volt, but can measure .0006 volt. Its electrostatic capacity is so small -that it can indicate rapid changes. Another form indicates potential -difference by the movement of a drop of sulphuric acid in a horizontal -glass tube, otherwise filled with mercury, and whose ends lead into two -mercury cups or reservoirs. The pair of electrodes to be tested are -connected to the mercury vessels. The drop moves towards the negative -pole, and its movement for small potential differences (less than one -volt) is proportional to the electro-motive force or potential -difference. - - -226 STANDARD ELECTRICAL DICTIONARY. - - -Electrometer Gauge. -An absolute electrometer (see Electrometer, Absolute) forming an -attachment to a Thomson quadrant electrometer. It is used to test the -potential of the flat needle connected with the inner surface of the -Leyden jar condenser of the apparatus. This it does by measuring the -attraction between itself and an attracting disc, the latter connected -by a conductor with the interior of the jar. - - -Electrometer, Lane's. -A Leyden jar with mounted discharger, so that when charged to a certain -point it discharges itself. It is connected with one coating of any jar -whose charge is to be measured, which jar is then charged by the other -coating. As the jar under trial becomes charged to a certain point the -electrometer jar discharges itself, and the number of discharges is the -measure of the charge of the other jar. It is really a unit jar, q. v. - - -Fig. 156. THOMSON'S QUADRANT ELECTROMETER. - - -Fig. 157. HENLEY'S QUADRANT ELECTROSCOPE. - - -227 STANDARD ELECTRICAL DICTIONARY. - - -Electrometer, Quadrant. -(a) Sir William Thomson's electrometer, a simple form of which is shown -in the cut, consists of four quadrants of metal placed horizontally; -above these a broad flat aluminum needle hangs by a very fine wire, -acting as torsional suspension. The quadrants are insulated from each -other, but the opposite ones connect with each other by wires. The -apparatus is adjusted so that, when the quadrants are in an unexcited -condition the needle is at rest over one of the diametrical divisions -between quadrants. The needle by its suspension wire is in communication -with the interior of a Leyden jar which is charged. The whole is covered -with a glass shade, and the air within is kept dry by a dish of -concentrated sulphuric acid so that the jar retains its charge for a -long time and keeps the needle at approximately a constant potential. If -now two pairs of quadrants are excited with opposite electricities, as -when connected with the opposite poles of an insulated galvanic cell, -the needle is repelled by one pair and attracted by the other, and -therefore rotates through an arc of greater or less extent. A small -concave mirror is attached above the needle and its image is reflected -on a graduated screen. This makes the smallest movement visible. -Sometimes the quadrants are double, forming almost a complete box, -within which the needle moves. - -(b) Henley's quadrant electrometer is for use on the prime conductor of -an electric machine, for roughly indicating the relative potential -thereof. It consists of a wooden standard attached perpendicularly to -the conductor. Near one end is attached a semi-circular or quadrant arc -of a circle graduated into degrees or angular divisions. An index, -consisting of a straw with a pith-bell attached to its end hangs from -the center of curvature of the arc. When the prime conductor is charged -the index moves up over the scale and its extent of motion indicates the -potential relatively. - -When the "quadrant electrometer" is spoken of it may always be assumed -that Sir William Thomson's instrument is alluded to. Henley's instrument -is properly termed a quadrant electroscope. (See Electroscope.) - - -Electro-motive Force. -The cause which produces currents of electricity. In general it can be -expressed in difference of potentials, although the term electro-motive -force should be restricted to potential difference causing a current. It -is often a sustained charging of the generator terminals whence the -current is taken. Its dimensions are - -(work done/the quantity of electricity involved), - -or ( M * (L^2) /(T^2 ) ) / ((M^.5) * (L^.5)) = ( (M^.5) * (L^1.5) ) /(T^2) - -The practical unit of electro-motive force is the volt, q. v. It is -often expressed in abbreviated form, as E. M. D. P., or simply as D. P., -i. e., potential difference. - -Electro-motive force and potential difference are in many cases -virtually identical, and distinctions drawn between them vary with -different authors. If we consider a closed electric circuit carrying a -current, a definite electro-motive force determined by Ohm's law from -the resistance and current obtains in it. But if we attempt to define -potential difference as proper to the circuit we may quite fail. -Potential difference in a circuit is the difference in potential between -defined points of such circuit. But no points in a closed circuit can be -found which differ in potential by an amount equal to the entire -electro-motive force of the circuit. Potential difference is properly -the measure of electro-motive force expended on the portion of a circuit -between any given points. Electro-motive force of an entire circuit, as -it is measured, as it were, between two consecutive points but around -the long portion of the circuit, is not conceivable as merely potential -difference. Taking the circle divided in to degrees as an analogy, the -electro-motive force of the entire circuit might be expressed as 360º, -which are the degrees intervening between two consecutive points, -measured the long way around the circle. But the potential difference -between the same two points would be only 1º, for it would be measured -by the nearest path. - -[Transcriber's notes: If 360º is the "long" way, 0º is the "short". A -formal restatement of the above definition of EMF: "If a charge Q passes -through a device and gains energy U, the net EMF for that device is the -energy gained per unit charge, or U/Q. The unit of EMF is a volt, or -newton-meter per coulomb."] - - -228 STANDARD ELECTRICAL DICTIONARY. - - -Electro-motive Force, Counter. -A current going through a circuit often has not only true or ohmic -resistance to overcome, but meets an opposing E. M. F. This is termed -counter-electro-motive force. It is often treated in calculations as -resistance, and is termed spurious resistance. It may be a part of the -impedance of a circuit. - -In a primary battery hydrogen accumulating on the negative plate -develops counter E. M. F. In the voltaic arc the differential heating of -the two carbons does the same. The storage battery is changed by a -current passing in the opposite direction to its own natural current; -the polarity of such a battery is counter E. M. F. - - -Electro-motive Force, Unit. -Unit electro-motive force is that which is created in a conductor moving -through a magnetic field at such a rate as to cut one unit line of force -per second. It is that which must be maintained in a circuit of unit -resistance to maintain a current of unit quantity therein. It is that -which must be maintained between the ends of a conductor in order that -unit current may do unit work in a second. - - -Electro-motive Intensity. -The force acting upon a unit charge of electricity. The mean force is -equal to the difference of potential between two points within the field -situated one centimeter apart, such distance being measured along the -lines of force. The term is due to J. Clerk Maxwell. - - -Electro-motive Series. -Arrangement of the metals and carbon in series with the most -electro-positive at one end, and electronegative at the other end. The -following are examples for different exciting liquids: - -Dilute Sulphuric Dilute Hydrochloric Caustic Potassium -Acid Acid. Potash. Sulphide. - -Zinc Zinc Zinc Zinc -Cadmium Cadmium Tin Copper -Tin Tin Cadmium Cadmium -Lead Lead Antimony Tin -Iron Iron Lead Silver -Nickel Copper Bismuth Antimony -Bismuth Bismuth Iron Lead -Antimony Nickel Copper Bismuth -Copper Silver Nickel Nickel -Silver Antimony Silver Iron -Gold -Platinum -Carbon - -In each series the upper metal is the positive, dissolved or attacked -element. - - -229 STANDARD ELECTRICAL DICTIONARY. - - -Electro-motograph. -An invention of Thomas A. Edison. A cylinder of chalk, moistened with -solution of caustic soda, is mounted so as to be rotated by a handle. A -diaphragm has an arm connected to its center. This arm is pressed -against the surface of the cylinder by a spring. When the cylinder is -rotated, a constant tension is exerted on the diaphragm. If a current is -passed through the junction of arm and cylinder the electrolytic action -alters the friction so as to change the stress upon the diaphragm. - -If the current producing this effect is of the type produced by the -human voice through a microphone the successive variations in strain -upon the diaphragm will cause it to emit articulate sounds. These are -produced directly by the movement of the cylinder, the electrolytic -action being rather the regulating portion of the operation. Hence very -loud sounds can be produced by it. This has given it the name of the -loud- speaking telephone. - -The same principle may be applied in other ways. But the practical -application of the motograph is in the telephone described. - - -Fig. 158. ELECTRO-MOTOGRAPH TELEPHONE - - -Electro-motor. -This term is sometimes applied to a current generator, such as a voltaic -battery. - - -Electro-muscular Excitation. -A term in medical electricity indicating the excitation of muscle as the -effect of electric currents of any kind. - - -Electro-negative. adj. -Appertaining to negative electrification; thus of the elements oxygen is -the most electro-negative, because if separated by electrolytic action -from any combination, it will be charged with negative electricity. - - -230 STANDARD ELECTRICAL DICTIONARY. - - -Electro-optics. -The branch of natural science treating of the relations between light -and electricity. Both are supposed to be phenomena of or due to the -luminiferous ether. To it may be referred the following: - -(a) Electro-magnetic Stress and Magnetic Rotary Polarization; - -(b) Dielectric Strain; all of which may be referred to in this book; - -(c) Change in the resistance of a conductor by changes in light to which -it is exposed (see Selenium); - -(d) The relation of the index of refraction of a dielectric to the -dielectric constant (see Electro-magnetic Theory of Light); - -(e) The identity (approximate) of the velocity of light in centimeters -and the relative values of the electrostatic and electro-magnet units -of intensity, the latter being 30,000,000,000 times greater than the -former, while the velocity of light is 30,000,000,000 centimeters per -second. - - -Electrophoric Action. -The action of an electrophorous; utilized in influence machines. (See -Electrophorous.) - - -Fig. 159. ELECTROPHOROUS. - - -Electrophorous. -An apparatus for the production of electric charges of high potential by -electrostatic induction, q. v. It consists of a disc of insulating -material B, such as resin or gutta percha, which is held in a shallow -metal-lined box or form. The disc may be half an inch thick and a foot -or more in diameter, or may be much smaller and thinner. A metal disc A, -smaller in diameter is provided with an insulating handle which may be -of glass, or simply silk suspension strings. To use it the disc B is -excited by friction with a cat-skin or other suitable substance. The -metallic disc is then placed on the cake of resin exactly in its centre, -so that the latter disc or cake projects on all sides. Owing to -roughness there is little real electric contact between the metal and -dielectric. On touching the metal disc a quantity of negative -electricity escapes to the earth. On raising it from the cake it comes -off excited positively, and gives a spark and is discharged. It can be -replaced, touched, removed and another spark can be taken from it, and -so on as long as the cake stays charged. - -The successive discharges represent electrical energy expended. This is -derived from the muscular energy expended by the operator in separating -the two discs when oppositely excited. As generally used it is therefore -an apparatus for converting muscular or mechanical energy into electric -energy. - - -231 STANDARD ELECTRICAL DICTIONARY. - - -Electro-physiology. -The science of the electric phenomena of the animal system. It may also -be extended to include plants. The great discovery of Galvani with the -frog's body fell into this branch of science. The electric fishes, -gymnotus, etc., present intense phenomena in the same. - - -Electroplating. -The deposition by electrolysis of a coating of metal upon a conducting -surface. The simplest system makes the object to be plated the negative -electrode or plate in a galvanic couple. Thus a spoon or other object -may be connected by a wire to a plate of zinc. A porous cup is placed -inside a battery jar. The spoon is placed in the porous cup and the zinc -outside it. A solution of copper sulphate is placed in the porous cup, -and water with a little sodium or zinc sulphate dissolved in it, -outside. A current starts through the couple, and copper is deposited on -the spoon. - -A less primitive way is to use a separate battery as the source of -current; to connect to the positive plate by a wire the object to be -plated, and a plate of copper, silver, nickel or other metal to the -other pole of the battery. On immersing both object and plate (anode) in -a bath of proper solution the object will become plated. - -In general the anode is of the same material as the metal to be -deposited, and dissolving keeps up the strength of the bath. There are a -great many points of technicality involved which cannot be given here. -The surface of the immersed object must be conductive. If not a fine -wire network stretched over it will gradually fill up in the bath and -give a matrix. More generally the surface is made conductive by being -brushed over with plumbago. This may be followed by a dusting of iron -dust, followed by immersion in solution ot copper sulphate. This has the -effect of depositing metallic copper over the surface as a starter for -the final coat. - -Attention must be paid to the perfect cleanliness of the objects, to the -condition of the bath, purity of anodes and current density. - -Voltaic batteries are largely used for the current as well as special -low resistance dynamos. Thermo-electric batteries are also used to some -extent but not generally. - - -Electro-pneumatic Signals. -Signals, such as railroad signals or semaphores, moved by compressed -air, which is controlled by valves operated by electricity. The House -telegraph, which was worked by air controlled by electricity, might come -under this term, but it is always understood as applied to railroad -signals, or their equivalent. - - -232 STANDARD ELECTRICAL DICTIONARY. - - -Electropoion Fluid. -An acid depolarizing solution for use in zinc-carbon couples, such as -the Grenet battery. The following are formulae for its preparation: - -(a) Dissolve one pound of potassium bichromate in ten pounds of water, -to which two and one-half pounds of concentrated sulphuric acid have -been gradually added. The better way is to use powdered potassium -bichromate, add it to the water first, and then gradually add the -sulphuric acid with constant stirring. - -(b) To three pints of water add five fluid ounces of concentrated -sulphuric acid; add six ounces pulverized potassium bichromate. - -(c) Mix one gallon concentrated sulphuric acid and three gallons of -water. In a separate vessel dissolve six pounds potassium bichromate in -two gallons of boiling water. Mix the two. - -The last is the best formula. Always use electropoion fluid cold. (See -Trouvé's Solution--Poggendorff's Solution--Kakogey's Solution-- -Tissandrier's Solution--Chutaux's Solution.) - - -Electro-positive. adj. -Appertaining to positive electrification; thus potassium is the most -electro-positive of the elements. (See Electro-negative.) - - -Electro-puncture. -The introduction into the system of a platinum point or needle, -insulated with vulcanite, except near its point, and connected as the -anode of a galvanic battery. The kathode is a metal one, covered with a -wet sponge and applied on the surface near the place of puncture. It is -used for treatment of aneurisms or diseased growths, and also for -removal of hair by electrolysis. (See Hair, Removal of by Electrolysis.) - -Synonym--Galvano-puncture. - - -Electro-receptive. adj. -A term applied to any device or apparatus designed to receive and absorb -electric energy. A motor is an example of an electro-receptive -mechanism. - - -Electroscope. -An apparatus for indicating the presence of an electric charge, and also -for determining the sign, or whether the charge is positive or negative. -The simplest form consists of a thread doubled at its centre and hung -therefrom. On being charged, or on being connected to a charged body the -threads diverge. A pair of pith balls may be suspended in a similar way, -or a couple of strips of gold leaf within a flask (the gold leaf -electroscope). To use an electroscope to determine the sign of the -charge it is first slightly charged. The body to be tested is then -applied to the point of suspension, or other charging point. If at once -further repelled the charge of the body is of the same sign as the -slight charge first imparted to the electroscope leaves; the leaves as -they become more excited will at once diverge more. If of different sign -they will at first approach as their charge is neutralized and will -afterwards diverge. - -The gold-leaf electroscope is generally enclosed in a glass bell jar or -flask. Sometimes a pair of posts rise, one on each side, to supply -points of induction from the earth to intensify the action. (See -Electrometer, Quadrant--Electroscope, Gold leaf, and others.) - - -233 STANDARD ELECTRICAL DICTIONARY. - - -Electroscope, Bennett's. -A gold-leaf electroscope, the suspended leaves of which are contained in -a glass shade or vessel of dry air. On the inside of the glass shade are -two strips of gold leaf, which rise from the lower edge a short -distance, being pasted to the glass, and connected to the ground. These -act by induction to increase the sensitiveness of the instruments. - - -Electroscope, Bohenberger's. -A condensing electroscope (see Electroscope, Condensing) with a single -strip of gold leaf suspended within the glass bell. This is at an equal -distance from the opposite poles of two dry piles (see Zamboni's Dry -Pile) standing on end, one on each side of it. As soon as the leaf is -excited it moves toward one and away from the other pile, and the sign -of its electrification is shown by the direction of its motion. - - -Electroscope, Condensing. -A gold leaf electroscope, the glass bell of which is surmounted by an -electrophorous or static condenser, to the lower plate of which the -leaves of gold are suspended or connected. - -In use the object to be tested is touched to the lower plate, and the -upper plate at the same time is touched by the finger. The plates are -now separated. This reduces the capacity of the lower plate greatly and -its charge acquires sufficient potential to affect the leaves, although -the simple touching may not have affected them at all. - - -Electroscope, Gold Leaf. -An electroscope consisting of two leaves of gold leaf hung in contact -with each other from the end of a conductor. When excited they diverge. -The leaves are enclosed in a glass vessel. - - -Fig. 160. GOLD LEAF ELECTROSCOPE. - - -234 STANDARD ELECTRICAL DICTIONARY. - - -Electroscope, Pith Ball. -Two pith balls suspended at opposite ends of a silk thread doubled in -the middle. When charged with like electricity they repel each other. -The extent of their repulsion indicates the potential of their charge. - - -Electrostatic Attraction and Repulsion. -The attraction and repulsion of electrostatically charged bodies for -each other, shown when charged with electricity. If charged with -electricity of the same sign they repel each other. If with opposite -they attract each other. The classic attraction and subsequent repulsion -of bits of straw and chaff by the excited piece of amber is a case of -electrostatic attraction and repulsion. (See Electricity, -Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction and -Repulsion.) - - -Electrostatic Induction, Coefficient of. -The coefficient expressing the ratio of the charge or change of charge -developed in one body to the potential of the inducing body. - - -Electrostatic Lines of Force. -Lines of force assumed to exist in an electrostatic field of force, and -to constitute the same. In general they correspond in action and -attributes with elcctro-magnetic lines of force. They involve in almost -all cases either a continuous circuit, or a termination at both ends in -oppositely charged surfaces. - - -Fig. 161. ELECTROSTATIC LINES OF FORCE BETWEEN NEAR SURFACES. - - -Fig. 162. ELECTROSTATIC LINKS OF FORCE BETWEEN DISTANT SURFACES. - - -235 STANDARD ELECTRICAL DICTIONARY. - - -The cut, Fig. 161, shows the general course taken by lines of force -between two excited surfaces when near together. Here most of them are -straight lines reaching straight across from surface to surface, while a -few of them arch across from near the edges, tending to spread. If the -bodies are drawn apart the spreading tendency increases and the -condition of things shown in the next cut, Fig. 162, obtains. There is -an axial line whose prolongations may be supposed to extend -indefinitely, as occupying a position of unstable equilibrium. Here the -existence of a straight and unterminated line of force may be assumed. - -A direction is predicated to lines of force corresponding with the -direction of an electric current. They are assumed to start from a -positively charged and to go towards a negatively charged surface. A -positively charged body placed in an electrostatic field of force will -be repelled from the region of positive into or towards the region of -negative potential following the direction of the lines of force, not -moving transversely to them, and having no transverse component in its -motion. - -[Transcriber's note: More precisely, "A positively charged body placed -in an electrostatic field of force will be repelled from the region of -positive into or towards the region of negative potential ACCELERATING -in the direction of the lines of force, not ACCELERATING transversely to -them, and having no transverse component in its ACCELERATION." -Previously acquired momentum can produce a transverse component of -VELOCITY.] - - -Electrostatics. -The division of electric science treating of the phenomena of electric -charge, or of electricity in repose, as contrasted with electro-dynamics -or electricity in motion or in current form. Charges of like sign repel, -and of unlike sign attract each other. The general inductive action is -explained by the use of the electrostatic field of force and -electrostatic lines of force, q. v. The force of attraction and -repulsion of small bodies or virtual points, which are near enough to -each other, vary as the square of the distance nearly, and with the -product of the quantities of the charges of the two bodies. - - -Electrostatic Refraction. -Dr. Kerr found that certain dielectrics exposed to electric strain by -being placed between two oppositely excited poles of a Holtz machine or -other source of very high tension possess double refracting powers, in -other words can rotate a beam of polarized light, or can develop two -complimentary beams from common light. Bisulphide of carbon shows the -phenomenon well, acting as glass would if the glass were stretched in -the direction of the electrostatic lines of force. To try it with glass, -holes are drilled in a plate and wires from an influence machine are -inserted therein. The discharge being maintained through the glass it -polarizes light. - -Synonym--Kerr Effect. - - -Electrostatic Series. -A table of substances arranged in the order in which they are -electrostatically charged by contact, generally by rubbing against each -other. The following series is due to Faraday. The first members become -positively excited when rubbed with any of the following members, and -vice versa. The first elements correspond to the carbon plate in a -galvanic battery, the succeeding elements to the zinc plate. - -Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--Flint -Glass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--the -Metals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are some -irregularities. A feather lightly drawn over canvas is negatively -electrified; if drawn through folds pressed against it it is positively -excited. Many other exceptions exist, so that the table is of little -value. - - -236 STANDARD ELECTRICAL DICTIONARY. - - -Electrostatic Stress. -The stress produced upon a transparent medium in an electrostatic field -of force by which it acquires double refracting or polarizing properties -as regards the action of such medium upon light. (See Electrostatic -Refraction.) - - -Electro-therapeutics or Therapy. -The science treating of the effects of electricity upon the animal -system in the treatment and diagnosis of disease. - - -Electrotonus. -An altered condition of functional activity occurring in a nerve -subjected to the passage of an electric current. If the activity is -decreased, which occurs near the anode, the state is one of -anelectrotonus, if the activity is increased which occurs near the -kathode the condition is one of kathelectrotonus. - - -Electrotype. -The reproduction of a form of type or of an engraving or of the like by -electroplating, for printing purposes. The form of type is pressed upon -a surface of wax contained in a shallow box. The wax is mixed with -plumbago, and if necessary some more is dusted and brushed over its -surface and some iron dust is sprinkled over it also. A matrix or -impression of the type is thus obtained, on which copper is deposited by -electroplating, q. v. - - -Element, Chemical. -The original forms of matter that cannot be separated into constituents -by any known process. They are about seventy in number. Some of the -rarer ones are being added to or cancelled with the progress of chemical -discovery. For their electric relations see Electro-chemical -Equivalents--Electro-chemical Series. - -The elements in entering into combination satisfy chemical affinity and -liberate energy, which may take the form of electric energy as in the -galvanic battery, or of heat energy, as in the combustion of carbon or -magnesium. Therefore an uncombined element is the seat of potential -energy. (See Energy, Potential.) In combining the elements always -combine in definite proportions. A series of numbers, one being proper -to each element which denote the smallest common multipliers of these -proportions, are called equivalents. Taking the theory of valency into -consideration the product of the equivalents by the valencies gives the -atomic weights. - - -237 STANDARD ELECTRICAL DICTIONARY. - - -Element, Mathematical. -A very small part of anything, corresponding in a general way to a -differential, as the element of a current. - - -Element of a Battery Cell. -The plates in a galvanic couple are termed elements, as the carbon and -zinc plates in a Bunsen cell. The plate unattacked by the solution, as -the carbon plate in the above battery, is termed the negative plate or -element; the one attacked, as the zinc plate, is termed the positive -plate or element. - -Synonym--Voltaic Element. - - -Elements, Electrical Classification of. -This may refer to Electro-chemical Series, Electrostatic Series, or -Thermo-electric Series, all of which may be referred to. - - -Element, Thermo-electric. -One of the metals or other conductors making a thermo-electric couple, -the heating of whose junction produces electro-motive force and a -current, if on closed circuit. The elements of a couple are respectively -positive and negative, and most conductors can be arranged in a series -according to their relative polarity. (See Thermo-electric Series.) - - -Elongation. -The throw of the magnetic needle. (See Throw.) - -Synonym--Throw. - - -Embosser, Telegraph. -A telegraphic receiver giving raised characters on a piece of paper. It -generally refers to an apparatus of the old Morse receiver type, one -using a dry point stylus, which pressing the paper into a groove in the -roller above the paper, gave raised characters in dots and lines. - - -Fig. 163. MORSE RECEIVER. - - -238 STANDARD ELECTRICAL DICTIONARY. - - -E. M. D. P. -Abbreviation for "electro-motive difference of potential" or for -electro-motive force producing a current as distinguished from mere -inert potential difference. - -E. M. F. -Abbreviation for "electro-motive force." - - -Fig. 164. END-ON METHOD. - - -End-on Method. -A method of determining the magnetic moment of a magnet. The magnet -under examination, N S, is placed at right angles to the magnetic -meridian, M O R, and pointing directly at or "end on" to the centre of a -compass needle, n s. From the deflection a of the latter the moment is -calculated. - - -Endosmose, Electric. -The inflowing current of electric osmose. (See Osmose, Electric.) - - -End Play. -The power to move horizontally in its bearings sometimes given to -armature shafts. This secures a more even wearing of the commutator -faces. End play is not permissible in disc armatures, as the attraction -of the field upon the face of the armature core would displace it -endwise. For such armatures thrust-bearings preventing end play have to -be provided. - - -Energy. -The capacity for doing work. It is measured by work units which involve -the exercise of force along a path of some length. A foot-pound, -centimeter-gram, and centimeter-dyne are units of energy and work. - -The absolute unit of energy is the erg, a force of one dyne exercised -over one centimeter of space. (See Dyne.) - -The dimensions of energy are - force (M * L / T^2) * space (L) = M * (L^2 / T^2). -Energy may be chemical (atomic or molecular), mechanical, -electrical, thermal, physical, potential, kinetic, or actual, and other -divisions could be formulated. - - -239 STANDARD ELECTRICAL DICTIONARY. - - -Energy, Atomic. -The potential energy due to atomic relations set free by atomic change; -a form of chemical energy, because chemistry refers to molecular as well -as to atomic changes. When atomic energy loses the potential form it -immediately manifests itself in some other form, such as heat or -electric energy. It may be considered as always being potential energy. -(See Energy, Chemical.) - -[Transcriber's note: This item refers to chemical energy, that is -manifest in work done by electric forces during re-arrangement of -electrons. Atomic energy now refers to re-arrangement of nucleons -(protons and neutrons) and the resulting conversion of mass into -energy.] - - -Energy, Chemical. -A form of potential energy (see Energy, Potential) possessed by elements -in virtue of their power of combining with liberation of energy, as in -the combination of carbon with oxygen in a furnace; or by compounds in -virtue of their power of entering into other combinations more -satisfying to the affinities of their respective elements or to their -own molecular affinity. Thus in a galvanic couple water is decomposed -with absorption of energy, but its oxygen combines with zinc with -evolution of greater amount of energy, so that in a voltaic couple the -net result is the setting free of chemical energy, which is at once -converted into electrical energy in current form, if the battery is on a -closed circuit. - - -Energy, Conservation of. -A doctrine accepted as true that the sum of energy in the universe is -fixed and invariable. This precludes the possibility of perpetual -motion. Energy may be unavailable to man, and in the universe the -available energy is continually decreasing, but the total energy is the -same and never changes. - -[Transcriber's note: If mass is counted a energy (E=m*(c^2)) then energy -is strictly conserved.] - - -Energy, Degradation of. -The reduction of energy to forms in which it cannot be utilized by man. -It involves the reduction of potential energy to kinetic energy, and the -reduction of kinetic energy of different degrees to energy of the same -degree. Thus when the whole universe shall have attained the same -temperature its energy will have become degraded or non-available. At -present in the sun we have a source of kinetic energy of high degree, in -coal a source of potential energy. The burning of all the coal will be -an example of the reduction of potential to kinetic energy, and the -cooling of the sun will illustrate the lowering in degree of kinetic -energy. (See Energy, Conservation of--Energy, Potential--Energy, -Kinetic.) - - -Energy, Electric. -The capacity for doing work possessed by electricity -under proper conditions. Electric energy may be either kinetic or -potential. As ordinary mechanical energy is a product of force and -space, so electric energy is a product of potential difference and -quantity. Thus a given number of coulombs of electricity in falling a -given number of volts develop electric energy. The dimensions are found -therefore by multiplying electric current intensity quantity - ((M^.5) * (L^.5)), -by electric potential - ((M^.5)*(L^1.5) / (T^2)), -giving (M * (L^2)/(T^2)), -the dimensions of energy in general as it should be. - -The absolute unit of electric energy in electro-magnetic measure is -(1E-7) volt coulombs. - - -240 STANDARD ELECTRICAL DICTIONARY. - - -The practical unit is the volt-coulomb. As the volt is equal to 1E8 -absolute units of potential and the coulomb to 0.1 absolute units of -quantity, the volt-coulomb is equal to 1E7 absolute units of energy. - -The volt-coulomb is very seldom used, and the unit of Electric Activity -or Power (see Power, Electric), the volt-ampere, is universally used. -This unit is sometimes called the Watt, q. v., and it indicates the rate -of expenditure or of production of electric energy. - -The storing up in a static accumulator or condenser of a given charge of -electricity, available for use with a given change of potential -represents potential electric energy. - -The passing of a given quantity through a conductor with a given fall of -potential represents kinetic electric energy. - -In a secondary battery there is no storage of energy, but the charging -current simply accumulates potential chemical energy in the battery, -which chemical energy is converted into electric energy in the discharge -or delivery of the battery. - -It is customary to discuss Ohm's law in this connection; it is properly -treated under Electric Power, to which the reader is referred. (See -Power, Electric.) - -[Transcriber's note: A volt-ampere or watt is a unit of power. A -volt-coulomb second or watt-second is a unit of energy. Power multiplied -by time yields energy.] - - -Energy, Electric Transmission of. -If an electric current passes through a conductor all its energy is -expended in the full circuit. Part of the circuit may be an electrical -generator that supplies energy as fast as expended. Part of the circuit -may be a motor which absorbs part of the energy, the rest being expended -in forcing a current through the connecting wires and through the -generator. The electric energy in the generator and connecting wires is -uselessly expended by conversion into heat. That in the motor in great -part is utilized by conversion into mechanical energy which can do -useful work. This represents the transmission of energy. Every electric -current system represents this operation, but the term is usually -restricted to the transmission of comparatively large quantities of -energy. - -A typical installation might be represented thus. At a waterfall a -turbine water wheel is established which drives a dynamo. From the -dynamo wires are carried to a distant factory, where a motor or several -motors are established, which receive current from the dynamo and drive -the machinery. The same current, if there is enough energy, may be used -for running lamps or electroplating. As electric energy (see Energy, -Electric,) is measured by the product of potential difference by -quantity, a very small wire will suffice for the transmission of a small -current at a high potential, giving a comparatively large quantity of -energy. It is calculated that the energy of Niagara Falls could be -transmitted through a circuit of iron telegraph wire a distance of over -1,000 miles, but a potential difference of 135,000,000 volts would be -required, something quite impossible to obtain or manage. - -[Transcriber's note: Contemporary long distance power transmission lines -use 115,000 to 1,200,000 volts. At higher voltages corona discharges -(arcing) create unacceptable losses.] - - -241 STANDARD ELECTRICAL DICTIONARY. - - -Energy, Kinetic. -Energy due to matter being actually in motion. It is sometimes called -actual energy. The energy varies directly with the mass and with the -square of the velocity. It is represented in formula by .5 *M * (v^2). - -Synonyms--Actual Energy--Energy of Motion--Dynamic Energy. - - -Energy, Mechanical. -The energy due to mechanical change or motion, virtually the same as -molar energy. (See Energy, Molar.) - - -Energy, Molar. -The energy of masses of matter due to movements of or positions of -matter in masses; such as the kinetic energy of a pound or of a ton in -motion, or the potential energy of a pound at an elevation of one -hundred feet. - - -Energy, Molecular. -The potential energy due to the relations of molecules and set free by -their change in the way of combination. It is potential for the same -reason that applies to atomic and chemical energy, of which latter it is -often a form, although it is often physical energy. The potential energy -stored up in vaporization is physical and molecular energy; the -potential energy stored up in uncombined potassium oxide and water, or -calcium oxide (quicklime) and water is molecular, and when either two -substances are brought together kinetic, thermal or heat energy is set -free, as in slaking lime for mortar. - - -Energy of an Electrified Body. -An electrified body implies the other two elements of a condenser. It is -the seat of energy set free when discharged. (See Dielectric, Energy -of.) The two oppositely charged bodies tend to approach. This tendency, -together with the distances separating them, represents a potential -energy. - - -Energy of Stress. -Potential energy due to stress, as the stretching of a spring. This is -hardly a form of potential energy. A stressed spring is merely in a -position to do work at the expense of its own thermal or kinetic energy -because it is cooled in doing work. If it possessed true potential -energy of stress it would not be so cooled. - - -Energy of Position. -Potential energy due to position, as the potential energy of a pound -weight raised ten feet (ten foot lbs.). (See Energy, Potential.) - - -Energy, Physical. -The potential energy stored up in physical position or set free in -physical change. Thus a vapor or gas absorbs energy in its vaporization, -which is potential energy, and appears as heat energy when the vapor -liquefies. - - -242 STANDARD ELECTRICAL DICTIONARY. - - -Energy, Potential, or Static Energy. -The capacity for doing work in a system due to advantage of position or -other cause, such as the stress of a spring. A pound weight supported -ten feet above a plane has ten foot lbs. of potential energy of position -referred to that plane. A given weight of an elementary substance -represents potential chemical energy, which will be liberated as actual -energy in its combination with some other element for which it has an -affinity. Thus a ton of coal represents a quantity of potential chemical -energy which appears in the kinetic form of thermal energy when the coal -is burning in a furnace. A charged Leyden jar represents a source of -potential electric energy, which becomes kinetic heat energy as the same -is discharged. - - -Energy, Thermal. -A form of kinetic molecular energy due to the molecular motion of bodies -caused by heat. - - -Entropy. -Non-available energy. As energy may in some way or other be generally -reduced to heat, it will be found that the equalizing of temperature, -actual and potential, in a system, while it leaves the total energy -unchanged, makes it all unavailable, because all work represents a fall -in degree of energy or a fall in temperature. But in a system such as -described no such fall could occur, therefore no work could be done. The -universe is obviously tending in that direction. On the earth the -exhaustion of coal is in the direction of degradation of its high -potential energy, so that the entropy of the universe tends to zero. -(See Energy, Degradation of.) - -[Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLE -ENERGY tends to zero.] - - -Entropy, Electric. -Clerk Maxwell thought it possible to recognize in the Peltier effect, q. -v., a change in entropy, a gain or loss according to whether the -thermo-electric junction was heated or cooled. This is termed Electric -Entropy. (See Energy, Degradation of.) - - -243 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 165. EPINUS' CONDENSER, - - -Epinus' Condenser. -Two circular brass plates, A and B, are mounted on insulating supports, -and arranged to be moved towards or away from each other as desired. -Between them is a plate of glass, C, or other dielectric. Pith balls may -be suspended back of each brass plate as shown. The apparatus is charged -by connecting one plate to an electric machine and the other to the -earth. The capacity of the plate connected to the machine is increased -by bringing near to it the grounded plate, by virtue of the principle of -bound charges. This apparatus is used to illustrate the principles of -the electric condenser. It was invented after the Leyden jar was -invented. - - -Fig. 166. EPINUS' CONDENSER. - - -E. P. S. -Initials of Electrical Power Storage; applied to a type of secondary -battery made by a company bearing that title. - - -Fig. 167. CAM EQUALIZER. - - -244 STANDARD ELECTRICAL DICTIONARY. - -Equalizer. -In electro-magnetic mechanism an arrangement for converting the pull of -the electro-magnet varying in intensity greatly over its range of -action, into a pull of sensibly equal strength throughout. The use of a -rocking lever acting as a cam, with leverage varying as the armature -approaches or recedes from the magnet core is one method of effecting -the result. Such is shown in the cut. E is an electro-magnet, with -armature a. A and B are the equalizer cams. The pull on the short end of -the cam B is sensibly equal for its whole length. - -Many other methods have been devised, involving different shapes of pole -pieces, armatures or mechanical devices other than the one just shown. - - -Equipotential. adj. -Equal in potential; generally applied to surfaces. Thus every magnetic -field is assumed to be made up of lines of force and intersecting those -lines, surfaces, plane, or more or less curved in contour, can be -determined, over all parts of each one of which the magnetic intensity -will be identical. Each surface is the locus of equal intensity. The -same type of surface can be constructed for any field of force, such as -an electrostatic field, and is termed an equipotential surface. - - -Equipotential Surface, Electrostatic. -A surface in an electrostatic field of force, which is the locus of all -points of a given potential in such field; a surface cutting all the -lines of force at a point of identical potential. Lines of force are cut -perpendicularly by an equipotential surface, or are normal thereto. - - -Equipotential Surface, Magnetic and Electro-magnetic. -A surface bearing the same relation to a magnetic or electro-magnetic -field of force that an electrostatic equipotential surface (see -Equipotential Surface, Electrostatic,) does to an electrostatic field of -force. - - -Equivalent, Chemical. -The quotient obtained by dividing the atomic weight of an element by its -valency. - - -Equivalents, Electro-chemical. -The weight of any substance set free by one coulomb of electricity. The -following give some equivalents expressed in milligrams: - -Hydrogen .0105 Mercury (mercurous) 2.10 -Gold .6877 Iron (ferric) .1964 -Silver 1.134 Iron (ferrous) .294 -Copper (cupric) .3307 Nickel .3098 -Mercury (mercuric) 1.05 Zinc .3413 -Lead 1.0868 Chlorine .3728 -Oxygen .89 - - -245 STANDARD ELECTRICAL DICTIONARY. - - -Equivalent, Electro-mechanical. -The work or energy equivalent to unit quantities of electric energy, q. -v.; or equivalent to a unit current in a conductor whose ends differ one -unit of potential. The unit of electric energy taken is the watt-second -or volt-coulomb. One volt-coulomb is equal to - Ergs 1E7 [10000000] - Foot Pound .737337 - Gram-degree C. .24068 - Horse Power Second .0013406 - Pound-degree F. .000955 - One horse power is equal to 745.943 volt coulombs per second. - - -Equivalent, Electro-thermal. -The heat produced by a unit current passing through a conductor with -unit difference of potential at its ends; the heat equivalent of a -volt-coulomb or watt-second. It is equal to - Gram-degree C. .24068 - Pound-degree F. .000955 - - -Equivalent, Thermo-chemical. -The calories evolved by the combination of one gram of any substance -with its equivalent of another substance being determined, the product -obtained by multiplying this number by the equivalent (atomic or -molecular weight / valency) of the first element or substance is the -thermo-chemical equivalent. If expressed in kilogram calories, the -product of the thermo-chemical equivalent by 0.43 gives the voltage -required to effect such decomposition. - -The following are thermo-chemical equivalents of a few combinations: - Water 34.5 - Zinc oxide 43.2 - Iron protoxide 34.5 - Iron Sesquioxide 31.9 X 3 - Copper oxide 19.2 - - -Equivolt. -"The mechanical energy of one volt electro-motive force exerted under -unit conditions through one equivalent of chemical action in grains." -(J. T. Sprague.) This unit is not in general use as the unit of electric -energy, the volt-coulomb and (for rate of electric energy) the -volt-ampere being always used. - - -Erg. -The absolute or fundamental C. G. S. unit of work or energy. The work -done or energy expended in moving a body through one centimeter against -a resistance of one dyne. - - -Erg-ten. -Ten millions of ergs, or ten meg-ergs. - - -Escape. -A term applied to leakage of current. - - -Etching, Electric. -A process of producing an etched plate. The plate is coated with wax, -and the design traced through as in common etching. It is then placed in -a bath and is connected to the positive terminal from a generator, whose -negative is immersed in the same bath, so that the metal is dissolved by -electrolytic action. By attaching to the other terminal and using a -plating bath, a rough relief plate may be secured, by deposition in the -lines of metal by electroplating. - -Synonym--Electric Engraving. - - -246 STANDARD ELECTRICAL DICTIONARY. - - -Ether. -The ether is a hypothetical thing that was invented to explain the -phenomena of light. Light is theoretically due to transverse vibrations -of the ether. Since the days of Young the conception of the ether has -extended, and now light, "radiant heat," and electricity are all treated -as phenomena of the ether. Electrical attraction and repulsion are -explained by considering them due to local stresses in the ether; -magnetic phenomena as due to local whirlpools therein. The ether was -originally called the luminiferous ether, but the adjective should now -be dropped. Its density is put at 936E-21 that of water, or equal to -that of the atmosphere at 210 miles above the earth's surface. Its -rigidity is about 1E-9 that of steel (see Ten, Powers of); as a whole it -is comparable to an all-pervading jelly, with almost perfect elasticity. -The most complete vacuum is filled with ether. - -All this is a hypothesis, for the ether has never been proved to exist. -Whether gravitation will ever be explained by It remains to be seen. - -[Transcriber's note: The Michelson-Morley experiment in 1887 (five years -before this book) cast serious doubt on the ether. In 1905 Einstein -explained electromagnetic phenomenon with photons. In 1963 Edward M. -Purcell used special relativity to derive the existence of magnetism and -radiation.] - - -Eudiometer. -A graduated glass tube for measuring the volumes of gases. In its -simplest form it is simply a cylindrical tube, with a scale etched or -engraved upon it, closed at one end and open at the other. The gas to be -measured is collected in it over a liquid, generally water, dilute -sulphuric acid in the gas voltameter, or mercury. Many different shapes -have been given them by Hoffmann, Ure, Bunsen and others. - - -Evaporation, Electric. -The superficial sublimation or evaporation of a substance under the -influence of negative electricity. It is one of the effects investigated -by Crookes in his experiments with high vacua. He found that when a -metal, even so infusible as platinum, was exposed to negative -electrification in one of his high vacuum tubes, that it was volatilized -perceptibly. A cadmium electrode heated and electrified negatively was -found to give a strong coating of metal on the walls of the tube. Even -in the open air the evaporation of water was found to be accelerated by -negative electrification. - - -Exchange, Telephone. -The office to which telephone wires lead in a general telephone system. -In the office by a multiple switch board, or other means, the different -telephones are interconnected by the office attendants, so that any -customers who desire it may be put into communication with each other. -The exchange is often termed the Central Office, although it may be only -a branch office. - - -Excitability, Faradic. -The action produced in nerve or muscle of the animal system by an -alternating or intermitting high potential discharge from an induction -coil. - - -247 STANDARD ELECTRICAL DICTIONARY. - - -Excitability, Galvanic. -The same as Faradic excitability, except that it refers to the effects -of the current from a galvanic battery. - - -Excitability of Animal System, Electric. -The susceptibility of a nerve or muscle to electric current shown by the -effect produced by its application. - - -Exciter. -A generator used for exciting the field magnet of a dynamo. In -alternating current dynamos, e. g., of the Westinghouse type, a special -dynamo is used simply to excite the field magnet. In central station -distribution the same is often done for direct current dynamos. - - -Exosmose, Electric. -The outflowing current of electric osmose. (See Osmose, Electric.) - - -Expansion, Coefficient of. -The number expressing the proportional increase in size, either length, -area or volume, of a substance under the influence generally of heat. -There are three sets of coefficients, (1) of linear expansion, (2) of -superficial expansion, (3) of cubic expansion or expansion of volume. -The first and third are the only ones much used. They vary for different -substances, and for the same substance at different temperatures. They -are usually expressed as decimals indicating the mixed number referred -to the length or volume of the body at the freezing point as unity. - - -Expansion, Electric. -(a) The increase in volume of a condenser, when charged -electrostatically. A Leyden jar expands when charged, and contracts when -discharged. - -(b) The increase in length of a bar of iron when magnetized. - -This is more properly called magnetic expansion or magnetic elongation. - - -Exploder. -(a) A small magneto-generator for producing a current for heating the -wire in an electric fuse of the Abel type (see Fuse, Electric), and -thereby determining an explosion. - -(b) The term may also be applied to a small frictional or influence -machine for producing a spark for exploding a spark fuse. - - -Explorer. -A coil, similar to a magnetizing coil (see Coil, Magnetizing), used for -investigating the electro-magnetic circuit and for similar purposes. If -placed around an electro-magnet and connected with a galvanometer, it -will produce a deflection, owing to a momentary induced current, upon -any change in the magnet, such as removing or replacing the armature. It -is useful in determining the leakage of lines of force and for general -investigations of that nature. It is often called an exploring coil. -Hughes' Induction Balance (see Induction Balance, Hughes') is sometimes -called a Magnetic Explorer. The exploring coil may be put in circuit -with a galvanometer for quantitative measurements or with a telephone -for qualitative ones. - - -248 STANDARD ELECTRICAL DICTIONARY. - - -Extension Bell Call. -A system of relay connection, q. v., by which a bell is made to continue -ringing after the current has ceased coming over the main line. It is -designed to prolong the alarm given by a magneto call bell, q. v., which -latter only rings as long as the magneto handle is turned. A vibrating -electric bell (see Bell, Electric,) is connected in circuit with a local -battery and a switch normally open, but so constructed as to close the -circuit when a current is passed and continue to do so indefinitely. The -distant circuit is connected to this switch. When the magneto is worked -it acts upon the switch, closes the local battery circuit and leaves it -closed, while the bell goes on ringing until the battery is exhausted or -the switch is opened by hand. - - -Eye, Electro-magnetic. -An apparatus used in exploring a field of electro-magnetic radiations. -It is a piece of copper wire 2 millimeters (.08 inch) in diameter, bent -into an almost complete circle 70 millimeters (.28 inch) in diameter, -with terminals separated by an air gap. This is moved about in the -region under examination, and by the production of a spark indicates the -locality of the loops or venters in systems of stationary waves. - - -F. -Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (See -Fahrenheit Scale.) - - -Fahrenheit Scale. -A thermometer scale in use in the United States and England. On this -scale the temperature of melting ice is 32°; that of condensing steam is -212°; the degrees are all of equal length. Its use is indicated by the -letter F., as 180° F. To convert its readings into centigrade, subtract -32 and multiply by 5/9. (b) To convert centigrade into F. multiply by -9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82.2° C. Again -180° C. = (180 * 9/5) + 32 = 324° F. - -[Transcribers note: 180° C. = (180 * 9/5) + 32 = 356° F. ] - -The additions and subtractions must be algebraic in all cases. Thus when -the degrees are minus or below zero the rules for conversion might be -put thus: To convert degrees F. below zero into centigrade to the number -of degrees F. add 32, multiply by 5/9 and place a minus sign (-) before -it. (b) To convert degrees centigrade below zero into Fahrenheit, -multiply the number of degrees by 9/5, subtract from 32 if smaller; if -greater than 32 subtract 32 therefrom, and prefix a minus sign, thus: --10° C. = 32 - (10 * 9/5) = 14°. Again, -30°C. = (30 * 9/5) - 32 = 22 = --22° F. - - -249 STANDARD ELECTRICAL DICTIONARY. - - -Farad. -The practical unit of electric capacity; the capacity of a conductor -which can retain one coulomb of electricity at a potential of one volt. - -The quantity of electricity charged upon a conducting surface raises its -potential; therefore a conductor of one farad capacity can hold two -coulombs at two volts potential, and three coulombs at three volts, and -so on. The electric capacity of a conductor, therefore, is relative -compared to others as regards its charge, for the latter may be as great -as compatible with absence of sparking and disruptive discharge. In -other words, a one farad or two farad conductor may hold a great many -coulombs. Charging a conductor with electricity is comparable to pumping -air into a receiver. Such a vessel may hold one cubic foot of air at -atmospheric pressure and two at two atmospheres, and yet be of one cubic -foot capacity however much air is pumped into it. - -The farad is equal to one fundamental electrostatic unit of capacity -multiplied by 9E11 and to one electro-magnetic unit multiplied by 1E-9. - -The farad although one of the practical units is far too large, so the -micro-farad is used in its place. The capacity of a sphere the size of -the earth is only .000636 of a farad. - -[Transcriber's note: Contemporary calculations give about .000720 -farad.] - - -Faraday, Effect. -The effect of rotation of its plane produced upon a polarized beam of -light by passage through a magnetic field. (See Magnetic Rotary -Polarization.) - - -Faraday's Cube. -To determine the surface action of a charge, Faraday constructed a room, -twelve feet cube, insulated, and lined with tinfoil. This room he -charged to a high potential, but within it he could detect no excitement -whatever. The reason was because the electricity induced in the bodies -within the room was exactly equal to the charge of the room-surface, and -was bound exactly by it. The room is termed Faraday's cube. - - -Faraday's Dark Space. -A non-luminous space between the negative and positive glows, produced -in an incompletely exhausted tube through which a static discharge, as -from an induction coil, is produced. It is perceptible in a rarefaction -of 6 millimeters (.24 inch) and upwards. If the exhaustion is very high -a dark space appears between the negative electrode and its discharge. -This is known as Crookes' dark space. - - -Faraday's Disc. -A disc of any metal, mounted so as to be susceptible of rotation in a -magnetic field of force, with its axis parallel to the general direction -of the lines of force. A spring bears against its periphery and another -spring against its axle. When rotated, if the springs are connected by a -conductor, a current is established through the circuit including the -disc and conductor. The radius of the disc between the spring contacts -represents a conductor cutting lines of force and generating a potential -difference, producing a current. If a current is sent through the -motionless wheel from centre to periphery it rotates, illustrating the -doctrine of reversibility. As a motor it is called Barlow's or -Sturgeon's Wheel. If the disc without connections is rapidly rotated it -produces Foucault currents, q. v., within its mass, which resist its -rotation and heat the disc. - - -250 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 168. "FARADAY'S NET." - - -Faraday's Net. -An apparatus for showing that the electric charge resides on the -surface. It consists of a net, conical in shape and rather deep, to -whose apex two threads, one on each side, are attached. Its mouth is -fastened to a vertical ring and the whole is mounted on an insulating -support. - -It is pulled out to its full extent and is electrified. No charge can be -detected inside it. By pulling one of the threads it is turned with the -other side out. Now all the charge is found on the outside just as -before, except that it is of course on the former inside surface of the -bag. The interior shows no charge. - - -Faraday's Transformer. -The first transformer. It was made by Michael Faraday. It was a ring of -soft iron 7/8 inch thick, and 6 inches in external diameter. It was -wound with bare wire, calico being used to prevent contact of the wire -with the ring and of the layers of wire with each other, while twine was -wound between the convolutions to prevent the wires from touching. -Seventy-two feet of copper wire, 1/20 inch diameter, were wound in three -superimposed coils, covering about one-half of the ring. On the other -half sixty feet of copper wire were wound in two superimposed coils. -Faraday connected his coils in different ways and used a galvanometer to -measure the current produced by making and breaking one of the circuits -used as a primary. - -The coil is of historic interest. - - -Faraday's Voltameter. -A voltameter, in which the coulombs of current are measured by the -volume of the gas evolved from acidulated water. (See Voltameter, Gas.) - - -Faradic. adj. -Referring to induced currents, produced from induction coils. As Faraday -was the original investigator of the phenomena of electro-magnetic -induction, the secondary or induced electro-magnetic currents and their -phenomena and apparatus are often qualified by the adjective Faradic, -especially in electro-therapeutics. A series of alternating -electrostatic discharges, as from an influence machine (Holtz), are -sometimes called Franklinic currents. They are virtually Faradic, except -as regards their production. - - -251 STANDARD ELECTRICAL DICTIONARY. - - -Faradic Brush. -A brush for application of electricity to the person. It is connected as -one of the electrodes of an induction coil or magneto generator. For -bristles wire of nickel plated copper is generally employed. - - -Faradization. -In medical electricity the analogue of galvanization; the effects due to -secondary or induced currents; galvanization referring to currents from -a galvanic battery; also the process of application of such currents. - - -Faults. -Sources of loss of current or of increased resistance or other troubles -in electric circuits. - - -Feeder. -A lead in an electric central station distribution system, which lead -runs from the station to some point in the district to supply current. -It is not used for any side connections, but runs direct to the point -where current is required, thus "feeding" the district directly. In the -two wire system a feeder may be positive or negative; in the three wire -system there is also a neutral feeder. Often the term feeder includes -the group of two or of three parallel lines. - - -Feeder Equalizer. -An adjustable resistance connected in circuit with a feeder at the -central station. The object of the feeder being to maintain a definite -potential difference at its termination, the resistance has to be varied -according to the current it is called on to carry. - - -Feeder, Main or Standard. -The main feeder of a district. The standard regulation of pressure -(potential difference between leads) in the district is often determined -by the pressure at the end of the feeder. - - -Feeder, Negative. -The lead or wire in a set of feeders, which is connected to the negative -terminal of the generator. - - -Feeder, Neutral. -In the three wire system the neutral wire in a set of feeders. It is -often made of less diameter than the positive and negative leads. - - -Feeder, Positive. -The lead or wire in a set of feeders, which wire is connected to the -positive terminal of the generator. - - -Ferranti Effect. -An effect as yet not definitely explained, observed in the mains of the -Deptford, Eng., alternating current plant. It is observed that the -potential difference between the members of a pair of mains rises or -increases with the distance the place of trial is from the station. - -[Transcriber's note: This effect is due to the voltage drop across the -line inductance (due to charging current) being in phase with the -sending end voltages. Both capacitance and inductance are responsible -for producing this phenomenon. The effect is more pronounced in -underground cables and with very light loads.] - - -252 STANDARD ELECTRICAL DICTIONARY. - - -Ferro-magnetic. adj. -Paramagnetic; possessing the magnetic polarity of iron. - - -Fibre and Spring Suspension. -A suspension of the galvanometer needle used in marine galvanometers. -The needle is supported at its centre of gravity by a vertically -stretched fibre attached at both its ends, but with a spring -intercalated between the needle and one section of the fibre. - - -Fibre Suspension. -Suspension, as of a galvanometer needle, by a vertical or hanging fibre -of silk or cocoon fibre, or a quartz fibre. (See Quartz.) - -This suspension, while the most delicate and reliable known, is very -subject to disturbance and exacts accurate levelling of the instrument. - -Fibre suspension is always characterized by a restitutive force. Pivot -suspension, q. v., on the other hand, has no such force. - - -Field, Air. -A field the lines of force of which pass through air; the position of a -field comprised within a volume of air. - - -Field, Alternating. -Polarity or direction being attributed to lines of force, if such -polarity is rapidly reversed, an alternating field results. Such field -may be of any kind, electro-magnetic or electrostatic. In one instance -the latter is of interest. It is supposed to be produced by high -frequency discharges of the secondary of an induction coil, existing in -the vicinity of the discharging terminals. - - -Field Density. -Field density or density of field is expressed in lines of force per -unit area of cross-section perpendicular to the lines of force. - - -Field, Distortion of. -The lines of force reaching from pole to pole of an excited field magnet -of a dynamo are normally symmetrical with respect to some axis and often -with respect to several. They go across from pole to pole, sometimes -bent out of their course by the armature core, but still symmetrical. -The presence of a mass of iron in the space between the pole pieces -concentrates the lines of force, but does not destroy the symmetry of -the field. - -When the armature of the dynamo is rotated the field becomes distorted, -and the lines of force are bent out of their natural shape. The new -directions of the lines of force are a resultant of the lines of force -of the armature proper and of the field magnet. For when the dynamo is -started the armature itself becomes a magnet, and plays its part in -forming the field. Owing to the lead of the brushes the polarity of the -armature is not symmetrical with that of the field magnets. Hence the -compound field shows distortion. In the cut is shown diagrammatically -the distortion of field in a dynamo with a ring armature. The arrow -denotes the direction of rotation, and n n * * * and s s * * * indicate -points of north and south polarity respectively. - - -253 STANDARD ELECTRICAL DICTIONARY. - - -The distorted lines must be regarded as resultants of the two induced -polarities of the armature, one polarity due to the induction of the -field, the other to the induction from its own windings. The positions -of the brushes have much to do with determining the amount and degree of -distortion. In the case of the ring armature it will be seen that some -of the lines of force within the armature persist in their polarity and -direction, almost as induced by the armature windings alone, and leak -across without contributing their quota to the field. Two such lines are -shown in dotted lines. - -In motors there is a similar but a reversed distortion. - - -Fig. 169. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE DYNAMO. - - -Fig. 170. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE MOTOR. - - -254 STANDARD ELECTRICAL DICTIONARY. - - -Field, Drag of. -When a conductor is moved through a field so that a current is generated -in it, the field due to that current blends with the other field and -with its lines of force, distorting the field, thereby producing a drag -upon its own motion, because lines of force always tend to straighten -themselves, and the straightening would represent cessation of motion in -the conductor. This tendency to straightening therefore resists the -motion of the conductor and acts a drag upon it. - - -Field of Force. -The space in the neighborhood of an attracting or repelling mass or -system. Of electric fields of force there are two kinds, the -Electrostatic and the Magnetic Fields of Force, both of which may be -referred to. A field of force may be laid out as a collection of -elements termed Lines of Force, and this nomenclature is universally -adopted in electricity. The system of lines may be so constructed that -(a) the work done in passing from one equipotential surface to the next -is always the same; or (b) the lines of force are so laid out and -distributed that at a place in which unit force is exercised there is a -single line of force passing through the corresponding equipotential -surface in each unit of area of that surface. The latter is the -universal method in describing electric fields. It secures the following -advantages:--First: The potential at any point in the field of space -surrounding the attracting or repelling mass or masses is found by -determining on which imaginary equipotential surface that point lies. -Second: If unit length of a line of force cross n equipotential -surfaces, the mean force along that line along the course of that part -of it is equal to n units; for the difference of potential of the two -ends of that part of the line of force = n; it is also equal to F s (F -= force), because it represents numerically a certain amount of work; -but s = I, whence n = F. Third: The force at any part of the field -corresponds to the extent to which the lines of force are crowded -together; and thence it may be determined by the number of lines of -force which pass through a unit of area of the corresponding -equipotential surface, that area being so chosen as to comprise the -point in question. (Daniell.) - - -Field of Force, Electrostatic. -The field established by the attracting, repelling and stressing -influence of an electrostatically charged body. It is often termed an -Electrostatic Field. (See Field of Force.) - - -255 STANDARD ELECTRICAL DICTIONARY. - - -Field of Force of a Current. -A current establishes a field of force around itself, whose lines of -force form circles with their centres on the axis of the current. The -cut, Fig. 172, shows the relation of lines of force to current. - - -Fig. 171. EXPERIMENT SHOWING LINES OF FORCE -SURROUNDING AN ACTIVE CONDUCTOR. - - -Fig. 172. DIAGRAM OF FIELD OF FORCE SURROUNDING AN ACTIVE CONDUCTOR. - - -Fig. 173. LINK OF FORCE INDUCED BY A CURRENT SHOWING THE MAGNETIC WHIRLS. - - -The existence of the field is easily shown by passing a conductor -vertically through a horizontal card. On causing a current to go through -the wire the field is formed, and iron filings dropped upon the card, -tend, when the latter is gently tapped, to take the form of circles. The -experiment gives a version of the well-known magnetic figures, q. v. See -Fig. 171. - -The cut shows by the arrows the relation of directions of current to the -direction of the lines of force, both being assumptions, and merely -indicating certain fixed relations, corresponding exactly to the -relations expressed by the directions of electro-magnetic or magnetic -lines of force - -256 STANDARD ELECTRICAL DICTIONARY. - - -Field, Pulsatory. -A field produced by pulsatory currents. By induction such field can -produce an alternating current. - - -Field, Rotating. -In a dynamo the field magnets are sometimes rotated instead of the -armature, the latter being stationary. In Mordey's alternator the -armature, nearly cylindrical, surrounds the field, and the latter -rotates within it, the arrangement being nearly the exact reverse of the -ordinary one. This produces a rotating field. - - -Field, Rotatory. -A magnetic field whose virtual poles keep rotating around its centre of -figure. If two alternating currents differing one quarter period in -phase are carried around four magnetizing coils placed and connected in -sets of two on the same diameter and at right angles to each other, the -polarity of the system will be a resultant of the combination of their -polarity, and the resultant poles will travel round and round in a -circle. In such a field, owing to eddy currents, masses of metal, -journaled like an armature, will rotate, with the speed of rotation of -the field. - - -Field, Stray. -The portion of a field of force outside of the regular circuit; -especially applied to the magnetic field of force of dynamos expressing -the portion which contributes nothing to the current generation. - -Synonym--Waste Field. - - -Field, Uniform. -A field of force of uniform density. (See Field Density.) - - -Figure of Merit. -In the case of a galvanometer, a coefficient expressing its delicacy. It -is the reciprocal of the current required to deflect the needle through -one degree. By using the reciprocal the smaller the current required the -larger is the figure of merit. The same term may be applied to other -instruments. - -It is often defined as the resistance of a circuit through which one -Daniell's element will produce a deflection of one degree on the scale -of the instrument. The circuit includes a Daniell's cell of resistance -r, a rheostat R, galvanometer G and shunt S. Assume that with the shunt -in parallel a deflection of a divisions is obtained. The resistance of -the shunted galvanometer is (GS/G+S ; the multiplying power m of the -shunt is S+G/S; the formula or figure of merit is m d (r+R +G S/G+S). - -The figure of merit is larger as the instrument is more sensitive. -Synonym--Formula of Merit. - - -257 STANDARD ELECTRICAL DICTIONARY. - - -Filament. -A thin long piece of a solid substance. In general it is so thin as to -act almost like a thread, to be capable of standing considerable -flexure. The distinction between filament and rod has been of much -importance in some patent cases concerning incandescent lamps. As used -by electricians the term generally applies to the carbon filament of -incandescent lamps. This as now made has not necessarily any fibres, but -is entitled to the name of filament, partly by convention, partly by its -relative thinness and want of stiffness. (See Incandescent -Lamps--Magnetic Filament.) - - -Fire Alarm, Electric, Automatic. -A system of telegraph circuits, at intervals supplied with thermostats -or other apparatus affected by a change of temperature, which on being -heated closes the circuit and causes a bell to ring. (See Thermostat.) - - -Fire Alarm Telegraph System. -A system of telegraphic lines for communicating the approximate location -of a fire to a central station and thence to the separate fire-engine -houses in a city or district. It includes alarm boxes, distributed at -frequent intervals, locked, with the place where the key is kept -designated, or in some systems left unlocked. On opening the door of the -box and pulling the handle or otherwise operating the alarm, a -designated signal is sent to the central station. From this it is -telegraphed by apparatus worked by the central station operator to the -engine houses. The engines respond according to the discipline of the -service. - - -Fire Cleansing. -Freeing the surface of an article to be plated from grease by heating. - - -Fire Extinguisher, Electric, Automatic. -A modification of the electric fire alarm (see Fire Alarm, Electric, -Automatic), in which the thermostats completing the circuits turn on -water which, escaping through the building, is supposed to reach and -extinguish a fire. - - -Flashing in a Dynamo or Magneto-electric Generator. -Bad adjustment of the brushes at the commutator, or other fault of -construction causes the production of voltaic arcs at the commutator of -a generator, to which the term flashing is applied. - - -Flashing of Incandescent Lamp Carbons. -A process of treatment for the filaments of incandescent lamps. The -chamber before sealing up is filled with a hydro-carbon vapor or gas, -such as the vapor of a very light naphtha (rhigolene). A current is then -passed through the filament heating it to redness. The more attenuated -parts or those of highest resistance are heated the highest, and -decompose most rapidly the hydro-carbon vapor, graphitic carbon being -deposited upon these parts, while hydrogen is set free. This goes on -until the filament is of uniform resistance throughout. It gives also a -way of making the resistance of the filament equal to any desired number -of ohms, provided it is originally of high enough resistance. The -process increases the conductivity of the filament. - -After flashing the chambers are pumped out and sealed up. - - -258 STANDARD ELECTRICAL DICTIONARY. - - -Flashing Over. -A phenomenon observed in high potential dynamos. On a sudden alteration -of the resistance of the circuit a long blue spark will be drawn out -around the surface of the commutator from brush to brush. The spark is -somewhat of the nature of an arc, and may seriously injure commutators -whose sections are only separated by mica, or other thin insulation. In -the case of commutators whose sections are separated by air spaces it is -not so injurious. - - -Flats. -In a commutator of a dynamo, the burning or wearing away of a commutator -segment to a lower level than the rest. Sometimes two adjacent bars will -be thus affected, causing a flat place on the commutator. It is not -always easy to account for the formation of flats. They may have their -origin in periodic vibrations due to bad mounting, or to sparking at the -particular point. - - -Floor Push. -A press or push button constructed to be set into the floor to be -operated by pressing with the foot. It is used to ring an alarm bell, -sound a buzzer or for similar service. - - -Fluid, Depolarizing. -A fluid used in voltaic batteries to dispose of the hydrogen, which goes -to the negative plate. This it does by oxidizing it. Chromic acid, -nitric acid, and chloric acids are among the constituents of liquid -depolarizers. (See Electropoion Fluid.) - - -Fluid, Electric. -The electric current and charge have sometimes been attributed to a -fluid. The theory, which never was much more than hypothetical, survives -to some extent in the single and double fluid theory. (See Single Fluid -Theory-Double Fluid Theory.) - - -Fluorescence. -The property of converting ether waves of one length, sometimes of -invisible length, into waves of another length (visible). AEsculin, -quinine salts, uranium glass and other substances exhibit this -phenomenon. The phenomenon is utilized in the production of Geissler -tubes. - - -Flush Boxes. -A heavy iron box covered with a heavy hand plate and laid flush (whence -the name), or even with the surface of a roadway. Into it conductors of -an underground system lead, and it is used to make connections therewith -and for examining the leakage of the conductors and for similar -purposes. It is a "man-hole" (q. v.) in miniature. - -Fluviograph. -An electric registering tide gauge or water level gauge. - - -259 STANDARD ELECTRICAL DICTIONARY. - - -Fly or Flyer, Electric. -A little wheel, ordinarily poised on a point, like a compass needle. It -carries several tangentially directed points, all pointing in the same -sense. When connected with a source of electricity of high potential it -revolves by reaction. The tension of its charge is highest at the -points, the air there is highly electrified and repelled, the reaction -pushing the wheel around like a Barker's mill or Hero's steam engine. -Sometimes the flyer is mounted with its axis horizontal and across the -rails on a railroad along which it travels. - -Synonym--Reaction Wheel. - - -Foci Magnetic. -The two points on the earth's surface where the magnetic intensity is -greatest. They nearly coincide in position with the magnetic poles. - - -Fog, Electric. -Fogs occurring when the atmosphere is at unusually high potential and -accompanied by frequent change of such polarity. - - -Following Horns. -In dynamo-electric machines the projecting ends of the pole pieces -towards which the outer uncovered perimeter of the armature turns in its -regular operations. The leading horns are those away from which the -armature rotates. In considering rotation the exposed portion of the -superficies of the armature is considered. The definition would have to -be reversed if the part facing the pole pieces were considered. - -Synonym--Trailing Horns. - - -Foot-candle. -A unit of illuminating power; the light given by one standard candle at -a distance of one foot. The ordinary units of illuminating power are -entirely relative; this is definite. It is due to Carl Herring. - - -Foot-pound. -A practical unit of work or energy. The quantity of work required to -raise a pound one foot, or one hundred pounds one-hundredth of a foot, -and so on; or the potential energy represented by a weight at an -elevation under these conditions. - - -Foot-step. -In a dynamo with armature at the lower end of its field magnets, the -plate generally of zinc, interposed between it and the iron base plate -to prevent the leakage of lines of force outside of the circuit. Any -diamagnetic material which is mechanically suitable may be used. - - -Force. -Force may be variously defined. -(a) Any cause of change of the condition of matter with respect to -motion or rest. - -(b) A measurable action upon a body under which the state of rest of -that body, or its state of uniform motion in a straight line, suffers -change. - -(c) It may be defined by its measurement as the rate of change of -momentum, or - -(d) as the rate at which work is done per unit of space traversed. - -Force is measured by the acceleration or change of motion it can impart -to a body of unit mass in a unit of time, or, calling -force, F, -mass, m -acceleration per second a -we have F = m a. - -The dimensions of force are -mass (M) * acceleration (L/(T^2)) = (M*L)/(T^2). - - -260 STANDARD ELECTRICAL DICTIONARY. - - -Force de Cheval. Horse power (French). -It is the French or metric horse power. -It is equal to: - 542.496 Foot lbs. per second. - .9864 English Horse Power. - 75.0 Kilogram-meters per second. - -Force, Electro-magnetic. -The mechanical force of attraction or repulsion acting on the -electro-magnetic unit of quantity. Its intensity varies with the square -of the distance. It may also be defined as electric force in the -electro-magnetic system. - -Its dimensions are equal to -mechanical force ((M*L)/(T^2)) divided by quantity ((M^.5)*(L^.5)) -= ((M^.5)*(L^.5))/(T^2). - - -Force, Electrostatic. -The force by which electric matter or electrified surfaces attract or -repel each other. It is also termed electric force (not good) and -electro-motive intensity. It is the mechanical force acting upon a unit -quantity of electricity. Its intensity varies with the square of the -distance. - -Its dimensions are therefore equal to -(quantity * unity / (square of distance) Q. * 1 / (L^2) - = ((M^.5) * (L^1.5) )/ T*1 / (L^2) - = ((M^.5) * (L^.5)) / T -These dimensions are also those of potential difference. - -[Transcriber's Note: The image of the preceding paragraph is included -for "clarity".] - -The objection to the term electric force is that it may be applied also -to electro-magnetic force, and hence be a source of confusion. - - -Forces, Parallelogram of. -The usual method of composing forces or resolving a force. The sides of -a parallelogram of forces represent component forces and the diagonal -represents the resultant. See Component--Resultant--Forces, Composition -of--Forces, Resolution of. - - -Forces, Composition of. -When several forces act in a different direction upon a point they may -be drawn or graphically represented as arrows or lines emanating from -the point in the proper direction and of lengths proportional to the -force they exercise. Any two can be treated as contiguous sides of a -parallelogram and the parallelogram can be completed. Then its diagonal, -called the resultant, will represent the combined action of the two -forces, both as regards direction and intensity. This is the composition -of two forces. - -If more than two forces act upon the given point the resultant can be -composed with any of the others and a new force developed. The new -resultant can be combined with another force, and the process kept up, -eliminating the components one by one until a final resultant of all is -obtained. This will give the exact direction and intensity of the -forces, however many or varied. - - -261 STANDARD ELECTRICAL DICTIONARY. - -Forces, Resolution of. -The developing from a single force treated as a resultant, two other -forces in any desired direction. The reverse of composition of forces. -(See Forces, Composition of--Forces, Parallelogram -of--Components--Resultant.) - - -Force, Tubes of. -Aggregations of lines of force, either electrostatic or magnetic. They -generally have a truncated, conical or pyramidal shape and are not -hollow. Every cross-section contains the same number of lines. The name -it will seem is not very expressive. - - -Force, Unit of. -The fundamental or C. G. S. unit or force is the dyne, q. v. - -The British unit of force is the poundal (the force which will produce -an acceleration of one foot per second in a mass of one pound). It is -equal to about 10/322 pound. A force cannot be expressed accurately in -weight units, because weight varies with the latitude. - - -Forming. -The process of producing secondary battery plates from lead plates by -alternately passing a charging current through the cell and then -allowing it to discharge itself and repeating the operation. (See -Battery, Secondary, Planté's.) - - -Foundation Ring. -In a dynamo armature the ring-shaped core on which Gramme ring armatures -and other ring armatures are wound. - - -Fourth State of Matter. -Gas so rarefied that its molecules do not collide, or rarely do so; -radiant matter, q. v. - -[Transcriber's note: This term now refers to plasma, an ionized gas, -which contains free electrons. The ions and electrons move somewhat -independently making plasma electrically conductive. It responds -strongly to electromagnetic fields.] - - -Frame. -In a dynamo the bed-piece is sometimes called the frame. - - -Franklin's Experiment. -Franklin proved the identity of lightning and electricity by flying a -kite in a thunder storm. The kite was of silk so as to endure the -wetting. When the string became wet sparks could be taken from a key -attached to its end. The main string was of hemp; at the lower end was a -length of silk to insulate it. The key was attached near the end of and -to the hemp string. - - -Franklin's Plate. -A simple form of condenser. It consists of a plate of glass coated on -each side with tinfoil with a margin of about an inch of clear glass. -One coating may be grounded as indicated in the cut, and the plate -charged like a Leyden jar. Or one side may be connected with one -terminal, and the other with the other terminal of an influence machine -and the pane will be thus charged. - -Synonym--Fulminating Pane. - - -262 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 174. FRANKLIN'S PLATE. - - -Franklin's Theory. -The single fluid theory, q. v., of electricity. - -Frequency. -The number of double reversals or complete alternations per second in an -alternating current. - -Synonym--Periodicity. - - -Frictional Electricity. -Electricity produced by friction of dissimilar substances. (See -Electrostatic Series.) The contact theory holds that friction plays only -a secondary rôle in this process; that it increases the thoroughness of -contact, and tends to dry the rubbing surfaces, but that the charges -induced are due to contact of dissimilar substances, not to friction of -one against the other. - - -Frictional Heating. -The heating of a conductor by the passage of a current; the Joule -effect, q. v. - - -Fringe. -The outlying edge of a magnetic field. - - -Frog, Galvani's Experiment With. -A classic experiment in electricity, leading to the discovery of current -or dynamic electricity. If a pair of legs of a recently killed frog are -prepared with the lumbar nerves exposed near the base of the spinal -column, and if a metallic conductor, one half-length zinc and the other -half-length copper, is held, one end between the lumbar nerves and the -spine, and the other end against one of the muscles of the thigh or -lower legs, the moment contact occurs and the circuit is completed -through the animal substance the muscles contract and the leg is -violently drawn upwards. Galvani, in 1786, first performed, by accident, -this famous experiment, it is said, with a scalpel with which he was -dissecting the animal. He gave his attention to the nerves and muscles. -Volta, more happily, gave his attention to the metals and invented the -voltaic battery, described by him in a letter to Sir Joseph Banks, dated -1800. - - -Frog, Rheoscopic. -If the nerve or living muscle of a frog is suddenly dropped upon another -living muscle so as to come in contact with its longitudinal and -transverse sections, the first muscle will contract on account of the -stimulation of its nerve due to the passage of a current derived from -the second muscle (Ganot). The experiment goes under the above title. - - -263 STANDARD ELECTRICAL DICTIONARY. - -Frying. -A term applied to a noise sometimes produced in a voltaic arc due to too -close approach of the carbons to each other. It has been suggested that -it may be due to volatilization of the carbon. (Elihu Thomson.) - - -Fulgurite. -An irregular and tubular mass of vitrified quartz, believed to be formed -by melting under the lightning stroke. - - -Fig. 175. CRUCIBLE, ELECTRIC. - - -Furnace, Electric. -A furnace in which the heat is produced by the electric current. It has -hitherto been practically used only in the extraction of aluminum and -silicium from their ores. The general principle involves the formation -of an arc between carbon electrodes. The substances to be treated are -exposed to the heat thus produced. Sometimes the substances in the arc -form imperfect conductors, and incandescence takes a part in the action. -Sometimes the substances are merely dropped through the arc. - -[Transcriber's note: Silicium is silicon.] - - -Fuse Board. -A tablet on which a number of safety fuses are mounted. Slate is -excellent material for the tablet, as it is incombustible, and is easily -drilled and worked. - - -Fuse Box. -A box containing a safety fuse. Porcelain is an excellent material for -its base. No combustible material should enter into its composition. - - -Fuse, Cockburn. -A safety fuse or cut off which consists of a wire of pure tin running -from terminal to terminal, to whose centre a leaden ball is secured by -being cast into position. The connection with the terminals is made by -rings at the ends of the wire through which the terminal screws are -passed and screwed home. When the tin softens under too heavy a current -the weight of the shot pulls it apart. - - -Fig. 176 COCKBURN SAFETY FUSE. - - -264 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 177. ELECTRIC FUSE. - - -Fuse, Electric. -A fuse for igniting an explosive by electricity. There are two kinds. In -one a thin wire unites the ends of the two conducting wires as they -enter the case of the fuse. The larger wires are secured to the case, so -that no strain comes on the fine wire. On passing a current of -sufficient strength the small wire is heated. In use the fuse is bedded -in powder, which again may be surrounded by fulminating powder, all -contained in a copper or other metallic case. Such a detonator is used -for exploding guncotton and other high explosives. - -The other kind of fuse is similar, but has no thin connecting wire. The -ends of the conductors are brought nearer together without touching. In -use a static discharge is produced across from end to end of the -conductors, igniting a proper explosive placed there as in the other -case. - -The first kind of fuse is generally operated by a battery or small -mechanical generator--the latter by a spark coil, frictional or -influence machine or by a Leyden jar. - - -Galvanic. adj. -Voltaic; relating to current electricity or the electrolytic and -electro-chemical relations of metals. (For titles in general under this -head see Voltaic--or the main title.) - - -Galvanic Element. -A galvanic couple with exciting fluid and adjuncts; a galvanic cell. The -word element is sometimes applied to the electrodes of a cell, as the -carbon element or zinc element. - - -265 STANDARD ELECTRICAL DICTIONARY. - - -Galvanic Polarization. -The polarization of a voltaic couple. (See Polarization.) - - -Galvanism. -The science of voltaic or current electricity. - - -Galvanization. -(a) Electroplating or depositing a metal over the surface of another by -electrolysis. - -(b) In medical electricity the effects produced on any part of the -system by the current of voltaic battery. Various descriptive -qualifications are prefixed, such as "general" galvanization, indicating -its application as applied to the whole body, "local" for the reverse -case, and so on. - - -Galvanization, Labile. -Application of the galvanic current in electro-therapeutics where one -sponge electrode is employed which is rubbed or moved over the body, the -other being in constant contact with the body. - - -Galvanized Iron. -Iron coated with zinc by cleaning and immersion in melted zinc. The iron -is prevented from rusting by galvanic action. It forms the negative -element in a couple of which the zinc is the positive element. From this -electric protective action the name is derived. - - -Galvano-cautery, Chemical. -Electro-therapeutic treatment with sharp electrodes, one of which is -inserted in the tissue and a current passed by completing the circuit -through the tissue so as to electrolyze or decompose the fluids of the -tissue. It is applied in the removal of hair or extirpation of the -follicle. The process is not one of heating, and is improperly named -cautery. - -Galvano-faradization. -In medical electricity the application of the voltaic and induced or -secondary current simultaneously to any part of the system. - - -Galvanometer. -An instrument for measuring current strength and sometimes for measuring -inferentially potential difference, depending on the action of a -magnetic field established by the current, such action being exerted on -a magnetic needle or its equivalent. - -A current passing through a conductor establishes circular lines of -force. A magnetic needle placed in their field is acted on and tends to -place itself parallel with the lines, in accordance with the principles -of current induction. (See Induction, Electro-magnetic.) A common -compass held near a conductor through which a current is passing tends -to place itself at right angles to such conductor. For a maximum effect -the conductor or the part nearest the needle should lie in the magnetic -meridian. If at right angles thereto its action will only strengthen the -directive force of the earth's induction or magnetic field, as the -needle naturally points north and south. Such combination is virtually a -galvanometer. - - -266 STANDARD ELECTRICAL DICTIONARY. - - -A typical galvanometer comprises a flat coil of wire placed horizontally -within which a magnetic needle is delicately poised, so as to be free to -rotate with the least possible friction. The needle may be supported on -a sharp point like a compass needle, or may be suspended by a long fine -filament. It should be covered by a glass plate and box, or by a glass -shade. Finally a graduated disc may be arranged to show the amount of -deflection of the needle. - -In use the apparatus is turned about until the needle, as acted on by -the earth's magnetic field, lies parallel to the direction of the coils -of wire. On passing a current through the coil the needle is deflected, -more or less, according to its strength. - -By using exceedingly fine wire, long enough to give high resistance, the -instrument can be used for very high potentials, or is in condition for -use in determining voltage. By using a coil of large wire and low -resistance it can be employed in determining amperage. In either case -the deflection is produced by the current. - -The needle is often placed above or below the coil so as only to receive -a portion of its effect, enough for all practical purposes in the -commoner class of instruments. - -The galvanometer was invented by Schweigger a short time after Oersted's -discovery, q. v. - - -Galvanometer, Absolute. -A galvanometer giving absolute readings; properly one whose law of -calibration can be deduced from its construction. Thus the diameter of -the coil, and the constants and position of a magnetic needle suspended -in its field being known, the current intensity required to deflect the -needle a given number of degrees could be calculated. - - -Galvanometer, Aperiodic. -A galvanometer whose needle is damped (see Damping) as, for instance, by -the proximity of a plate of metal, by an air vane or otherwise, so that -it reaches its reading with hardly any oscillation. A very light needle -and a strong magnetic field also conduce to vibrations of short period -dying out very quickly. Such galvanometers are termed "dead-beat." No -instrument is absolutely dead-beat, only relatively so. - - -267 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 178. ASTATIC GALVANOMETER. - - -Galvanometer, Astatic. -A galvanometer with a pair of magnetic needles connected astatically, or -parallel with their poles in opposition. (See Astatic Needle.) Each -needle has its own coil, the coils being wound in opposite directions so -as to unite in producing deflections in the same sense. As there should -be some directive tendency this is obtained by one of the magnets being -slightly stronger than the other or by the proximity of a fixed and -adjustable controlling magnet, placed nearer one needle than the other. - -For small deflections the currents producing them are proportional to -their extent. - - -Galvanometer, Ballistic. -A galvanometer whose deflected element has considerable moment of -inertia; the exact opposite of an aperiodic or dead beat galvanometer. -(See Galvanometer, Aperiodic.) All damping by air vanes or otherwise -must be carefully done away with. - - -Fig. 179. SIEMENS & HALSKE'S GALVANOMETER. - - -Siemens & Halske's galvanometer is of the reflecting or mirror type (see -Galvanometer, Reflecting) with suspended, bell-shaped magnet, in place -of the ordinary magnetic needle, or astatic combination of the lightest -possible weight in the regular instrument. A copper ball drilled out to -admit the magnet is used as damper in the ordinary use of the -instrument. To convert it into a ballistic galvanometer the copper ball -is removed. The heavy suspended magnet then by its inertia introduces -the desired element into the instrument. - - -268 STANDARD ELECTRICAL DICTIONARY. - - -Referring to the cut, Fig. 179, M is the suspended magnet, with north -and south poles n and s; S is the reflecting mirror; r is the tube -containing the suspending thread; R is the damper removed for ballistic -work. - -The ballistic galvanometer is used to measure quantities of electricity -in an instantaneous discharge, which discharge should be completed -before the heavy needle begins to move. The extreme elongation or throw -of the needle is observed, and depends (1) on the number of coulombs (K) -that pass during the discharge; (2) on the moment of inertia of the -needle and attached parts; (3) on the moment of the controlling forces, -i. e., the forces tending to pull the needle back to zero; (4) on the -moment of the damping forces; (5) on the moment of the deflecting forces -due to a given constant current. The formula is thus expressed: - -K = (P / PI ) * A * sin( kº / 2 ) / tan( aº ) - -in which K = coulombs discharged; P = periodic time of vibration of -needle; A = amperes producing a steady deflection equal to aº ; kº = -first angular deflection of needle. For accuracy kº and aº should both -be small and the damping so slight as to be negligible. Otherwise a -correction for the latter must be applied. For approximate work for kº -and aº the deflections read on the scale may be used with the following -formula: - -K = (P / PI ) * ( A / 2 ) * ( kº / aº ) - - -Galvanometer Constant. -Assume a galvanometer with a very short needle and so placed with -respect to its coils that the magnetic field produced by a current -circulating in them is sensibly uniform in the neighborhood of the -needle, with its lines of force at right angles thereto. The field is -proportional to the current i, so that it may be denoted by G i. Then G -is the galvanometer constant. If now the angle of deflection of the -needle is ? against the earth's field H, M being the magnetic moment of -the needle we have G i M cos ? = H M sin ? or i = (H/G)* tan ?. H/G is -the reduction factor; variable as H varies for different places. - -For a tangent galvanometer the constant G is equal to 2*PI*(n/a), in -which n denotes the number of turns of wire, and a denotes the radius of -the circle. - - -Galvanometer, Differential. -A galvanometer in which the needle is acted on by two coils wound in -opposition, each of equal deflecting action and of equal resistance. If -a current is divided between two branches or parallel conductors, each -including one of the coils, when the needle points to zero the -resistances of the two branches will bc equal. In the cut, C C' -represent the coils, and A and B the two leads into which the circuit, P -Q, is divided. - - -269 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 180. THEORY OF DIFFERENTIAL GALVANOMETER. - - -Fig. 181. DIFFERENTIAL GALVANOMETER. - - -Galvanometer, Direct Reading. -A calibrated galvanometer, whose scale is graduated by volts or amperes, -instead of degrees. - - -Galvanometer, Marine. (Sir William Thomson's.) -A galvanometer of the reflecting type, for use on shipboard. A fibre -suspension is adopted for the needle. The fibre is attached to a fixed -support at one end and to a spring at the other, and the needle is -suspended by its centre of gravity. This secures it to a considerable -extent from disturbance due to the rolling of the ship. A thick iron box -encloses the needle, etc., to cut off any magnetic action from the ship. -(See Galvanometer, Reflecting.) - - -Galvanometer, Potential. -A galvanometer wound with fine German silver wire to secure high -resistance used for determination of potential difference. - - -Galvanometer, Proportional. -A galvanometer so constructed that the deflections of its index are -proportional to the current passing. It is made by causing the -deflecting force to increase as the needle is deflected, more and more, -or by causing the restitutive force to diminish under like conditions, -or by both. The condition is obtained in some cases by the shape and -position of the deflecting coils. - - -Galvanometer, Quantity. -A galvanometer for determining quantities of electricity, by the -deflections produced by discharging the quantities through their coils. -It is a ballistic galvanometer with very little or no damping. - - -270 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 182. PRINCIPLE OF REFLECTING GALVANOMETER. - - -Fig. 183. REFLECTING GALVANOMETER. - - -Galvanometer, Reflecting. -A galvanometer the deflections of whose needle are read by an image -projected by light reflected from a mirror attached to the needle or to -a vertical wire carrying the needle. A lamp is placed in front of the -instrument facing the mirror. The light of the lamp is reflected by the -mirror upon a horizontal scale above the lamp. An image of a slit or of -a wire may be caused thus to fall upon the scale, the mirror being -slightly convex, or a lens being used to produce the projection. - - -271 STANDARD ELECTRICAL DICTIONARY. - - -If the mirror swings through a horizontal arc, the reflected image will -move, in virtue of a simple geometrical principle, through an arc of -twice as many degrees. The scale can be placed far from the mirror, so -that the ray of light will represent a weightless index of very great -length, and minute deflections of the needle will be shown distinctly -upon the scale. - -In the cut, Fig. 182, the ray of light from the lamp passes through the -aperture, m m, and is made parallel by the lens, L. At s is the mirror -attached to the needle and moving with it. A scale placed at t receives -the reflection from the mirror. The cut, Fig. 183, shows one form of the -instrument set up for use. - -Synonym--Mirror Galvanometer. - - -Galvanometer Shunt. -To prevent too much current passing through a galvanometer (for fear of -injury to its insulation) a shunt is sometimes placed in parallel with -it. The total current will be distributed between galvanometer and shunt -in the inverse ratio of their respective resistances. (See Multiplying -Power of a Shunt.) - - -272 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 184. SINE GALVANOMETER. - - -Galvanometer, Sine. -A galvanometer whose measurements depend upon the sine of the angle of -deflection produced when the coil and needle lie in the same vertical -plane. - -The needle, which may be a long one, is surrounded by a coil, which can -be rotated about a vertical axis passing through the point of suspension -of the needle. Starting with the needle at rest in the plane of the -coil, a current is passed through the coil deflecting the needle, the -coil is swung around deflecting the needle still more, until the needle -lies in the plane of the coil; the intensity of the current will then be -in proportion to the sine of the angle through which the coil and needle -move. - -In the galvanometer M is a circle carrying the coil, N is a scale over -which the needles, m and n, move, the former being a magnetic needle, -the latter an index at right angles and attached thereto; a and b are -wires carrying the current to be measured. The circles, M and N, are -carried by a base, O, around which they rotate. H is a fixed horizontal -graduated circle. In use the circle, M, is placed in the magnetic -meridian, the current is passed through the coil, M; the needle is -deflected; M is turned until its plane coincides with the direction of -the needle, m. The current strength is proportional to the sine of the -angle of deflection. This angle is measured by the vernier, C, on the -circle, H. The knob, A, is used to turn the circle, M. - - -273 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 185. TANGENT GALVANOMETER. - - -Galvanometer, Tangent. -A galvanometer in which the tangents of the angles of deflection are -proportional to the currents producing such deflections. - -For this law to apply the instrument in general must fulfill the -following conditions: - -(1) The needle must be controlled by a uniform magnetic field such as -that of the earth; - -(2) the diameter of the coil must be large compared to the length of the -needle; - -(3) the centre of suspension of the needle must be at the centre of the -coil; - -(4) the magnetic axis of the needle must lie in the plane of the coil -when no current is passing. - -If a single current strength is to be measured the best results will be -attained when the deflection is 45°; in comparing two currents the best -results will be attained when the deflections as nearly as possible are -at equal distances on both sides of 45°. - -The needle should not exceed in length one-tenth the diameter of the -coil. - -For very small deflections any galvanometer follows the law of -tangential deflection. - -As for very small deflections the tangents are practically equal to the -arcs subtended, for such deflections the currents are proportional to -the deflections they produce. - -The sensibility is directly proportional to the number of convolutions -of wire and inversely proportional to their diameter. - -The tangent law is most accurately fulfilled when the depth of the coil -in the radial direction is to the breadth in the axial direction as -squareRoot(3):squareRoot(2), or about as 11:9. - - -Galvanometer, Torsion. -A galvanometer whose needle is suspended by a long filament or by a -thread and spiral spring against whose force of torsion the movements of -the needle are produced. The current strength is determined by bringing -the needle back to its position of rest by turning a hand-button or -other arrangement. The angle through which this is turned gives the -angle of torsion. From this the current strength is calculated on the -general basis that it is proportional to the angle of torsion. - - -Fig. 186. TORSION GALVANOMETER. - - -274 STANDARD ELECTRICAL DICTIONARY. - - -Galvanometer, Vertical. -A galvanometer whose needle is mounted on a horizontal axis and is -deflected in a vertical plane. One of the poles is weighted to keep it -normally vertical, representing the control. It is not used for accurate -work. - -Synonym--Upright Galvanometer. - - -Fig. 187. VERTICAL GALVANOMETER. - - -Galvanometer, Volt- and Ampere-meter. -A galvanometer of Sir William Thomson's invention embodying the tangent -principle, and having its sensibility adjustable by moving the magnetic -needle horizontally along a scale (the "meter") towards or away from the -coil. A curved magnet is used to adjust the control. The leads are -twisted to prevent induction. - -The instrument is made with a high resistance coil for voltage -determinations, and with a low resistance coil for amperage -determinations. - -At one end of a long base board a vertical coil with its plane at right -angles to the axis of the board is mounted. A scale (the "meter" of the -name) runs down the centre of the board. A groove also runs down the -centre. The magnetic needle is contained in a quadrant-shaped -glass-covered box which slides up and down the groove. A number of short -parallel needles mounted together, with an aluminum pointer are used. - - -Fig. 188. SIR WILLIAM THOMSON'S AMPERE-METER GALVANOMETER. - - -275 STANDARD ELECTRICAL DICTIONARY. - - -In the cut P is the base board, M is a glass covered case containing the -magnetic needle, and sliding along the base board, being guided by the -central groove, C, is the coil. Between the coil and the needle is the -arched or bent controlling magnet. The long twisted connecting wires are -seen on the right hand. - - -Galvano-plastics. -The deposition of metals by electrolysis, a disused term replaced -by electro-deposition, electroplating, and electro-metallurgy. - - -Galvano-puncture. -An operation in medical electricity. (See Electro-puncture.) - - -Galvanoscope. -An instrument, generally of the galvanometer type, used for ascertaining -whether a current is flowing or not. Any galvanoscope, when calibrated, -if susceptible thereof, becomes a galvanometer. - - -Gas, Electrolytic. -Gas produced by the decomposition, generally of water, by electrolysis. -It may be hydrogen or oxygen, or a mixture of the two, according to how -it is collected. (See Gases, Mixed.) - - -Gases, Mixed. -The mixture of approximately one volume of oxygen and two volumes of -hydrogen collected in the eudiometer of a gas voltameter or other -electrolytic apparatus. - - -Gassing. -The evolution of gas from the plates of a storage battery in the -charging process, due to too high voltage in the circuit of the charging -dynamo. - - -Gastroscope. -An apparatus for illuminating by an incandescent lamp the interior of -the stomach, and with prisms to refract the rays of light so that the -part can be seen. The stomach is inflated with air, if desirable, to -give a better view. An incandescent platinum spiral in a water jacket -has been employed for the illumination. - - -Gassiot's Cascade. -A goblet lined for half its interior surface with tinfoil. It is placed -in the receiver of an air pump from the top of whose bell a conductor -descends into it, not touching the foil. On producing a good -rarefaction, and discharging high tension electricity from between the -conductor just mentioned and the metal of the machine, a luminous effect -is produced, as if the electricity, pale blue in color, was overflowing -the goblet. - - -Gauss. -A name suggested for unit intensity of magnetic field. Sylvanus P. -Thomson proposed for its value the intensity of a field of 1E8 C. G. S. -electro-magnetic units. J. A. Fleming proposed the strength of field -which would develop one volt potential difference in a wire 1E6 -centimeters long, moving through such field with a velocity of one -centimeter per second. This is one hundred times greater than Thomson's -standard. Sir William Thomson suggested the intensity of field produced -by a current of one ampere at a distance of one centimeter - -The gauss is not used to any extent; practical calculations are based on -electro-magnetic lines of force. - - -276 STANDARD ELECTRICAL DICTIONARY. - - -Gauss' Principle. -An electric circuit acts upon a magnetic pole in such a way as to make -the number of lines of force that pass through the circuit a maximum. - - -Fig. 189. GAUSS' TANGENT POSITION. - - -Gauss, Tangent Positions of. -The "end on" and "broadside" methods of determining magnetization -involve positions which have been thus termed. (See Broadside Method and -End on Method.) - - -Gear, Magnetic Friction. -Friction gear in which the component wheels are pressed against each -other by electromagnetic action. In the cut, repeated from Adherence, -Electro-magnetic, the magnetizing coil makes the wheels, which are of -iron, press strongly together. - - -Fig. 190. MAGNETIC FRICTION GEAR. - - -277 STANDARD ELECTRICAL DICTIONARY. - - -Geissler Tubes. -Sealed tubes of glass containing highly rarefied gases, and provided -with platinum electrodes extending through the glass tightly sealed as -they pass through it, and often extending a short distance beyond its -interior surface. - -On passing through them the static discharge luminous effects are -produced varying with the degree of exhaustion, the contents (gas), the -glass itself, or solutions surrounding it. The two latter conditions -involve fluorescence phenomena often of a very beautiful description. - -The pressure of the gas is less than one-half of a millimeter of -mercury. If a complete vacuum is produced the discharge will not pass. -If too high rarefaction is produced radiant matter phenomena (see -Radiant State) occur. - -Geissler tubes have been used for lighting purposes as in mines, or for -illuminating the interior cavities of the body in surgical or medical -operations. - - -Generating Plate. -The positive plate in a voltaic couple, or the plate which is dissolved; -generally a plate of zinc. - -Synonyms--Positive Plate--Positive Element. - - -Generator, Current. -Any apparatus for maintaining an electric current. It may be as regards -the form of energy it converts into electrical energy, mechanical, as a -magneto or dynamo electric machine or generator; thermal, as a -thermo-electric battery; or chemical, as a voltaic battery; all of which -may be consulted. - -Generator, Secondary. -A secondary or storage battery. (See Battery, Secondary.) - - -German Silver. -An alloy of copper, 2 parts, nickel, 1 part, and zinc, 1 part. Owing to -its high resistance and moderate cost and small variation in resistance -with change of temperature, it is much used for resistances. From Dr. -Mathiessen's experiment the following constants are deduced in legal -ohms: - Relative Resistance (Silver = 1), 13.92 - Specific Resistance at 0° C. (32F.), 20.93 microhms. - Resistance of a wire, - (a) 1 foot long, weighing 1 grain, 2.622 ohms. - 1 foot long, 1/1000 inch thick, 125.91 " - 1 meter long, weighing 1 gram, 1.830 " - 1 meter long, 1 millimeter thick, 0.2666 " - Resistance of a 1 inch cube at 0°C. (32° F.), 8.240 microhms. - -Approximate percentage increase of resistance per 1° C. (1.8° F.) at -about 20° C. (68° F.), 0.044 per cent. - - -Gilding, Electro-. -The deposition of gold by an electric current, or electrolytically in -the electroplating bath. - - -Gilding Metal. -A special kind of brass, with a high percentage of copper, used to make -objects which are to be gilded by electrolysis. - - -278 STANDARD ELECTRICAL DICTIONARY. - - -Gimbals. -A suspension used for ships' compasses and sometimes for other -apparatus. It consists of a ring held by two journals, so as to bc free -to swing in one plane. The compass is swung upon this ring, being placed -concentrically therewith. Its journals are at right angles to those of -the ring. This gives a universal joint by which the compass, weighted -below its line of support, is always kept horizontal. - - -Fig. 191. COMPASS SUSPENDED IN GIMBALS. - - -Glass. -A fused mixture of silicates of various oxides. It is of extremely -varied composition and its electric constants vary greatly. Many -determinations of its specific resistance have been made. For flint -glass at 100° C. (212° F.) about (2.06E14) ohms --at 60° C (140° F.) -(1.020E15) (Thomas Gray) is given, while another observer (Beetz) gives -for glass at ordinary temperatures an immeasurably high resistance. It -is therefore a non-conductor of very high order if dry. As a dielectric -the specific inductive capacity of different samples of flint glass is -given as 6.57--6.85--7.4--10.1 (Hopkinson), thus exceeding all other -ordinary dielectrics. The densest glass, other things being equal, has -the highest specific inductive capacity. - - -Gold. -A metal, one of the elements; symbol Au. c .; atomic weight, 196.8; -equivalent, 65.6; valency, 3; specific gravity 19.5. -It is a conductor of electricity. - - Annealed. Hard drawn. -Relative Resistance (Annealed Silver = 1), 1.369 1.393 -Specific Resistance, 2.058 2.094 -Resistance of a wire at 0° C. (32°F.) -(a) 1 foot long, weighing 1 grain, 57.85 58.84 ohms -(b) 1 foot long, 1/1000 inch thick, 12.38 12.60 " -(c) 1 meter long, weighing 1 gram, .4035 .4104 " -(d) 1 meter long, 1 millimeter thick, .02620 .02668 " -Resistance of a 1 inch cube at 0° C.(32° F.) .8102 .8247 - -Approximate increase in resistance per 0° C., (1.8° F) -at about 20° C. (68° F.), 0.365 per cent. - -Electro-chemical equivalent (Hydrogen = .0105), .6888 - - -279 STANDARD ELECTRICAL DICTIONARY. - - -Gold Bath. -A solution of gold used for depositing the metal in the electroplating -process. - -A great number of formulae have been devised, of which a few -representative ones are given here. - COLD BATHS. HOT BATHS. -Water, 10,000 10,000 10,000 10,000 5,000 3,000 -Potassium Cyanide, 200 -- 200 10 -- 50 -Gold, 100 15 100 10 10 10 -Potassium Ferrocyanide, -- 200 -- -- 150 -- -Potassium Carbonate, -- 150 -- -- 50 -- -Ammonium Chloride, -- 30 -- -- 20 -- -Aqua Ammoniae, -- -- 500 -- -- -- -Sodium Phosphate, -- -- -- 600 -- -- -Sodium Bisulphite, -- -- -- 100 -- -- - -(Roseleur.) - -In the baths the gold is added in the form of neutral chloride, Auric -chloride (Au Cl6). - - -Gold Stripping Bath. -A bath for removing gold from plated articles without dissolving the -base in order to save the precious metal. A bath of 10 parts of -potassium cyanide and 100 parts of water may be used, the articles to be -stripped being immersed therein as the anode of an active circuit. If -the gilding is on a silver or copper basis, or on an alloy of these -metals the same solution attacks the base and dissolves it, which is -objectionable. For silver articles it is enough to heat to cherry red -and throw into dilute sulphuric acid. The gold scales off in metallic -spangles. For copper articles, a mixture of 10 volumes concentrated -sulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acid -may be used by immersion only, or with a battery. The sulphuric acid in -such large excess is supposed to protect the copper. For copper articles -concentrated sulphuric acid alone with the battery may be used. This -does not sensibly attack the copper if it is not allowed to become -diluted. Even the dampness of the air may act to dilute it. - - -Graduator. -Apparatus for enabling the same line to be used for telegraph signals -and telephoning. - -One type consists in coils with iron cores or simply electromagnets. -These act to retard the current in reaching its full power and also -prolong it. This gives a graduated effect to the signals, so that the -telephone diaphragm is not audibly affected by the impulses. - -The telephoning current is so slight and so rapid in its characteristic -changes that it is without effect upon the ordinary telegraph. - - -280 STANDARD ELECTRICAL DICTIONARY. - - -Gram. -The unit of weight in the metric system; accepted as the unit of -mass in the absolute of C. G. S. system of units. It is the -one-thousandth part of mass of a standard weight preserved under proper -conditions in Paris, and supposed to be the mass of a cubic decimeter of -distilled water at the temperature of the maximum density of water. The -standard is the kilogram; the temperature is 3.9º C. (39º F.). The -standard kilogram is found to be not exactly the weight of a cubic -decimeter of water, the latter weighing 1.000013 kilogram. - -If therefore the defined gram on the water basis is taken as the unit it -varies very slightly from the accepted gram. - -1 gram is equal to 15.43234874 grains. (Prof. W. H. Miller.) - - -Gram-atom. -The number of grams of an element equal numerically to the atomic -weight, as 16 grams of oxygen, 1 gram of hydrogen, 35.5 grams of -chlorine; all which might be expressed as gram-atoms of oxygen, hydrogen -and chlorine respectively. - -The gram-atom approximately expresses the number of gram-calories -required to heat one gram of the substance 1º C. (1.8º F.). This is in -virtue of Dulong and Petit's discovery that the atomic weight of an -element multiplied by its specific heat gives approximately a constant -for all elements. - -[Transcriber's note: A gram-atom is the mass, in grams, of one mole of -atoms in a monatomic element. A mole consists of Avogadro's number of -atoms, approximately 6.02214E23.] - - -Gram-molecule. -The number of grams of a substance equal numerically to its molecular -weight. - - -Graphite. -Carbon; one of three allotropic modifications of this element. It occurs -in nature as a mineral. - -It is used as a lubricant for machinery; for commutator brushes; for -making surfaces to be plated conductive, and for mixing with manganese -binoxide in Leclanché cells. - - -Gravitation. -A natural force which causes all masses of matter to attract each other. -Its cause is unknown; it is often supposed to be due to the luminiferous -ether. - -[Transcriber's note: Einstein's explanation of gravity, General -Relativity and the curvature of space-time, came 23 years later, 1915.] - - -281 STANDARD ELECTRICAL DICTIONARY. - - -Gravity, Acceleration of. -The velocity imparted to a body in one second by the action of -gravitation at any standard point upon the earth's surface in a vacuum. -This will vary at different places, owing principally to the variation -in centrifugal force due to the earth's rotation. For standard valuation -it must be reduced to sea level. The following are examples of its -variation: - -Equator, 978.1028 centimeters per second -Paris, 980.94 " -Greenwich 981.I7 " -Edinburgh, 981.54 " -Pole (N. or S.), 983.1084 (theoretical) " - -As round numbers for approximate calculations 981 centimeters or 32.2 -feet may be employed. - -[Transcriber's note: The acceleration of gravity at the equator is also -reduced by the increased distance from the center of the earth -(equatorial bulge). Increased altitude reduces gravity. Reduced air -density at altitude reduces buoyancy and increases apparent weight. -Local variations of rock density affects gravity.] - - -Gravity, Control. -Control by weight. In some ammeters and voltmeters gravity is the -controlling force. - - -Grid. -A lead plate perforated or ridged for use in a storage battery as the -supporter of the active materials and in part as contributing thereto -from its own substance. - - -Ground. -The contact of a conductor of an electric circuit with the earth, -permitting the escape of current if another ground exists. - - -Ground-wire. -A metaphorical term applied to the earth when used as a return circuit. - - -Fig. 192. GROVE'S GAS BATTERY. - - -Grove's Gas Battery. -A voltaic battery depending for its action on the oxidation of hydrogen -instead of the oxidation of zinc. Its action is more particularly -described under Battery, Gas. In the cut B, B1 * * * are the terminals -of the positive or hydrogen electrodes, marked H, and A, Al * * * are -the terminals of the negative or oxygen electrodes marked O, while M, M1 -* * * is dilute sulphuric acid. - - -282 STANDARD ELECTRICAL DICTIONARY. - - -Guard Ring. -An annular horizontal surface surrounding the balanced disc in the -absolute electrometer. (See Electrometer, Absolute.) - - -Guard Tube. -A metal tube surrounding a dry pile used with a quadrant electrometer, -or other electrometers of that type. It prevents the capacity of the -lower brass end of the pile (which brass end closes the glass tube -containing the discs) from momentary change by approach of some -conductor connected to the earth. There are other guard tubes also. - - -Gun, Electro-magnetic. -An electro-magnet with tubular core. If, when it is excited a piece of -an iron rod is pushed into the central aperture of the core and is -released, the magnetic circle will try to complete itself by pushing the -rod out so that it can thus be discharged, as if from a popgun. - -Synonym--Electric Popgun. - - -Fig. 193. "ELECTRIC POPGUN." - - -Gutta Percha. -The hardened milky juice of a tree, the Isonandra gutta, growing in -Malacca and other parts of the Eastern Archipelago. It is much used as -an insulator or constituent of insulators. - -Resistance after several minutes electrification per 1 centimeter cube -at 54º C. (75º F.), 4.50E14 ohms. - -The specific resistance varies--from 2.5E13 to 5.0E14 ohms. A usual -specification is 2.0E14 ohms. The influence of temperature on its -resistance is given in Clark & Bright's empirical formula, R = R0 at, in -which R is the resistance at temperature tº C--Ro the resistance at 0º C -(32º F), a is the coefficient .8944. - -The resistance increases with the time of passage of the current, the -variation being less the higher the temperature. - - -283 STANDARD ELECTRICAL DICTIONARY. - - -Time of Relative Resistance Relative Resistance -Electrification. at 0º C (32º F.) at 24º C (75º F.) - 1 minute 100 5.51 - 2 " 127.9 6. - 5 " 163.1 6.66 - 10 " 190.9 6.94 - 20 " 230.8 7.38 - 30 " 250.6 7.44 - 60 " 290.4 7.6 - 90 " 318.3 7.66 - -In cable testing one minute is generally taken as the time of -electrification. - -Pressure increases the resistance by the formula Rp=R (1+ .00327 P) in -which Rp is the resistance at pressure p--R resistance at atmospheric -pressure--p pressure in atmospheres. Thus in the ocean at a depth of -4,000 meters (2.4855 miles), the resistance is more than doubled. The -longer the pressure is applied, the greater is the resistance. - -The specific inductive capacity of gutta percha is 4.2. - -Good gutta percha should not break when struck with a hammer, should -recover its shape slowly, and it should support much more than 300 times -its own weight. - - -Gyrostatic Action of Armatures. -Owing to gyrostatic action a rotating armature resists any change of -direction of its axis. On ships and in railway motors which have to turn -curves this action occurs. A 148 lb. armature running at 1,300 -revolutions per minute may press with 30 lbs. on each journal as the -ship rolls through an angle of 20° in 16 seconds. - - -H. -(a) The symbol for the horizontal component of the earth's -magnetization. - -(b) The symbol for the intensity of a magnetizing force or field. The -symbol H, as it is generally used, may mean either the number of dynes -which act upon a unit pole, or the number of lines of force per -centimeter. - -(c) The symbol for the unit of self-induction. - - -Hair, Removal of, by Electrolysis. -A method of depilation by destruction of individual hair follicles by -electrolysis. - -A fine platinum electrode is thrust into a hair follicle. It is the -negative electrode. The positive electrode is in contact with the body -of the person under treatment; it is often a sponge electrode simply -held in his hand. A current of two to four milliamperes from an E. M. F. -of 15 to 20 volts, is passed. This destroys the follicle, the hair is -removed and never grows again. A gradual increase of current is advised -for the face. As only one hair is removed at once, but a small number -are taken out at a sitting. - - -284 STANDARD ELECTRICAL DICTIONARY. - - -Haldat's Figures. -With a pole of a strong bar magnet, used like a pencil, imaginary -figures are drawn upon a hard steel plate, such as a saw-blade. The -pattern is gone over several times. By dusting iron filings on a sheet -of paper laid over the steel plate, while horizontal, very complicated -magnetic figures are produced. - - -Hall's Experiment. -A cross of thin metal, such as gold leaf, is secured upon a pane of -glass. To two opposite arms a battery is connected in circuit with them. -To the other two arms a galvanometer is connected in circuit. If the -cross is put into a field of force whose lines are perpendicular -thereto, the galvanometer will disclose a constant current. The current -is pushed, as it were, into the galvanometer circuit. Other metals have -been used with similar results. They must be thin or the experiment -fails. If the arm receiving the battery current is horizontal, and if it -flows from left to right, and if the lines of force go from downward -through the cross, the current in the galvanometer circuit will flow -from the observer through the other arms of the cross, if the cross is -of gold, silver, platinum or tin, and the reverse if of iron. The -experiment has indicated a possible way of reaching the velocity of -electricity in absolute measure. - - -Hall Effect. -The effect observed in Hall's experiment, q. v. - - -Hall Effect, Real. -A transverse electro-motive force in a conductor through which a current -is passing produced by a magnetic field. - - -Hall Effect, Spurious. -A spurious electro-motive force produced in a conductor, through which a -current is passing by changes in conductivity of the conductor brought -about by a magnetic field. - - -Hanger Board. -A board containing two terminals, a suspending hook, and a switch, so -that an arc lamp can be introduced into a circuit thereby, or can be -removed as desired. - - -Harmonic Receiver. -A receiver containing a vibrating reed, acted on by an electro-magnet. -Such a reed answers only to impulses tuned to its own pitch. If such are -received from the magnet it will vibrate. Impulses not in tune with it -will not affect it. (See Telegraph, Harmonic.) - - -Head Bath, Electric. -A fanciful name for an electro-medical treatment of the head. The -patient is insulated by an insulating stool or otherwise. His person is -connected with one terminal of an influence machine. An insulated -metallic circle, with points of metal projecting inward or downward, is -placed about the head. The circle is connected with the other pole of -the machine. On working it a silent or brush discharge with air -convection streams occurs between the patient's head and the circle of -points. - - -285 STANDARD ELECTRICAL DICTIONARY. - - -Head-light, Electric. -An electric head-light for locomotives has been experimented with. It -includes the parabolic reflection of the regular light with an arc-lamp -in place of the oil lamp. An incandescent lamp may be used in the same -place, but has no great advantage over oil as regards illuminating -power. - - -Heat. -A form of kinetic energy, due to a confused oscillatory movement of the -molecules of a body. Heat is not motion, as a heated body does not -change its place; it is not momentum, but it is the energy of motion. If -the quantity of molecular motion is doubled the momentum of the -molecules is also doubled, but the molecular mechanical energy or heat -is quadrupled. - -As a form of energy it is measured by thermal units. The calorie is the -most important, and unfortunately the same term applies to two units, -the gram-degree C. and the kilogram-degree C. (See Calorie.) Calories -are determined by a calorimeter, q. v. - -Independent of quantity of heat a body may be hotter or colder. -Thermometers are used to determine its temperature. - -Heat is transmitted by conduction, a body conducting it slowly for some -distance through its own substance. Bodies vary greatly in their -conductivity for heat. It is also transmitted by convection of gases or -liquids, when the heated molecules traveling through the mass impart -their heat to other parts. Finally it is transmitted by ether waves with -probably the speed of light. This mode of transmission and the phenomena -of it were attributed to radiant heat. As a scientific term this is now -dropped by many scientists. This practice very properly restricts the -term "heat" to kinetic molecular motion. - -The mechanical equivalent of heat is the number of units of work which -the energy of one unit quantity of heat represents. (See Equivalents, -Mechanical and Physical.) - - -Heat, Atomic. -The product of the specific heat of an element by its atomic weight. The -product is approximately the same for all the elements, and varies as -determined between 5.39 and 6.87. The variations are by some attributed -principally to imperfection of the work in determining them. The atomic -heat represents the number of gram calories required to raise the -temperature of a gram atom (a number of grams equal numerically to the -atomic weight) one degree centigrade. - - -286 STANDARD ELECTRICAL DICTIONARY. - - -Heat, Electric. -This term has been given to the heat produced by the passage of a -current of electricity through a conductor. It is really electrically -produced heat, the above term being a misnomer. - -The rise of temperature produced in a cylindrical conductor by a current -depends upon the diameter of the conductor and on the current. The -length of the wire has only the indirect connection that the current -will depend upon the resistance and consequently upon its length. - -The quantity of heat produced in a conductor by a current is in -gram-degree C. units equal to the product of the current, by the -electro-motive force or potential difference maintained between the ends -of the wire, by .24. - -The cube of the diameter of a wire for a given rise of temperature -produced in such conductor by a current is equal approximately to the -product of the square of the current, by the specific resistance (q. v.) -of the material of the conductor, by .000391, the whole divided by the -desired temperature in centigrade units. - - -Heat, Electrical Convection of. -A term applied to the phenomena included under the Thomson effect, q. -v., the unequal or differential heating effect produced by a current of -electricity in conductors whose different parts are maintained at -different temperatures. - - -Heater, Electric. -An apparatus for converting electrical energy into thermal energy. - -An incandescent lamp represents the principle, and in the Edison meter -has been used as such to maintain the temperature of the solutions. -Heaters for warming water and other purposes have been constructed, -utilizing conductors heated by the passage of the current as a source of -heat. (See also Heating Magnet.) - - -Heating Error. -In voltmeters the error due to alteration of resistance of the coil by -heating. If too strong a current is sent through the instrument, the -coils become heated and their resistance increased. They then do not -pass as much current as they should for the potential difference to -which they may be exposed. Their readings then will be too low. One way -of avoiding the trouble is to have a key in circuit, and to pass only an -instantaneous or very brief current through the instrument and thus get -the reading before the coils have time to heat. - -The heating error does not exist for ammeters, as they are constructed -to receive the entire current, and any heating "error" within their -range is allowed for in the dividing of the scale. - - -Heating Magnet. -An electro-magnet designed to be heated by Foucault currents induced in -its core by varying currents in the windings. It has been proposed as a -source of artificial heat, a species of electric heating apparatus for -warming water, or other purposes. - - -287 STANDARD ELECTRICAL DICTIONARY. - - -Heat, Irreversible. -The heat produced by an electric current in a conductor of identical -qualities and temperature throughout. Such heat is the same whatever the -direction of the current. The heating effect is irreversible because of -the absence of the Thomson effect, q. v.) or Peltier effect, q. v. - - -Heat, Mechanical Equivalent of. -The mechanical energy corresponding to a given quantity of heat energy. -Mechanical energy is generally represented by some unit of weight and -height, such as the foot-pound; and heat energy is represented by a -given weight of water heated a given amount, such as a pound-degree -centigrade. Joule's equivalent is usually accepted; it states that -772.55 foot pounds of mechanical energy are equivalent to 1 pound-degree -F. (one pound avds. of water raised in temperature one degree -Fahrenheit). Other equivalencies have also been deduced. - - -Heat, Molecular. -The product of a specific heat of the compound by its molecular weight. -It is approximately equal to the sum of the atomic heats of its -constituent elements. - -The molecular heat represents the number of gram calories required to -raise the temperature of a gram-molecule (a number of grams equal -numerically to the molecular weight) one degree centigrade. - -The molecular heat is approximately equal for all substances. - - -Heat, Specific. -The capacity of a body for heat; a coefficient representing the relative -quantity of heat required to raise the temperature of an identical -weight of a given body a defined and identical amount. - -The standard of comparison is water; its specific heat is taken as -unity. The specific heats by weight of other substances are less than -unity. The specific heat varies with the temperature. Thus the specific -heat of water is more strictly 1+.00015 tº C. - -Specific heat is greater when a substance is in the liquid than when it -is in the solid state. Thus the specific heat of ice is 0.489; less -than half that of water. It differs with the allotropic modifications of -bodies; the specific heat of graphite is .202; of diamond, .147. - -The product of the specific heat by the atomic weight of elements gives -a figure approximately the same. A similar law applies in the case of -molecules. (See Heat, Atomic-Heat, Molecular.) - -The true specific heat of a substance should be separated from the heat -expended in expanding a body against molecular and atomic forces, and -against the atmospheric pressure. So far this separation has not been -possible to introduce in any calculations. - - -288 STANDARD ELECTRICAL DICTIONARY. - - -Heat, Specific, of Electricity. -A proposed term to account for the heat absorbed or given out in -unhomogeneous conductors, by the Thomson effect, or Peltier effect (see -Effect, Thomson--Effect, Peltier.) If a current of electricity be -assumed to exist, then under the action of these effects it may be -regarded as absorbing or giving out so many coulombs of heat, and thus -establishing a basis for specific heat. - - -Heat Units. -The British unit of heat is the pound degree F--the quantity of heat -required to raise the temperature of a pound of water from 32° to 33° F. - -The C. G. S. unit is the gram-degree C.; another metric unit is the -kilogram-degree C. The latter is the calorie; the former is sometimes -called the small calorie or the joule; the latter is sometimes called -the large calorie. The term joule is also applied to a quantity of heat -equivalent to the energy of a watt-second or volt-coulomb. This is equal -to .24l gram degree calorie. - - -Hecto. -A prefix to terms of measurement--meaning one hundred times, as -hectometer, one hundred meters. - - -Heliograph. -An apparatus for reflecting flashes of light to a distant observer. By -using the Morse telegraph code messages may thus be transmitted long -distances. When possible the sun's light is used. - - -Helix. -A coil of wire; properly a coil wound so as to follow the outlines of a -screw without overlaying itself. - - -Fig. 194. LEFT-HANDED HELIX. - - -Fig. 195. RIGHT-HANDED HELIX. - - -Henry. -The practical unit of electro-magnetic or magnetic inductance. It is -equal to 1E9 C. G. S., or absolute units of inductance. As the -dimensions of inductance are a length the henry is equal to 1E9 -centimeters, or approximately to one quadrant of the earth measured on -the meridian. - -Synonyms--Secohm--Quadrant--Quad. - - -289 STANDARD ELECTRICAL DICTIONARY. - - -Hermetically Sealed. -Closed absolutely tight. Glass vessels, such as the bulbs of -incandescent lamps, are hermetically sealed often by melting the glass -together over any opening into their interior. - - -Heterostatic Method. -A method of using the absolute or attracted disc electrometer. (See -Electrometer Absolute.) The formula for its idiostatic use, q. v., -involves the determination of d, the distance between the suspended and -fixed discs. As this is difficult to determine the suspended disc and -guard ring may be kept at one potential and the lower fixed disc is then -connected successively with the two points whose potential difference is -to be determined. Their difference is determined by the difference -between d and d', the two distances between the discs. This difference -is the distance through which the micrometer screw is moved. The -heterostatic formula is: - -V' - V = (d' - d)* squareRoot( 8*PI*F / S ) - -in which V and V' are potentials of the two points; d' and d the two -distances between the discs necessary for equilibrium; S the area of the -disc and F the force of attraction in dynes. (See Idiostatic Method.) - - -High Bars of Commutator. -Commutator bars, which in the natural wear of the commutator, project -beyond the others. The surface then requires turning down, as it should -be quite cylindrical. - - -High Frequency. -A term used as a noun or as an adjective to indicate in an alternating -current, the production of a very great number of alternations per unit -of time--usually expressed as alternations per second. - - -Hissing. -A term applied to a noise sometimes produced by a voltaic arc; probably -due to the same cause as frying, q. v. - - -Hittorf's Solution. -A solution used as a resistance. It is a solution of cadmium iodide in -amylic alcohol. Ten per cent. of the salt is used. It is contained in a -tube with metallic cadmium electrodes. (See Resistance, Hittorf' s.) - - -Fig. 196. HITTORF'S RESISTANCE TUBE. - - -290 STANDARD ELECTRICAL DICTIONARY. - - -Holders. -(a) The adjustable clamps for holding the armature brushes of dynamos -and motors. - -(b) The clamps for holding the carbons of arc lamps. - -(c) The clamps for holding safety fuses, q. v. - -(d) Holders for Jablochkoff candles and other electric candles. (See -Candle Holders.) - -(e) A box or block of porcelain for holding safety fuses. - - -Hood. -A tin hood placed over an arc-lamp. Such hoods are often truncated cones -in shape, with the small end upwards. They reflect a certain amount of -light besides protecting the lamp to some extent from rain. - - -Horns. -The extensions of the pole pieces of a dynamo or motor. (See Following -Horns-Leading Horns.) - -Synonym--Pole Tips. - - -Horse Power. -A unit of rate of work or activity. There are two horse powers. - -The British horse power is equal to 33,000 pounds raised one foot per -minute, or 550 foot pounds per second, or 1.0138 metric horse power. - -The metric horse power (French) is equal to 75 kilogram-meters, or 542 -foot pounds per second, or .986356 British horse power. - -H. P. is the abbreviation for horse power. (See Horse Power, Electric.) - - -Horse Power, Actual. -The rate of activity of a machine, as actually developed in condition -for use. It is less than the indicated or total horse power, because -diminished by the hurtful resistances of friction, and other sources of -waste. It is the horse power that can be used in practise, and which in -the case of a motor can be taken from the fly-wheel. - - -Horse Power, Electric. -The equivalent of a mechanical horse power in electric units, generally -in volt-amperes or watts; 745.943 watts are equivalent to the activity -of one British horse power; 735.75 are equivalent to one metric horse -power. The number 746 is usually taken in practical calculations to give -the equivalency. - -[Transcriber's note: Contemporary values are: Mechanical (British) -horsepower = 745.6999 Watts; Metric horsepower = 735.49875 Watts] - - -Horse Power, Indicated. -The horse power of an engine as indicated by its steam pressure, length -of stroke, and piston area, and vacuum, without making any deduction for -friction or hurtful resistances. The steam pressure is in accurate work -deduced from indicator diagrams. - - -Horse Power, Hour. -A horse power exerted for one hour, or the equivalent thereof. As the -horse power is a unit of activity, the horse power hour is a unit of -work or of energy. It is equal to 1,980,000 foot pounds. - - -H. P. -Abbreviation for "horse power." - - -291 STANDARD ELECTRICAL DICTIONARY. - - -Hughes' Electro-magnet. -A horseshoe electro-magnet with polarized core. It is made by mounting -two bobbins of insulated wire on the ends of a permanent horseshoe -magnet. It was devised for use in Hughes' printing telegraph, where very -quick action is required. The contact lasts only .053 second, 185 -letters being transmitted per minute. - - -Fig. 197 HUGHES' ELECTRO-MAGNET. - - -Fig. 198. HUGHES' INDUCTION BALANCE. - - -Hughes' Induction Balance. -An apparatus for determining the presence of a concealed mass of metal. -The apparatus is variously connected. The cut shows a representative -form; a and a' are two primary coils, each consisting of 100 meters (328 -feet) of No. 32 silk covered copper wire (0.009 inch diameter) wound on -a boxwood spool ten inches in depth; b and b' are secondary coils. All -coils are supposed to be alike. The primary coils are joined in series -with a battery of three or four Daniell cells. A microphone m is -included in the same circuit. The secondary coils are joined in series -with a telephone and in opposition with each other. The clock is used to -produce a sound affecting the microphone. If all is exactly balanced -there will be no sound produced in the telephone. This balance is -brought about by slightly varying the distance of one of the secondaries -from the primary, until there is no sound in the telephone. If now a -piece of metal is placed within either of the coils, it disturbs the -balance and the telephone sounds. - - -292 STANDARD ELECTRICAL DICTIONARY. - - -To measure the forces acting a sonometer or audiometer is used. This is -shown in the upper part of the cut. Two fixed coils, c and e are mounted -at the ends of a graduated bar. A movable coil d is connected in the -telephone circuit; c and e by a switch can be connected with the battery -and microphone circuit, leaving out the induction balance coils. The -ends of the coils c and e, facing each other are of the same polarity. -If these coils, c and e, were equal in all respects, no sound would be -produced when d was midway between them. But they are so wound that the -zero position for d is very near one of them, c. - -Assume that a balance has been obtained in the induction balance with -the coil d at zero. No sound is heard whether the switch is moved to -throw the current into one or the other circuit. A piece of metal placed -in one of the balance coils will cause the production of a sound. The -current is turned into the sonometer and d is moved until the same -sound, as tested by rapid movements of the switch, is heard in both -circuits. The displacement of d gives the value of the sound. - -A milligram of copper is enough to produce a loud sound. Two coins can -be balanced against each other, and by rubbing one of them, or by -breathing on one of them, the balance will be disturbed and a sound will -be produced. - -Prof. Hughes has also dispensed with the audiometer. He has used a strip -of zinc tapering from a width of 4 mm. (.16 inch) at one end to a sharp -edge or point at the other. The piece to be tested being in place in one -coil, the strip is moved across the face of the other until a balance is -obtained. - -As possible uses the detection of counterfeit coins, the testing of -metals for similarity of composition and the location of bullets in the -body have been suggested. Care has to be taken that no masses of metal -interfere. Thus in tests of the person of a wounded man, the presence of -an iron truss, or of metallic bed springs may invalidate all -conclusions. - -The same principle is carried out in an apparatus in which the parts are -arranged like the members of a Wheatstone bridge. One pair of coils is -used, which react on each other as primary and secondary coils. One of -the coils is in series with a telephone in the member of the bridge -corresponding to that containing the galvanometer of the Wheatstone -bridge. The latter is more properly termed an induction bridge. - -Synonyms--Inductance Bridge--Inductance Balance--Induction Bridge. - - -293 STANDARD ELECTRICAL DICTIONARY. - - -Hydro-electric. adj. -(a) A current produced by a voltaic couple or the couple itself is -sometimes thus characterized or designated as a "hydro-electric current" -or a "hydro-electric couple." It distinguishes them from -thermo-electric. - -(b) Armstrong's steam boiler electric machine (see Hydroelectric -Machine) is also termed a hydro-electric machine. - - -Hydro-electric Machine. -An apparatus for generating high potential difference by the escape of -steam through proper nozzles. - -It consists of a boiler mounted on four glass legs or otherwise -insulated. An escape pipe terminates in a series of outlets so shaped as -to impede the escape of the steam by forcing it out of the direct -course. These jets are lined with hard wood. They are enclosed in or led -through a box which is filled with cold water. - - -Fig. 199. ARMSTRONG'S HYDRO-ELECTRIC MACHINE. - - -This is to partly condense the steam so as to get it into the vesicular -state, which is found essential to its action. Dry steam produces no -excitation. If the boiler is fired and the steam is permitted to escape -under the above conditions the vesicles presumably, or the "steam" is -found to be electrified. A collecting comb held against the jet becomes -charged and charges any connected surface. - - -294 STANDARD ELECTRICAL DICTIONARY. - - -The boiler in the above case is negatively and the escaping "steam" is -positively charged. By changing the material of the linings of the jets, -or by adding turpentine the sign of the electricity is reversed. If the -water contains acid or salts no electricity is produced. The regular -hydro-electric machine is due to Sir William Armstrong. - -Faraday obtained similar results with moist air currents. - - -Hydrogen. -An element existing under all except the most extreme artificial -conditions of pressure and cold as a gas. It is the lightest of known -substances. Atomic weight, 1; molecular weight, 2; equivalent, 1; -valency, 1; specific gravity, .0691-.0695. (Dumas & Boussingault.) - -It is a dielectric of about the same resistance as air. Its specific -inductive capacity at atmospheric pressure is: - .9997 (Baltzman) .9998 (Ayrton) - -Electro-chemical equivalent, .0105 milligram. -The above is usually taken as correct. Other values are as follows: -.010521 (Kohllrausch) .010415 (Mascart) - -The electro-chemical equivalent of any element is obtained by -multiplying its equivalent by the electro-chemical equivalent of -hydrogen. The value .0105 has been used throughout this book. - - -Hygrometer. -An instrument for determining the moisture in the air. One form consists -of a pair of thermometers, one of which has its bulb wrapped in cloth -which is kept moist during the observation. The evaporation is more or -less rapid according to the dryness or moisture of the air, and as the -temperature varies with this evaporation the relative readings of the -two thermometers give the basis for calculating the hygrometric state of -the air. Another form determines the temperature at which dew is -deposited on a silver surface, whence the calculations are made. - - -Hysteresis, Magnetic. -A phenomenon of magnetization of iron. It may be attributed to a sort of -internal or molecular friction, causing energy to be absorbed when iron -is magnetized. Whenever therefore the polarity or direction of -magnetization of a mass of iron is rapidly changed a considerable -expenditure of energy is required. It is attributed to the work done in -bringing the molecules into the position of polarity. - - -295 STANDARD ELECTRICAL DICTIONARY. - - -The electric energy lost by hysteresis may be reduced by vibrations or -jarring imparted to the iron, thus virtually substituting mechanical for -electrical work. - -On account of hysteresis the induced magnetization of a piece of iron or -steel for fields of low intensity will depend on the manner in which the -material has been already magnetized. Let the intensity of field -increase, the magnetization increasing also; then lower the intensity; -the substance tends to and does retain some of its magnetism. Then on -again strengthening the field it will have something to build on, so -that when it attains its former intensity the magnetization will exceed -its former value. For a moderate value of intensity of field the -magnetization can have many values within certain limits. - -Synonym--Hysteresis--Hysteresis, Static--Magnetic Friction. - - -Hysteresis, Viscous. -The gradual increase or creeping up of magnetization when a magnetic -force is applied with absolute steadiness to a piece of iron. It may -last for half an hour or more and amount to several per cent. of the -total magnetization. It is a true magnetic lag. - - -I. -A symbol sometimes used to indicate current intensity. Thus Ohm's law is -often expressed I = E/R, meaning current intensity is equal to -electro-motive force divided by resistance. C is the more general symbol -for current intensity. - - -Ideoelectrics or Idioelectrics. -Bodies which become electric by friction. This was the old definition, -the term originating with Gilbert. It was based on a misconception, as -insulation is all that is requisite for frictional electrification, -metals being thus electrified if held by insulating handles. The term is -virtually obsolete; as far as it means anything it means insulating -substances such as scaling wax, sulphur, or glass. - - -Idle Coils. -Coils in a dynamo, in which coils no electro-motive force is being -generated. This may occur when, as a coil breaks connection with the -commutator brush, it enters a region void of lines of magnetic force, or -where the lines are tangential to the circle of the armature. - - -Idiostatic Method. -A method of using the absolute or attracted disc electrometer. (See -Electrometer, Absolute.) The suspended disc and guard ring are kept at -the same potential, which is that of one of the points whose potential -difference is to be determined; the lower fixed disc is connected to the -other of the points whose potential difference is to be determined. Then -we have the formula - -V = d * SquareRoot( 8 * PI * F ) / S - -in which d is the distance between the discs, V is the difference of -potential of the two points, F the force of attraction between the discs -in dynes, and S the area of the suspended disc. (See Heterostatic -Method.) - - -296 STANDARD ELECTRICAL DICTIONARY. - - -Idle Poles. -Poles of wire sealed into Crookes' tubes, not used for the discharge -connections, but for experimental connections to test the effect of -different excitation on the discharge. - - -Idle Wire. -In a dynamo the wire which plays no part in generating electro-motive -force. In a Gramme ring the wire on the inside of the ring is idle wire. - - -Igniter. -In arc lamps with fixed parallel carbons of the Jablochkoff type (see -Candle, Jablochkoff) a strip of carbon connects the ends of the carbons -in the unused candle. This is necessary to start the current. Such strip -is called an igniter. It burns away in a very short time when an arc -forms producing the light, and lasts, if all goes well, until the candle -burns down to its end. Without the igniter the current would not start -and no arc would form. - - -I. H. P. -Symbol for indicated horse-power. - - -Illuminating Power. -The relative light given by any source compared with a standard light, -and stated in terms of the same, as a burner giving an illuminating -power of sixteen candles. For standards see Candle, Carcel--Methven -Standard--Pentane Standard. - - -Illuminating Power, Spherical. -The illuminating power of a lamp or source of light may vary in -different directions, as in the case of a gas burner or incandescent -lamp. The average illuminating power determined by photometric test or -by calculation in all directions from the source of light is called the -spherical illuminating power, or if stated in candles is called the -spherical candle power. - - -Illumination, Unit of. -An absolute standard of light received by a surface. Preece proposed as -such the light received from a standard candle (see Candle, Standard) at -a distance of 12.7 inches. The object of selecting this distance was to -make it equal to the Carcel Standard (see Carcel), which is the light -given by a Carcel lamp at a distance of one meter. - -From one-tenth to one-fiftieth this degree of illumination was found in -gas-lighted streets by Preece, depending on the proximity of the gas -lamps. - - -Image, Electric. -An electrified point or system of points on one side of a surface which -would produce on the other side of that surface the same electrical -action which the actual electrification of that surface really does -produce. (Maxwell.) - -The method of investigating the distribution of electricity by electric -images is due to Sir William Thomson. The conception is purely a -theoretical one, and is of mathematical value and interest. - - -297 STANDARD ELECTRICAL DICTIONARY. - - -Impedance. -The ratio of any impressed electro-motive force to the current which it -produces in a conductor. For steady currents it is only the resistance. -For variable currents it may include besides resistance inductance and -permittance. It is the sum of all factors opposing a current, both ohmic -and spurious resistances. It is often determined and expressed as ohms. - -Synonym--Apparent Resistance--Virtual Resistance. - - -Impedance, Oscillatory. -The counter-electro-motive force offered to an oscillatory discharge, as -that of a Leyden jar. It varies with the frequency of the discharge -current. - -Synonym--Impulsive Impedance. - - -Impressed Electro-motive Force. -The electro-motive force expending itself in producing current induction -in a neighboring circuit. - - -Impulse. -(a) An electro-magnetic impulse is the impulse produced upon the -luminiferous ether by an oscillatory discharge or other varying type of -current; the impulse is supposed to be identical, except as regards -wave-length, with a light wave. - -(b) An electro-motive impulse is the electro-motive force which rises so -high as to produce an impulsive or oscillatory discharge, such as that -of a Leyden jar. - - -Incandescence, Electric. -The heating or a conductor to red, or, more etymologically, to white -heat by the passage of an electric current. The practical conditions are -a high intensity of current and a low degree of conductance of the -conductor relatively speaking. - - -Inclination Map. -A map showing the locus of equal inclination or dips of the magnetic -needle. The map shows a series of lines, each one of which follows the -places at which the dip of the magnetic needle is identical. The map -changes from year to year. (See Magnetic Elements.) - - -Independence of Currents in Parallel Circuits. -If a number of parallel circuits of comparatively high resistance are -supplied by a single generator of comparatively low resistance, the -current passed through each one will be almost the same whether a single -one or all are connected. Under the conditions named the currents are -practically independent of each other. - -[Transcriber's note: The current in each parallel branch depends on the -resistance/impedance of that branch. Only if they all have the same -impedance will the current be the same.] - - -Indicating Bell. -An electric bell arranged to drop a shutter or disclose in some other -way a designating number or character when rung. - - -298 STANDARD ELECTRICAL DICTIONARY. - - -Indicator. -(a) An apparatus for indicating the condition of a distant element, such -as the water level in a reservoir, the temperature of a drying room or -cold storage room or any other datum. They are of the most varied -constructions. - -(b) The receiving instrument in a telegraph system is sometimes thus -termed. - - -Indicator, Circuit. -A galvanometer used to show when a circuit is active, and to give an -approximate measurement of its strength. It is a less accurate and -delicate form of instrument than the laboratory appliance. - - -Inductance. -The property of a circuit in virtue of which it exercises induction and -develops lines of force. It is defined variously. As clear and -satisfactory a definition as any is the following, due to Sumpner and -Fleming: Inductance is the ratio between the total induction through a -circuit to the current producing it. "Thus taking a simple helix of five -turns carrying a current of two units, and assuming that 1,000 lines of -force passed through the central turn, of which owing to leakage only -900 thread the next adjacent on each side, and again only 800 through -the end turns, there would be 800 + 900 + 1000 + 900 + 800, or 4,400 -linkages of lines with the wire, and this being with 2 units of current, -there would be 2,200 linkages with unit current, and consequently the -self-inductance of the helix would be 2,200 centimetres." (Kennelly.) -Inductance, as regards its dimensions is usually reduced to a length, -hence the last word of the preceding quotation. - -The practical unit of inductance is termed the henry, from Prof. Joseph -Henry; the secohm, or the quad or quadrant. The latter alludes to the -quadrant of the earth, the value in length of the unit in question. - -[Transcriber's note: (L (di/dt) = V). A current changing at the rate of -one ampere per second through a one henry inductance produces one volt. -A sinusoidal current produces a voltage 90 degrees ahead of the current, -a cosine (the derivative of sine is cosine). One volt across one henry -causes the current to increase at one ampere per second.] - - -Induction, Coefficient of Self. -The coefficient of self-induction of a circuit is the quantity of -induction passing through it per unit current in it. If a given circuit -is carrying a varying current it is producing a varying quantity of -magnetic induction through itself. The quantity of induction through the -circuit due to its current is generally proportional to its current. The -quantity for unit current is the coefficient of self-induction. -(Emtage.) - - -Induction, Cross. -The induction of magnetic lines of force in a dynamo armature core by -the current passing around such armature. These lines in a symmetrical -two pole machine are at right angles to the lines of force which would -normally extend across the space between the two magnet poles. The joint -magnetizing effect of the field and of the cross induction produces a -distorted field between the poles . - -Synonym--Cross-magnetizing Effect. - - -299 STANDARD ELECTRICAL DICTIONARY. - - -Induction, Electro-magnetic. -The inter-reaction of electromagnetic lines of force with the production -of currents thereby. - -A current passing through a conductor establishes around it a field of -force representing a series of circular lines of force concentric with -the axis of the conductor and perpendicular thereto. These lines of -force have attributed to them, as a representative of their polarity, -direction. This is of course purely conventional. If one is supposed to -be looking at the end of a section of conductor, assuming a current be -passing through it towards the observer, the lines of force will have a -direction opposite to the motion of the hands of a watch. The idea of -direction may be referred to a magnet. In it the lines of force are -assumed to go from the north pole through the air or other surrounding -dielectric to the south pole. - -Two parallel wires having currents passing through them in the same -direction will attract each other. This is because the oppositely -directed segments of lines of force between the conductors destroy each -other, and the resultant of the two circles is an approximation to an -ellipse. As lines of force tend to be as short as possible the -conductors tend to approach each other to make the ellipse become of as -small area as possible, in other words to become a circle. - -If on the other hand the currents in the conductors are in opposite -directions the segments of the lines of force between them will have -similar directions, will, as it were, crowd the intervening ether and -the wires will be repelled. - - -Fig. 200. ATTRACTION OF CONDUCTORS CARRYING SIMILAR CURRENTS. - - -By Ampére's theory of magnetism, (see Magnetism, Ampére's Theory of,) a -magnet is assumed to be encircled by currents moving in the direction -opposite to that of the hands of a watch as the observer faces the north -pole. A magnet near a wire tends to place the Ampérian currents parallel -to the wire, and so that the portion of the Ampérian currents nearest -thereto will correspond in direction with the current in the wire. - - -300 STANDARD ELECTRICAL DICTIONARY. - - -This is the principle of the galvanometer. A number of methods of -memoria technica have been proposed to remember it by. - -Thus if we imagine a person swimming with the current and always facing -the axis of the conductor, a magnetic needle held where the person is -supposed to be will have its north pole deflected to the right hand of -the person. - - -Fig. 201. REPULSION OF CONDUCTORS CARRYING OPPOSITE CURRENTS. - - -Again if we think of a corkscrew, which as it is turned screws itself -along with the current, the motion of the handle shows the direction of -the lines of force and the direction in which the north pole of a needle -is deflected. This much is perhaps more properly electro-dynamics, but -is necessary as a basis for the expression of induction. - -If a current is varied in intensity in one conductor it will induce a -temporary current in another conductor, part of which is parallel to the -inducing current and which conductor is closed so as to form a circuit. -If the inducing current is decreased the induced current in the near and -parallel portion of the other circuit will be of identical direction; if -increased the induced current will be of opposite direction. - -This is easiest figured by thinking of the lines of force surrounding -the inducing conductor. If the current is decreased these can be -imagined as receiving a twist or turn contrary to their normal -direction, as thereby establishing a turn or twist in the ether -surrounding the other wire corresponding in direction with the direction -of the original lines of force, or what is the same thing, opposite in -direction to the original twist. But we may assume that the -establishment of such a disturbance causes a current, which must be -governed in direction with the requirements of the new lines of force. - -The same reasoning applies to the opposite case. - - -301 STANDARD ELECTRICAL DICTIONARY. - - -The general statement of a variable current acting on a neighboring -circuit also applies to the approach or recession of an unvarying -current, and to the cutting of lines of force by a conductor at right -angles thereto. For it is evident that the case of a varying current is -the case of a varying number of lines of force cutting or being cut by -the neighboring conductor. As lines of force always imply a current, -they always imply a direction of such current. The cutting of any lines -of force by a closed conductor always implies a change of position with -reference to all portions of such conductor and to the current and -consequently an induced current or currents in one or the other -direction in the moving conductor. - -As the inducing of a current represents energy abstracted from that of -the inducing circuit, the direction of the induced current is determined -by (Lenz's Law) the rule that the new current will increase already -existing resistances or develop new ones to the disturbance of the -inducing field. - -In saying that a conductor cutting lines of force at right angles to -itself has a current induced in it, it must be understood that if not at -right angles the right angle component of the direction of the wire acts -in generating the current. The case resolves itself into the number of -lines of force cut at any angle by the moving wire. - -The lines of force may be produced by a magnet, permanent or electro. -This introduces no new element. The magnet may be referred, as regards -direction of its lines of force, to its encircling currents, actual or -Ampérian, and the application of the laws just cited will cover all -cases. - - -Induction, Coefficient of Mutual. -The coefficient of mutual induction of two circuits is the quantity of -magnetic induction passing through either of them per unit current in -the other. (Emtage.) It is also defined as the work which must be done -on either circuit, against the action of unit current in each, to take -it away from its given position to an infinite distance from the other; -and also as the work which would be done by either circuit on the other -in consequence of unit current in each, as the other moves from an -infinite distance to its given position with respect to the other -conductor. It depends on the form, size, and relative position of the -two circuits; and on the magnetic susceptibilities of neighboring -substances. - -The ether surrounding two circuits of intensity i' and i" must possess -energy, expressible (Maxwell) as 1/2 L i2 + M i i + 1/2 N i12. It can be -shown that M i i1 in any given position of the two circuits is -numerically equal (1) to the mutual potential energy of the two circuits -(2) to the number of lines of induction, which being due to A, pass from -A through B, or equally being due to B, pass from B through A, and M is -styled the coefficient of mutual induction. (Daniell.) - - -302 STANDARD ELECTRICAL DICTIONARY. - - -Induction, Electrostatic. -An electrostatic charge has always an opposite and bound charge. This -may be so distributed as not to be distinguishable, in which case the -charge is termed, incorrectly but conventionally, a free charge. But -when a charge is produced an opposite and equal one always is formed, -which is the bound charge. The region between the two charges and -permeated by their lines of force, often curving out so as to embrace a -volume of cross-sectional area larger than the mean facing area of the -excited surfaces, is an electrostatic field of force. The establishing -of an electrostatic field, and the production of a bound charge are -electrostatic induction. - -An insulated conductor brought into such a field suffers a -redistribution of its electricity, or undergoes electrostatic induction. -The parts nearest respectively, the two loci of the original and the -bound charges, are excited oppositely to such charges. The conductor -presents two new bound charges, one referred to the original charge, the -other to the first bound charge. - - -Induction, Horizontal. -In an iron or steel ship the induction exercised upon the compass needle -by the horizontal members of the structure, such as deck-beams, when -they are polarized by the earth's magnetic induction. This induction -disappears four times in swinging a ship through a circle; deviation due -to it is termed quadrantal deviation. (See Deviation, Quadrantal.) - - -Induction, Lateral. -A term formerly used to express the phenomenon of the alternative -discharge of a Leyden jar or other oscillatory discharge of electricity. -(See Discharge, Alternative.) - - -Induction, Magnetic. -The magnetization of iron or other paramagnetic substance by a magnetic -field. - -On account of its permeability or multiplying power for lines of force, -a paramagnetic body always concentrates lines of force in itself if -placed in a magnetic field, and hence becomes for the time being a -magnet, or is said to be polarized. - -As the tendency of lines of force is to follow the most permeable path, -a paramagnetic bar places itself lengthwise or parallel with the -prevailing direction of the lines of force so as to carry them as far on -their way as possible. Every other position of the bar is one of -unstable equilibrium or of no equilibrium. The end of the bar where the -lines of force enter (see Lines of Force) is a south pole and is -attracted towards the north pole of the magnet. - -The production of magnetic poles under these conditions in the bar is -shown by throwing iron filings upon it. They adhere to both ends but not -to the middle. - - -Induction, Mutual, Electro-magnetic. -The induction due to two electric currents reacting on each other. - - -303 STANDARD ELECTRICAL DICTIONARY. - - -Induction, Mutual, Electrostatic. -A charged body always induces a charge upon any other body near it; and -the same charge in the second body will induce the other charge in the -first body if the latter is unexcited. In other words the second body's -induction from the first is the measure of the charge the second would -require to induce in the first its own (the second's) induced charge. -This is the law of mutual electrostatic induction. - - -Induction, Open Circuit. -Inductive effects produced in open circuits. By oscillatory discharges a -discharge can be produced across a break in a circuit otherwise -complete. The requirements for its production involve a correspondence -or relation of its dimensions to the inducing discharge. The whole is -analogous to the phenomena of sound resonators and sympathetic -vibrations. Synonym--Oscillatory induction. - - -Induction, Self-. -(a) A phenomenon of electric currents analogous to the inertia of -matter. Just as water which fills a pipe would resist a sudden change in -its rate of motion, whether to start from rest, to cease or decrease its -motion, so an electric current requires an appreciable time to start and -stop. It is produced most strongly in a coiled conductor, especially if -a core of iron is contained within it. - -As in the case of two parallel wires, one bearing currents which vary, -momentary currents are induced in the other wire, so in a single -conductor a species of inertia is found which retards and prolongs the -current. If a single conductor is twisted into a helix or corresponding -shape, its separate turns react one on the other in accordance with the -general principles of electromagnetic induction. (See Induction, -Electro-magnetic.) Thus when a current is suddenly formed the coils -acting upon each other retard for an instant its passage, producing the -effect of a reverse induced current or extra current opposing the -principal current. Of course no extra current is perceptible, but only -the diminution. When the current is passing regularly and the current is -broken, the corresponding action prolongs the current or rather -intensifies it for an instant, producing the true extra current. This is -current self-induction. - -[Transcriber's note: See inductance.] - -Synonyms--Electric Inertia--Electro-dynamic Capacity. - -(b) A permanent magnet is said to tend to repel its own magnetism, and -thus to weaken itself; the tendency is due to magnetic self-induction. - - -Induction Sheath. -In the brush dynamo a thin sheet of copper surrounding the magnet cores -with edges soldered together. The winding is outside of it. Its object -is to absorb extra currents set up by variations in magnetic intensity -in the cores. These currents otherwise would circulate in the cores. - - -304 STANDARD ELECTRICAL DICTIONARY. - - -Induction, Unit of Self-. -The unit of self-induction is the same as that of induction in general. -It is the henry, q. v. - - -Induction, Unipolar. -Induction produced in a conductor which continuously cuts the lines of -force issuing from one pole of a magnet. As the lines of force are -always cut in the same sense a continuous and constant direction current -is produced. - - -Induction, Vertical. -In an iron or steel ship the induction or attraction exercised in the -compass by vertical elements of the structure. Such vertical masses of -iron in the northern hemisphere would have their upper ends polarized as -south poles, and would affect the magnet as soon as the vessel swung out -of the magnetic meridian. Thus this induction disappears twice in -swinging a ship through a complete circle; deviation due to it is termed -semi-circular deviation. (See Deviation, Semi-circular.) - - -Fig. 202. INDUCTOR DYNAMO. - - -Inductophone. -A method of train telegraphy. The train carries a circuit including a -coil, and messages are picked up by it from coils along the line into -which an alternating current is passed. A telephone is used as a -receiver in place of a sounder or relay. The invention, never -practically used, is due to Willoughby Smith. - - -305 STANDARD ELECTRICAL DICTIONARY. - - -Inductor. -(a) In a current generator a mass of iron, generally laminated, which is -moved past a magnet pole to increase the number of lines of force -issuing therefrom. It is used in inductor dynamos. (See Dynamo -Inductor.) In the cut Fig. 202, of an inductor dynamo i, i, are the -laminated inductors. - -(b) In influence machines the paper or tinfoil armatures on which the -electrification is induced. - - -Inertia. -A force in virtue of which every body persists in its state of motion or -rest except so far as it is acted on by some force. - - -Inertia, Electro-magnetic. -This term is sometimes applied to the phenomena of self-induction, or -rather to the cause of these phenomena. - - -Infinity Plug. -A plug in a resistance box, which on being pulled out of its seat opens -the circuit or makes it of infinite resistance. The plug seats itself -between two brass plates which are not connected with each other in any -way. The other plates are connected by resistance coils of varying -resistance. - - -Influence, Electric. -Electric induction, which may be either electrostatic, current, or -electro-magnetic. - - -Insolation, Electric. -Exposure to powerful arc-light produces effects resembling those of -sun-stroke. The above term or the term "electric sun-stroke" has been -applied to them. - -[Transcriber's note: Operators of arc welders are prone to skin cancer -from ultra violet rays if not properly protected.] - - -Installation. -The entire apparatus, buildings and appurtenances of a technical or -manufacturing establishment. An electric light installation, for -instance, would include the generating plant, any special buildings, the -mains and lamps. - - -Insulating Stool. -A support for a person, used in experiments with static generators. It -has ordinarily a wooden top and glass legs. It separates one standing on -it from the earth and enables his surface to receive an electrostatic -charge. This tends to make his hair stand on end, and anyone on the -floor who touches him will receive a shock. - - -Insulating Tape. -Prepared tape used in covering the ends of wire where stripped for -making joints. After the stripped ends of two pieces are twisted -together, and if necessary soldered and carefully cleaned of soldering -fluid, they may be insulated by being wound with insulating tape. - -The tape is variously prepared. It may be common cotton or other tape -saturated with any insulating compound, or may be a strip of gutta -percha or of some flexible cement-like composition. - - -306 STANDARD ELECTRICAL DICTIONARY. - - -Insulating Varnish. -Varnish used to coat the surface of glass electrical apparatus, to -prevent the deposition of hygrometric moisture, and also in the -construction of magnetizing and induction coils and the like. Shellac -dissolved in alcohol is much used. Gum copal dissolved in ether is -another. A solution of sealing wax in alcohol is also used. If applied -in quantities these may need baking to bring about the last drying. (See -Shellac Varnish.) - - -Insulator. -(a) Any insulating substance. - -(b) A telegraph or line insulator for telegraph wires. (See Insulator, -Line or Telegraph.) - -Synonyms--Dielectric--Non-conductor. - - -Insulator Cap. -A covering or hood, generally of iron, placed over an insulator to -protect it from injury by fracture with stones or missiles. - - -Insulator, Fluid. -(a) For very high potentials, as in induction coils or alternating -circuits, fluid insulators, such as petroleum or resin oil, have been -used. Their principal merit is that if a discharge does take place -through them the opening at once closes, so that they are self-healing. - -(b) Also a form of telegraph or line insulator in which the lower rim is -turned up and inwards, so as to form an annular cup which is filled with -oil. - - -Insulator, Line or Telegraph. -A support often in the shape of a collar or cap, for a telegraph or -other wire, made of insulating material. Glass is generally used in the -United States, porcelain is adopted for special cases; pottery or stone -ware insulators have been used a great deal in other countries. -Sometimes the insulator is an iron hook set into a glass screw, which is -inserted into a hole in a telegraph bracket. Sometimes a hook is caused -to depend from the interior of an inverted cup and the space between the -shank of the hook and cup is filled with paraffine run in while melted. - -Insulators are tested by measuring their resistance while immersed in a -vessel of water. - - -Intensity. Strength. -The intensity of a current or its amperage or strength; the intensity or -strength of a magnetic field or its magnetic density; the intensity or -strength of a light are examples of its use. In the case of dynamic -electricity it must be distinguished from tension. The latter -corresponds to potential difference or voltage and is not an attribute -of current; intensity has no reference to potential and is a -characteristic of current. - - -Intensity of a Magnetic Field. -The intensity of a magnetic field at any point is measured by the force -with which it acts on a unit magnet pole placed at that point. Hence -unit intensity of field is that intensity of field which acts on a unit -pole with a force of one dyne. (S. P. Thomson.) (See Magnetic Lines of -Force.) - - -307 STANDARD ELECTRICAL DICTIONARY. - - -Intercrossing. -Crossing a pair of conductors of a metallic circuit from side to side to -avoid induction from outside sources. - - -Intermittent. -Acting at intervals, as an intermittent contact, earth, or grounding of -a telegraph wire. - - -Interpolar Conductor. -A conductor connecting the two poles of a battery or current generator; -the external circuit in a galvanic circuit. - - -Interpolation. -A process used in getting a closer approximation to the truth from two -varying observations, as of a galvanometer. The process varies for -different cases, but amounts to determining an average or deducing a -proportional reading from the discrepant observed ones. - - -Interrupter. -A circuit breaker. It may be operated by hand or be automatic. (See -Circuit Breaker--Circuit Breaker, Automatic--and others.) - - -Interrupter, Electro-magnetic, for a Tuning Fork. -An apparatus for interrupting a current which passes through an -electromagnet near and facing one of the limbs of a tuning fork. The -circuit is made and broken by the vibrations of another tuning fork -through which the current passes. The second one is thus made to -vibrate, although it may be very far off and may not be in exact unison -with the first. The first tuning fork has a contact point on one of its -limbs, to close the circuit; it may be one which dips into a mercury -cup. - - -Intrapolar Region. -A term in medical electricity, denoting the part of a nerve through -which a current is passing. - - -Ions. -The products of decomposition produced in any given electrolysis are -termed ions, the one which appears at the anode or negative electrode is -the anion. The electrode connected to the carbon or copper plate of a -wet battery is an anode. Thus in the electrolysis of water oxygen is the -anion and hydrogen is termed the kation. In this case both anion and -kation are elements. In the decomposition of copper sulphate the anion -is properly speaking sulphion (S O4), a radical, and the kation is -copper, an element. Electro-negative elements or radicals are anions, -such as oxygen, sulphion, etc., while electro-positive ones are kations, -such as potassium. Again one substance may be an anion referred to one -below it and a kation referred to one above it, in the electro-chemical -series, q. v. Anion means the ion which goes to the anode or positive -electrode; kation, the ion which goes to the kathode or negative -electrode. - -[Transcriber's note: An ion is an atom or molecule that has lost or -gained one or more valence electrons, giving it a positive or negative -electrical charge. A negatively charged ion, with more electrons than -protons in its nuclei, is an anion. A positively charged ion, with fewer -electrons than protons, is a cation. The electron was discovered five -years after this publication.] - - -308 STANDARD ELECTRICAL DICTIONARY. - - -Iron. -A metal; one of the elements; symbol, Fe; atomic weight, 56; -equivalent, 28 and 14, ; valency, 4 and 2. -It is a conductor of electricity. The following data are at -0° C. 32° F., with annealed metal. - - Specific Resistance, 9.716 microhms. - Relative Resistance. 6.460 - Resistance of a wire, - (a) 1 foot long weighing 1 grain, 1.085 ohms. - (b) 1 foot long 1/1000 inch thick, 58.45 " - (c) 1 meter long weighing 1 gram, .7570 " - (d) 1 meter long, 1 millimeter thick, .1237 " -Percentage increase in resistance per degree C. (1.8° F.) - at about 20° C. (68°F.), about 0.5 per cent. -Resistance of a 1 inch cube, 3.825 microhms. -Electro-chemical equivalent (Hydrogen = .0105), .147 and .294 - - -Iron, Electrolytic. -Iron deposited by electrolytic action. Various baths are employed for -its formation. (See Steeling.) It has very low coercive power, only -seven to ten times that of nickel. - - -Ironwork Fault of a Dynamo. -A short circuiting of a dynamo by, or any connection of its coils with, -the iron magnet cores or other iron parts. - - -Isochronism. -Equality of periodic time; as of the times of successive beats of a -tuning fork, or of the times of oscillations of a pendulum. - - -Isoclinic Lines. -The lines denoting the locus of sets of equal dips or inclinations of -the magnetic needle upon the earth's surface, the magnetic parallels, q. -v. These lines are very irregular. (See Magnetic Elements.) - - -Isoclinic Map. -A map showing the position of isoclinic lines. - - -Isodynamic Lines. -Lines marking the locus of places of equal magnetic intensity on the -earth's surface. (See Magnetic Elements, Poles of Intensity.) - - -Isodynamic Map. -A map showing the position of isodynamic lines. (See Poles of -Intensity.) - -Isogonic Lines. -Lines on a map marking the locus of or connecting those points where the -declination or variation of the magnetic needle is the same. (See -Magnetic Elements--Declination of Magnetic Needle.) - -Synonyms--Isogonal Lines--Halleyan Lines. - - -309 STANDARD ELECTRICAL DICTIONARY. - - -Isogonic Map. -A map showing the isogonic lines. On such a map each line is -characterized and marked with the degrees and direction of variation of -the compass upon itself. - -Synonym--Declination Map. - - -Isolated Plant, Distribution or Supply. -The system of supplying electric energy by independent generating -systems, dynamo or battery, for each house, factory or other place, as -contra-distinguished from Central Station Distribution or Supply. - - -Isotropic. -(Greek, equal in manner.) - -Having equal properties in all directions; the reverse of anisotropic, -q. v. Thus a homogeneous mass of copper or silver has the same specific -resistance in all directions and is an isotropic conductor. Glass has -the same specific inductive capacity in all directions and is an -isotropic medium or dielectric. The same applies to magnetism. Iron is -an isotropic paramagnetic substance. (See Anisotropic.) The term applies -to other branches of physics also. - - -I. W. G. -Contraction for Indian Wire Gauge--the gauge adopted in British India. - - -J. -Symbol for the unit joule, the unit of electric energy. - - -Jacobi's Law. -A law of electric motors. It states that the maximum work of a motor is -performed when the counter-electromotive force is equal to one-half the -electro-motive force expended on the motor. - - -Jewelry. -Small incandescent lamps are sometimes mounted as articles of jewelry in -scarf-pins or in the hair. They may be supplied with current from -storage or from portable batteries carried on the person. - - -Joint, American Twist. -A joint for connecting telegraph wires, especially aerial lines. Its -construction is shown in the cut. The end of each wire is closely wound -around the straight portion of the other wire for a few turns. - - -Fig. 203. AMERICAN TWIST JOINT. - - -310 STANDARD ELECTRICAL DICTIONARY. - - -Joint, Britannia. -A joint for uniting the ends of telegraph and electric wires. The ends -of the wires are scraped clean and laid alongside each other for two -inches, the extreme ends being bent up at about right angles to the -wire. A thin wire is wound four or five times around one of the wires, -back of the joint, the winding is then continued over the lapped -portion, and a few more turns are taken around the other single wire. -The whole is then soldered. - - -Fig. 204. BRITANNIA JOINT. - - -Joint, Butt. -A joint in belting or in wire in which the ends to be joined are cut off -square across, placed in contact and secured. It ensures even running -when used in belting. Any irregularity in thickness of a belt affects -the speed of the driven pulley. As dynamos are generally driven by -belts, and it is important to drive them at an even speed to prevent -variations in the electro-motive force, butt joints should be used on -belting for them, unless a very perfect lap joint is made, which does -not affect either the thickness or the stiffness of the belt. - -When a butt joint is used in wire a sleeve may be used to receive the -abutting ends, which may be secured therein by soldering. This species -of joint has been used on lightning rods and may more properly be termed -a sleeve joint. - - -Joint, Lap. -(a) In belting a joint in which the ends are overlapped, and riveted or -otherwise secured in place. If made without reducing the thickness of -the ends it is a bad joint for electrical work, as it prevents even -running of machinery to which it is applied. Hence dynamo belts should -be joined by butt joints, or if by lap joints the ends should be shaved -off so that when joined and riveted, there will be no variation in the -thickness of the belt. - -(b) In wire lap joints are made by overlapping the ends of the wire and -soldering or otherwise securing. The Britannia joint (see Joint, -Britannia,) may be considered a lap-joint. - - -Joint, Marriage. -A joint for stranded conductors used for Galende's cables. It is made -somewhat like a sailor's long splice. Each one of the strands is wound -separately into the place whence the opposite strand is unwound and the -ends are cut off so as to abutt. In this way all are smoothly laid in -place and soldering is next applied. - - -Fig. 205. MARRIAGE JOINT. - - -311 STANDARD ELECTRICAL DICTIONARY. - - -Joint, Sleeve. -A joint in electric conductors, in which the ends of the wires are -inserted into and secured in a metallic sleeve or tube, whose internal -diameter is just sufficient to admit them. - - -Joint, Splayed. -The method of joining the ends of stranded conductors. The insulating -covering is removed, the wires are opened out, and the center wire, -heart or core of the cable is cut off short. The two ends are brought -together, the opened out wires are interlaced or crotched like the -fingers of the two hands, and the ends are wound around the body of the -cable in opposite directions. The joint is trimmed and well soldered. -Tinned wire with rosin flux for the soldering is to be recommended. -Insulating material is finally applied by hand, with heat if necessary. - -Joints in Belts. -Belt-joints for electric plants where the belts drive dynamos should be -made with special care. The least inequality affects the electro-motive -force. Butt joints are, generally speaking, the best, where the ends of -the belt are placed in contact and laced. Lap-joints are made by -overlapping the belt, and unless the belt is carefully tapered so as to -preserve uniform strength, the speed of the dynamo will vary and also -the electromotive force. - - -Joulad. -A name proposed to be substituted for "joule," q. v. It has not been -adopted. - - -Joule. -This term has been applied to several units. - -(a) The practical C. G. S. unit of electric energy and work--the -volt-coulomb. It is equal to 1E7 ergs--0.73734 foot pound.--.00134 horse -power seconds. A volt-ampere represents one joule per second. - -(b) It has also been used as the name of the gram-degree C. thermal -unit--the small calorie. - -Synonym--Joulad. - - -Joule Effect. -The heating effect of a current passing through a conductor. It varies -with the product of the resistance by the square of the current, or with -(C^2)*R. - - -Joule's Equivalent. -The mechanical equivalent of heat, which if stated in foot-pounds per -pound-degree F. units, is 772 (772.55). (See Equivalents.) - - -Junction Box. -In underground distribution systems, an iron casing or box in which the -feeders and mains are joined, and where other junctions are made. - -Synonym--Fishing Box. - - -K. -The symbol for electrostatic capacity. - - -Kaolin. -A product of decomposition of feldspar, consisting approximately of -silica, 45, alumina, 40, water, 15. It was used in electric candles of -the Jablochkoff type as a constituent of the insulating layer or -colombin. Later it was abandoned for another substance, as it was found -that it melted and acted as a conductor. - - -312 STANDARD ELECTRICAL DICTIONARY. - - -Kapp Line of Force. -A line of force proposed by Kapp. It is equal to 6,000 C. G. S. lines of -force, and the unit of area is the square inch. Unfortunately it has -been adopted by many manufacturers, but its use should be discouraged, -as it is a departure from the uniform system of units. - -One Kapp line per square inch = 930 C. G. S. lines per square -centimeter. - - -Kathelectrotonus. -A term used in medical electricity or electro-therapeutics to indicate -the increased functional activity induced in a nerve by the proximity of -the kathode of an active circuit which is completed through the nerve. -The converse of anelectrotonus. - - -Kathode. -The terminal of an electric circuit whence an electrolyzing current -passes from a solution. It is the terminal connected to the zinc plate -of a primary battery. - - -Kathodic Closure Contraction. -A term in electro-therapeutics; the contractions near where the kathode -of an active circuit is applied to the body, which are observed at the -instant when the circuit is closed. - - -Kathodic Duration Contraction. -A term in electro-therapeutics; the contraction near where the kathode -of an active circuit is applied to the body for a period of time. - - -K. C. C. -Abbreviation for Kathodic Closure Contraction, q. v. - - -K. D. C. -Abbreviation for Kathodic Duration Contraction, q. v. - - -Keeper. -A bar of soft iron used to connect the opposite poles of a horseshoe -magnet or the opposite poles of two bar magnets placed side by side. It -is designed to prevent loss of magnetism. The armature of a horseshoe -magnet is generally used as its keeper. For bar magnets a keeper is used -for each end, the magnets being laid side by side, with their poles in -opposite direction but not touching, and a keeper laid across at each -end connecting the opposite poles. - - -Kerr Effect. -The effect of an electrostatic field upon polarized light traversing a -dielectric contained within the field. (See Electrostatic Refraction.) - - -Kerr's Experiment. -Polarized light reflected from the polished face of a magnet pole has -its plane of polarization rotated; when it is reflected from the north -pole the rotation is from left to right. - - -313 STANDARD ELECTRICAL DICTIONARY. - - -Key. -A switch adapted for making and breaking contact easily when worked by -hand, as a Morse telegraph key. - - -Key Board. -A board or tablet on which keys or switches are mounted. - - -Key-board. -(a) A switch board, q. v. - -(b) A set of lettered keys similar to those of a typewriter employed in -some telegraph instruments. As each key is depressed it produces the -contact or break requisite for the sending of the signal corresponding -to the letter marked upon the key. The signal in printing telegraphs, on -which such key-boards are used, is the reprinting of the letter at the -distant end of the line. - - -Key, Bridge. -A key for use with a Wheatstone Bridge, q.v. It is desirable to first -send a current through the four arms of the bridge in using it for -testing resistances and then through the galvanometer, because it takes -a definite time for the current to reach its full strength. This is -especially the case if the element being measured has high static -capacity, as a long ocean cable. If the galvanometer connections were -completed simultaneously with the bridge connections a momentary swing -would be produced even if the arms bore the proper relation to each -other. This would cause delay in the testing. A bridge key avoids this -by first connecting the battery circuit through the arms of the bridge, -and then as it is still further depressed the galvanometer circuit is -completed. - - -314 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 206. CHARGE AND DISCHARGE KEY - - -Key, Charge and Discharge. -A key for use in observing the discharge of a condenser immediately -after removing the battery. In one typical form it has two contacts, one -below and one above, and being a spring in itself is pressed up against -the upper one. Connections are so made that when in its upper position -it brings the two coatings of the condenser in circuit with the -galvanometer. When depressed it does the same for a battery. In use it -is depressed and suddenly released when the galvanometer receives the -full charge, before there has been time for leakage. This is one method -of connection illustrating its principle. - -In the cut L is the spring-key proper. S2, is the upper contact screw -against which the spring normally presses. In this position the -galvanometer G is in circuit with the opposite coatings of the condenser -C. On depressing the contact S2, is broken and S1, is made. This brings -the battery B in circuit with the condenser coatings. On releasing the -key it springs up and the galvanometer receives the effect of the charge -of the condenser as derived from the battery. - - -Key, Double Contact. -A key arranged to close two distinct circuits, holding the first closed -until the second is completed. It is used for Wheatstone bridge work. - - -Key, Double Tapper. -A telegraph key giving contacts alternately for currents in opposite -directions, used in needle telegraphy. - - -Key, Increment. -A key for use in duplex and quadruplex telegraphy. Its action is to -increase the line current, not merely to suddenly turn current into it. - - -315 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 207. KEMPE'S DISCHARGE KEY. - - -Key, Kempe's Discharge. -A key giving a charging, discharging and insulating connection, for -static condenser work. Referring to the cut l is a lever or spring with -upper discharging contact s, and lower charging contact s'. In use it is -pressed down by the insulating handle or finger piece C, until caught by -the hook attached to the key I. This hook is lower down than that on the -key D, and holds it in contact with the charging contact piece S'. On -pressing the key I, marked or designated "Insulate," it springs up, -breaks contact at S', and catching against the hook on D, which key is -designated "Discharge," remains insulated from both contacts; next on -pressing D it is released and springs up and closes the discharge -contact S. It is a form of charge and discharge key. (See Key, Charge -and Discharge.) - - -Key, Magneto-electric. -A telegraph key whose movements operate what is virtually a small -magneto-generator, so as to produce currents of alternating direction, -one impulse for each motion of the key. It is employed for telegraphing -without a line battery, a polarized relay being used. In one very simple -form a key is mounted on a base with a permanent magnet and connected to -the armature, so that when the key is pressed downwards it draws the -armature away from the poles of the magnet. If the magnet or its -armature is wound with insulated wire this action of the key will cause -instantaneous currents to go through a circuit connected to the magnet -or armature coils. - - -Fig. 208. SIEMENS' MAGNETO-ELECTRIC KEY. - - -In Siemens & Halske's key an H armature E is pivoted between the poles N -S, of a powerful compound horseshoe magnet, G G. It is wound with fine -wire and a key handle H is provided for working it. In its normal -position the handle is drawn upward, and the end S S of the armature -core is in contact with the south pole S of the permanent magnet, and -the end D D with the north pole. This establishes the polarity of the -armature. On depressing the key the contacts are broken and in their -place the end D D comes in contact with the south pole and the end S S -with the north pole. This suddenly reverses the polarity of the armature -and sends a momentary current through the armature coil which is in -circuit with the line. The cut only shows the principle of the key, -whose construction is quite complicated. - - -316 STANDARD ELECTRICAL DICTIONARY. - - -Key, Make and Break. -An ordinary electric key, usually making a contact when depressed, and -rising by spring action when released, and in its rise breaking the -contact. - - -Fig. 209. PLUG KEY - - -Key, Plug. -An appliance for closing a circuit. Two brass blocks are connected to -the terminals, but are disconnected from each other. A brass plug -slightly coned or with its end split so as to give it spring action is -thrust between the blocks to complete the circuit. It is used in -Resistance coils and elsewhere. (See Coil, Resistance.) Grooves are -formed in the blocks to receive the plug. - - -Key, Reversing. -(a) A double key, arranged so that by depressing one key a current flows -in one direction, and by depressing the other a current flows in the -opposite direction. It is used in connection with a galvanometer in -experimental, testing or measuring operations. - -(b) A key effecting the same result used in quadruplex telegraphy. - - -Key, Sliding-Contact. -A name given to the key used for making instantaneous contacts with the -metre wire of a metre bridge, q. v. The name is not strictly correct, -because it is important that there should be no sliding contact made, as -it would wear out the wire and make it of uneven resistance. - -It is a key which slides along over the wire and which, when depressed, -presses a platinum tipped knife edge upon the wire. On being released -from pressure the key handle springs up and takes the knife edge off the -wire. This removal is essential to avoid wearing the wire, whose -resistance per unit of length must be absolutely uniform. - - -Key, Telegraph. -The key used in telegraphy for sending currents as desired over the -line. It consists of a pivoted lever with finger piece, which lever when -depressed makes contact between a contact point on its end and a -stationary contact point on the base. This closes the circuit through -the line. When released it springs up and opens the line circuit. - - -Kilo. -A prefix to the names of units; it indicates one thousand times, as -kilogram, one thousand grams. A few such units are given below. - - -Kilodyne. -A compound unit; one thousand dynes. (See Dyne.) - - -Kilogram. -A compound unit; one thousand grams; 2.2046 pounds avds. - - -317 STANDARD ELECTRICAL DICTIONARY. - - -Kilojoule. -A compound unit; one thousand joules, q. v. - - -Kilometer. -A compound unit; one thousand meters; 3280.899 feet; 0.621382 statute -miles. (See Meter.) - - -Kilowatt. -A compound unit; one thousand watts, q. v. - - -Kine. -An absolute or C. G. S. unit of velocity or rate of motion; one -centimeter per second; proposed by the British Association. - - -Kirchoff's Laws. -These relate to divided circuits. - -I. When a steady current branches, the quantity of electricity arriving -by the single wire is equal to the quantity leaving the junction by the -branches. The algebraical sum of the intensities of the currents passing -towards (or passing from) the junction is equal to zero; Summation(C) = -0 (Daniell.) In the last sentence currents flowing towards the point are -considered of one sign and those flowing away from it of the other. - -II. In a metallic circuit comprising within it a source of permanent -difference of potential, E, the products of the intensity of the current -within each part of the circuit into the corresponding resistance are, -if the elements of current be all taken in cyclical order together, -equal to E; Summation(C * r) =E. In a metallic circuit in which there is -no source of permanent difference of potential E = 0, and Summation(C * -r) = 0. - -This law applies to each several mesh of a wire network as well as to a -single metallic loop, and it holds good even when an extraneous current -is passed through the loop. (Daniell.) - -In this statement of the two laws E stands for electro-motive force, C -for current intensity; and r for resistance of a single member of the -circuit. - -[Transcriber's note: These laws may be restated as: At any point in an -steady-state electrical circuit, the directed sum of currents flowing -towards that point is zero. The directed sum of the electrical potential -differences around any closed circuit is zero.] - - -Knife-edge Suspension. -The suspension of an object on a sharp edge of steel or agate. The knife -edge should abut against a plane. The knife edge is generally carried by -the poised object. Its edge then faces downward and on the support one -or more plane or approximately plane surfaces are provided on which it -rests. In the ordinary balance this suspension can be seen. It is -sometimes used in the dipping needle. - -It is applied in cases where vertical oscillations are to be provided -for. - - -Knot. -The geographical mile; a term derived from the knots on the log line, -used by navigators. It is equal to 6,087 feet. - -Synonyms--Nautical Mile--Geographical Mile. - -[Transcriber's note: A knot is a velocity, 1 nautical mile per hour, not -a distance. The contemporary definition is: 1 international knot = 1 -nautical mile per hour = 1.852 kilometres per hour = 1.1507794 miles per -hour = 0.51444444 meters per second = 6076.1152 feet per hour.] - - -318 STANDARD ELECTRICAL DICTIONARY. - - -Kohlrausch's Law. -A law of the rate of travel of the elements and radicals in solutions -under the effects of electrolysis. It states that each element under the -effects of electrolysis has a rate of travel for a given liquid, which -is independent of the element with which it was combined. The rates of -travel are stated for different elements in centimeters per hour for a -potential difference of one or more volts per centimeter of path. - -[Friedrich Wilhelm Georg Kohlrausch (1840-1910)] - - -Kookogey's Solution. -An acid exciting and depolarizing solution for a zinc-carbon couple, -such as a Bunsen battery. Its formula is: Potassium bichromate, 227 -parts; water, boiling, 1,134 parts; while boiling add very carefully and -slowly 1,558 parts concentrated sulphuric acid. All parts are by weight. -Use cold. - - -Krizik's Cores. -Cores of iron for use with magnetizing coils, q. v. They are so shaped, -the metal increasing in quantity per unit of length, as the centre is -approached, that the pull of the excited coil upon them will as far as -possible be equal in all positions. A uniform cylinder is attracted with -varying force according to its position; the Krizik bars or cores are -attracted approximately uniformly through a considerable range. - - -L. -Symbol for length and also for the unit of inductance or coefficient of -induction, because the dimensions of inductance are length. - - -Lag, Angle of. -(a) The angle of displacement of the magnetic axis of an armature of a -dynamo, due to its magnetic lag. The axis of magnetism is displaced in -the direction of rotation. (See Magnetic Lag.) - -(b) The angle expressing the lag of alternating current and -electro-motive force phases. - - -Laminated. adj. -Made up of thin plates, as a laminated armature core or converter core. - - -Lamination. -The building up of an armature core or other thing out of plates. The -cores of dynamo armatures or of alternating current converters are often -laminated. Thus a drum armature core may consist of a quantity of thin -iron discs, strung upon a rod and rigidly secured, either with or -without paper insulation between the discs. If no paper is used the film -of oxide on the iron is relied on for insulation. The object of -lamination is to break up the electrical continuity of the core, so as -to avoid Foucault currents. (See Currents, Foucault.) The laminations -should be at right angles to the direction of the Foucault currents -which would be produced, or in most cases should be at right angles to -the active parts of the wire windings. - - -319 STANDARD ELECTRICAL DICTIONARY. - - -Lamination of Armature Conductors. -These are sometimes laminated to prevent the formation of eddy currents. -The lamination should be radial, and the strips composing it should be -insulated from each other by superficial oxidation, oiling or -enamelling, and should be united only at their ends. - - -Fig. 210. PILSEN ARC LAMP. - - -Lamp, Arc. -A lamp in which the light is produced by a voltaic arc. Carbon -electrodes are almost universally employed. Special mechanism, operating -partly by spring or gravity and partly by electricity, is employed to -regulate the distance apart of the carbons, to let them touch when no -current passes, and to separate them when current is first turned on. - -The most varied constructions have been employed, examples of which will -be found in their places. Lamps may in general be divided into classes -as follows, according to their regulating mechanism and other features: - -(a) Single light regulators or monophotes. Lamps through whose -regulating mechanism the whole current passes. These are only adapted to -work singly; if several are placed in series on the same circuit, the -action of one regulator interferes with that of the next one. - -(b) Multiple light regulators or polyphotes. In these the regulating -mechanism and the carbons with their arc are in parallel; the regulating -device may be a single magnet or solenoid constituting a derived or -shunt-circuit lamp, or it may include two magnets working differentially -against or in opposition to each other constituting a differential lamp. - - -320 STANDARD ELECTRICAL DICTIONARY. - - -(c) Lamps with fixed parallel carbons termed candles (q. v., of various -types). - -(d) Lamps without regulating mechanism. These include lamps with -converging carbons, whose object was to dispense with the regulating -mechanism, but which in some cases have about as much regulating -mechanism as any of the ordinary arc lamps. - - -Lamp, Contact. -A lamp depending for its action on loose contact between two carbon -electrodes. At the contact a species of incandescence with incipient -arcs is produced. One of the electrodes is usually flat or nearly so, -and the other one of pencil shape rests upon it. - - -Lamp, Differential Arc. -An arc lamp, the regulation of the distance between whose carbons -depends on the differential action of two separate electrical coils. The -diagram illustrates the principle. The two carbons are seen in black; -the upper one is movable, The current arrives at A. It divides, and the -greater part goes through the low resistance coil M to a contact roller -r, and thence by the frame to the upper carbon, and through the arc and -lower carbon to B, where it leaves the lamp. A smaller portion of the -current goes through the coil M1 of higher resistance and leaves the -lamp also at B. A double conical iron core is seen, to which the upper -carbon holder is attached. This is attracted in opposite directions by -the two coils. If the arc grows too long its resistance increases and -the coil M1 receiving more current draws it down and thus shortens the -arc. If the arc grows too short, its resistance falls, and the coil M -receives more current and draws the core upwards, thus lengthening the -arc. This differential action of the two cores gives the lamp its name. -R is a pulley over which a cord passes, one end attached to the core and -the other to a counterpoise weight, W. - - -Fig. 211. DIAGRAM OF THE PILSEN DIFFERENTIAL ARC LAMP. - - -321 STANDARD ELECTRICAL DICTIONARY. - - -Lamp, Holophote. -A lamp designed for use alone upon its own circuit. These have the -regulating mechanism in series with the carbon and arc, so that the -whole current goes through both. (See Lamp, Arc.) - -Synonym--Monophote Lamp. - - -Lamp-hour. -A unit of commercial supply of electric energy; the volt-coulombs -required to maintain an electric lamp for one hour. A sixteen-candle -power incandescent lamp is practically the lamp alluded to, and requires -about half an ampere current at 110 volts, making a lamp-hour equal to -about 198,000 volt-coulombs. - -[Transcriber's note: 0.55 KW hours.] - - -Lamp, Incandescent. -An electric lamp in which the light is produced by heating to whiteness -a refractory conductor by the passage of a current of electricity. It is -distinguished from an arc lamp (which etymologically is also an -incandescent lamp) by the absence of any break in the continuity of its -refractory conductor. Many different forms and methods of construction -have been tried, but now all have settled into approximately the same -type. - -The incandescent lamp consists of a small glass bulb, called the -lamp-chamber, which is exhausted of air and hermetically sealed. It -contains a filament of carbon, bent into a loop of more or less simple -shape. This shape prevents any tensile strain upon the loop and also -approximates to the outline of a regular flame. - - -Fig. 212. INCANDESCENT ELECTRIC LAMP. - - -322 STANDARD ELECTRICAL DICTIONARY. - - -The loop is attached at its ends to two short pieces of platinum wire, -which pass through the glass of the bulb and around which the glass is -fused. As platinum has almost exactly the same coefficient of -heat-expansion as glass, the wires do not cause the glass to crack. - -The process of manufacture includes the preparation of the filament. -This is made from paper, silk, bamboo fibre, tamidine, q. v., or other -material. After shaping into the form of the filament the material is -carbonized at a high heat, while embedded in charcoal, or otherwise -protected from the air. The flashing process (see Flashing of -incandescent Lamp Carbons) may also be applied. The attachment to the -platinum wires is effected by a minute clamp or by electric soldering. -The loop is inserted and secured within the open globe, which the glass -blower nearly closes, leaving one opening for exhaustion. - -The air is pumped out, perhaps first by a piston pump, but always at the -end by a mercurial air pump. (See Pump, Geissler--and others.) As the -exhaustion becomes high a current is passed through the carbons heating -them eventually to white heat so as to expel occluded gas. The occluded -gases are exhausted by the pump and the lamp is sealed by melting the -glass with a blowpipe or blast-lamp flame. For the exhaustion several -lamps are usually fastened together by branching glass tubes, and are -sealed off one by one. - -The incandescent lamps require about 3.5 watts to the candle power, or -give about 12 sixteen-candle lamps to the horse power expended on them. - -Generally incandescent lamps are run in parallel or on multiple arc -circuits. All that is necessary in such distribution systems is to -maintain a proper potential difference between the two leads across -which the lamps are connected. In the manufacture of lamps they are -brought to an even resistance and the proper voltage at which they -should be run is often marked upon them. This may be fifty volts and -upward. One hundred and ten volts is a very usual figure. As current one -ampere for a fifty-volt, or about one-half an ampere for a one hundred -and ten volt lamp is employed. - - -Lamp, Incandescent, Three Filament. -A three filament lamp is used for three phase currents. It has three -filaments whose inner ends are connected, and each of which has one -leading-in wire. The three wires are connected to the three wires of the -circuit. Each filament receives a current varying in intensity, so that -there is always one filament passing a current equal to the sum of the -currents in the other two filaments. - - -Lamp, Lighthouse. -A special type of arc light. It is adapted for use in a lighthouse -dioptric lantern, and hence its arc has to be maintained in the same -position, in the focus of the lenses. The lamps are so constructed as to -feed both carbons instead of only one, thereby securing the above -object. - - -323 STANDARD ELECTRICAL DICTIONARY. - - -Lamp, Pilot. -A lamp connected to a dynamo, and used by its degree of illumination to -show when the dynamo on starting becomes excited, or builds itself up. - - -Lamp, Polyphote. -An arc lamp adapted to be used, a number in series, upon the same -circuit. The electric regulating mechanism is placed in shunt or in -parallel with the carbons and arc. (See Lamp, Arc.) - - -Lamps, Bank of. -A number of lamps mounted on a board or other base, and connected to -serve as voltage indicator or to show the existence of grounds, or for -other purposes. - - -Lamp, Semi-incandescent. -A lamp partaking of the characteristics of both arc and incandescence; a -lamp in which the imperfect contact of two carbon electrodes produces a -part of or all of the resistance to the current which causes -incandescence. - -The usual type of these lamps includes a thin carbon rod which rests -against a block of carbon. The species of arc formed at the junction of -the two heats the carbons. Sometimes the upper carbon or at least its -end is heated also by true incandescence, the current being conveyed -near to its end before entering it. - -Semi-incandescent lamps are not used to any extent now. - - -Lamp Socket. -A receptacle for an incandescent lamp; the lamp being inserted the -necessary connections with the two leads are automatically made in most -sockets. The lamps may be screwed or simply thrust into the socket and -different ones are constructed for different types of lamps. A key for -turning the current on and off is often a part of the socket. - - -Latent Electricity. -The bound charge of static electricity. (See Charge, Bound.) - - -Law of Intermediate Metals. -A law of thermo-electricity. The electro-motive force between any two -metals is equal to the sum of electro-motive forces between each of the -two metals and any intermediate metal in the thermo-electric series, or -the electro-motive force between any two metals is equal to the sum of -the electromotive forces between all the intermediate ones and the -original two metals; it is the analogue of Volta's Law, q. v. - - -Law of Inverse Squares. -When force is exercised through space from a point, its intensity varies -inversely with the square of the distance. Thus the intensity of light -radiated by a luminous point at twice a given distance therefrom is of -one-fourth the intensity it had at the distance in question. -Gravitation, electric and magnetic attraction and repulsion and other -radiant forces are subject to the same law. - - -324 STANDARD ELECTRICAL DICTIONARY. - - -Law of Successive Temperatures. -A law of thermo-electricity. The electro-motive force due to a given -difference of temperature between the opposite junctions of the metals -is equal to the sum of the electro-motive forces produced by fractional -differences of temperature, whose sum is equal to the given difference -and whose sum exactly fills the given range of temperature. - - -Law, Right-handed Screw. -This rather crude name is given by Emtage to a law expressing the -relation of direction of current in a circuit to the positive direction -of the axis of a magnet acted on by such current. It is thus expressed: -A right-handed screw placed along the axis of the magnet and turned in -the direction of the current will move in the positive direction, i. e., -towards the north pole of the axis of the magnet. - -Lead. -A metal; one of the elements; symbol Pb. Atomic weight, 207; -equivalent, 103-1/2; valency, 2. -Lead may also be a tetrad, when its equivalent is 51.75. -The following data are at 0º C. (32º F.) with compressed metal: -Relative Resistance, (Silver = l) 13.05 -Specific Resistance, 19.63 microhms. -Resistance of a wire, -(a) 1 ft. long, weighing 1 grain, 3.200 ohms. -(b) 1 meter long, weighing 1 gram, 2.232 " -(c) 1 meter long, 1 millimeter thick, .2498 " -Resistance of 1 inch cube, 7.728 microhms. -Electro-Chemical Equivalent (Hydrogen = .0105) 1.086 mgs. - - -Leading Horns. -The tips of pole pieces in a dynamo, which extend in the direction of -movement of the armature. - - -Leading-in Wires. -The platinum wires passing through the glass of an incandescent -lamp-chamber, to effect the connection of the carbon filament with the -wires of the circuit. - - -Lead of Brushes, Negative. -In a motor the brushes are set backwards from their normal position, or -in a position towards the direction of armature rotation or given a -negative lead instead of a positive one, such as is given to dynamo -brushes. - - -Leak. -A loss or escape of electricity by accidental connection either with the -ground or with some conductor. There are various kinds of leak to which -descriptive terms are applied. - - -Leakage. -The loss of current from conductors; due to grounding at least at two -places, or to very slight grounding at a great many places, or all along -a line owing to poor insulation. In aerial or pole telegraph lines in -wet weather there is often a very large leakage down the wet poles from -the wire. (See Surface Leakage--Magnetic Leakage.) - - -325 STANDARD ELECTRICAL DICTIONARY. - - -Leakage Conductor. -A conductor placed on telegraph poles to conduct directly to earth any -leakage from a wire and thus prevent any but a very small portion -finding its way into the other wires on the same pole. It presents a -choice of evils, as it increases the electrostatic capacity of the line, -and thus does harm as well as good. It consists simply of a wire -grounded and secured to the pole. - - -Leg of Circuit. -One lead or side of a complete metallic circuit. - - -Lenz's Law. -A law expressing the relations of direction of an inducing current or -field of force to the current induced by any disturbance in the -relations between such field and any closed conductor within its -influence. It may be variously expressed. - -(a) If the relative position of two conductors, A and B, be changed, of -which A is traversed by a current, a current is induced in B in such a -direction that, by its electro-dynamic action on the current in A, it -would have imparted to the conductors a motion of the contrary kind to -that by which the inducing action was produced. (Ganot.) - -(b) The new (induced) current will increase the already existing -resistances, or develop new resistance to that disturbance of the field -which is the cause of induction. (Daniell.) - -(c) When a conductor is moving in a magnetic field a current is induced -in the conductor in such a direction as by its mechanical action to -oppose the motion. (Emtage.) - -(d) The induced currents are such as to develop resistance to the change -brought about. - - -Letter Boxes, Electric. -Letter boxes with electrical connections to a bell or indicator of some -sort, which is caused to act by putting a letter into the box. - - -Leyden Jar. -A form of static condenser. - -In its usual form it consists of a glass jar. Tinfoil is pasted around -the lower portions of its exterior and interior surfaces, covering from -one-quarter to three-quarters of the walls in ordinary examples. The -rest of the glass is preferably shellacked or painted over with -insulating varnish, q. v. The mouth is closed with a wooden or cork -stopper and through its centre a brass rod passes which by a short chain -or wire is in connection with the interior coating of the jar. The top -of the rod carries a brass knob or ball. - -If such a jar is held by the tinfoil-covered surface in one hand and its -knob is held against the excited prime conductor of a static machine its -interior becomes charged; an equivalent quantity of the same electricity -is repelled through the person of the experimenter to the earth and when -removed from the conductor it will be found to hold a bound charge. If -the outer coating and knob are both touched or nearly touched by a -conductor a disruptive discharge through it takes place. - - -326 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 213. LEYDEN JAR WITH DISCHARGER. - - -If one or more persons act as discharging conductors they will receive a -shock. This is done by their joining hands, a person at one end touching -the outer coating and another person at the other end touching the knob. - -From an influence machine a charge can be taken by connecting the -coating to one electrode and the knob to the other. - - -Fig. 214. SULPHURIC ACID LEYDEN JAR. - - -327 STANDARD ELECTRICAL DICTIONARY. - - -Leyden Jar, Sir William Thomson's. -An especially efficient form of Leyden jar. It consists of a jar with -outer tinfoil coating only. For the interior coating is substituted a -quantity of concentrated sulphuric acid. The central rod is of lead with -a foot, which is immersed in the acid and from which the rod rises. A -wooden cover partly closes the jar, as the central tube through which -the rod passes is so large as not to allow the wood to touch it. Thus -any leakage from inner to outer coating has to pass over the inside and -outside glass surfaces. In the common form of jar the wooden cover may -short circuit the uncoated portion of the inner glass surface. In the -cut a simplified form of Thomson's Leyden jar is shown, adapted for -scientific work. - - -Lichtenberg's Figures. -If the knob of a Leyden jar or other exited electrode is rubbed over the -surface of ebonite, shellac, resin or other non-conducting surface it -leaves it electrified in the path of the knob. If fine powder such as -flowers of sulphur or lycopodium is dusted over the surface and the -excess is blown away, the powder will adhere where the surface was -electrified, forming what are called Lichtenberg's Figures, Lycopodium -and sulphur show both positive and negative figures, that is to say, -figures produced by a positively or negatively charged conductor. Red -lead adheres only to negative figures. If both positive and negative -figures are made and the surface is sprinkled with both red lead and -flowers of sulphur each picks out its own figure, the sulphur going -principally to the positive one. - -The red lead takes the form of small circular heaps, the sulphur -arranges itself in tufts with numerous diverging branches. This -indicates the difference in the two electricities. The figures have been -described as "a very sensitive electrosope for investigating the -distribution of electricity on an insulating surface." (Ganot.) - - -Life of Incandescent Lamps. -The period of time a lamp remains in action before the carbon filament -is destroyed. The cause of a lamp failing may be the volatilization of -the carbon of the filament, causing it to become thin and to break; or -the chamber may leak. The life of the lamp varies; 600 hours is a fair -estimate. Sometimes they last several times this period. - -The higher the intensity at which they are used the shorter is their -life. From their prime cost and the cost of current the most economical -way to run them can be approximately calculated. - -[Transcriber's note: Contemporary incandecent buls are rated for 1000 -hours; flourescent bulbs up to 24000 hours; LED lamps up to 100000 hours.] - - -Lightning. -The electrostatic discharge to the earth or among themselves of clouds -floating in the atmosphere. The discharge is accompanied by a spark or -other luminous effect, which may be very bright and the effects, thermal -and mechanical, are often of enormous intensity. - -The lightning flash is white near the earth, but in the upper regions -where the air is rarefied it is of a blue tint, like the spark of the -electric machine. The flashes are often over a mile in length, and -sometimes are four or five miles long. They have sometimes a curious -sinuous and often a branching shape, which has been determined by -photography only recently. To the eye the shape seems zigzag. - - -328 STANDARD ELECTRICAL DICTIONARY. - - -In the case of a mile-long flash it has been estimated that 3,516,480 De -la Rue cells, q. v., would be required for the development of the -potential, giving the flash over three and one-half millions of volts. -But as it is uncertain how far the discharge is helped on its course by -the rain drops this estimate may be too high. - -There are two general types of flash. The so-called zigzag flash -resembles the spark of an electric machine, and is undoubtedly due to -the disruptive discharge from cloud to earth. Sheet lightning has no -shape, simply is a sudden glow, and from examination of the spectrum -appears to be brush discharges (see Discharge, Brush) between clouds. -Heat lightning is attributed to flashes below the horizon whose light -only is seen by us. Globe or ball lightning takes the form of globes of -fire, sometimes visible for ten seconds, descending from the clouds. On -reaching the earth they sometimes rebound, and sometimes explode with a -loud detonation. No adequate explanation has been found for them. - -The flash does not exceed one-millionth of a second in duration; its -absolute light is believed to be comparable to that of the sun, but its -brief duration makes its total light far less than that of the sun for -any period of time. - -If the disruptive discharge passes through a living animal it is often -fatal. As it reaches the earth it often has power enough to fuse sand, -producing fulgurites, q. v. (See also Back Shock or Stroke of -Lightning.) - -Volcanic lightning, which accompanies the eruptions of volcanoes, is -attributed to friction of the volcanic dust and to vapor condensation. - -[Transcriber's note: The origin of lightning is still (2008) not fully -understood, but is thought to relate to charge separation in the -vertical motion of water droplets and ice crystals in cloud updrafts. A -lightning bolt carries a current of 40,000 to 120,000 amperes, and -transfers a charge of about five coulombs. Nearby air is heated to about -10,000 °C (18,000 °F), almost twice the temperature of the Sun’s -surface.] - - -Lightning Arrester. -An apparatus for use with electric lines to carry off to earth any -lightning discharge such lines may pick up. Such discharge would imperil -life as well as property in telegraph offices and the like. - -Arresters are generally constructed on the following lines. The line -wires have connected to them a plate with teeth; a second similar plate -is placed near this with its teeth opposite to those of the first plate -and nearly touching it. The second plate is connected by a low -resistance conductor to ground. Any lightning discharge is apt to jump -across the interval, of a small fraction of an inch, between the -oppositely placed points and go to earth. - -Another type consists of two plates, placed face to face, and pressing -between them a piece of paper or mica. The lightning is supposed to -perforate this and go to earth. One plate is connected to the line, the -other one is grounded. - -The lightning arrester is placed near the end of the line before it -reaches any instrument. (See Alternative Paths.) - - -329 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 215. COMB OR TOOTHED LIGHTNING ARRESTER. - - -Fig. 216. FILM OR PLATE LIGHTNING ARRESTER. - - -Lightning Arrester, Counter-electro-motive Force. -An invention of Prof. Elihu Thompson. A lightning arrester in which the -lightning discharge sets up a counter-electro-motive force opposed to -its own. This it does by an induction coil. If a discharge to earth -takes place it selects the primary of the coil as it has low -self-induction. In its discharge it induces in the secondary a reverse -electro-motive force which protects the line. - - -Lightning Arrester Plates. -The toothed plates nearly in contact, tooth for tooth, or the flat -plates of a film lightning arrester, which constitute a lightning -arrester. Some advocate restricting the term to the plate connected to -the line. - - -Lightning Arrester, Vacuum. -A glass tube, almost completely exhausted, into which the line wire is -fused, while a wire leading to an earth connection has its end fused in -also. - -A high tension discharge, such as that of lightning, goes to earth -across the partial vacuum in preference to going through the line, which -by its capacity and self-induction opposes the passage through it of a -lightning discharge. - -It is especially adapted for underground and submarine lines. - - -330 STANDARD ELECTRICAL DICTIONARY. - - -Lightning, Ascending. -Lightning is sometimes observed which seems to ascend. It is thought -that this may be due to positive electrification of the earth and -negative electrification of the clouds. - - -Lightning, Globe or Globular. -A very unusual form of lightning discharge, in which the flashes appear -as globes or balls of light. They are sometimes visible for ten seconds, -moving so slowly that the eye can follow them. They often rebound on -striking the ground, and sometimes explode with a noise like a cannon. -They have never been satisfactorily explained. Sometimes the phenomenon -is probably subjective and due to persistence of vision. - - -Lightning Jar. -A Leyden jar whose coatings are of metallic filings dusted on to the -surface while shellacked, and before the varnish has had time to dry. In -its discharge a scintillation of sparks appears all over the surface. - - -Line of Contact. -The line joining the points of contact of the commutator brushes in a -dynamo or motor. - -Synonym--Diameter of Commutation. - - -Lines of Force. -Imaginary lines denoting the direction of repulsion or attraction in a -field of force, q. v. They may also be so distributed as to indicate the -relative intensity of all different parts of the field. They are normal -to equipotential surfaces. (See Electro-magnetic Lines of -Force--Electrostatic Lines of Force--Magnetic Lines of Force.) - - -Lines of Induction. -Imaginary lines within a body marking the direction taken within it by -magnetic induction. These are not necessarily parallel to lines of -force, but may, in bodies of uniform agglomeration, or in crystalline -bodies, take various directions. - -Synonym--Lines of Magnetic Induction. - - -Lines of Slope. -Lines in a field of force which mark the directions in which the -intensity of force in the field most rapidly falls away. - - -Links, Fuse. -Links made of more or less easily fusible metal, for use as safety -fuses. - - -Listening Cam. -In a telephone exchange a cam or species of switch used to connect the -operator's telephone with a subscriber's line. - - -331 STANDARD ELECTRICAL DICTIONARY. - - -Lithanode. -A block of compressed lead binoxide, with platinum connecting foils for -use as an electrode in a storage battery. It has considerable capacity, -over 5 ampere-hours per pound of plates, but has not met with any -extended adoption. - - -Load. -In a dynamo the amperes of current delivered by it under any given -conditions. - - -Local Action. -(a) In its most usual sense the electric currents within a battery, due -to impurities in the zinc, which currents may circulate in exceedingly -minute circuits, and which waste zinc and chemicals and contribute -nothing to the regular current of the battery. Amalgamated or chemically -pure zinc develops no local action. - -(b) The term is sometimes applied to currents set up within the armature -core or pole pieces of a dynamo. (See Currents, Foucault.) - - -Local Battery. -A battery supplying a local circuit (q. v.); in telegraphy, where it is -principally used, the battery is thrown in and out of action by a relay, -and its current does the work of actuating the sounder and any other -local or station instruments. (See Relay.) - - -Local Circuit. -A short circuit on which are placed local apparatus or instruments. Such -circuit is of low resistance and its current is supplied by a local -battery, q. v. Its action is determined by the current from the main -line throwing its battery in and out of circuit by a relay, q. v., or -some equivalent. - - -Local Currents. -Currents within the metal parts of a dynamo. (See Currents, Foucault.) -In a galvanic battery. where there is local action, q. v., there are -also local currents, though they are not often referred to. - - -Localization. -Determining the position of anything, such as a break in a cable, or a -grounding in a telegraph line. In ocean cables two typical cases are the -localization of a break in the conductor and of a defect in the -insulation admitting water. The first is done by determining the static -capacity of the portion of the line which includes the unbroken portion -of the conductor; the other by determining the resistance of the line on -a grounded circuit. - - -Locus. -A place. The word is used to designate the locality or position of, or -series of positions of definite conditions and the like. Thus an -isogonic line is the locus of equal declinations of the magnetic needle; -it is a line passing through all places on the earth's surface where the -condition of a given declination is found to exist. - - -332 STANDARD ELECTRICAL DICTIONARY. - - -Lodestone. -Magnetic magnetite; magnetite is an ore of iron, Fe3 04 which is -attracted by the magnet. Some samples possess polarity and attract iron. -The latter are lodestones. - -Synonym--Hercules Stone - - -Logarithm. -The exponent of the power to which it is necessary to raise a fixed -number to produce a given number. The fixed number is the base of the -system. There are two systems; one, called the ordinary system, has 10 -for its base, the other, called the Naperian system, has 2.71828 for its -base. The latter are also termed hyperbolic logarithms, and are only -used in special calculations. - - -Log, Electric. -An apparatus for measuring the speed of a ship. A rotating helical vane -of known pitch is dragged behind the vessel. As the helix rotates its -movements may actuate electric machinery for registering its rotations. -The number of these in a given time, multiplied by the pitch of the -vane, gives the distance traversed in such time. - - -Loop. -A portion of a circuit introduced in series into another circuit. The -latter circuit is opened by a spring-jack, q. v. or other device, and -the loop inserted. By loops any number of connections can be inserted -into a circuit in series therewith, and in series or in parallel with -one another. - - -Loop Break. -A double bracket or similar arrangement for holding on insulators the -ends of a conductor which is cut between them, and to which are -connected the ends of a loop. The space between the insulators may be -about a foot. - - -Luces. -This may be used as the plural of lux, q. v. It is the Latin plural. - - -Luminous Jar. -A Leyden jar whose coatings are of lozenge-shaped pieces of tinfoil -between which are very short intervals. When discharged, sparks appear -all over the surface where the lozenges nearly join. - - -Lux. -A standard of illumination, q. v., as distinguished from illuminating -power. - -It is the light given by one candle at a distance of 12.7 inches--by a -carcel, q. v., at a distance of one meter---or by 10,000 candles at -105.8 feet. - -It was proposed by W. H. Preece. All the above valuations are identical. - - -M. -(a) Symbol of gaseous pressure equal to one-millionth of an atmosphere. - -(b) The Greek m, µ, is used as the symbol of magnetic permeability. - - -333 STANDARD ELECTRICAL DICTIONARY. - - -Machine, Cylinder Electric. -A frictional electric machine whose rotating glass is in the shape of a -cylinder instead of a disc as in the more recent machines. - - -Fig. 217. PLATE FRICTIONAL ELECTRIC MACHINE. - - -Machine, Frictional Electric. -An apparatus for development of high tension electricity by contact -action, brought about by friction. - -It consists of a plate or cylinder of glass mounted on insulating -standards and provided with a handle for turning it. One or more -cushions of leather are held on an insulated support, so as to rub -against the plate or cylinder as it is turned. A metal comb or combs are -held on another insulating support so as to be nearly in contact with -the surface of the glass plate at a point as far removed as possible -from the rubbers. The combs are attached to a brass ball or round-ended -cylinder, which is termed the prime conductor. - -In use either the prime conductor or cushions are connected by a chain -or otherwise with the earth. Assume it to be the cushions. As the -machine is worked by turning the plate, the glass and cushion being in -contact develop opposite electricities. The glass is charged with -positive electricity, and as it turns carries it off and as it reaches -the prime conductor by induction and conduction robs it of its negative -electricity. Meanwhile the cushions negatively excited deliver their -charge to the earth. The action thus goes on, the prime conductor being -charged with positive electricity. - - -334 STANDARD ELECTRICAL DICTIONARY. - - -If the prime conductor is connected to the earth and the cushions are -left insulated, negative electricity can be collected from the cushions. - -In some machines both prime conductor and cushions are kept insulated -and without ground contact. Electrodes connecting with each are brought -with their ends close enough to maintain a sparking discharge. - - -Machine Influence. -A static electric machine working by induction to build up charges of -opposite nature on two separate prime conductors. In general they are -based on the principle of the electrophorous. Work is done by the -operator turning the handle. This rotates a disc and draws excited parts -of it away from their bound charges. This represents a resistance to -mechanical motion. The work absorbed in overcoming this mechanical -resistance appears as electric energy. There are various types of -influence machines, the Holtz, Toeppler-Holtz and Wimshurst being the -most used. The electrophorous, q. v., is a type of influence machine. - - -Machine, Holtz Influence. -A static electric machine. It includes two plates, one of which is -rapidly rotated in front of the other. Two armatures of paper are -secured to the back of the stationary plate at opposite ends of a -diameter. To start it one of these is charged with electricity. This -charge by induction acts through the two thicknesses of glass upon a -metal bar carrying combs, which lies in front of the further side of the -movable plate. The points opposite the armature repel electrified air, -which strikes the movable disc and charges it. A second rod with comb at -the opposite end of the same diameter acts in the reverse way. Thus -opposite sections of the disc are oppositely charged and the combs with -them. By induction these portions of the disc react upon the two -armatures. The opposite electricities escape from the armatures by paper -tongues which are attached thereto and press against the back of the -movable plate. As the plate rotates the opposite electricities on its -face neutralize the electricity repelled from the combs. The charges on -the back strengthen the charges of the armatures and brass combs. Thus -the machine builds up, and eventually a discharge of sparks takes place -from the poles of the brass combs. - - -335 STANDARD ELECTRICAL DICTIONARY. - - -Machine, Toeppler-Holtz. -A modification of the Holtz machine. The priming charge of the armatures -is produced by friction of metallic brushes against metallic buttons on -the face of the rotating plate. (See Machine, Holtz.) - - -Machine, Wimshurst. -A form of static influence machine. It consists of two plates of glass, -on which radial sectors of tinfoil are pasted. Both plates are rotated -in opposite directions. The sectors of the two plates react one upon the -other, and electric charges of opposite sign accumulate on the opposite -sides of the plates and are collected therefrom by collecting combs. - - -Mack. -A name, derived from Maxwell, and suggested for the unit of inductance. -It is due to Oliver Heaviside, but has never been adopted. (See Henry.) - - -Magne-Crystallic Action. -The action of a supposed force of the same name, proposed by Faraday. It -relates to the different action of a magnetic field upon crystalline -bodies, according to the position of their axes of crystallization. A -needle of tourmaline, normally paramagnetic, if poised with its axis -horizontal, is diamagnetic. Bismuth illustrates the same phenomenon. The -subject is obscure. Faraday thought that he saw in it the action of a -specific force. - - -Magnet. -A body which tends when suspended by its centre of gravity to lay itself -in a definite direction, and to place a definite line within it, its -magnetic axis, q. v., in a definite direction, which, roughly speaking, -lies north and south. The same bodies have the power of attracting iron -(Daniell), also nickel and cobalt. - -Magnets are substances which possess the power of attracting iron. -(Ganot.) - -[Transcriber's note: Edward Purcell and others have explained magnetic -and electromagnetic phenomenon as relativistic effects related to -electrostatic attraction. Magnetism is caused by Lorentz contraction of -space along the direction of a current. Electromagnetic waves are caused -by charge acceleration and the resulting disturbance of the -electrostatic field. (Electricity and Magnetism: Berkeley Physics -Course Volume 2, 1960)] - - -Magnet, Anomalous. -A magnet possessing more than the normal number (two) of poles. If two -straight magnets are placed end to end with their south poles in -juxtaposition the compound bar will seem to possess three poles, one at -each end and one in the middle. The apparent pole in the middle is -really made up of two consequent poles, q. v. It sometimes happens that -when a single long thin bar is magnetized consequent poles are produced, -although such magnet is in one piece. This may be accidental, as in such -case it is quite hard to avoid anomalous poles, or, as in the field -magnets of some forms of dynamos, anomalous poles may be purposely -produced. - - -Magnet, Artificial. -A magnet formed artificially by any method of magnetization (see -Magnetism) applicable to permanent magnets, electro-magnets and -solenoids. It expresses the distinction from the natural magnets or -lodestone, q. v. It is made of steel in practice magnetized by some of -the methods described under Magnetization. - - -336 STANDARD ELECTRICAL DICTIONARY. - - -Magnet, Axial. -A straight-solenoid with axial core. - - -Magnet, Bar. -A bar magnet is one in the shape of a bar, i. c., straight with parallel -sides and considerably longer than wide or deep. - - -Magnet, Bell-shaped. -A form of permanent magnet used in some galvanometers. In shape it is a -thick-sided cylindrical box with two slots cut out of opposite sides, so -as to make it represent a horseshoe magnet. Its shape enables it to be -surrounded closely by a mass of copper, for damping its motion, to -render the instrument dead-beat. Such a magnet is used in Siemens & -Halske's galvanometer. - - -Magnet Coil. -A coil to be thrust over an iron core, to make an electro-magnet. They -are often wound upon paper or wooden bobbins or spools, so as to be -removable from the core if desired. - - -Magnet, Compensating. -(a) A magnet fastened near a compass on an iron or steel ship to -compensate the action of the metal of the ship upon the magnetic needle. -The ship itself always has some polarity and this is neutralized by one -or more compensating magnets. - -(b) See below. - - -Magnet, Controlling. -A magnet attached to a galvanometer by which the directive tendency of -its magnetic needle is adjusted. In the reflecting galvanometer it often -is a slightly curved magnet carried by a vertical brass spindle rising -from the center of the instrument, and which magnet may be slid up and -down on the spindle to regulate or adjust its action. - -Synonym--Compensating Magnet. - - -Magnet, Compound. -A permanent magnet, built up of a number of magnets. Small bars can be -more strongly magnetized than large. Hence a compound magnet may be made -more powerful than a simple one. - - -Magnet Core. -The iron bar or other mass of iron around which insulated wire is wound -for the production of an electro-magnet. The shapes vary greatly, -especially for field magnets of dynamos and motors. For these they are -usually made of cast iron, although wrought iron is preferable from the -point of view of permeability. - - -Magnet, Damping. -A damping magnet is one used for bringing an oscillating body to rest. -The body may be a metallic disc or needle, and the action of the magnet -depends on its lines of force which it establishes, so that the body has -to cut them, and hence has its motion resisted. - - -337 STANDARD ELECTRICAL DICTIONARY. - - -Magnet, Deflection of. -The change of position of a magnet from the plane of the earth's -meridian in which it normally is at rest into another position at some -angle thereto, by the effect of an artificial magnetic field, as the -deflection of a galvanometer needle. - - -Magnet, Electro-. -A magnet consisting of a bar of iron, bundle of iron wires, iron tube or -some equivalent, around which a coil of insulated wire is wound. Such -combination becomes polarized when a current is passed through it and is -an active magnet. On the cessation of the current its magnetism in part -or almost completely disappears. (See Electro-magnet.) - - -Magnet, Equator of. -In a magnet the locus of points of no attractive power and of no -polarity. In a symmetrical, evenly polarized magnet it is the imaginary -line girdling the centre. The terms Neutral Point or Neutral Line have -displaced it. - -Synonyms--Neutral Line--Neutral Point. - - -Magnet, Field. -A magnet, generally an electro-magnet, used to produce the field in a -dynamo or motor. - - -Magnet, Haarlem. -Celebrated magnets made in Haarlem, Holland. Logeman, Van Wetteren, -Funckler and Van der Willigen were the makers who gave the celebrity to -the magnets. They were generally horseshoe magnets, and would carry -about twenty times their own weight. - - -Magnet, Horseshoe. -A magnet of U shape--properly one with the poles brought a little closer -together than the rest of the limbs. For direct lifting and attractive -effects it is the most generally adopted type. Its advantage as regards -lifting effect is due to small reluctance, q. v., offered by a complete -iron circuit, such as the armature and magnet together produce. As the -term is now used it is applied to any U shaped magnet. - - -Fig. 218. JOULE'S ELECTRO-MAGNET. - - -Magnet, Joule's Electro. -An electro-magnet of the shape of a cylinder with a longitudinal segment -cut-off. It is wound with wire as shown. The segment cut-off is a piece -of the same shape as the armature. It is of high power. - - -338 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Adherence. -The tendency of a mass of iron to adhere to the poles of a magnet. It is -best figured as due to the virtual shortening of lines of force, as the -more permeable iron gives a better path for them than the air can -afford, and consequently a virtually shorter one. - - -Magnetic Attraction and Repulsion. -The attraction of a magnet for iron, steel, nickel and cobalt and of -unlike poles of magnets for each other. It is identical with -electro-magnetic attraction, q.v. (Also see Electro-magnetism.) - - -Magnetic Attraction and Repulsion, Coulomb's Law of. -Magnetic attraction and repulsion are inversely as the square of the -distance. (Ganot.) - -While theoretically true in the case of isolated poles, in practise it -does not generally apply on account of the large diameter and relative -shortness of magnets. - - -Magnetic Axis. -The line connecting the poles of a magnet. It does not generally -coincide exactly with any symmetrical axis of figure. In such cases an -error is introduced into the indications of the needle which must be -determined and allowed for in compasses. To determine it with a magnetic -needle the suspension cup is made removable, so that the needle can be -reversed. Readings are taken with one side of the needle and then with -the other side of the needle up, and the average corresponds with the -position of the magnetic axis in both positions of the needle. - - -Magnetic Azimuth. -The angle, measured on a horizontal circle, between the magnetic -meridian and a great circle of the earth passing through the observer -and any observed body. It is the astronomical azimuth of a body referred -to the magnetic meridian and therefore subject to the variation of the -compass. The angle is the magnetic azimuth of the observed body. - - -Magnetic Battery. -A name for a compound permanent magnet; one made up by bolting or -clamping together, or to single soft iron pole pieces, a number of -single permanent magnets. There are a number of forms of compound -magnets. In making them care has to be taken to have them of even -strength. It is also well to have them slightly separated. The object of -both these precautions is to prevent a stronger element or magnet from -depolarizing its neighbor. - -Synonym--Compound Magnet. - - -Magnetic Bridge. -An apparatus for testing the relative permeability of iron. It consists -of a rectangular system of iron cores. Three of the sides are wound with -wire as shown. The other side is built up of double bars, and from the -centre two curved arms rise, as shown in the cut. The arms do not touch. -Between them a short magnet is suspended by a filament, which also -carries a mirror and an index. - - -339 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 219. MAGNETIC BRIDGE. - - -A lamp and scale are provided as in the reflecting galvanometer. When -adjusted the magnetic needle hangs as shown in the cut, Fig. 219, -without any tendency to turn towards either curved pole piece. If all -iron parts are symmetrical and of similar metal, a current through the -coils will make no difference. It will work in magnetic opposition upon -the two arms, or, in other words, will maintain both arms at identical -potential. - - -Fig. 220. POLE PIECES, MAGNETIC NEEDLE AND MIRROR OF MAGNETIC BRIDGE. - - -If there is the least difference in permeability, length or thickness -between any of the iron bars the magnetic potential of the two curved -arms will differ, and the magnetic needle will turn one way or the -other. In practical use different samples of iron are substituted for -the unwound members of the fourth side of the parallelogram, and the -needle by its motions indicates the permeability. - -In the cut, Fig. 220, D D are the ends of the curved pole pieces; A the -wire carrying the mirror B and magnetic needle N, and E is the index -which shows the larger deflections. - - -340 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Circuit. -A magnetic field of force is characterized by the presence of lines of -force, which, while approximately parallel, curve around and tend to -form closed curves. The polarity of a field of force is referred to an -imaginary direction of the lines of force from the north pole through -space to the south pole, and in the part of the field corresponding to -the body of the magnet, from the south to the north pole. The cut -indicates these features. Hence the magnetic field of force is termed -the magnetic circuit, and to it are attributed a species of resistance -termed reluctance, q. v., and the producing cause of the field or lines -of force is termed sometimes magneto-motive force, q. v.) corresponding -to the electro-motive force. The modern treatment of the magnetic -circuit is similar to the application of Ohm's law and the laws of -resistance and conductivity to the electric circuit. - - -Magnetic Circuit, Double. -A magnetic circuit which virtually represents two horseshoe magnets -placed with their like poles in contact. It is used for field magnets, -the armatures occupying a place between the consequent poles. - - -Fig. 221. ONE-HALF PORTION OF A DOUBLE MAGNETIC CIRCUIT. - - -Magnetic Concentration of Ores. -The concentration of ores or the freeing them from their gangue by -magnetic attraction. It is only applicable to those cases in which -either the ore itself or the gangue is attracted by the magnet. Its -principal application is to the concentration of magnetic iron sands. -(See Magnetic Concentration.) - - -Magnetic Concentrator. -An apparatus similar to a magnetic separator, q. v., but used to -concentrate magnetic iron sands. By the action of electro-magnets the -magnetic iron sand (magnetite) is separated from the sand with which it -is mixed. - - -Magnetic Conductivity and Conductance. -The first notion of permeance and of the magnetic circuit included the -idea of magnetic conductivity, which conducted lines of force urged by -magneto-motive force through a magnetic circuit. The terms are displaced -by permeability and permeance. - - -341 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Continuity. -The completeness of a magnetic circuit, as when the armature of a -horseshoe magnet is in contact with both poles. It is an attribute of a -paramagnetic substance only and is identical for permanent magnets or -for electro-magnets. An air space intervening between armature and -magnet poles, or a space filled with any diamagnetic substance prevents -continuity, although the lines of force to some extent still find their -way around. The leakage is increased by discontinuity. - - -Magnetic Control. -Control of a magnetic needle, magnet, iron index or armature, in a -galvanometer, ammeter or voltmeter by a magnetic field; the restitutive -force being derived from a permanent magnet. - - -Magnetic Couple. -The couple of magnetic force which tends to bring the magnetic needle -into the plane of the magnetic meridian. One force is represented by the -imaginary pull upon the north pole, and the other by the opposite pull -upon the south pole of the needle. The moment of the couple varies from -a maximum when the needle is at right angles to the plane of the -magnetic meridian to zero when it is in such plane. - - -Magnetic Creeping. -Viscous hysteresis; the slow increase of magnetism in a paramagnetic -body when exposed to induction. - - -Fig. 222. MAGNETIC CURVES OR FIGURES. - - -Magnetic Curves. -The pictorial representation of magnetic lines of force. It is generally -produced by scattering filings on a sheet of paper or pane of glass held -over a magnet. The filings arrange themselves in characteristic curves. -Tapping the paper or pane of glass facilitates the arrangement, or -jarring the filings off a smaller magnet, so that they fall polarized -upon the paper, is thought by some to improve the effect. The group of -curves forms what are termed magnetic figures, q. v. - - -342 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Declination. -The angular deviation of the magnetic needle, causing it to rest at an -angle with the true meridian; the variation of the compass. (See -Magnetic Elements.) - - -Magnetic Density. -The intensity of magnetization expressed in lines of force per stated -area of cross-section in a plane at right angles to the lines of force. - - -Magnetic Dip. -The inclination from the horizontal assumed by a magnetic needle free to -move in the vertical plane. (See Magnetic Elements.) The angle of dip or -inclination is entirely a function of the earth, not of the needle. - - -Magnetic Discontinuity. -A break or gap in a magnetic circuit. To make a complete circuit the -iron or other core must be continuous. If the armature of a horseshoe -magnet is in contact with both poles the continuity is complete. If the -armature is not in contact magnetic continuity gives place to -discontinuity. It is an attribute of a paramagnetic substance only, and -is identical for permanent magnets, or for electro-magnets. - - -Magnetic Elements. -The qualities of the terrestrial magnetism at any place as expressed in -its action upon the magnetic needle. Three data are involved. - -I. The Declination or Variation. -II. The Inclination or Dip. -III. The Force or Intensity. - -I. The Declination is the variation expressed in angular degrees of the -magnetic needle from the true north and south, or is the angle which the -plane of the magnetic meridian makes with that of the geographical -meridian. It is expressed as east or west variation according to the -position of the north pole; east when the north pole of the needle is to -the east of the true meridian, and vice versa. Declination is different -for different places; it is at present west in Europe and Africa, and -east in Asia and the greater part of North and South America. The -declination is subject to (a) secular, (b) annual and (c) diurnal -variations. These are classed as regular; others due to magnetic storms -are transitory and are classed as irregular, (a) Secular variations. The -following table shows the secular variations during some three hundred -years at Paris. These changes are termed secular, because they require -centuries for their completion. - - -343 STANDARD ELECTRICAL DICTIONARY. - -Table of Declination or Variation at Paris. -Year. Declination. -1580 11º 30' E. -1663 0° -1700 8° 10' W. -1780 19º 55' W. -1785 22º 00' W. -1805 22º 5' W. -1814 22º 34' W. -1825 22° 22' W. -1830 22º 12' W. -1835 22º 4' W. -1850 20º 30' W. -1855 19º 57' W. -1860 19º 32' W. -1865 18º 44' W. -1875 17º 21' W. -1878 17º 00' W. -[Transcriber's note The value for 2008 is about 0° 48' W, changing by -0° 7' E/year.] - -On scrutinizing these figures it will be seen that there is part of a -cycle represented and that the declination is slowly returning to the -zero point after having reached its maximum western variation in 1814. -Upwards of 300 years would be required for its completion on the basis -of what is known. In other places, notably the coast of Newfoundland, -the Gulf of the St. Lawrence and the rest of the North American seaboard -and in the British Channel, the secular variations are much more rapid -in progress. (b) Annual variations--These were first discovered in 1780 -by Cassini. They represent a cycle of annual change of small extent, -from 15' to 18' only. In Paris and London the annual variation is -greatest about the vernal equinox, or March 21st, and diminishes for the -next three months, and slowly increases again during the nine following -months. It varies during different epochs. (c) Diurnal variations were -discovered in 1722 by Graham. A long needle has to be employed, or the -reflection of a ray of light, as in the reflecting galvanometer, has to -be used to observe them. In England the north pole of the magnetic -needle moves every day from east to west from sunrise until 1 or 2 P. -M.; it then tends towards the east and recovers its original position by -10 P. M. During the night the needle is almost stationary. As regards -range the mean amplitude of diurnal variations at Paris is from April to -September 13' to 15'; for the other months from 8' to 10'. On some days -it amounts to 25' and sometimes is no more than 5'. The amplitude of -diurnal variations decreases from the poles to the equator. Irregular -variations accompany earthquakes, the aurora borealis and volcanic -eruptions. In Polar regions the auroral variations may be very great; -even at 40° latitude they may be 1° or 2°. Simultaneous irregularities -sometimes extend over large areas. Such are attributed to magnetic -storms. II. The Inclination is the angle which the magnetic needle makes -with the horizon, when the vertical plane in which the needle is assumed -to be free to move coincides with the magnetic meridian. It is sometimes -called the dip of the needle. It varies as does the declination, as -shown in the following table of inclinations of London. - - -344 STANDARD ELECTRICAL DICTIONARY. - - -Table of Inclination or Dip at London -Year. Inclination. -1576 71° 50' -1600 72° -1676 73° 30' -1723 74° 42' -1773 72° 19' -1780 72° 8' -1790 71° 33' -1800 70° 35' -1821 70° 31' -1828 69° 47' -1838 69° 17' -1854 68° 31' -1859 68° 21' -1874 67° 43' -1876 67° 39' -1878 67° 36' -1880 67° 35' -1881 67° 35' - -III. Force or Intensity is the directive force of the earth. It varies -with the squares of the number of oscillations the magnetic needle will -make if caused to oscillate from a determined initial range. The -intensity is supposed to be subject to secular change. According to -Gauss the total magnetic intensity of the earth is equal to that which -would be exerted if in each cubic yard there were eight bar magnets, -each weighing one pound. This is, of course, a rough way of expressing -the degree of intensity. Intensity is least near the magnetic equator -and greatest near the magnetic poles; the places of maximum intensity -are termed the magnetic foci. It varies with the time of day and -possibly with changes in altitude. - - -Magnetic Elongation. -The elongation a bar of iron or steel undergoes when magnetized. By -magnetization it becomes a little longer and thinner, there being no -perceptible change in volume. The change is accompanied by a slight -sound--the magnetic tick. An exceedingly delicate adjustment of -apparatus is required for its observation. - - -Magnetic Equator. -A locus of the earth's surface where the magnet has no tendency to dip. -It is, approximately speaking, a line equally distant from the magnetic -poles, and is called also the aclinic line. It is not a great circle of -the earth. - - -345 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Field of Force. -The field of force established by a magnet pole. The attractions and -repulsions exercised by such a field follow the course of the electro- -magnetic lines of force. (See also Field of Force.) Thus the tendency of -a polarized needle attracted or repelled is to follow, always keeping -tangential to curved lines, the direction of the lines of force, however -sweeping they may be. The direction of magnetic lines of force is -assumed to be the direction in which a positive pole is repelled or a -negative one attracted; in other words, from the north pole of a magnet -to its south pole in the outer circuit. The direction of lines of force -at any point, and the intensity or strength of the field at that point, -express the conditions there. The intensity may bc expressed in terms of -that which a unit pole at unit distance would produce. This intensity as -unitary it has been proposed to term a Gauss. (See Weber.) - -The direction of the lines of force in a magnetic field are shown by the -time-honored experiment of sprinkling filings of iron upon a sheet of -paper held over a magnet pole or poles. They arrange themselves, if the -paper is tapped, in more or less curved lines tending to reach from one -pole of the magnet to the other. Many figures may be produced by -different conditions. Two near poles of like name produce lines of force -which repel each other. (See Magnetic Curves.) - -A magnetic and an electro-magnetic field are identical in all essential -respects; the magnetic field may be regarded as a special form of the -electro-magnetic field, but only special as regards its production and -its defined north and south polar regions. - -Synonyms--Magnetic Spin (not much used). - - -Magnetic Field, Uniform. -A field of identical strength in all parts, such as the earth's magnetic -field. If artificially produced, which can only be approximately done, -it implies large cross-section of magnet pole in proportion to the -length of the magnetic needle affected by it, which is used in -determining its uniformity. - - -Magnetic Figures. -The figures produced by iron filings upon paper or glass held near -magnetic poles. By these figures the direction of lines of force is -approximately given, and a species of map of the field is shown. (See -Magnetic Field of Force--Magnetic Curves.) - - -Magnetic Filament. -The successive rows of polarized molecules assumed to exist in -magnetized iron. Each molecule represents an infinitely small magnet, -and its north pole points to the south pole of the next molecule. Such a -string or row is a theoretical conception based on the idea that the -molecules in a magnet are all swung in to parallelism in the magnetizing -process. A magnetic filament may be termed the longitudinal element of a -magnet. (See Magnetism, Hughes' Theory of.) - -[Transcriber's note: This description parallels the modern -notion of electron spin as the basis of magnetism in materials.] - - -Magnetic Fluids. -A two-fluid theory of magnetism has been evolved, analogous to the -two-fluid theory of electricity. It assumes north fluid or "red -magnetism" and a south fluid or "blue magnetism." Each magnetism is -supposed to predominate at its own pole and to attract its opposite. -Before magnetization the fluids are supposed to neutralize each other -about each molecule; magnetization is assumed to separate them, -accumulating quantities of them at the poles. - - -Magnetic Flux. -Magnetic induction; the number of lines of force that pass through a -magnetic circuit. - -Synonym--Magnetic Flow. - - -346 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Force. -The forces of attraction and repulsion exercised by a magnet. By -Ampere's theory it is identical with the forces of attraction and -repulsion of electric currents. - - -Magnetic Friction. -The damping effect produced on the movements of a mass of metal by -proximity to a magnet; the phenomenon illustrated in Arago's wheel, q. -v. When a mass of metal moves in the vicinity of a magnet it cuts the -lines of force emanating from its poles, thereby producing currents in -its mass; as the production of these currents absorbs energy a damping -effect is produced upon the movements of the mass. - - -Magnetic Gear. -Friction gear in which electro-magnetic adherence is employed to draw -the wheels together. (See Adherence, Electro-magnetic--Electro-magnetic -Friction Gear.) - - -Magnetic Inclination. -The inclination from the horizontal of a magnetic needle placed in the -magnetic meridian. (See Magnetic Element--Inclination Map.) - -Synonym--Magnetic Dip. - - -Magnetic Induction. -The force of magnetization within an induced magnet. It is in part due -to the action of the surrounding particles of polarized material; in -part to the magnetic field. (See Magnetic Induction, Coefficient of.) - -In a more general way it is the action of a magnet upon bodies in its -field of force. In some cases the magnetism induced causes the north -pole of the induced magnet to place itself as far as possible from the -north pole of the inducing magnet and the same for the south poles. Such -substances are called paramagnetic or ferromagnetic. They lie parallel -or tangential to the lines of force. In other cases the bodies lie at -right angles or normal to the lines of force. Such bodies are called -diamagnetic. - -Some bodies are crystalline or not homogeneous in structure, and in them -the lines of magnetic induction may take irregular or eccentric paths. -(See AEolotropic.) - -Synonym--Magnetic Influence. - - -Magnetic Induction, Apparent Coefficient of. -The apparent permeability of a paramagnetic body as affected by the -presence of Foucault currents in the material itself. These currents act -exactly as do the currents in the coils surrounding the cores of -electro-magnets. They produce lines of force which may exhaust the -permeability of the iron, or may, if in an opposite direction, add to -its apparent permeability. - - -Magnetic Induction, Coefficient of. -The number, obtained by dividing the magnetization of a body, expressed -in lines of force produced in it, by the magnetizing force which has -produced such magnetization, expressed in lines of force producible by -the force in question in air. It always exceeds unity for iron, nickel -and cobalt. It is also obtained by multiplying the coefficient of -induced magnetization by 4 PI (4 * 3.14159) and adding 1. (See Magnetic -Susceptibility--Magnetization, Coefficient of Induced.) - - -347 STANDARD ELECTRICAL DICTIONARY. - - -The coefficient of magnetic induction varies with the material of the -induced mass, and varies with the intensity of the magnetizing force. -This variation is due to the fact that as the induced magnetism in a -body increases, the magnetizing force required to maintain such -induction, increases in a more rapid ratio. The coefficient of magnetic -induction is the same as magnetic permeability, and in a certain sense -is the analogue of conductivity. It is also termed the multiplying power -of the body or core magnetized. It is the coefficient of induced -magnetization (see Magnetization, Coefficient of Induced) referred to a -mass of matter. For diamagnetic bodies the coefficient has a negative -sign; for paramagnetic bodies it has a positive sign. - -Synonyms--Permeability--Multiplying Power--Magnetic Inductive Capacity. - - -Magnetic Induction, Dynamic. -The induction produced by a magnetic field which moves with respect to a -body, or where the body if moving moves at a different rate, or where -the body moves and the field is stationary. In the case where both move, -part of the induction may be dynamic and part static. (See Magnetic -Induction, Static.) - - -Magnetic Induction, Static. -Magnetic induction produced by a stationary field acting upon a -stationary body. - - -Magnetic Induction, Tube of. -An approximate cylinder or frustrum of a cone whose sides are formed of -lines of magnetic induction. (See Magnetic Induction, Lines of.) The -term tube is very curiously applied in this case, because the element or -portion of a magnetic field thus designated is in no sense hollow or -tubular. - - -Magnetic Inertia. -A sensible time is required to magnetize iron, or for it to part with -its magnetism, however soft it may be. This is due to its magnetic -inertia and is termed the lag. Permanent or residual magnetism is a -phase of it. It is analogous to self-induction of an electric circuit, -or to the residual capacity of a dielectric. - - -Magnetic Insulation. -Only approximate insulation of magnetism is possible. There is no -perfect insulator. The best ones are only 10,000 times less permeable -than iron. Hence lines of force find their way through air and all other -substance, being simply crowded together more in paths of iron or other -paramagnetic substance. - - -348 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Intensity. -The intensity of the magnetization of a body. It is measured by the -magnetic lines of force passing through a unit area of the body, such -area being at right angles to the direction of the lines of force. - - -Magnetic Lag. -In magnetism the tendency of hard iron or steel especially to take up -magnetism slowly, and to part with it slowly. (See Magnetic Inertia.) -The lag affects the action of a dynamo, and is a minor cause of those -necessitating the lead of the brushes. - -Synonym--Magnetic Retardation. - - -Magnetic Latitude. -Latitude referred to the magnetic equator and isoclinic lines. - - -Magnetic Leakage. -The lines of force in a field magnet which pass through the air and not -through the armature are useless and represent a waste of field. Such -lines constitute magnetic leakage. - - -Magnetic Limit. -The temperature beyond which a paramagnetic metal cannot be magnetized. -The magnetic limit of iron is from a red to a white heat; of cobalt, far -beyond a white heat; of chromium, below a red heat; of nickel at about -350° C. (662°F.) of manganese, from 15° C. to 20° C. (59° to 68° F.) - - -Magnetic Lines of Force. -Lines of force indicating the distribution of magnetic force, which is -due presumably to whirls of the ether. A wire or conductor through which -a current is passing is surrounded by an electro-magnetic field of -force, q. v., whose lines of force form circles surrounding the -conductor in question. A magnet marks the existence of a similar -electro-magnetic field of force whose lines form circuits comprising -part of and in some places all of the body of the magnet, and which are -completed through the air or any surrounding paramagnetic or diamagnetic -body. They may be thought of as formed by the Ampérian sheet of current, -and analogous to those just mentioned as surrounding a conductor. - - -Fig. 223. MAGNETIC LINES OF FORCE, DIRECTION OF. - - -A magnetic line of force may be thought of as a set of vortices or -whirls, parallel to each other, and strung along the line of force which -is the locus of their centres. - -If as many lines are drawn per square centimeter as there are dynes (per -unit pole) of force at the point in question, each such line will be a -unitary c. g. s. line of force. - - -349 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Mass. -A term for a quantity of magnetism. Unit mass is the quantity which at -unit distance exercises unit force. - - -Magnetic Matter. -Imaginary matter assumed as a cause of magnetism. Two kinds, one -positive and one negative, may be assumed as in the two fluid theory of -electricity, or only one kind, as in the single fluid theory of -electricity. Various theories of magnetic matter have been presented -whose value is only in their convenience. - -[Transcriber's note: See "magnet" and Edward Purcell's explanation of -magnetism using general relativity.] - - -Magnetic Memory. -The property of retaining magnetism; coercive force; magnetic inertia; -residual magnetism. - -[Transcriber's note: Small ferrite magnetic donuts were used as computer -main memory from 1950 to 1970.] - - -Magnetic Meridian. -A line formed on the earth's surface by the intersection therewith of a -plane passing through the magnetic axis. It is a line determined by the -direction of the compass needle. The meridians constantly change in -direction and correspond in a general way to the geographical meridians. - - -Magnetic Moment. -The statical couple with which a magnet would be acted on by a uniform -magnetic field of unit intensity if placed with its magnetic axis at -right angles to the lines of force of the field. (Emtage.) A uniformly -and longitudinally magnetized bar has a magnetic moment equal to the -product of its length by the strength of its positive pole. - - -Magnetic Needle. -A magnet with a cup or small depression at its centre and poised upon a -sharp pin so as to be free to rotate or oscillate in a horizontal plane. -The cup is often made of agate. Left free to take any position, it -places its magnetic axis in the magnetic meridian. - - -Magnetic Parallels. -Lines roughly parallel to the magnetic equator on all parts of each of -which the dip of the magnetic needle is the same; also called Isoclinic -Lines. These lines mark the places of the intersection of equipotential -surfaces with the earth's surface. They are not true circles, and near -the poles are irregular ellipses; the magnet there points toward their -centres of curvature. They correspond in a general way with the -Geographical Parallels of Latitude. - - -Magnetic Permeability. -The specific susceptibility of any substance, existing in a mass, for -magnetic induction. (See Magnetic Induction, Coefficient of, synonym for -Magnetic Permeability and Magnetization, Coefficient of Induced.) - -Synonyms--Magnetic Inductive Capacity--Multiplying Power--Coefficient of -Magnetic Induction. - - -350 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Perturbations. -Irregular disturbances of the terrestrial magnetism, as by the aurora -and in electric storms. - - -Magnetic Poles. -The points where the equipotential surfaces of the terrestrial field of -force graze the earth's surface; the points toward which the north or -south poles of the magnetic needle is attracted. Over a magnetic pole -the magnetic needle tends to stand in a vertical position. There are two -poles, Arctic or negative, and Antarctic or positive. Magnetic needles -surrounding them do not necessarily point toward them, as they point to -the centres of curvature of their respective magnetic parallels. The -poles constantly change in position. The line joining them does not -coincide with anything which may be termed the magnetic axis of the -earth. - - -Magnetic Poles, False. -Poles on the earth's surface other than the two regular magnetic poles. -There seem by observation to be several such poles, while analogy would -limit true magnetic poles to two in number. - - -Magnetic Potential. -The potential at any point of a magnetic field is the work which would -be done by the magnetic forces of the field upon a positive unit of -magnetism as it moves from that point to an infinite distance. (Emtage.) - - -Magnetic Proof Piece. -A piece of iron used for testing magnets and the distribution of -magnetism in bars, by suspending or supporting above or near the magnet, -by detaching after adherence, and in other ways. - - -Magnetic Proof Plane. -An exploring coil used for testing the distribution of magnetism. It is -connected in circuit with a galvanometer, and exposed to alternation of -current, or to other disturbing action produced by the magnet or field -under examination. This affects the galvanometer, and from its movements -the current produced in the coil, and thence the magnetic induction to -which it was exposed, are calculated. - -Synonym--Exploring Coil. - - -Magnetic Quantity. -The magnetism possessed by a body; it is proportional to the action of -similar poles upon each other, or to the field produced by the pole in -question. It is also called the strength of a pole. - -The force exercised by two similar poles upon each other varies with -their product and inversely with the square of the distance separating -them; or it may be expressed thus (m * m) / (L^2). This is a force, and -the dimensions of a force are ML/(T^2). Therefore, (m^2)/(L^2) = -ML/(T^2) or m = (M^.5)*(L^1.5)/T. - - -351 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Reluctance. -The reciprocal of permeance; magnetic resistance; the relative -resistance to the passage of lines of force offered by different -substances. The idea is derived from treating the magnetic circuit like -an electric one, and basing its action on magneto-motive force acting -through a circuit possessing magnetic reluctance. - - -Magnetic Reluctivity. -The reciprocal of magnetic permeability, q. v. - -Synonym--Magnetic Resistance. - - -Magnetic Retentivity. -The property of steel or hard iron by which it slowly takes up and -slowly parts with a magnetic condition--traditionally (Daniell) called -coercitive force. - - -Magnetic Rotary Polarization. -If a plane polarized beam of light is sent through a transparent medium -in a magnetic field its plane of polarization is rotated, and this -phenomenon is denoted as above. (Compare Refraction, Electric, and see -Electro-magnetic Stress.) This has been made the basis of a method for -measuring current. A field of force varies with the current; the -polarization produced by such field is therefore proportional to the -current. (Becquerel & Rayleigh.) - -A plane polarized beam of light passing through the transparent medium -in the magnetic field by the retardation or acceleration of one of its -circular components has its plane of polarization rotated as described. -The direction of the lines of force and the nature of the medium -determine the sense of the rotation; the amount depends upon the -intensity of the field resolved in the direction of the ray, and on the -thickness and nature of the medium. - - -Magnetic Saturation. -The maximum magnetic force which can be permanently imparted to a steel -bar. A bar may be magnetized beyond this point, but soon sinks to it. -The magnetism produced in a bar is prevented from depolarization by the -retentivity or coercive force of the bar. The higher the degree of -magnetization the greater the tendency to depolarization. - -It is also defined as the maximum intensity of magnetism produced in a -paramagnetic substance by a magnetic field as far as affected by the -permeability of the substance in question. The more lines of force -passed through such a substance the lower is its residual permeability. -It is assumed that this becomes zero after a certain point, and then the -point of saturation is reached. After this point is reached the addition -of any lines of force is referred entirely to the field and not at all -to the permeability of the substance. But such a zero is only definable -approximately. - - -Magnetic Screen. -A box or case of soft iron, as thick as practicable, for protecting -bodies within it from the action of a magnetic field. The lines of force -to a great extent keep within the metal of the box on account of its -permeability, and but a comparatively few of them cross the space within -it. - -Such screens are used to prevent watches from being magnetized, and are -a part of Sir William Thomson's Marine galvanometer. - -A magnetic screen may be a sphere, an infinite or very large plane, or -of the shape of any equipotential surface. - -Synonym--Magnetic Shield. - - -352 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Self-induction. -The cause of a magnet weakening is on account of this quality, which is -due to the direction of the lines of force within a magnet from the -positive towards the negative pole. "A magnet thus tends to repel its -own magnetism and to weaken itself by self-induction." (Daniell.) - - -Magnetic Separator. -An apparatus for separating magnetic substances from mixtures. Such -separators depend on the action of electro-magnets. In one form the -material falls upon an iron drum, magnetized by coils. Any magnetic -substance adheres to the drum and is thereby separated. They are used by -porcelain makers for withdrawing iron particles from clay, by machinists -to separate iron filings and chips from brass, and for similar purposes. - - -Fig. 224. MAGNETIC SEPARATOR. - - -Magnetic Shell. -A theoretical conception of a cause of a magnetic field or of a -distribution of magnetism. If we imagine a quantity of very short -magnets arranged in contact with their like poles all pointing in the -same direction so as to make a metal sheet, we have a magnetic shell. -Its magnetic moment is equal to the sum of the magnetic moment of all -its parts. If the shell is of uniform strength the magnetic moment of a -unit area gives the strength of the shell; it is equal to the magnetic -quantity per unit of area, multiplied by the thickness of the shell. - -If its strength is uniform throughout a magnetic shell is called simple; -if its strength varies it is termed complex. - -Emtage thus defines it: A magnetic shell is an indefinitely thin sheet -magnetized everywhere in the direction normal to itself. - - -Magnetic Shell, Strength of. -The magnetic quantity per unit of area of the shell multiplied by the -thickness of the shell. - - -353 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Shield. -In general a magnetic screen, q. v. Sometimes a strong local field is -made to act as a shield, by its predominance overcoming any local or -terrestrial field to which the needle to be protected may be exposed. - - -Magnetic Shunt. -The conception of a magnetic circuit being formed, the shunt is a -corollary of the theory. It is any piece of iron which connects points -of a magnet differing in polarity, so as to divert part of the lines of -force from the armature or yoke. The shunt is especially applicable in -the case of horseshoe magnets. Thus a bar of iron placed across from -limb to limb a short distance back from the poles would act as a shunt -to the armature and would divert to itself part of the lines of force -which would otherwise go through the armature and would weaken the -attraction of the magnet for the latter. In dynamos a bar of iron used -as a magnetic shunt has been used to diminish the lines of force going -through the armature and hence to weaken the field and diminish the -electro-motive force. By moving the shunt nearer or further from the -poles the dynamo is regulated. - -In the cut the projections between the yoke and poles of the magnet -shown act as a shunt to the yoke, taking some lines of force therefrom. - - -Fig. 225. MAGNETIC SHUNT. - - -Magnetic Storms. -Terrestrial magnetic disturbances sometimes covering very wide areas, -and affecting the magnetic declination and inclination. One such -disturbance was felt simultaneously at Toronto, Canada, the Cape of Good -Hope, Prague and Van Diemen's Land. (Sabine.) - - -354 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Strain. -The strain produced by magnetic lines of force in substances exposed to -their action. It is observed in substances placed between the poles of a -strong electro-magnet, and evinces itself in the alteration of the -optical properties of transparent substances. - - -Magnetic Stress. -The stress produced by magnetic lines of force on substances through -which they pass, evidenced in alteration of the optical properties of -transparent bodies thus treated. - - -Magnetic Susceptibility. -The specific intrinsic susceptibility of any material for magnetic -induction. It refers to the particle of matter, and not to the mass, as -in the latter its own particles react on each other and bring about what -is termed permeability, q. v. (See also Magnetization, Coefficient of -Induced, and Magnetic Induction, Coefficient of.) - -Synonym--Coefficient of Induced Magnetization. - - -Magnetic Tick. -When a bar of iron is suddenly magnetized or demagnetized it emits a -slight sound, called the Page sound, or the magnetic tick. This has been -utilized in a telephone by Reiss. The telephone will receive sound, but -is very weak. It consists of a bar surrounded with a coil of insulated -wire. Variations in current produce sounds, which may be articulate if -the currents are produced by a telephonic transmitter. - - -Magnetic Twist. -A bar of iron held in the magnetic meridian and pointing to the pole and -twisted becomes to some extent permanently magnetized. Conversely a bar -when magnetized seems to have a twist set up in it. The latter is -magnetic twist. - - -Magnetic Variations. -Changes in the value of magnetic declination or inclination. (See -Magnetic Elements.) - - -Magnetism, Ampére's Theory of. -A theory accounting for magnetic phenomena by assuming the existence of -currents circulating around the molecules of permanent magnets. If such -currents so circulate and all in the same direction, the result is the -same as if the body of the magnet was enveloped in currents representing -those of an electro-magnet or solenoid. This is because in the interior -the current around one molecule would counteract the current around its -neighboring ones in part, so that the only virtual currents left would -be represented by those on the outer surfaces of the outer shell of -molecules, and these virtually resolve themselves into one general -current sheet, surrounding the magnet and coinciding with its surface. - -The theory assumes that such currents permanently circulate around the -molecules of paramagnetic substances. Under ordinary conditions there is -no coincidence in their direction and no resultant current is produced. -When magnetized or polarized the molecules are brought into order, so -that the direction of their current coincides and the body becomes a -magnet. - - -355 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 226. AMPÉRIAN CURRENTS IN MAGNETS. - - -At the north pole of the magnet the direction of the Ampérian currents -is the reverse of that of a watch when the observer faces the pole; the -reverse obtains for the south pole. - -The attraction of opposite and repulsion of similar poles is explained -by the actions of the Ampérian currents upon each other. If north and -south pole are placed together these currents will coincide in direction -and hence will attract each other. If two like poles are put together -the currents will have opposite directions and will repel each other. - -No energy is supposed to be required to maintain currents around or in a -single molecule. - - -Fig. 227. NORTH AND SOUTH POLES OF A MAGNET SHOWING DIRECTION OF -AMPÉRIAN CURRENTS. - - -Magnetism, Blue. -A term arising from the two fluid theory of magnetism; the magnetism of -the south pole of a magnet. (See Magnetic Fluids.) The magnetism of the -north pole is termed red magnetism. Both terms originated presumably in -the painting of magnets, and are little used. - -Synonym--South Magnetic Fluid. - - -356 STANDARD ELECTRICAL DICTIONARY. - - -Magnetism, Components of Earth's. -The magnetic force of the earth acts in the plane of the magnetic -meridian and in direction generally lies oblique to the plane of the -horizon. It can be resolved into two components, one vertical, which has -no directive effect upon the magnetic needle, the other horizontal, -which represents the directive element for the usual compass needle. For -the dipping needle, q. v., the vertical component is the only active -one. A magnetic needle mounted on a universal joint at its centre of -gravity would be acted on by both components. - - -Magnetism, Creeping of. -The gradual increase of magnetism when a magnetic force is applied with -absolute steadiness to a piece of iron. It is a form of magnetic lag. It -may last for half an hour and involve an increase of several per cent. -of the total magnetism. - -Synonym--Viscous Hysteresis. - - -Magnet, Iron Clad. -A magnet with a casing of iron connected at one end to the core. The -term is generally applied to electromagnets of this form. - -Synonyms--Tubular Magnet--Jacketed Magnet. - - -Magnetism, Decay of. -The gradual loss of magnetism by permanent magnets, due to accidental -shocks, changes of temperature, slow spontaneous annealing of the iron -and other similar causes. - - -Magnetism, Discharge of. -The loosing of magnetization. Thus in a shunt-wound dynamo there is a -critical resistance for the outer circuit, below which the field ceases -to be magnetized, as enough current ceases to be shunted into it to -magnetize it. The machine is said to unbuild itself, and a discharge of -magnetism occurs from the field magnet. - - -Magnetism, Ewing's Theory of. -Ewing found by a model consisting of a number of pivoted magnetic -needles that the observed phenomena of magnetization could be -represented thereby. Thus there would be no need of assuming internal -frictional forces of Maxwell, nor the closed rings or chains of Hughes. -The theory retains the notion, however, of paramagnetic matter, -consisting of an assemblage of molecular magnets. The loss of energy by -hysteresis is represented in the model by the energy lost by the needles -in beating against the air. - - -357 STANDARD ELECTRICAL DICTIONARY. - - -Magnetism, Free. -The magnetism or magnetic field outside of a magnetic circuit. It is due -to escape of lines of force and to the magnetic leakage through the air. -The lines of force are never, under the most favorable circumstances, -confined to the metallic circuit of the magnet and armature. In a simple -magnet without armature all the lines of force have to follow an air -path, and the field is at its strongest. As the magnetism is strongest -at the surface near the poles, the term is sometimes understood as -applying to the surface attraction. In such case it is defined as the -distribution, on a magnetized bar or mass, of magnetic lines of force as -they emerge from its surface. - -Synonym--Surface Magnetization. - - -Magnetism, Hughes' Theory of. -A theory accounting for magnetic phenomena by assuming that each -molecule is a magnet, and that in a polarized or magnetized body they -are all arranged with their poles in the same direction, while in an -unmagnetized body their poles, alternating in direction, neutralize each -other. - -Magnetization consists in a partial rotation of the molecules so as to -make them agree in position, thus, as a resultant developing north and -south poles at the ends of the bar. - -The theory is in a certain sense simpler than Ampere's theory, but is -not so generally adopted. - - -Magnetism, Lamellar Distribution of. -The distribution of magnetism in thin and uniform or "simple magnetic -shells," q. v. A given distribution is termed lamellar if the substance -in which it exists can be divided into simple magnetic shells, which -either form closed surfaces, or have their edges in the surface of the -substance. In lamellar distribution the polar area is very large -compared with the distance between opposite poles. - - -Magnetism of Gases. -Faraday experimented on this point by coloring gases with a little vapor -of iodine or other colored gas, and letting them flow between the two -poles of a powerful electromagnet. In this way he found some are -repelled, some attracted, and in the case of oxygen, it is attracted at -one temperature and repelled at another. At ordinary temperatures a -cubic yard of oxygen possesses the magnetism of 5.5 grains of iron and -when liquefied it is strongly attracted. - - -Magnetism or Magnetization, Temporary. -When a mass of iron is magnetized by a current, when the current ceases -the portion of its magnetism which disappears is the temporary -magnetism; the portion retained is the residual or permanent magnetism. - - -Magnetism, Red. -A term arising from the two fluid theory of magnetism; the magnetism of -the north pole of a magnet. (See Magnetic Fluids.) The magnetism of the -south pole is termed blue magnetism. Both terms originated in the -painting of magnets. They are but little used. - -Synonym--North Magnetic Fluid. - - -358 STANDARD ELECTRICAL DICTIONARY. - - -Magnetic Remanence. -The residual magnetism left in a bar of steel or other paramagnetic -material after the application of a powerful magnet. It is distinguished -from coercive force, as the latter is the amount of negative magnetizing -or of demagnetizing force required to reduce the remanent magnetism to -zero. - -Synonym--Remanence--Residual Magnetism. - - -Magnetism, Solenoidal Distribution of. -The distribution of magnetism in such a way that the poles are very far -apart in proportion to their area. The magnetization of a long thin bar -of steel illustrates solenoidal distribution. - - -Magnetism Sub-permanent. -The magnetism of a paramagnetic substance which presents a considerable -degree of permanency, but which gradually disappears, leaving the -permanent magnetism present. It is noticeable in iron or steel ships -whose magnetism gradually reduced in quantity, eventually becomes fully -permanent. - - -Magnetism, Weber's Theory of. -The molecules of a magnetizable material by this theory are supposed to -be magnets with their poles lying in every direction, and hence -neutralizing each other. By magnetization these are supposed to be -turned with their similar poles in the same direction, and their axis -parallel, hence acting like a group of magnets. It is practically -identical with Hughes' theory. - - -Magnetism, Terrestrial. -The magnetism of the earth. (See Magnetic Elements.) - - -Fig. 228. MAGNETIZATION BY DOUBLE TOUCH. - - -Magnetization by Double Touch. -The process of magnetizing a steel bar by simultaneously stroking it -with two poles of a horseshoe magnet or with two opposite poles of two -bar magnets. The poles must be close but not touching. A block of wood -may be placed between the ends if single magnets are used. The poles are -placed on the middle of the bar and carried back and forth to one end, -then to the other, and so on, ending at the middle of the bar in such -direction as to give each end the same number of strokes. The poles must -be close together or consequent poles will be produced. If bar magnets -are used they may be held inclined at an angle of 15º to 20º with the -horizontal bar to be magnetized. The ends of the latter may rest on -poles of two other magnets, each end on a pole of the same name as that -of the magnetizing magnet on its side. (See Magnetization, Hoffer's -Method.) - - -359 STANDARD ELECTRICAL DICTIONARY. - - -Magnetization by Separate Touch. -A method of magnetization. Two magnets are used. Held in an inclined -position two opposite poles are touched to the bar near its centre, and -are drawn off to the two ends. They are returned through the air and the -process is repeated. - - -Magnetization by Single Touch. -A method of polarizing or magnetizing steel bars, by stroking them -always in one direction with one pole of a magnet, returning it through -the air. The stroking is best done on both sides. The stroking may begin -at one end and end at the other, or it may be commenced in the center of -the bar and be carried to one end with one pole, and the same done for -the other half with the other pole. - - -Magnetization by the Earth. -The earth imparts magnetism to iron masses. If a rod of steel is held -parallel to the inclination and in the magnetic meridian it exhibits -polarity, which by jarring or hammering, can be made to some extent -permanent. A piece of soft iron held vertically, or still better in the -line of the dip as above, and which is twisted when in that position, -becomes magnetized with some degree of permanence. Many other instances -are cited, such as fire-irons, lamp-posts, iron gates, lathe turnings, -all of which often exhibit polarity, having been magnetized by the -earth's field. - -[Transcriber's note: The earth's magnetic field is believed to originate -it electric currents in the moving molten core.] - - -Magnetization, Coefficient of Induced. -The coefficient (q. v.) expressing the relation between the specific -intensity of magnetization of a particle and the magnetizing force. The -magnetizing force is measured by the lines of force it can produce in a -field of air. The coefficient of induced magnetization is the factor by -which the intensity of a magnetizing field must be multiplied to produce -the magnetization imparted by it to a particle of any substance. This -coefficient varies for different substances, and is also called magnetic -susceptibility. It is distinguished from permeability as referring only -to a particle isolated from influence of a mass of surrounding particles -of its own kind. It is definable as the intensity of the magnetization -assumed by an exceedingly long and exceedingly thin bar placed in a unit -field. If a mass of metal were placed in such a field all its particles -would become affected and within the mass no unit field could exist. -Hence magnetic susceptibility (another name for this coefficient) does -not apply to the case of large cores of electro-magnets and -dynamo-armatures, but is really a theoretical rather than a practical -figure. - -The sign of the coefficient of diamagnetic bodies is negative; of -paramagnetic bodies is positive. - -Synonym--Magnetic Susceptibility. \ - - -360 STANDARD ELECTRICAL DICTIONARY. - - -Magnetization, Cycle of. -A cycle of positive or of positive and negative magnetization represents -the application of a magnetizing force beginning at a fixed value, -generally zero, rising to a maximum, or to a value of maximum distance -from the initial and then returning to the original basis. It is -virtually a full wave of magnetization and may extend on both sides of a -zero line giving positive and negative values. - -Cycles of magnetization apply especially to transformers and other -apparatus of that character used with the alternating current system. - - -Magnetization, Hoffer's Method. -For horseshoe bars an armature is placed against the poles of the magnet -bar to be treated. The poles of a strong horseshoe magnet are stroked -over it from poles to bend and returned through the air, or vice versa. -In the first case the poles will be the same as those of the inducing -magnet; in the second case they will be opposite. A maximum effect is -produced in ten strokes. The stroking should be applied to both sides. -An electro-magnet may be used as inducer as shown, but an armature -should be used; in the cut it is omitted. - - -Fig. 229. MAGNETIZING A HORSESHOE MAGNET. - - -Magnetization, Intensity of. -The amount of magnetism induced in or present in a body. It is expressed -in Magnetic Lines of Force, q. v., per cross-sectional area. - - -Magnetization, Isthmus Method of. -A method used by Ewing in a research on the magnetization of iron in -very strong fields. He used samples of iron turned down in the centre to -a narrow neck, and thus concentrated the lines of force greatly. - - -Magnetization, Elias' Method. -The bar to be magnetized is surrounded by a magnetizing coil, q. v. A -strong current is passed through it, and the coil is moved back and -forth a few times. - - -Magnetization, Jacobi's Method. -For horseshoe bars. The bar is placed with its poles against those of a -horseshoe magnet. A bar of soft iron, long enough to reach from outside -to outside of the legs, is laid across near the junction and is drawn -along towards the bend of the new bar and away from it. This is repeated -a few times on both sides. - - -361 STANDARD ELECTRICAL DICTIONARY. - - -Magnetization, Limit of. -As the induction of magnetizing force increases, magnetization of -paramagnetic metals tends towards a limit, the increase in magnetization -being continually less and less as the metal becomes more highly -magnetized. In diamagnetic substances no limit is discernible. - -Synonym--Maximum Magnetization. - - -Magnetization, Specific. -The magnetic moment per gram of a substance. - - -Magnet-keeper. -A bar of iron connecting the two poles of a permanent magnet. Often the -same bar serves as armature and keeper. - - -Magnet, Lamination of. -It is advantageous to make magnets of laminated construction, or of thin -plates of steel. The thin metal can be better tempered or hardened than -thick metal. A slight separation of the plates is advantageous from some -points of view. If in actual contact there is some danger that the -weaker members will have their polarity reversed by the stronger ones. -This is counteracted to some extent by separation. - - -Magnet, Long Coil. -A high resistance electro-magnet; one whose coil is of thin wire of -considerable length. - - -Magnet, Natural. -The lodestone, q. v.; a variety of magnetite or magnetic oxide of iron, -exhibiting permanent magnetism, attracting iron, and possessing north -and south poles. - - -Magnet, Neutral Line of. -A line at right angles to the magnetic axis of a magnet, q.v., and -nearly or quite at the centre, so situated with reference to the poles -on either end that it marks the locus of no polarity. It has been called -the equator of the magnet. It is defined by the intersection of the -plane of no magnetism with the surface of the bar. - -Synonym--Magnetic Equator. - - -Magnet, Normal. -A bar or compound bar magnet, magnetized to such an extent that the -curves of the lines of force run into each other in the middle, is thus -termed by Jamin. - - -Magneto. -Abbreviation for Magneto-electric Generator. (See Magneto-electric -Generator.) - - -Magneto Call Bell. -A call operated by current from a magneto-electric generator. It is very -generally used in telephone systems. - - -362 STANDARD ELECTRICAL DICTIONARY. - - -Magneto-electric. adj. -Relating to induced electric effects due to the cutting of true magnetic -lines of force by, or equivalent action of or upon a conductor. These -effects are identical with electro-magnetic effects and are only -distinguished from them by the field being due to a permanent magnet -instead of an electromagnet. - - -Magneto-electric Brake. -A device for bringing to rest an oscillating galvanometer needle. It -consists essentially of a coil in circuit with a key and with the -galvanometer. On opening the circuit an inverse current is established -by induction, tending to bring the needle to rest. - - -Magneto-electric Generator. -A current generator operating by maintaining a potential difference at -its terminals, by reactions in a field of force, which field is -established by a permanent magnet. - -The cut, Fig. 230, shows the general principle of construction of a -direct current generator. The armature is rotated between the poles of a -permanent magnet. Any of the regular types of dynamo armature can be -used. From its commutator the current is taken by brushes. - - -Fig. 230. MAGNETO-ELECTRIC GENERATOR. - - -Fig. 231. MAGNETO-ELECTRIC GENERATOR. - - -363 STANDARD ELECTRICAL DICTIONARY. - - -The cut, Fig. 231, shows an alternating current machine. In it a pair of -bobbins, wound in series, and both either right-handed or left-handed, -are rotated between permanent magnet poles. The current may be taken off -by two brushes bearing on two collecting rings on the axis of the -bobbins, the ends of the wire being connected thereto. Or if a shocking -current is desired, one of the brushes or springs may strike a series of -pins forming virtually a broken or interrupted collecting ring. This -gives a current for medical purposes. - -Synonyms--Magneto-dynamo--Magneto-electric Machine. - - -Magnetograph. -An apparatus for recording variations in magnetic elements. One type -includes a magnetic needle to which a concave mirror is attached. The -light ray from the mirror is reflected upon sensitized paper where its -movements are photographically reproduced. The movements of the spot are -due to the movements of the needle and act as the record of the same. - - -Magneto-Inductor. -An instrument for use with a ballistic galvanometer to reproduce a -definite current impulse. Two magnets are fastened together in one -straight line, the north poles almost touching. This is mounted at the -end of a rod like a pendulum, the axis of the magnets transverse to the -rod. The magnets are carried by a frame and oscillate at the end of the -rod, back and forth within a fixed coil, which is one-half the length -of the double magnet. A bob is attached to the bottom of the frame by -which the whole can be swung. As the magnets are of fixed value, their -time of oscillation constant, and the coil fixed in size, the apparatus -provides a means of getting a definite instantaneous current of -identical value whenever needed. - - -Fig. 232. MAGNETO-INDUCTOR. - - -364 STANDARD ELECTRICAL DICTIONARY. - - -Magnetometer. -(a) A reflecting galvanometer, with heavy magnetic needle, dampened by a -copper frame. It was devised by Weber. - -(b) An apparatus for measuring the intensity of magnetic force. It may -consist of a magnet suspended by bifilar or by torsion suspension. A -reflecting mirror and scale as in the reflecting galvanometer may be -used to act as indicator of its motions. It is used in investigations of -the intensity of the earth's field. - -If the motions of the spot of light are received on a moving strip of -sensitized paper and are thereby reproduced photographically, the -instrument is self-recording. Such an apparatus is used in the Kew -Observatory, Eng., for recording the terrestrial magnetic elements. - - -Magnetometry. -The determination of the magnetic moment of a magnet. - -It involves the determination by experiment of--( a) the product of the -magnetic moment, M, of the magnet by the horizontal component, H, of the -earth's magnetism; (b) the quotient of M divided by H. Knowing these two -quantities, M is given by the formula M = SquareRoot( )M * H) * (M/H) ) -and if desired H is given by the formula H = SquareRoot( (M*H) / (M/H)). - -M*H is determined by the method of vibrations. A very long, thin magnet -suspended by a torsion filament is caused to oscillate, and its period -is determined. Calling such period T and the moment of inertia of the -magnet I, we have the formula T= 2* PI * SquareRoot( I / (H*M) ) (a), -whence H*M is calculated, I of course being known or separately -determined. - - -Fig. 233 END-ON METHOD. - - -Fig. 234. BROADSIDE METHOD. - - -M/H is determined by the End-on deflection method, or the Broadside -deflection method. In both cases the deflection of a compass needle by -the magnet in question is the basis of the work. - -In the end-on method AB is the magnet under examination; DE the compass -needle; a the angle of deflection; d the distance between C and the -middle of AB, which should be considerable compared with the length of -DE; 2l, the length of AB. We then have the formula - tan a = (M/H) * (2d / (d^2 - l^2)^2), -which if 2l is small compared to d reduces to - tan a = M/Hd 3 - -(b), which gives M/H, a and d being known. - - -365 STANDARD ELECTRICAL DICTIONARY. - -In the broadside method the line d is the magnetic meridian, and the -diagram shows the relative positions. We then have the formula - tan a = (M/H) / (d2 + l2)^1.5; -which if 1 is relatively small reduces to - tan a = M/(H * d3 )(C.) - -[Transcriber's note: The image of the above paragraphs is included here.] - -a and c or a and b can be combined giving M and H in C.G.S. measurement. - - -Magnetometer, Differential. -An apparatus, invented by Eickemeyer, for testing the magnetic qualities -of different samples of iron. It is very similar in construction and -principle to the magnetic bridge, q. v. - - -Magneto-motive Force. -The force producing a magnetic field or forcing lines of force around a -magnetic circuit. It is usually applied only to electro-magnets and is -expressible in turns of the wire winding multiplied by amperes of -current, or in ampere-turns. - - -Magnet Operation. -A term in surgery; the use of the electro-magnet or permanent magnet for -removing particles of iron from the eye. - - -Magnetoscope. -An apparatus for detecting the presence of magnetism, without measuring -its intensity. A simple magneto-scope consists of a magnetized bit of -watch-spring suspended in a vertical glass tube by a fine filament. A -bit of unmagnetized soft iron wire may be used in the same way. The -first has the advantage of indicating polarity; the latter merely shows -magnetic attraction. A cork may be used as base of the instrument. - - -Fig. 235. MAGNETOSCOPE. - - -366 STANDARD ELECTRICAL DICTIONARY. - - -Magnet, Permanent. -A bar of steel charged with residual magnetism. Steel possesses high -coercive force in virtue of which when once magnetized it retains part -of the magnetization. - -Permanent magnets are generally straight bars or U shaped; they are -termed bar magnets, magnetic needles, horseshoe magnets, machine magnets -and otherwise, according to their shape or uses. - - -Magnet Pole. -The part of a magnet showing strongest polarity; the part which attracts -iron the most powerfully, and acts as the starting point for lines of -force. - - -Magnet Poles, Secondary. -Magnet poles are often not situated at the ends. Owing to inequality of -the material or other causes they may occupy intermediate positions on -the magnet. Such poles are called secondary poles. - - -Magnet Pole, Unit. -A unit magnet pole is one which exerts unit force on another unit pole -placed at unit distance from it. Unit force is the dyne; unit distance -is one centimeter. - - -Magnet, Portative Power of. -The power of sustaining a weight by attraction of its armature possessed -by a magnet. In general terms the adherence of the armature of a magnet -to the pole varies with the square of the number of lines of force which -pass through the point of contact. Hence an increased adherence of the -armature to a horseshoe electro-magnet is sometimes obtained by -diminishing the area of contact of one pole which concentrates the lines -of force. Steel magnets were frequently made with rounded ends to -increase the portative power. - - -Magnet, Simple. -A magnet made of one piece of metal, or at least magnetized as such; the -reverse of a compound magnet, which is magnetized piece by piece and -then fastened together. - - -Magnet, Solenoidal. -A magnet which is so uniformly magnetized and is so long in proportion -to its other dimensions that it virtually establishes two magnetic -poles, one at either end. It is a long thin bar so magnetized that all -its molecules would, considered as magnets, be absolutely equal. -(Daniell.) It acts like a solenoid, except that it is longer in -proportion than the solenoid generally is constructed. - - -Magnet, Sucking. -A magnet coil with movable or loose axial bar of soft iron. - -The whole is usually mounted vertically. When a strong enough current is -passed the bar is drawn up into the coil as if by suction, whence the -name. - - -367 STANDARD ELECTRICAL DICTIONARY. - - -Magnet, Unipolar. -No such thing as a unipolar magnet is possible. The name is given to -poised or suspended magnets, one of whose poles lies in the axis of -suspension. It is obvious that such a magnet will act, as far as its -directive tendency and rotatory movements are concerned, as if it had -only one pole. As shown in the cut, the pole s in both magnets lies in -the axis of suspension or directly under the filament by which they are -suspended, while the other pole n is the active pole in causing rotation -or directive tendency; c c are counterweights or counterpoises. - - -Fig. 236. UNIPOLAR MAGNETS. - - -Magnetophone. -An apparatus for producing a loud sound, involving the principles of the -telephone. A rapidly alternating or make and break current being -produced by any means and being transmitted through the telephone gives -a loud note of pitch dependent on the current producing it. Sometimes a -perforated metallic disc is rotated in a magnetic field, and produces -the requisite type of current. - - -Magnus' Law. -A law of thermo-electricity. In a homogeneous circuit, however, the -temperature varies from point to point; there is no current. - -Whatever potential differences may be established by the variations in -temperature it is evident that they must counteract each other and -reduce to zero. - - -Mains, Electric. -The larger conductors in a system of electric light or power -distribution. - - -Make. v. -To complete a circuit, as by closing a switch. - - -Make and Break Current. -A current which is continually broken or interrupted and started again. -It is applied only where the "makes" and "breaks" succeed each other -with great rapidity, as in the action of an induction coil or pole -changer, etc. It has had considerable importance in litigation affecting -the Bell telephone patents, the courts holding that the original Bell -patent (No. 174,465, of 1876,) covered the undulating current, for the -transmission of speech. Many efforts have been made by litigants to -prove that specific telephones have transmitted articulate speech by the -make and break current, but without success. If this could have been -proved the assumption is that the courts would have sustained the use of -such device as not infringing upon the claims of the Bell patent. - - -Malapterurus. -A fish, sometimes called the thunder fish, an inhabitant of African -rivers, occurring in the Nile and Senegal. It possesses considerable -electric power, similar to that of the gymnotus and torpedo, although -inferior in amount. - - -368 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 237. MALAPTERURUS. - - -Man-hole. -The cistern-like depression in the ground for giving access to the ends -of tubes in electric conduits. (See Conduit, Electric Subway.) - - -Marked End or Pole. -The north pole or north seeking pole of a magnet, so called because it -is usually marked with a notch or scratch by the maker. The south pole -is called the unmarked end. - - -Mass. -The quantity of matter in a body. The C. G. S. unit of mass is the -quantity of matter in a gram. While weight varies with latitude and -other circumstances, mass is invariable. - -The unit of mass is also defined as the quantity of matter which in a -balance will counterpoise a standard mass, the gram or pound. As the -gram is intended to be the mass of one cubic centimeter of water at -3.09º C. (39º F.), the C. G. S. unit of mass is really 1.000013 gram. - -As a primary unit its dimensions are indicated by M. - - -Mass, Electric. -A term for quantity of electricity. The unit mass is such a quantity as -at unit distance will act with unit force. - - -Matter, Electric. -The imaginary substance constituting electricity; a conception used -purely as a matter of convenience. - -[Transcriber's note: The electron was discovered five years after this -publication.] - - -Matter, Radiant. -Matter in the ultra-gaseous or so-called fourth state. In the gaseous -state the molecules of a gas are in perpetual kinetic motion, colliding -actually or virtually with each other, rebounding from such approach, -and striking also the walls of the containing vessel. But except for -these deflections, which are of enormous frequency, the paths of the -molecules would be perfectly straight. - -In the radiant state matter exists in so high a vacuum that collisions -of the molecules rarely occur, and the molecules simply beat back and -forth in straight lines from side to side of the containing vessel. - -A layer of gas in this condition is termed a Crookes' layer, from Prof. -William Crookes, who discovered and investigated these phenomena. - - -369 STANDARD ELECTRICAL DICTIONARY. - - -Luminous streams of the molecules are produced by electric high -potential discharges between electrodes. The course of the discharge is -normal, in general terms, to the surfaces of the electrodes, and reaches -from one to the other in a curve or straight line, as the case may be. - -These luminous streams are deflected by a magnetic field; if brought to -a focus can heat refractory material in that focus to a full white heat, -and can develop phosphorescence. The latter is termed electric -phosphorescence. A great variety of experiments have been devised to -illustrate the phenomena of radiant matter. The vacuum is generally -produced in a hermetically sealed glass vessel into which the electrodes -are sealed, and which contain the phosphorescent substances or other -essentials for the experiments. The vessels are termed Crookes' Tubes. - -[Transcriber's note: Crookes reported on "radiant matter" in 1879. It is -actually electrons, but he failed to distinguish them from ordinary -atoms. Thompson properly described electrons in 1897.] - - -Matteueci's Experiment. -An experiment for showing the inductive effect of the discharge of a -Leyden jar. Two glass plates are supported on standards in a vertical -position. Flat coils of wire are wound or coiled and secured to one -surface of each plate. One plate has much finer and longer wire than the -other. Metal handles are connected to the ends of the coarser wire coil. -The plates are placed with their coils facing each other. A Leyden jar -is discharged through the coarser coil, while the handles are grasped by -a person. The shock of the discharge is felt by him. - - -Matting, Electric Floor. -Matting or floor covering underlaid with burglar alarm contacts, so -arranged as to be closed by anyone walking on the matting. The contacts -are connected to a burglar alarm system. The object is to provide an -alarm if a burglar enters a house, in case he should enter a door or -window without sounding the bell. The latter can be done by cutting out -the window or part of the door instead of opening it. - - -Maxwell's Theory of Light. -A theory of light. It is due to J. Clerk Maxwell. - -It supposes the phenomena of electric induction to be due to the ether, -q. v. It supposes the condition of the ether when conveying light to be -the same as if exposed to the induction of rapidly alternating currents -or discharges (in this case synonymous). It therefore is an -electro-magnetic effect if the theory is correct. - -An electric stress such as one due to the induction of an -electrostatically charged body is not a wave-creating element or factor, -but is a simple stress. But let this stress be stopped and renewed and -at once it appears as a wave-forming agency. - -This stoppage and renewal represents evidently a discharge succeeded by -a charge, or if repeated is equivalent to an intermittent current or an -alternating one. - - -370 STANDARD ELECTRICAL DICTIONARY. - - -Again the electrostatic stress kept constant may by being carried -through space carry with it a wave, just as a moving projectile carries -a wave of air in advance of itself. - -Admitting this much the following consequences follow: - -Since in non-conductors the displacement produces a restitution force, -which varies as the displacement which is requisite or is a criterion -for the propagation of waves, while in conductors no such force is -manifested and the electric energy appears as heat, it follows that -light vibrations are not possible in conductors, because -electro-magnetic waves do not exist in them when they are in circuit, -and conductors should be opaque, while the reverse is true for -non-conductors. (Daniell.) - -This is carried out often enough to make a striking evidence in favor of -Maxwell's theory. - -The velocity of propagation of an electro-magnetic disturbance in a -non-conductor should be equal to that of light. This constant is proved -by mathematical considerations, to be approximately the same as the -ratio of the electrostatic to the electromagnetic unit of intensity or -quantity. This ratio is 3E10 (30,000,000,000), which is almost exactly -the velocity of light. - -It also follows from what has been said that if an electrostatically -charged body were whirled around a galvanometer needle at the rate of -3E10 revolutions per second it should affect it like a circulating -current. This rate of rotation cannot be attained, but Rowland has made -manifest the effect of a rotating statically charged body upon a -magnetic needle. - -The above is the merest outline of Maxwell's theory. The full -development must be studied in his own and succeeding works. - - -Mayer's Floating Magnets. -An experiment due to Prof. Mayer. A number of sewing needles are -magnetized and thrust into bits of cork, almost all the way through, -with their like poles projecting. They are floated in a basin of water -and take, under the effects of attraction and repulsion, when approached -by a magnet pole, regular geometric positions, marking out the positions -of angles of polygons. - - -Measurements. -The determination of the value of quantities; determination of the -factor by which the unitary value must be multiplied to produce the -quantity under examination. Such are the measurement of the voltage of a -galvanic battery, or of the ohms of resistance of a conductor. -Electricity has been termed the science of measurement. - - -Meg or Mega. -A prefix, meaning one million times. A megohm is one million ohms; a -megerg is one million ergs; a megadyne is one million dynes. - - -371 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 238. MAYER'S FLOATING MAGNETS. - - -Mercury. -A metal; one of the elements; symbol, Hg; atomic weight, 200 ; -equivalent, 200 or 100; valency, 1 and 2. -It is a conductor of electricity. -The following data are 0º C. (32º F.) - Relative Resistance, 62.73 - Specific Resistance, 94.32 microhms. - Resistance of a wire, - (a) 1 foot long, weighing 1 grain, 18.51 ohms. - (b) 1 foot long, 1/1000 inch thick, 572.3 " - (c) 1 meter long, weighing 1 gram, 12.91 " - (d) I meter long, 1 millimeter thick 1.211 " - Resistance of a 1 inch cube, 37.15 microhms. - Percentage increase of resistance per degree C. 1.8° F. - at about 20° C. (68° F.), .72 per cent. - Electro-chemical equivalent (Hydrogen = .0105), 2.10 mgs. - 1.05 " - -372 STANDARD ELECTRICAL DICTIONARY. - - -Mercury Cup. -A cup of iron, wood or some material that does not amalgamate or is -unattacked by mercury, which is filled with mercury and made an -electrode of a circuit. By dipping the other terminal of the circuit -into the mercury a very good contact is obtained. It is well to cover -the mercury with alcohol. The cup may be filled so that the mercury -rises in a meniscus or semi-globule above its edges. - -For some purposes this form is useful, as for contacts with the end of a -swinging wire or pendulum, because in such cases the contact can be made -without the contact point entering the cup. The point swings through the -projecting meniscus without touching the edges of the cup. A mercury cup -and contact constitute a mercury break. - - -Meridian, Astronomical. -The great circle passing through the north and south poles of the -celestial sphere. It lies in a plane with the corresponding geographical -or terrestrial meridian. - - -Meridian, Geographic. -The true north and south meridian; the approximate great circle formed -by the intersection of a plane passing through north and south poles of -the earth with the earth's surface. - - -373 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 239. SCHALLENBERG'S ALTERNATING CURRENT METER. - - -Meter, Alternating Current. -A meter for measuring alternating current, as supplied to consumers, -from an alternating current system. Like most commercial meters its only -function is the measurement of quantity; the potential difference is -maintained at a constant figure by the generating plant. - -The cut shows the Schallenberg meter. It is simply an alternating -current motor (see Motor, Alternating Current), with air vanes mounted -on its spindle. A main coil passes all the current. Within this is a -second coil complete in itself, and not touching or connecting with the -other. The latter is built up of copper rings. Within the two coils, and -concentric with both is a disc of copper carried by a vertical spindle. -The same spindle carries air vanes, and is free to rotate. As it does so -it moves the indicating machinery. - -The current in the outer coil induces one in the inner coil. Owing to -lag, the current in the inner one differs in phase from that in the -outer one, and a rotatory field is produced. The copper disc acquires -induced polarity, and rotates with speed which normally would be in -proportion to the square of the current. But the object of the meter is -to register the current only. The air vanes effect this. The resistance -of the air to their motion causes the rate of rotation to vary directly -as the speed. - - -Meter Bridge. -A form of Wheatstone's bridge in which one lateral pair of arms is -represented by a straight wire. The other pair comprise a known -resistance, and the resistance to be determined. The galvanometer is -connected on one side between the known and unknown resistance. On the -other side its connection is moved back and forth along the straight -wire until the balance is secured and the galvanometer reads zero. - -The relative lengths of wire intercepted between the two ends thereof -and the movable galvanometer connection are proportional to the -resistance of these parts and give the necessary data with the one known -resistance for determining the unknown resistance. - - -374 STANDARD ELECTRICAL DICTIONARY. - - -In the original meter bridge the wire was one meter long, whence its -name, and was stretched straight. In more recent examples the wire -varies in length and in one form is bent into a circle or spiral, so as -to make the instrument more compact. - -The contact is not a sliding one, but is adjusted by trial. The contact -piece is slid along, but not touching the wire, and from time to time is -pressed down against the wire. This prevents wear of the wire. The wire -may be made of platinum or of platinum-iridium alloy. The latter is -very hard and not easily worn out. - -Sometimes, as shown in the cut, three parallel wires are stretched along -the baseboard of the instrument, and arranged so that a single wire, two -wires or three wires in series can be used for the proportional sides of -the bridge, thus making it a two-meter or three-meter bridge as desired. -On the other hand some are made of restricted length, as a half or -quarter meter only. - - -Fig. 240. METER BRIDGE. - - -In the cut J K is the wire, traversed by the contact key. By moving the -contact C back and forth in the slot it can be brought over any of the -three divisions of the wire. H is the handle for depressing the key. S -is a flat spring, carrying the contact piece and holding it up from the -wires, except when pressed downwards. As shown in the cut, it is in use -for calibrating a voltmeter V, by Poggendorff's method, G being the -galvanometer and r1 and r2 being resistances. - -Synonyms--Slide Bridge--Slide Balance. - - -Meter Candle. -A unit of illuminating power; the light given by one standard candle at -a distance of one meter. The ordinary units of illuminating power are -altogether relative; this one is definite. - - -375 STANDARD ELECTRICAL DICTIONARY. - - -Meter, Chemical Electric. -A current meter in which the current is determined by the amount of -chemical decomposition which it can effect. In the Edison meter the -solution is one of zinc sulphate. Two electrodes of zinc are immersed in -it, and a fractional part of the current is passed through it. The gain -in weight of one electrode and the loss in the other are proportional to -the current. Both electrodes are weighed periodically, one acting as -check upon the other. - - -Meter, Current. -An instrument for measuring the quantity of electricity in current form -supplied to consumers. It may be of various types. The general principle -involved is that in commercial installations for incandescent light and -power supply a fixed potential is usually maintained, the multiple arc -system being employed. Hence all that is requisite is to measure the -coulombs or the ampere-hours to know what quantity of energy has been -supplied. - - -Meter, Electro-magnetic. -A current meter in which the current is measured by its electro-magnetic -effects. - - -Meter-millimeter. -A unit of resistance. (See Resistance, Meter-millimeter.) - - -Meter, Thermal Electric. -A current meter in which the current is measured by the heat it imparts -to a conductor. In one meter a very light helix of mica is poised -horizontally over a conductor, and the whole is enclosed in a case. As -the wire is heated it causes an ascending current of air which rotates -the vane, and the latter moves delicate clockwork which moves indicating -hands. The hotter the wire the more rapidly the air ascends, and -consequently the speed of the vane is proportional to the current, -because the heat of the conductor is proportional thereto. - - -Meter, Time Electric. -An electric meter which measures the length of time during which current -is used. It assumes a constant current and potential. It is virtually a -clock, which is turned on when the current passes, and is turned off -with the current. - - -Meter, Watt. -A combined current and potential meter. It is constructed on the general -lines of a Siemens' Electro Dynamometer. If in it one coil is made of -coarse wire and is placed in series with the current conductor, and if -the other is wound with fine wire and is connected as a shunt from point -to point whose potential difference is to be determined, the instrument -becomes a watt meter. - -Synonym--Energy Meter. - - -Methven Standard or Screen. -A standard of illuminating power. It is the light emitted by a -three-inch Argand gas flame through a rectangular aperture in a silver -plate carried by a screen. The aperture is of such size and so far -distant from the flame as to permit the passage of exactly two candles -illuminating power. - - -Fig. 241. METHVEN SCREEN - - -376 STANDARD ELECTRICAL DICTIONARY. - - -Mho. -A unit of conductance, not in very general use. It is the reciprocal of -the ohm. Thus a resistance of ten ohms is a conductance of one-tenth -mho. - - -Mica. -A natural mineral, a silicate of several oxides; muscovite. It is used -as an insulator and dielectric. Its resistance per centimeter cube after -several minutes electrification at 20º C. (68º F.) is 8.4E13 ohms -(Ayrton). Its specific inductive capacity is 5, air being taken at 1. - - -Mica, Moulded. -An insulating material, whose body is made of mica pulverized and -cemented together with heat and pressure and some suitable cement. -Shellac is often used as the cement. - - -Micro. -A prefix meaning "one-millionth of;" a micro-farad is one-millionth of a -farad. - - -Micrometer. -An instrument for measuring small distances or small differences. It -generally is based upon an accurate screw which may have a worm wheel -for head, actuated by a worm or helix with graduated head, so that -exceedingly small advances of the screw may be produced. The pitch of -the screw being known its actual advance is known. - - -Micrometer, Arc. -A micrometer for measuring the distance between voltaic arc electrodes. - - -Micron. -A unit of length. It is one-millionth of a meter or four -one-hundred-thousandths of an inch. - - -377 STANDARD ELECTRICAL DICTIONARY. - - -Microphone. -An apparatus which includes a contact of variable resistance; such -resistance can be varied in amount by slight vibrations, such as those -produced by sound waves. The apparatus in use forms part of a circuit -including a telephone and current generator. As the contact is varied -the resistance of the circuit and consequently the current intensity -changes and sounds are emitted by the telephone corresponding to such -changes. If the microphone is spoken to, the telephone will emit -corresponding sounds, reproducing the voice. - -It has been found in practice that carbon gives the best microphone -contact. One of the simplest and earliest forms is shown in the cut. A -short rod or pencil of carbon, A, such as used in batteries, is -sharpened at the ends and rests loosely in a vertical position between -two blocks of carbon, C C, in each of which a hole is drilled to receive -one of the points. The blocks are carried on a standard and base D. The -blocks are connected with two terminals x, y, of a circuit, including a -telephone and battery. There are two contacts to be disturbed. - -If delicately adjusted a fly walking over the base-board will disturb -the contacts enough to produce sounds in the telephone. These sounds are -possibly not due only to sound waves, but in part to absolute mechanical -disturbances. - -The various forms of telephone transmitter are generally microphones. - - -Fig. 242. MICROPHONE. - - -Microphone Relay. -A combined microphone and telephone. A microphone is placed close to the -diaphragm of a telephone. The slight sound waves emitted by the -telephone affect the microphone and are repeated in its circuit. The -microphone circuit includes a local battery and telephone. - - -Microtasimeter. -An apparatus for indicating minute changes in temperature or atmospheric -moisture. - - -378 STANDARD ELECTRICAL DICTIONARY. - - -A button of compressed lampblack is placed in series with a battery and -galvanometer. A strip of some substance, affected in its length either -by heat or by moisture, is held pressing against the button. A slight -change in length of the strip varies the resistance of the button and -hence affects the galvanometer. In this way exceedingly slight changes -in heat or moisture may be indicated. - -For heat indications vulcanite may be used. The heat of the hand held -near it is enough to affect the galvanometer. For moisture a slip of -gelatine is used. The moisture of a damp slip of paper two or three -inches distant is sufficient to affect the galvanometer. - -In the cut, Fig. 2, shows the general distribution of the apparatus in -circuit with a battery and galvanometer. C is the base of the apparatus, -from which the standard, B, with adjusting screw, H, rises. The strip of -vulcanite is held between I and G. Within D is the carbon button (F in -Fig. 3) pressed between G and E; A is a standard to carry the parts last -described. In Fig. I it is shown as part of a Wheatstone bridge, a, b -and c being resistance coils; l the tasimeter, and g the galvanometer. -If a balance is secured, any variation in the resistance of the -tasimeter will disturb the galvanometer. - -Synonym--Tasimeter. - - -Fig. 243. MICROTASIMETER. - - -379 STANDARD ELECTRICAL DICTIONARY. - - -Mil. -A unit of length; one-thousandth part of a lineal inch. - -It is equal to -.025399 millimeter; -.000083 foot; -.001000 inch. - - -Mil, Circular. -A unit of area; employed in designating the cross-sectional area of -wires and other circular conductors. - -It is equal to - .78540 square mil; - .000507 square millimeter; - 7.8E-7 (.00000078) square inch. - -If the diameter of a wire is given in mils, the square of its diameter -gives its cross-sectional area in circular mils. - - -Mil-foot. -A unit of resistance. (See Resistance, Mil-foot, Unit of). - - -Mil, Square. -A unit of area; one-millionth of a square inch. - -It is equal to - .000645 square millimeter; - 1.2733 circular mil; - .000001 square inch. - - -Milli. -A prefix; one-thousandth. Thus a milligram is one-thousandth of a gram; -a millimeter is one thousandth of a meter. - - -Milligram. -A unit of weight ; one-thousandth of a gram, q. v. - -It is equal to - .015432 grain; - .000032 troy ounce. - - -Millimeter. -A unit of length; one-thousandth of a meter. - -It is equal to - 39.37079 mils; - .03937 inch; - .00109 yard. - - -380 STANDARD ELECTRICAL DICTIONARY. - - -Milli-oerstedt. -A proposed but not adopted unit of current; one-thousandth of an -oerstedt. It is equal to one-thousandth of an ampere. - -[Transcriber's note: oersted: 1. CGS unit of magnetic intensity, equal -to the magnetic pole of unit strength when undergoing a force of one -dyne in a vacuum. 2. Formerly, the unit of magnetic reluctance equal to -the reluctance of a centimeter cube of vacuum between parallel -surfaces.] - - -mm. -Contraction for millimeters. - -Molar. -Referring to phenomena of mass as gravitation. Mechanics -generally treats of molar laws and phenomena. - -[Transcriber's note: Molar, or mole, often refers to a quantity of a -substance containing an Avagadro number (6.02E23) of molecules--a weight -equal to the atomic weight of the molecule. For example, a mole of -hydrogen (H2) is 2.015 grams; sodium chloride (NaCl) is 58.443 grams.] - - -Molar Attraction. -The attraction of mass for mass; gravitation. Synonyms--Mass -Attraction--Gravitation. - - -Molecular Affinity. -The attraction of molecules for each other as seen in the formation of -double salts, the combining of water of crystallization with a salt, and -in other cases; a phase of affinity belonging to chemistry, although -outside of true atomic attraction. - - -Molecular Attraction. -The attraction of molecules; physical affinity. Cohesion, the attraction -of similar molecules for each other, and adhesion, that of dissimilar -molecules, are examples. This should be distinguished from molecular -affinity, a phase of chemical force. - - -Molecular Bombardment. -When a gas contained in a vessel is brought to a sufficient state of -rarefaction the molecules cease to be subject to the laws of diffusion, -but move back and forth in straight lines from side to side of the -vessel. Their courses can be affected by electric discharge, which can -cause them to all impinge upon one of the electrodes, the positive one, -producing luminous effects. The path, if referred to the negative -electrode, tends to be normal to its surface, so that the resultant path -may be curved, as the stream of molecules go to the positive electrode. -The fanciful name of molecular bombardment is given to the phenomenon, -the luminous effect being attributed to the impinging of the molecules -against the positive electrode as they are projected from the positive. -The course of the molecules is comparable to the stream of carbon -particles from the positive to the negative electrode in an arc lamp. -(See Matter, Radiant.) - - -Molecular Chain. -The theoretical rows of molecules supposed to extend from anode to -cathode in an electrolytic cell (see Cell, Electric--Grothüss' -Hypothesis) are called molecular chains. - - -381 STANDARD ELECTRICAL DICTIONARY. - - -Molecular Rigidity. -The tendency of the molecules of a mass to retain their position in a -mass in resistance to polarizing or depolarizing force, the first being -the effect of a magnetic field. It is the theoretical cause of coercive -force, q. v., and of residual magnetism. (See Magnetism, Residual.) - - -Molecule. -The smallest particle of matter that can exist alone. It is made up of -atoms, but an atom can never exist alone, but only, with one or two -possible exceptions, combined with one or more other atoms as a -molecule. The molecules under present conditions are not in constant -contact with each other, but are perpetually vibrating through paths, in -solids probably in defined paths, in liquids and gases in perpetually -new paths. The molecules collide with each other and rebound. This -motion is the kinetic motion termed heat. At the absolute zero--minus -273.72° C. (-460.7° F.) the molecules would be in contact and quiescent. -In the gaseous state the molecules of most substances occupy the same -volume; those of a few elements occupy one-half and of others twice the -normal volume. The mean free path of the molecule of hydrogen is about -1/20,000 mm. (1/508,000 inch) (Maxwell) or twice this length (Crookes), -the collisions in hydrogen are about 17,750 millions per second; the -diameter is about 8/10,000,000 mm. (8/254,000,000 inch) ; A particle of -matter 1/4,000 mm. (1/102,000 inch) contains, it is supposed, about -40,000 molecules. The results of different authorities vary so widely as -to deprive the subject of much of its interest. A Sprengel pump, such as -used for exhausting Geissler tubes, or incandescent lamp bulbs, may -leave only one hundred-millionth (1/100,000,000,) of an atmosphere -present, giving the molecules a capability of an average free path of -vibration 33 feet long. - - -Moment. -When a force is applied so as to tend to produce rotation around a -point, the product of the force by the shortest distance from the point -of rotation to the extension of the line of the force. Such distance is -the perpendicular to the extension of the line through the point of -rotation. - - -Mordey Effect. -A phenomenon observed in dynamo armatures. At full loads the hysteresis -decreases. The effect is thus expressed by S. P. Thompson. "When an -armature core is rotated in a strong magnetic field, the magnetization -of the iron is being continually carried through a cycle, but in a -manner quite different from that in which it is carried when the -magnetizing force is periodically reversed, as in the core of a -transformer. Mordey has found the losses by hysteresis to be somewhat -smaller in the former case than in the latter." - - -Morse Receiver. -The receiving instrument formerly universally used in the Morse system. -It is now but little employed, the sounder having displaced it. Several -types were invented. - -It consists of machinery which carries a reel of paper ribbon arranged -to be fed over a roller by clockwork. A pencil, inking roller, or -embossing stylus (for the latter the roller must have a groove) is -carried by an arm with restricted range of vibration just over the paper -and roller. The armature of an electro-magnet is attached to the arm. -When the magnet is excited the armature is attracted and the marking -device is pressed on the paper. If the clockwork is in operation the -marker will make a line as long as the armature is attracted. When -released no mark will be produced. In this way the dots and dashes of -the Morse code are made on a ribbon of paper. - -As an inking arrangement a small roller is carried by the end of the -vibrating arm. The embosser, or dry point stylus, was very extensively -used. The clockwork was generally driven by descending weights. - -Synonym--Morse Recorder. - - -382 STANDARD ELECTRICAL DICTIONARY. - - -Mortar, Electric. -An electric toy which may have various modifications. In the cut a -wooden mortar with recess to receive a ball is shown. Two wires enter -the base but do not touch. On placing the ball in position and passing a -spark from a Leyden jar across the interval between the wires, the heat -and disturbance are enough to project the ball. Gunpowder may be used, -the discharge being passed through a wet string to prolong the spark. - - -Fig. 244. ELECTRIC MORTAR. - - -Motor, Compound or Compound Wound. -A motor which has two windings on the field magnets, one in parallel -with that on the armature, the other in series therewith, exactly as in -a compound dynamo. (See Dynamo, Compound.) - - -Motor, Differential. -A differentially wound motor; with a compound wound field, whose series -coil and shunt coil are wound in opposition to each other. It is -virtually a compound wound dynamo. (See Dynamo, Compound Wound.) - - -Motor, Electric. -A machine or apparatus for converting electric energy into mechanical -kinetic energy. The electric energy is generally of the dynamic or -current type, that is to say, of comparatively low potential and -continuous or virtually continuous flow. Some electrostatic motors have, -however, been made, and an influence machine can often be operated as a -static motor. - -Electric motors of the current type may be divided into two -classes--direct current and alternating current motors. - -Direct current motors are generally based on the same lines of -construction as dynamos. One of the great discoveries in modern -electricity was that if a current is passed through a dynamo, the -armature will rotate. This fact constitutes the principle of the -reversibility of the dynamo. - - -383 STANDARD ELECTRICAL DICTIONARY. - - -Motors built on the dynamo model may be series wound, shunt wound, or -compound wound, or of the magneto type, in the latter case having a -fixed field irrespective of any current sent through them. The field may -be produced by an electro-magnet separately excited and unaffected by -the current sent through the motor. - -A current passed through a magneto or motor with separately excited -field will turn it in the direction opposite to that required to produce -the same current from it were it worked as a generator. - -A current passed through a series wound motor acts exactly as above. - -Both these facts follow from Lenz's law, q. v. - -A current passed through a shunt wound motor acts oppositely to the -above. The direction of rotation is the same as that required to produce -a current of the same direction. This is because the field being in -parallel with the armature the motor current goes through the magnet -coils in the direction the reverse of that of the current produced in -the armature when it is used as a dynamo. Hence this also carries out -Lenz's law. - -The compound wound motor acts one way or the other according as its -shunt or series winding preponderates. The two may exactly balance each -other, when there will be no motion at all. The series connections of a -compound wound dynamo should therefore be reversed, making both series -and shunt work in unison, if the dynamo is to be used as a motor. - -The general principles of the electric motor of the dynamo, or -continuous rotation type, can only be outlined here. The current passing -through the field magnets polarizes them and creates a field. Entering -the armature by the brushes and commutators it polarizes its core, but -in such a way that the north pole is away from the south pole of the -field magnet, and the same for the south pole. Hence the armature -rotates. As it does this the brushes connect with other commutator -sections, and the poles of the armature are shifted back. This action -continues indefinitely. - -Another class of motors is of the reciprocating type. These are now very -little used. (See Motor, Reciprocating.) - -One valuable feature of continuous rotation electric motors is the fact -that they absorb energy, to a great extent proportional in amount to the -work they have to do. The rotation of the armature in the field of the -motor involves the cutting of lines of force by its coils. This -generates an electro-motive force contrary in direction to that -producing the actuating current. The more rapid the rotation the greater -is this counter-electro-motive force. The motor armature naturally -revolves faster with diminished resistance to the motion of the -armature. This increases the counter-electromotive force, so that less -energy is absorbed. When the motor is called on to do work, the armature -rotates more slowly, and the counter-electro-motive force diminishes, so -that the machine absorbs more energy. (See Jacobi's Law.) - - -384 STANDARD ELECTRICAL DICTIONARY. - - -Motor Electro-motive Force. -The counter-electro-motive force of a motor. (F. J. Sprague.) - -A motor rotates in virtue of the pull of the field magnet upon the poles -of the core of its armature. In responding to this pull the windings of -the armature cuts lines of force and hence generates a -counter-electro-motive force, for which the above term was suggested. - - -Motor-Generator. -A combined motor and generator used to lower the potential difference in -a portion of a circuit, e. g., that part within a building. - -A motor-generator is a dynamo whose armature carries two commutators, -with two separate windings, one of fine wire of many turns, the other of -coarse wire of few turns. If the potential of the system is to be -lowered, the main current is passed through the fine winding. This -causes the armature to turn motor-fashion, and a potential difference is -generated by the rotation of the large coils in the field. This -potential difference is comparatively low and by properly proportioning -the windings may be lowered to as great a degree as required. - -The same apparatus may be inverted so as to raise potential difference. -It acts for continuous current systems as the induction coil transformer -does for alternating current systems. - -Synonym--Continuous Current Transformer. - - -Motor, Multiphase. -A motor driven by multiphase currents. It is arranged in general terms -for distribution of the multi phase currents in coils symmetrically -arranged around the circle of the field. These coils are wound on cores -of soft iron. A rotating field is thus produced, and a permanent magnet -or a polarized armature pivoted in such a field will rotate with the -field, its poles following the poles of the rotatory field. - -The cut, Fig. 245, illustrates the principles of action of a four phase -current motor, connected to a four phase current dynamo or generator. -The generator is shown on the left hand of the cut and the motor on the -right hand. In the generator the armature N S is supposed to be turned -by power in the direction shown by the arrow. Each one of the pair of -coils is wound in the reverse sense of the one opposite to it, and the -two are connected in series with each other, and with a corresponding -pair in the motor. The connection can be readily traced by the letters A -A', a a' for one set of coils and B B' b b' for the other set. - - -385 STANDARD ELECTRICAL DICTIONARY. - - -For each rotation of the armature two currents, each in opposite -direction, are produced in A A', and the same is the case for B B'. -These currents which have an absolutely constant relation of phase, and -which it will be seen alternate four times for each rotation of the -armature, regulate the polarity of the field of the motor. The resultant -of their action is to keep the poles of the field magnet of the motor -constantly traveling around its circle. Hence the armature N S of the -motor, seen on the right hand of the cut, tends to travel around also -its north and south poles, following the south and north poles of the -rotatory field respectively. - - -Fig. 245. FOUR-PHASE CURRENT GENERATOR AND MOTOR. - - -It is not essential that the armature should be a magnet or polarized. -Any mass of soft iron will by induction be polarized and will be -rotated, although not necessarily synchronously, with the rotatory -field. Any mass of copper, such as a disc or cylinder, will have -Foucault currents induced in it and will also rotate. The only -components of such currents which are useful in driving the motor are -those which are at right angles to the lines of force and to the -direction of motion. A very good type of armature based on these -considerations is a core of soft iron wound with insulated copper wire -in one or more closed coils; and so wound as to develop the currents of -proper direction. - -Such an armature is used in the Tesla alternating current motor. An -efficiency of 85 per cent. has been attained with some of the Tesla -motors. - - -Motor, Prime. -A machine used for producing mechanical motion against resistance. It -may operate by converting heat or any other form of kinetic or potential -energy into mechanical energy of the moving type. A steam-engine and a -water-wheel are examples of prime motors. - - -Motor, Reciprocating. -The early type of motor depending upon reciprocating motion, such as the -motion of a coil in a solenoid. These were based upon the lines of a -steam engine, and have been abandoned except for special purposes where -reciprocating motion is especially required, as in the case of rock -drills. - - -386 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 246. RICORDON'S RECIPROCATING MOTOR. - - -In the cut, B is an electro-magnet; A is an armature; E a pole piece. -The current enters by the springs, b b, and by commutation is supplied -and cut off alternately, thus maintaining a reciprocating movement of -the armature and rotation of the fly-wheel. - -Synonym--Pulsating Motor. - - -Motor, Series. -A motor whose winding on the armature is in series with the winding on -the field. It is similar to a series dynamo. (See Dynamo, Series.) - - -Motor, Shunt. -A motor whose winding on the armature is in parallel with the winding on -the field magnets. It is similar to a shunt wound dynamo. (See Dynamo, -Shunt.) - - -Fig. 247. MULTIPLE ARC CONNECTION. - - -Multiple. -A term expressing connection of electric apparatus such as battery -couples, or lamps in parallel with each other. In the ordinary -incandescent lamp circuits the lamps are connected in multiple. - -Synonym--Multiple Arc. - - -387 STANDARD ELECTRICAL DICTIONARY. - - -Multiple Arc Box. -A resistance box arranged so that the coils may be plugged in multiple -instead of in series. Such can be used as a rheostat, as the resistance -can be very gradually changed by putting the coils one by one into -parallel with each other. Thus by adding in parallel with a 10 ohm coil -a 10,000 ohm coil the resistance is decreased to 9.999001 ohms, and thus -the resistance can be very slowly changed without sudden stops or abrupt -changes. - -[Transcriber's note: The correct value is 9.99001] - - -Multiple Series. -Arrangements of electric apparatus in a circuit in a number of series, -which minor series are then arranged in parallel. The term may be used -as a noun, as "arranged in multiple-series," or as an adjective, as "a -multiple-series circuit." - - -Fig. 248. MULTIPLE SERIES CONNECTION. - - -Multiple Switch Board. -A switch board on whose face connecting spring jacks or other devices -are repeated for the same circuits, so that different operators have -each the entire set of connections repeated on the section of the board -immediately in front of and within their reach. This multiplication of -the same set of connections, giving one complete set to each operator, -gives the title "multiple" to the type of switch board in question. The -typical multiple switch board used in telephone exchanges is the best -example of this construction. The calling annunciators of the -subscribers are distributed along the bottom of the board extending its -full length. To each operator a given number is assigned, all within -reach of the right or left hand. This gives five or six feet length of -board to each, and an operator only responds to those subscribers within -his range. But anyone of his subscribers may want to connect with any of -the others in the entire central station. Accordingly in front of each -operator spring jacks are arranged, one for each of the entire set of -subscribers connected in that office. The operator connects as required -any of the calling subscribers, who are comparatively few, to any one of -the large number served by the central station. Thus the entire set of -subscribers' spring jacks are multiplied over and over again so as to -give one set to each operator. - - -388 STANDARD ELECTRICAL DICTIONARY. - - -Multiple Wire Method for Working Electro-magnets. -A method for suppressing sparking in working electro-magnets -intermittently. The magnet core is wound with a number (from four to -twenty) of separate layers of fine wire. A separate wire is taken for -each layer and all are wound in the same direction, from one end to the -other of the space or bobbin without returning. The ends are then joined -so as to bring all the wires in parallel. The effect of this is that as -the coils vary in diameter the time constants of each is different from -that of the others, the coefficient of self-induction being less, and -the resistance being greater for the coils farthest from the central -axis. Thus the extra currents run differently in the different coils, -and only a comparatively small spark can be produced owing to the -division of forces thus brought about. - - -Fig. 249. DIAGRAM ILLUSTRATING MULTIPLE WIRE WORKING. - - -Multiplex Telegraphy. -Any system of telegraphy transmitting more than four messages -simultaneously over a single wire. Properly it should apply to all -transmitting more than one, but conventionally has the above restricted -meaning, distinguishing it from duplex and quadruplex telegraphy. - - -Multiplying Power of a Shunt. -When a resistance is placed in parallel with a galvanometer on a circuit -the following relation obtains. Let s and g equal the resistances of the -shunt and galvanometer respectively, S and G the currents in amperes -passing through them, V the potential difference between their common -terminals, and A the whole current in amperes. Then we have - A = ( (s + g ) / s ) * G -and ( (s + g ) / s ) is termed the multiplying power of the shunt, as it -is the factor by which the current passing through the galvanometer must -be multiplied by to produce the total current. - - -Muscular Pile. -A species of voltaic battery, often termed Matteueci's pile, made up of -alternate pieces of muscle cut longitudinally and transversely -respectively. The different pieces represent the elements of a battery, -and their difference of potential is naturally possessed by the pieces. - - -Myria. -A prefix; one million times. Thus myriavolt means one million volts. - -[Transcriber's note: Contemporary usage is mega, as in megavolt.] - - -389 STANDARD ELECTRICAL DICTIONARY. - - -N. -(a) Symbol for north pole or north-seeking pole of a magnet. - -(b) Symbol for the number of lines of force in a magnetic circuit. - - -Nairne's Electrical Machine. -The cylinder electrical machine, q.v. - - -Napierian Logarithms. -A series of logarithms the base of whose system is 2.72818. They are -also called hyperbolic logarithms. - - -Nascent State. -An element just separating from a combination possesses at that time -higher affinities than after separation, and can effect more powerful -chemical changes. - -It is sometimes attributed to a differential time of existence in the -atomic modification, before the freed atoms have united to form -molecules. - - -Natural Currents. -A term for earth currents. (See Current, Earth.) - - -Needle. -(a) A term applied to a bar magnet poised horizontally upon a vertical -point, or suspended in a horizontal position by a filament. Thus the -magnet in a mariner's compass, which may be a substantial bar magnet, is -called a magnetic needle. - -(b) An indicator in general shape like the hand of a clock. (Sec -Annunciator, Needle- Telegraph, Needle.) - - -Needle of Oscillation. -The magnetic needle poised horizontally, and used for measuring the -intensity of the earth's magnetic field, or of an artificial magnetic -field, by the method of oscillations. The intensities of the field is -inversely as the square of the number of oscillations performed in a -given time. - - -Needle, Telegraphic. -The index in needle telegraphy (see Telegraph, Needle), whose motions -indicate the characters it is desired to transmit. - - -Negative Charge. -One of the two kinds of electric charges. The other is the positive. - -By the double fluid hypothesis this is assumed to be a charge of a -particular kind of electricity--negative electricity. - -By the single fluid hypothesis it is supposed to be caused by the -absence of part of the normal electricity of a surface. The reverse is -held by some theorists. - -The subject is so purely theoretical that neither of the two hypotheses -is accepted as final. - -[Transcriber's note: Current is a wire is the motion of negative -electrons. Current in a electrolyte is the motion of positive ions and -negative ions. Current in a plasma is the motion of electrons and -positive ions.] - - -390 STANDARD ELECTRICAL DICTIONARY. - - -Negative Electricity. -The kind of electricity with which a piece of amber is charged by -friction with flannel; resinous electricity. (See Electrostatic Series.) - - -In a galvanic battery the surface of the zinc plate is charged with -negative electricity. - -According to the single fluid theory negative electrification consists -in a deficiency of electricity. - -[Transcriber's note: Negative electrification is an excess of -electrons.] - - -Negative Element. -In a voltaic cell the plate not dissolved by the solution; the one which -is positively charged; the copper, platinum, or carbon plate in the -usual type of battery. - -The current is assumed to flow from negative element to positive element -(the zinc plate) through the wire or other external conductor. - - -Nerve Currents. -Currents of electricity obtained from nerves. They are much more feeble -than those obtained from muscle, but are produced in the same general -ways. - - -Network. -Conductors in parallel and crossing each other, with connections at the -junctions. - -The term is sometimes so loosely applied as to include parallel -conductors. - - -Neutral Line of Commutator. -The diameter of a commutator which connects its Neutral Points, q. v.; -sometimes termed the diameter of commutation; the diameter approximately -at right angles with the lines of force. The commutator brushes are -applied at the extremities of this diameter. - - -Neutral Point of a Commutator. -The points of a commutator at which no lines of force are cut; the -points at the extremities of a diameter which, except for the lag, would -be at right angles to the lines of force; the points at which the -brushes touch the commutator. - - -Neutral Point, Thermo-electric. -A temperature marking a point of no thermo-electric difference of -potential. If the junctions of a thermo-electric couple are at -temperatures, one a little over and the other an equal amount under the -neutral point, no current will be developed. At the neutral point the -thermo-electric polarities are reversed. Differences of temperature -above it give currents of reverse direction to those given by -corresponding differences below it. For an iron-copper couple the -neutral point is 274.5° C. (526° F.) - -Synonym--Neutral Temperature. - - -Neutral Relay Armature. -An unpolarizable armature for use with a relay; an armature of soft iron -or iron wire; as distinguished from a polarized armature. - - -391 STANDARD ELECTRICAL DICTIONARY. - - -Neutral Wire. -The central wire in the three wire system, q. v., of electric -distribution; the wire connected to a point between the two dynamos, or -otherwise to the central point of the current generator. - - -Fig. 250. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE. - - -Neutral Wire Ampere Meter. -An ampere meter connected in the circuit of the neutral wire to -determine the current passing through it. Such determination is for the -purpose of ascertaining how much more work is being done by one of the -lateral leads than by the other. - -Synonym--Balance Ampere Meter. - - -N. H. P. -Symbol or contraction for "nominal horse power." This is a basis for -rating the size of an engine. - - -Nickel. -A metal; one of the elements; atomic weight, 58.8 ; equivalent, 29.4; -valency, 2; specific gravity, 8.8. It is a conductor of electricity. - Relative resistance, annealed (Silver = 1), 8.285 - Specific Resistance, 12.47 microhms. - Resistance of a wire - (a) 1 foot long, weighing 1 grain, 15.206 ohms. - (b) 1 foot long, 1/1000 inch thick, 74.963 " - (c) 1 meter long, weighing 1 gram, 1.060 " - (d) 1 meter long, 1 millimeter thick, .1587 " - Resistance of a 1-inch cube, 4.907 microhms. - Electro-chemical equivalent, (Hydrogen = .0105) .3087 mgs. - -It is strongly paramagnetic, but loses this quality at 350º C. (662º F.) - -It is important as a constituent of German silver, an alloy much used -for resistance coils. - - - -Nickel, Bath. -A bath for the electro-deposition of nickel. A great many -formulae have been given. Metallic nickel is dissolved in 1 vol. -sulphuric acid mixed with 2 vols. water. Neutralize with ammonia, and -add of ammonium sulphate one-half the weight of metallic nickel -originally used; 135 parts of nickel will be enough for a bath of 10,000 -parts. - - -392 STANDARD ELECTRICAL DICTIONARY. - - -Other formulae are as follows: - Double nickel-ammonium sulphate, 4 parts. - Ammonium carbonate, 3 " - Water 100 " - Nickel sulphate, nitrate or chloride, 1 " - Sodium bisulphate, 1 " - Water, 20 " - -Nickel anodes are used in the bath to maintain the strength. Too much -care cannot be exercised in the absolute cleanliness of the articles to -be plated. A too alkaline bath gives a disagreeable yellow color to the -deposit; too acid a bath gives badly adhering deposits. - - -Night Bell. -An alarm bell in a telegraph office, which bell is connected at night to -give a loud signal to attract the operator's attention. It is used in -telephone exchanges and is connected so as to ring as long as a -subscriber remains unanswered after calling. - - -Nobili's Rings. -When a dilute solution of copper acetate is placed on a bright silver -plate and a strip of zinc is touched to the silver beneath the copper, a -series of rings of copper are formed by electrolysis around the zinc. -These are Nobili's rings. - -If for the copper acetate a solution of lead oxide in potassium hydrate -solution is substituted, and if the polished plate which may be German -silver is connected to the positive electrode of a battery, and a -platinum wire connected to the negative pole is immersed in the liquid, -it determines the formation of beautiful iridescent rings of lead -binoxide. The platinum wire is sometimes sealed in glass so that only -its point projects. - -The colors are due to interference of light, the layers of lead oxide -being extremely thin. - -The lead binoxide is formed by secondary reaction. Metallic lead is -first deposited on the negative pole. The oxygen which goes to the -positive pole formed by the polished plate produces lead binoxide which -is deposited there in rings. The reaction is comparable to that of a -storage battery. - -Synonyms--Metallochromes--Electric Rings. - - -Nodular Deposit. -A deposit obtained in electroplating, characterized by irregular -thickness; due to too low density of current. - - -Non-conductor. -A material that does not conduct electricity except with great -difficulty; a substance of very high resistance. - -Synonym--Insulator--Dielectric. - - -North Pole. -(a) The north-seeking pole of a magnet; the pole of a magnet which tends -to point to the north, and whence lines of force are assumed to issue on -their course to the other pole of the magnet. - -(b) The North Pole of the earth. Treating the earth as a magnet, and -accepting the above nomenclature the north pole should be termed the -south pole. (See Austral Pole--Boreal Pole.) - - -393 STANDARD ELECTRICAL DICTIONARY. - - -North-seeking Pole. -The pole of a magnet which tends to point to the north; the north pole -of a magnet. - - -Null Method. -Any method of obtaining measurements or comparisons, in which the -measurement is correct when the deflection of the galvanometer or other -indicator is zero, nought or null. The Wheatstone Bridge (see Bridge, -Wheatstone) is an example of a null method. - -Two obvious advantages attach to null methods in electric galvanometer -work. One is that an uncalibrated galvanometer can be employed. The -other is that a galvanometer of any high degree of sensitiveness can be -employed, there being no restriction as to its fineness of winding or -highness of resistance. - - -"Upper case Omega Graphic". -(Greek capital" Omega") symbol for megohm. -[Transcriber's note: Now used for ohms.] - - -"Lower case Omega Graphic". -(Greek omega) symbol for ohm. -[Transcriber's note: Now used for angular velocity, 2*PI*frequency.] - - -Occlusion. -An absorption of gases by metals. Palladium will, if used as the -hydrogen evolving electrode in decomposing water, absorb 980 times its -volume of hydrogen, which is said to be occluded. The metal may also be -heated in hydrogen and allowed to cool therein, when occlusion occurs. -Platinum will occlude 4 times its volume of hydrogen; iron, 4.15 times -its volume of carbon-monoxide; silver, 7 times its volume of oxygen. -Metals with occluded gases may serve as elements in a galvanic couple. -(See Gas Battery.) A metal expands in occluding a gas. - -In the storage battery it is believed that occlusion plays a part, -hydrogen and oxygen being respectively absorbed by the two sets of -plates, and acting as they do in Groves' gas battery. - - -Oerstedt. -Name proposed for the unit of current strength, but not adopted. The -ampere is the accepted name. - - -394 STANDARD ELECTRICAL DICTIONARY. - - -Oerstedt's Discovery. -Oerstedt discovered in 1820 that a magnetic needle tended to place -itself at right angles to a current of electricity. This fundamental -experiment is the basis of the galvanometer. - - -Fig. 251. OERSTEDT'S DISCOVERY. - - -Ohm. -The practical unit of resistance; 1E9 C. G. S. electro-magnetic units. -The legal ohm is the resistance of a mercury column 1 square millimeter -in cross-sectional area and 106 centimeters in length. There has been -considerable confusion, owing to inaccuracy in early determinations, in -the valuation of the ohm. In this work the legal ohm is used. The -different ohms will be found defined in their place. Resistance units of -various names may also be consulted. - -The following table gives the relative values of the different ohms. - - Length of - Mercury Board of - Column in True B. A. Trade Legal - Centimetre. Ohm. Ohm. Ohm. Ohm. - -True Ohm, 106.24 1. 1.0128 .9994 1.0022 -B. A. Ohm, 104.9 .9874 1. .9868 .9889 -Board of Trade Ohm 106.3 1.00050 1.0133 1. 1.0028 -Legal Ohm, 106.0 .9977 1.0112 .9971 1. - - -Ohmage. -The Resistance of a circuit expressed in ohms. - - -Ohm, B. A. -The British Association unit of resistance; the resistance of a column -of mercury 1 square millimeter in cross sectional area and 104.9 -centimeters long; the B. A. Unit of Resistance. - - -Ohm, Board of Trade. -The approximate ohm as recommended by the British Board of Trade on the -advice of a committee (Sir W. Thomson, Dr. J. Hopkinson, Lord Rayleigh -and others). It is the resistance of a mercury column one square -millimeter in section, and 106.3 centimeters long at 0º C. (32º F.) - -Synonym--New Ohm. - - -395 STANDARD ELECTRICAL DICTIONARY. - - -Ohmic Resistance. -True resistance as distinguished from spurious resistance, or -counter-electro-motive force. - - -Ohm, Legal. -The practical unit of resistance. The resistance of a column of mercury -one square millimeter in cross-sectional area and 106 centimetres long -at 0º C. (32º F.) The ohm used previously to 1884 is the B. A. Unit of -Resistance, q. v. - -One legal ohm = 1.0112 B. A. Units, and I B. A. Unit = 0.9889 legal ohm. - -The resistance of a copper wire 1 foot long and 1/1000 inch in diameter -is about 10 ohms. The resistance of 1 mile of iron wire 1/3 inch in -diameter is about 10 ohms. - -Synonym--Congress Ohm. - - -396 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 252. THEORY OF OHMMETER. - - -Fig. 253. OHMMETER. - - -Ohmmeter. -An instrument for measuring directly the resistance of a conductor or of -any part of a circuit through which a strong current is passing. It is -the invention of Prof. W. E. Ayrton. - -It contains two fixed coils at right angles to each other acting on the -same needle of soft iron. One coil is of thick wire and is placed in -series with the resistance to be measured. The other is of very thin -wire and is placed in parallel with the same resistance. One wire acts -by the total current, the other by the potential difference between the -ends of the resistance. The action on the soft iron needle is due to the -ratio of potential difference to total currents, or to the resistance -itself. By properly designing and proportioning the coils the angular -deflections of the needle are made proportional to the resistance. - -In use the thick wire may be kept permanently in circuit. On connecting -the binding posts of the thin wire coil to any two parts of the circuit -its resistance is at once given by the deflection of the needle. - -When no current is passing the needle rests in any position. A current -in the thick coil brings it to zero. A current simultaneously passing -through the thin high resistance coil brings about the deflection. - -The instrument is a commercial rather than a scientific one. - - -Ohm's Law. -The fundamental law expressing the relations between current, -electro-motive force and resistance in an active electric circuit. It -may be expressed thus: - -(a) The current strength is equal to the electro-motive force divided by -the resistance. - -(b) The electro-motive force is equal to the current strength multiplied -by the resistance. - -(c) The resistance is equal to the electro-motive force divided by the -current strength. All these are different forms of the same statement. -Algebraically the law is usually expressed thus, (a) C = E/R. It may -also be expressed thus: (b) E = C*R and (c) R= E/C, in which R denotes -resistance, C denotes current strength, and E denotes electro-motive -force. - - -Ohm, True. -The true ohm is the resistance of a column of mercury 1 square -millimeter in cross-sectional area, and 106.24 centimeters long. (See -Ohm.) - -Synonym-Rayleigh Ohm. - - -Oil Insulation. -Oil insulation has received several applications in electrical work. It -has been proposed for use in underground conduits. These it was proposed -to fill with oil after the insertion of the conductors, the latter -properly wrapped with cotton or other covering. For induction coils it -has been very successfully used. Its principal utility depends on the -fact that it is liquid, so that if pierced by a spark it at once closes -again. A solid insulator if pierced is permanently injured. It is also -used in telegraph insulators (see Insulator, Liquid) to prevent surface -leakage. - - -397 STANDARD ELECTRICAL DICTIONARY. - - -Olefiant Gas. -A compound gas; C2H4; composed of carbon, 24; hydrogen, 4; molecular -weight, 28; specific gravity, .981. - -It is a dielectric of about the resistance of air. Its specific -inductive capacity at atmospheric pressure is 1.000722 (Boltzman.) - -Synonym--Ethene; heavy carburetted hydrogen. - -[Transcriber's note: Also called ethylene. A primary use is polyethylene -plastic.] - - -Open. adj. -An electric circuit is said to be open when it is cut or broken so that -no current can pass through it. The term may be recollected by thinking -of a switch; when open no current can pass through it. The same -adjective is applied to magnetic circuits, an air gap implying an open -circuit. - - -Open Circuit Oscillation. -An oscillation of current in open circuit so that a spark discharge -accompanies it. It is produced by electric resonance in a simple circle -or loop of wire with ends placed near together but not touching, if the -circuit is of such size that its period of oscillation corresponds with -that of the inducing discharge. (See Resonance, Electric.) Its period -depends entirely on the self-induction of the circuit. - - -Ordinate. -In a system of plane co-ordinates (see Co-ordinates), the distance of -any point from the axis of abscissas measured parallel to the axis of -ordinates. - - -Ordinates, Axis of. -The vertical axis in a system of co-ordinates, q. v. - -Synonym--Axis of Y. - - -Organ, Electric. -An organ in which the air blast is admitted or excluded from the -different pipes by electric mechanism. - -The outlines of the system are a series of contacts worked by the keys -and stops, which cause, when operated by the organist, a current to pass -through electro-magnets, opening the valves of the different pipes. Thus -the manual may be at any distance from the organ, and a number of organs -may be worked upon the same manual. As many as five in a single -cathedral are thus connected to a manual in the chancel. - - -Orientation of a Magnetic Needle. -The acquirement by a magnetic needle of its position of rest, with its -magnetic axis in the magnetic meridian. - - -Origin of Co-ordinates. -In a system of linear co-ordinates the point of intersection of the -axes; the point whose co-ordinates are both zero. - - -398 STANDARD ELECTRICAL DICTIONARY. - - -Oscillating Needle. -A small light bar magnet suspended by a filament and employed in -determining the intensity of a magnetic field by the oscillations it -completes in a given time after a given disturbance. - - -Oscillations, Electric. -In static electricity the sudden and very rapid alternations in the -discharge of a static condenser. This discharge of the disruptive order -seems a single one, but is really composed of a number of discharges -alternating in direction and producing electro-magnetic ether waves, -probably identical with light waves except that they are longer and far -less rapid. - - -Oscillatory Electro-motive Force. -Electro-motive force rapidly changing in sense or in direction, so that -it presents an oscillatory character. The alternating current and the -telephone current as used in practice are actuated by this type of -electro-motive force. - - -Osmose, Electric. -When two liquids are separated by a porous diaphragm, and a strong -current of electricity is passed through from the liquid on one side, -through the diaphragm, to the liquid on the other side, the liquid on -the side towards which the current is passing rises in level. The -process is termed electric osmose. When a liquid is forced through a -diaphragm a current is produced; in other words electric osmose is -reversible. The current thus produced is termed a diaphragm current. - - -Oscillation, Electric. -The phase of discharge of a static condenser in one direction. It is -usually followed by a discharge in the opposite direction constituting a -second oscillation, and so on, so that a great number of exceedingly -short oscillations are comprised. Thus, in the discharge of the Leyden -jar a large number of oscillations of current back and forth are -produced, the current alternating like the swings of a pendulum. - -These oscillations are supposed to affect the ether, producing waves in -it identical with light waves, except that we have not been able yet to -produce them short enough to affect the visual organs. The waves thus -produced can be reflected or refracted; some substances are transparent -for them and others opaque. There is a possibility that man may yet -succeed in producing electric oscillations of sufficient frequency to -bring about the direct production of light. - - -Oscillatory Displacement. -Hypothetical displacement currents of rapidly alternating direction -produced in the oscillatory discharge of a Leyden jar or static -condenser. - - -Oscillatory Induction. -Induction produced by sympathetic action of an oscillatory discharge or -by electric resonance. (See Oscillations, Electric--Resonance, -Electric--Resonator, Electric.) - - -399 STANDARD ELECTRICAL DICTIONARY. - - -Outlet. -The part of an electrolier or electric light fixture out of which the -wires are led for attachment of an incandescent light socket. - - -Output. -The rate of energy delivered or of work done by a machine. In the case -of a current generator it is the volt-coulombs per given second, or -better the volt-amperes delivered at its outer circuit terminals. - - -Output, Magnetic. -The analogue in a magnetic circuit of the output of an electric circuit. -It is the product of the magnetizing force by the induced magnetism. - - -Output, Unit of. -As a unit of output of a dynamo Prof. Sylvanus P. Thompson has proposed -1,000 watts, or one kilowatt. This unit is now frequently used. To -completely define the dynamo, however, the amperage or the voltage must -also be given, as a 10 kilowatt--110 volt machine, or a 10 kilowatt--99 -ampere machine. - -[Transcriber's note: 10 kilowatt at 110 volts is 91 amperes.] - - -Over-Compounding. -A proportioning of the series and shunt windings of a compound dynamo, -so that the voltage of the terminals rises with the load or output -enough to allow for the drop in mains, thus maintaining the potential -for full load at distant points in a district. It is carried out by an -increase of ampere-turns in the series winding. - - -Overload. -In an electric motor a mechanical load put upon it so great as to -prevent economical working. One effect of such a load is to make the -armature run so slowly as to unduly reduce the counter-electro-motive -force and hence to permit so much current to pass through the coils as -to heat them, perhaps injuriously. In this case the production of heat -implies the waste of energy. - - -Overtype Dynamo or Motor. -A dynamo or motor whose armature is placed above or in the upper part of -the field magnets, the yoke piece of the magnets being in or resting -upon the base of the machine. - - -Ozone. -An allotropic form of oxygen. It possesses much more energetic chemical -properties than oxygen. It is supposed to contain three atoms of oxygen -in its molecule, represented thus: - O - / \ - O---O - -It is produced by electric discharges and it is its peculiar odor which -is noticed about an electric machine, and sometimes in a thunderstorm -near the path of a lightning flash. - -In the electrolysis of water some ozone may be produced, thus -diminishing the volume of the oxygen or of the mixed gases given off. -This is a source of inaccuracy in a gas voltameter. - - -400 STANDARD ELECTRICAL DICTIONARY. - - -Pacinotti's Inductor. -The Pacinotti or Gramme Ring. (See Pacinotti's Ring.) - - -Pacinotti's Ring. -A ring of iron wire wound with coils of insulated wire at right angles -to its circular axis, and used as the armature of a dynamo or motor. A -number of connections are taken from the coils to a central commutator. - - -Fig. 254. PACINOTTI'S MACHINE, WITH RING ARMATURE. - - -If such a ring with its coils is rotated in a field, current can be -taken from points of the commutator on a line at right angles to the -lines of force entering the ring. - -The ring was discovered in 1862 by Pacinotti, and later was -independently discovered by Gramme. It is often known as the Gramme -ring. - - -Pacinotti Teeth. -Projections on a cylindrical or drum armature, between which in the -grooves formed thereby, the wire is wound. The teeth being of iron tend -to diminish the reluctance or magnetic resistance of the interpolar -space, or interval between the poles of the field magnet. - -Synonym--Pacinotti Projections. - - -Paillard Alloys. -Non-magnetic palladium alloys, invented by Paillard, of -Switzerland, used in anti-magnetic watches. The following are given as -the compositions of several such alloys: - - I. II. -Palladium, 60 to 75 parts 50 to 75 parts -Copper, I5 to 25 " 20 to 30 " -Iron. 1 to 5 " 5 to 20 " - - -401 STANDARD ELECTRICAL DICTIONARY. - - -The following are more complex: - I. II. -Palladium, 65 to 75 parts 45 to 50 parts -Copper, 15 to 25 " 15 to 25 " -Nickel, 1 to 5 " 2 to 5 " -Silver, 3 to 10 " 20 to 25 " -Gold, 1 to 2-1/2 " 2 to 5 " -Platinum, 1/2 to 2 " 2 to 5 " -Steel, 1 to 5 " 2 to 5 " - -These alloys are used for balance springs, as well as for the balance -wheels and escapement parts of watches. The elasticity of recently -produced springs has been found to be very satisfactory. - - -Page Effect. -The sounds produced by magnetizing and demagnetizing a bar of iron or -steel; the magnetic tick. The sounds are strong enough to produce a -telephonic effect. (See Magnetic Tick.) - - -Palladium. -A metal of the platinum series. It has the highest power of occlusion, -q.v., of all metals. It is the characteristic ingredient of non-magnetic -watch alloys. - -Palladium used as an electrode in the electrolysis of water will occlude -936 volumes of hydrogen, and the hydrogen-palladium alloy will exceed in -size the original electrode. - - -Fig. 255. LUMINOUS PANE. - - -Pane, Luminous. -A pane of glass, one side of which has pasted to it a long zigzag strip -of tinfoil. A design is made by cutting through the strip. On -discharging a Leyden jar or an electric machine through the strip sparks -appear where the tinfoil is severed, thus producing the design in a -luminous effect. Many variations can be employed in their construction. - - -402 STANDARD ELECTRICAL DICTIONARY. - - -Pantelegraphy. -A system of telegraphy for transmitting designs, maps, drawing, and the -like by telegraphy. (See Telegraphy, Facsimile.) - - -Paper Filaments. -Filaments of carbon for incandescent lamps made from paper. - -This is one of the earliest materials practically used. The paper is cut -out of proper shape, and is carbonized in a close vessel, while embedded -in powdered charcoal or some other form of carbon to absolutely cut off -access of air. It is then placed in the lamp chamber and flashed or -subjected to the regular treatment. - - -Parabola. -A curve; one of the conic sections. It is approximately represented by a -small arc of a circle, but if extended becomes rapidly deeper than a -half circle. - -If, from a point within called the focus, lines are drawn to the curve -and then other lines are drawn from these points parallel to the axis, -the angles of incidence will he equal to the angles of reflection as -referred to tangents at the points where the lines touch the curve. - -[Transcriber's note; The general equation of a parabola is - A*x^2 + B*x*y + C*y^2 + D*x + E*y + F = 0 -such that B^2 = 4*A*C, all of the coefficients are real, and A and C are -not zero. A parabola positioned at the origin and symmetrical on the y -axis is simplified to y = a*x^2 ] - - -Parabolic Reflector. -A reflector for a light, a paraboloid or surface of revolution whose -section is a parabola. A light placed at its focus has its rays -reflected parallel to each other. - -Examples of parabolic reflectors are seen in electric search lights and -in locomotive head-lights. They are employed in electric search lights. -The arc light must be of such construction as to maintain its ignited -points always at the same point, the focus of the paraboloid. - - -Paraffine. v. -To coat or saturate with paraffine wax. Paper may be paraffined by -dipping in the wax, or by being sprinkled with fragments of wax, -subsequently melted in with a hot iron or otherwise. The tops of battery -carbons are often paraffined to prevent the acid from rising in the -pores by capillary attraction and rusting the connections. - - -403 STANDARD ELECTRICAL DICTIONARY. - - -Paraffine Wax. -A hydro-carbon composed principally of mixtures of the higher members of -the paraffine series C n H2 n + 2. It is made from cannel coal, coal -tar, or petroleum by distillation. It is an insulator. Its resistance at -46° C. (114.8° F.) per centimeter cube is 3.4E16 ohms, or about the -highest resistance known. - -Its specific inductive capacity (for milky wax) is 2.47 (Schiller). For -clear wax it is given as follows by different authorities: - 1.92 Ayrton. - 1.96 Wüllner. - 1.977 Gibson & Barclay. - 2.32 Baltzmann. - -It is extensively used in condensers and other electric apparatus as a -dielectric and insulator. - - -Paragrêles. -Protectors against hail; lightning rods used to guard fields against -hail; of little or no real utility. - - -Parallax. -The apparent change in position of an object when looked at from two -points of view. By looking at an object a few feet distant first with -one eye and then with the other, the shifting in apparent position is -seen. - -In reading the position of an indicator or needle over a scale parallax -introduces an error unless the eye is held vertically over the needle. -By making the dial of looking- glass and holding the eye so that the -reflection of its pupil is bisected by the needle this verticality is -ensured. - - -Parallel. -(a) In the nomenclature of electric circuits two or more conductors -leading from one point to another, are said to be in parallel. - -(b) When two or more conductors connect two main leads of comparatively -large size and low resistance they are said to be in parallel or in -multiple arc. This order is easiest pictured as the rungs of a ladder in -parallel connecting its two sides representing the main leads. - -It may be used as a noun as "arranged in parallel," or as an adjective -as "a parallel circuit," the opposite of series, q. v. - - -Paramagnetic. adj. -Possessing paramagnetic properties; tending to occupy a position with -the longer axis parallel to the lines of force of a magnetic field; -having magnetism; attracted by a magnet. - -"If a homogeneous isotropic substance is placed in a magnetic field it -becomes magnetized at every point in the direction of the magnetic -intensity at that point, and with an intensity of magnetization -proportional to the magnetic intensity. When the positive direction of -the induced magnetization is the same as that of the magnetic intensity -the substance is called Magnetic or Paramagnetic; when it is opposite, -the substance is called Diamagnetic." (Emtage.) - -A paramagnetic substance has high permeability or multiplying power for -lines of force, hence in a magnetic field a bar of iron, etc., is in -unstable equilibrium unless its longer axis is parallel with the lines -of force in order to reduce as much as possible the reluctance of the -circuit. - - -404 STANDARD ELECTRICAL DICTIONARY. - - -Iron is the most paramagnetic of all substances. Other paramagnetic -metals are: Nickel, cobalt, manganese, platinum, cerium, osmium, -palladium. Diamagnetic metals are bismuth, antimony, zinc, tin, mercury, -lead, silver, copper, gold, arsenic. Bismuth is the most diamagnetic of -all metals. - -Of gases oxygen is most paramagnetic. Becquerel calculated that a cubic -yard of oxygen condensed would act on a magnetic needle as powerfully as -5.5 grains of metallic iron. Liquefied oxygen will adhere to the poles -of a magnet. - -Changes of temperature and of other conditions may affect a body's -magnetism. Thus hot oxygen is diamagnetic, and a substance paramagnetic -in a vacuum may be diamagnetic in air. - -Of liquids, solutions of iron or cobalt are paramagnetic; water, blood, -milk, alcohol, ether, oil of turpentine and most saline solutions are -diamagnetic. - - -Paramagnetism. -(a) The science or study of paramagnetic substances and phenomena. - -(b) The magnetic property of a paramagnetic substance; that of being -attracted by a magnet, and of arranging itself with its longer axis -parallel with the lines of force of a magnetic field. - - -Parchmentizing. -If cellulose is treated with a mixture of two parts of sulphuric acid -and one part of water perfectly cold, it becomes like parchment. It -should at once be washed with water, and then with ammonia and water. -The Swan incandescent light fibres are made of parchmentized cotton -thread, which is afterward carbonized. - - -Partial Earth. -A fault in a conductor caused by imperfect connection with the earth, -where insulation from the earth is desired. - - -Passive State. -A state of a substance in virtue of which it is unattacked by a solvent -which ordinarily would dissolve or attack it. Iron in strong nitric acid -is unattacked or assumes the passive state. This particular case is -supposed to be due to a coating of magnetic oxide, so that there would -be properly speaking no question of a passive state, but only one of -superficial protection. - -The existence of a true passive state of any substance is very doubtful. - - -P. D. -Abbreviation for potential difference or difference of potential, or for -electro-motive force. - - -405 STANDARD ELECTRICAL DICTIONARY. - - -Peltier Effect. -The thermal effect produced by the passage of a current through the -junction of two unlike conductors. Such junction is generally the seat -of thermo-electric effects, and a current is generally produced by -heating such a junction. If an independent current is passed in the same -direction as that of the thermoelectric current, it cools the junction, -and warms it if passed in the other direction. In general terms, -referring to thermo-electric couples, if passed through them it tends to -cool the hot and heat the cool junction. The phenomenon does not occur -in zinc-copper junctions. - - -Peltier's Cross. -A bar of bismuth and a bar of antimony soldered centre to centre at -right angles, being notched or halved there to receive or to set into -each other. It is used to demonstrate the Peltier effect, q. v. To one -pair of ends are connected the terminals of a battery circuit; to the -other pair are connected the terminals of a galvanometer. - -The galvanometer by its deflections in one and then in the other -direction indicates that the junction is heated when the current passes -from antimony to bismuth and vice versa. It thus illustrates the heating -and cooling of a thermo-electric junction by a current of electricity. -The current from the battery by the Peltier effect either heats or cools -the junction, as the case may be. This heating or cooling them produces -a thermo-electric current in the galvanometer circuit. The battery has -no direct influence on the galvanometer. - - -Pendant Cord. -A double conductor or pair of conductors, insulated from each other and -covered with a worsted, silk, or cotton covering and used to suspend -incandescent lamps and at the same time to conduct the current to them. -It is also used for other similar service, such as acting as conductors -for small motors. Often each conductor is composed of a number of thin -wires laid together. This gives flexibility to the cord. - -Synonym--Flexible Cord. - - -Pendulum, Electric. -(a) A pendulum operated by the intermittent action of an electro-magnet, -whose circuit is opened and closed by the pendulum itself. A point at -the lower end of the pendulum swinging through a globule of mercury may -close and open the circuit. Various other methods of accomplishing the -same end are employed .. - -(b) A pith ball suspended by a thread from an insulating stand. It is -used to show the attraction exercised by a piece of sealing wax or other -substance excited by rubbing. - - -406 STANDARD ELECTRICAL DICTIONARY. - - -Pen, Electric. -A stylus for producing a series of perforations in paper, so that the -paper may act as a stencil for the reproduction of a great number of -copies of the original matter. Various kinds of electric pens have been -invented. One kind, invented by Edison, consists of a handle carrying an -electric motor actuating a needle, which is driven in and out of the -other end of the handle with high rapidity. It is used by being held -vertically on the paper with the needle end downward, and is moved so as -to describe perforated letters or designs. The paper is then used as a -stencil with an ink roller to reproduce the writing or design ad -libitum. A simpler kind dispenses with the motor and depends on the -perforations produced by the electric spark. As shown in the cut the -stylus is one terminal of an induction coil circuit. The support on -which the paper rests is the other terminal and must be a conductor. In -use the induction coil is started, and the stylus is moved over the -paper; a series of sparks pass through the paper from stylus to the -supporting tablet, perforating the paper and producing a stencil to be -used for reproduction. - - -Fig. 256. ELECTRIC PEN. - - -Pentane Standard, Harcourt's. -A standard of illuminating power; in it the combustible substance is a -gas made by mixing one cubic foot of air with three cubic inches of -liquid pentane, measured at 60° F. or, if measured as gases, 20 volumes -of air to 7 of pentane. It is burned at the rate of 0.5 cubic foot per -hour from a cylindrical tube one inch in diameter, closed at the top by -a disc 0.5 inch thick with a hole 0.25 inch in diameter, through which -the gas issues. It gives a flame 2.5 inches high. - -The pentane used is the distillate of petroleum which boils at 50° C. -(122° F.) ; it has a specific gravity at 15° C. (60° F.) of from 0.628 -to 0.631. It is almost pure pentane (C5H12). - -As long as the rate of consumption is between 0.48 and 0.52 cubic foot -per hour the flame gives practically the same light. - - -407 STANDARD ELECTRICAL DICTIONARY. - - -Perforator. -An apparatus used in automatic high speed telegraphy for perforating -strips of paper. These are then used by drawing between a roller and -contact spring for making and breaking the telegraphic circuit for the -production of a record, such as the Morse record, at the distant -receiving station. - -The perforated strip has different classes of holes punched in it to -represent dots or dashes. It is fed by machinery very rapidly, so that -the message is transmitted with the highest speed. Several operators may -simultaneously prepare the paper strips, and thus in conjunction with -its rapid feeding in the transmitter, far surpass the time of ordinary -direct transmission. - - -Fig. 257. PERFORATOR FOR WHEATSTONE'S AUTOMATIC TELEGRAPH. - - -Perforators may be entirely mechanical but are sometimes pneumatic, -compressed air being used to operate them. The holes they make are on -different levels of the paper strip, as shown in the cut. - - -Period. -The time required for the completion of one complete element of periodic -motion. This may be a complete alternation (See Alternation, Complete) -of an alternating current, or of an oscillatory discharge. - - -Periodicity. -The rate of succession of alternations or of other fixed phases; the -rate of recurrence of phenomena. - - -408 STANDARD ELECTRICAL DICTIONARY. - - -Permanency. -In electric current conductors the property of possessing conductivity -unaffected by lapse of time. Generally the permanency of conductors is -very high. In some cases a slow annealing takes place which causes a -gradual change with the lapse of time. Annealed German silver wire has -been found to increase in conductivity at about .02 per cent. in a year. -(Matthiessen.) Wire, whether annealed or not, is left in a strained -condition after the drawing operations, and such a change is consonant -with this fact. The figure only applies to the samples tested by -Matthiessen. - - -Permanent State. -In a telegraph line or other current conductor, the condition when a -uniform current strength obtains over the whole line. When a current is -started it advances through the line with a sort of wave front gradually -increasing in strength. At the further end some time may elapse before -it attains its full intensity. When its does the permanent state -prevails. Until then the variable state, q. v., exists in the line. - - -Permeameter. -An apparatus for determining the permeability of samples of iron. It -consists of a large slotted block of iron. A coil is placed within the -slot. A hole is drilled through one end, and a rod of the iron to be -tested is passed through this hole and through the coil to the bottom of -the slot. The lower end of the rod must be accurately faced off. The -current is turned on, upon which the rod adheres to the bottom of the -slot. The force required to detach it is determined with a spring -balance. The permeation through its face is proportional to the square -of the force required. - - -Fig. 258. PERMEAMETER. - - -Permeance. -The multiplying or the conducting power for magnetic lines of force -possessed by a given mass of material. It varies with the shape and size -of the substance as well as with the inducing force. It is distinguished -from permeability, as the latter is a specific quality proper to the -material, and expressed as such; the permeance is the permeability as -affected by size and shape of the object as well as by its material. - - -409 STANDARD ELECTRICAL DICTIONARY. - - -Pflüger's Law. -A law of electro-therapeutics. It states that stimulation of a nerve is -only produced by successive appearance of the kathelectrotonic state, -and disappearance of the anelectrotonic state. - - -Phantom Wires. -The extra transmission circuits obtained in multiplex telegraph systems. -A single line arranged for four separate simultaneous transmissions by -quadruplex apparatus is said to establish three phantom wires. - - -Phase. -In wave motion, oscillating motion, simple harmonic motion, or similar -periodic phenomena, the interval of time passed from the time the moving -particle moved through the middle point of its course to the instant -when the phase is to be stated. - - -Pherope. -An apparatus for the electric transmission of pictures. (See Telephote.) - -[Transcriber's note: Precursor of the contemporary Fax and scanner.] - - -Philosopher's Egg. -An ellipsoidal vessel mounted with its long axis vertical and with two -vertical electrodes, the upper one sliding, and arranged to be attached -to an air pump. A discharge through it when the air is exhausted takes -the general shape of an egg. - - -Phonautograph. -An apparatus for registering the vibrations of a stylus, which is -mounted on a diaphragm and is acted on by sound waves. - -It is virtually a resonating chamber, over one of whose ends a parchment -diaphragm is stretched. To the centre of the parchment a needle or -stylus is attached. A cylinder covered with soot is rotated in contact -with the point of the stylus. As the chamber is spoken into the -diaphragm and stylus vibrate and the vibrations are marked on the -cylinder. It is of some electric interest in connection with telephony. - - -Phone. -Colloquial abbreviation for telephone. - - -Phonic Wheel. -A form of small motor of very simple construction. It consists of a -toothed wheel of soft iron. A bar electro-magnet is fixed with one pole -facing the teeth of the wheel. By a tuning fork make and break a -succession of impulses of rapid frequency and short duration are sent -through the magnet. The teeth act as armatures and are successively -attracted by the magnet. The regulated speed is one tooth for each -impulse, but it may rotate at one-half the speed, giving two teeth for -each impulse, or at certain other sub-multiples of its regular speed. It -is the invention of Paul Lecour. - - -410 STANDARD ELECTRICAL DICTIONARY. - - -Phonograph. -An apparatus for reproducing articulate speech. It is not electric, -except as it may be driven by electricity. - -It consists of a cylinder of wax-like material which is rotated and -moved slowly, longitudinally, screw fashion, at an even speed. A glass -diaphragm carrying a needle point is supported with the point barely -touching the wax. If the diaphragm is agitated, as by being spoken -against, the needle is driven back and forwards cutting a broken line or -groove following the direction of the thread of a screw in the wax, the -depth of which line or groove continually varies. - -This imprints the message. If the needle is set back and the cylinder is -rotated so as to carry the needle point over the line thus impressed, -the varying depth throws the needle and diaphragm into motion and the -sound is reproduced. - -The cylinder is rotated often by an electric motor, with a centrifugal -governor. - -[Transcriber's note; Due to T. A. Edison, 1877, fifteen years before -this book.] - - -Phonozenograph. -An apparatus for indicating the direction of the point where a sound is -produced. It operates by a microphone and telephone in conjunction with -a Wheatstone bridge to determine the locality. - - -Phosphorescence. -The emission of light rays by a substance not heated, but whose -luminosity is due to the persistence of luminous vibration after light -has fallen upon it. - -A phosphorescent body, after exposure to light, is luminous itself. -Phosphorescence may be induced by rubbing or friction, by heat, by -molecular bombardment, as in Crookes' tubes, and by static discharge of -electricity, as well as by simple exposure to light. - -Another form of phosphorescence may be due to slow chemical combustion. -This is the cause of the luminosity of phosphorous. - - -Phosphorous, Electrical Reduction of. -Phosphorous is reduced from bone phosphate by the heat of the electric -arc. The phosphate mixed with charcoal is exposed to the heat of the -voltaic are, and reduction of the phosphorous with its volatilization at -once ensues. The phosphorous as it volatilizes is condensed and -collected. - - -Photo-electricity. -The development of electrical properties by exposure to light. Crystals -of fluor spar are electrified not only by heat (see Pyro-electricity) -but also by exposure to sunlight or to the light of the voltaic arc. - -[Transcribers note: Although first observed in 1839 by Becquerel, it -was not explained until 1905 by Albert Einstein with the introduction of -photons.] - - -Photo-electric Microscope. -A projection, solar or magic-lantern microscope worked by the electric -light. - - -Photo-electro-motive Force. -Electro-motive force produced in a substance by the action of light. - - -411 STANDARD ELECTRICAL DICTIONARY. - - -Photometer. -An apparatus for measuring the intensity of light emitted by a given -lamp or other source of illuminating power. They may be classified into -several types. - -Calorimetric or Heat Photometers act by measuring relatively the heat -produced by the ether waves (so-called radiant heat) emitted by the -source. The accuracy of the instrument is increased by passing the rays -through an alum solution. A thermopile, or an air thermometer, may be -used to receive the rays. - -Chemical Photometers. In these the light falls upon sensitized -photographic paper. The depth of coloration is used as the index of -illuminating power. - -Direct Visual Photometers. These include Rumford's Shadow Photometer, -Bunsen's Bar Photometer, and Wheatstone's Bead Photometer, in which the -light is estimated by direct visual comparison of its effects. - -Optical Photometers. These include Polarization Photometers, in which -the light is polarized; Dispersion Photometers, in which a diverging -lens is placed in the path of the rays of light so as to reduce the -illuminating power in more rapid ratio than that of the square of the -distance. - -Selenium Photometers, in which the variations in resistance of selenium -as light of varying intensity falls upon it is used as the indicator of -the intensity of the light. - -Jet Photometers, for gas only, in which the height of a flame under -given conditions, or the conditions requisite to maintain a flame of -given height, is used to indicate the illuminating power. - -The subject of photometers has acquired more importance than ever in -view of the extensive introduction of the electric light. (See Candle, -Standard--Carcel--Violé's Standard--and Photometers of various kinds.) - - -Photometer, Actinic. -A photometer whose registrations are produced by the action of the light -being tested upon sensitized paper or plates, such as used in -photography. Some efforts at self-registering photometers have been -based on actinic registration of the height of a flame of the gas to be -tested. - - -Photometer, Bar. -A photometer in which the two lights to be compared are fixed at or -opposite to the ends of a bar or scale of known length, generally 60 or -100 inches. The bar is divided by the rule of the inverse square of the -distances, so that if a screen is placed on any part of the bar where it -receives an equal amount of light from both sources, the figure on the -bar will indicate the relative illuminating power of the larger lamp or -light in terms of the smaller. The divisions of the bar are laid out on -the principle that the illuminating power of the two sources of light -will vary inversely with the square of their distance from the screen. - - -412 STANDARD ELECTRICAL DICTIONARY. - - -The screen used is sometimes the Bunsen disc. This is a disc of paper -with a spot of paraffine wax in the centre melted thoroughly into the -paper or with a ring of paraffine wax surrounding the untouched centre. -When this disc is equally illuminated on both sides the spot is nearly -invisible. Inequality of illumination brings it out more visibly. -Sometimes a Leeson disc is used. This consists of three pieces of paper, -two thin ones between which a thicker piece, out of which a star is cut, -is laid. When equally illuminated on both sides the star appears equally -bright on both sides. - -The bar photometer is the standard form. A candle or pair of candles may -be burned at one end and an incandescent lamp at the other, or a gas -flame may first be rated by candles and used as a standard. - -Synonyms--Bunsen's Photometer--Translucent Disc Photometer. - - -Fig. 259. BAR PHOTOMETER. - - -Photometer. Calorimetric. -A photometer in which the radiant energy, so called radiant heat, is -used as the measurer of the light. - -In one type a differential air thermometer is used, one of whose bulbs -is blackened. On exposing this bulb to a source of light it will become -heated, and if lights of the same character are used the heating will be -in proportion to their illuminating power quite closely. The heating is -shown by the movements of the index. By careful calibration the -instrument may be made quite reliable. - - -Photometer, Dispersion. -A photometer in which the rays from one of the lights under comparison -are made more divergent by a concave lens. In this way a strong light, -such as all arc lamp can be photometered more readily than where only -the natural divergence of the beam exists. The law of the variation of -the intensity of light with the square of the distance is abrogated for -a law of more rapid variation by the use of a concave lens. - -The diagram, Fig. 260, illustrates the principle. E represents a -powerful light, an arc light, to be tested. Its distance from the screen -is e. Its light goes through the concave lens L and is dispersed as -shown over an area A1, instead of the much smaller area A, which the -same rays would otherwise cover. Calling l the distance of the lens from -the screen, f its focus, and c the distance of the standard candle from -the screen when the shadows are of equal intensity, we have the -proportion. - -Illuminating power of lamps: ditto of standard candle:: - (l (e-l) + fe)2 : (c f)2 - - -413 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 260. DIAGRAM OF PRINCIPLE OF THE DISPERSION PHOTOMETER. - - -The cut, Fig. 261, gives a perspective view of Ayrton's Dispersion -Photometer. C is the standard candle, L the concave lens, R the rod for -producing the two shadows on the screen S. - - -Fig. 261. AYRTON'S DISPERSION PHOTOMETER. - - -The mirror M is fixed at an angle of 45° with the stem on which it -rotates. The light of the arc lamp is received by the mirror and is -reflected through the lens. The candle holder slides along a graduated -bar C, and at D is an index plate to show the angle at which the spindle -carrying the mirror is set. - - -414 STANDARD ELECTRICAL DICTIONARY. - - -Dr. J. Hopkinson in his dispersion photometer uses a double convex lens. -This gives a focal image of the arc-lamp between the lens and screen, -whence the rays diverge very rapidly, thus giving the desired dispersion -effect. - -It is principally for arc lamps that dispersion photometers are used. - - -Photometer, Shadow. -A photometer in which the relative intensity of the two lights is -estimated by the intensity or strength of shadows of the same object -which they respectively cast. - - -Fig. 262. RUMFORD'S SHADOW PHOTOMETER. - - -Fig. 263. RUMFORD'S SHADOW PHOTOMETER ARRANGED FOR TESTING -INCANDESCENT LAMPS. - - -415 STANDARD ELECTRICAL DICTIONARY. - - -A rod is supported in a vertical position. Back of it is a screen of -white paper. The two lights to be compared are arranged in front of the -rod and at a little distance from each other. They are shifted about -until the two shadows appear of equal darkness. The relative intensity -of the lights varies inversely with the square of their distances from -the shadows cast respectively by them on the screen. - -The cut, Fig. 262, shows the simplest type of the shadow photometer. In -the cut, Fig. 263, a shadow photometer for testing incandescent lamps is -shown. In it E is the lamp under trial supported by a clamp H. A is an -ampere meter in circuit with the lamp, and V is a voltmeter. A candle C -can be moved along a graduated scale G G. R is the vertical rod, and S -is the screen on which the shadows fall. - - -Photophore. -An instrument for medical examination of the cavities of the body. It -includes an incandescent lamp mounted in a tube with a concave mirror -and convex lens. - - -Photo-voltaic Effect. -The change in resistance of some substances effected by light. Selenium, -of all substances, is most susceptible to this effect. (See Selenium.) - - -Piano, Electric. -A piano whose manual or key-board operates to close electric circuits, -whereby electro-magnets are caused to operate to drive the hammers -against the strings. - - -Pickle. -An acid solution for cleaning metal surfaces before electro-plating, -galvanizing or other deposition of metal upon them. - - -Picture, Electric. -A picture produced by passing a strong discharge through a piece of gold -leaf clamped or firmly pressed upon a sheet of paper. The gold leaf is -cut out of the desired shape, or else a stencil of paper overlays it. -The discharge dissipates the gold, and produces a purple colored -reproduction of the design upon the paper. The design is due to the -deposition of an exceedingly thin film of metallic gold. - -Synonym--Electric Portrait. - - -Pile. -A galvanic or voltaic battery. It is sometimes restricted to a number of -voltaic couples connected. It should be only applied to batteries with -superimposed plates and no containing vessel such as the Dry Pile, q. -v., or Volta's Pile, q. v. - - -Pilot Transformer. -In alternating current distribution a small transformer placed at any -part of the system and connected to a voltmeter in the central station, -to indicate the potential difference of the leads. - - -Pilot Wires. -Wires brought from distant parts of electric light or power mains, and -leading to voltmeters at the central station, so that the potential of -distant parts of the system can be watched. The wires can be very small, -as they have but little current to transmit. - - -416 STANDARD ELECTRICAL DICTIONARY. - - -Pistol, Electric. -An experimental apparatus for exhibiting the power of electric -incandescence or of the electric spark. A tube is mounted with a handle -like a pistol. A plug is provided to screw in and out of its side. The -plug carries two wires connected on its inner side by a fine platinum -wire, or else disconnected but with their ends brought near together to -act as terminals for the production of a spark. To use it the tube is -filled with a mixture of air and gas, the latter either hydrogen, -hydro-carbon or other combustible gas. The tube when full is corked. The -wire is heated to incandescence by a current, or a spark is passed from -a Leyden jar or other source of electrostatic excitation. The mixture, -if properly proportioned, explodes and expels the cork violently. - - -Fig. 264. ELECTRIC PISTOL. - - -Pith. -A light and soft cellular tissue forming the central core of exogenous -trees and plants. In the older parts of the tree the woody tissue often -encroaches in and partly obliterates it. - -For electrical pith-balls, the pith of the elder, of corn, or, best of -all, of sun-flower stems is used. - - -Pith-balls. -Ball made of pith. They are used in the construction of electroscopes -and for other experiments in static electricity. - -They are cut out with a sharp knife and their shape may be improved by -gentle rolling in the hand or between the fingers. - - -Pivot Suspension. -Suspension poising or supporting of an object on a sharp pivot. This is -used for the needle in the ordinary compass. A cavity or inverted cup, -which may be made of agate, is attached to the middle of the needle -which has a hole for its reception. The centre of gravity of the needle -comes below the bottom of the cup. - -Pivot suspension is not perfect, as it has considerable friction. There -is no restitution force, as with torsion filaments. - - -417 STANDARD ELECTRICAL DICTIONARY. - - -Plant. -The apparatus for commercial manufacturing or technical works. An -electric lighting plant includes the boilers, engines and dynamos for -producing the current, and the electric mains and subsidiary apparatus. - - -Plant Electricity. -Electricity manifested by plant life. By means of a galvanometer -potential differences are found to exist in different parts of trees or -fruits. The roots and interior portions are negative, and the flowers, -smaller branches and fruit are positive. - -In some cases a contraction of the tissue of plants can be produced by -an electric current. The sensitive plant and others exhibit this -phenomenon, exactly analogous to the action of muscular tissue. - - -Plate, Arrester. -In a lightning arrester the plate connected to the circuit. Sometimes -both plates are designated arrester plates. - - -Plate Condenser. -A static condenser having a flat plate of glass for dielectric. (See -Epinus' Condenser.) - - -Plate Electrical Machine. -A frictional electric machine, in which a circular plate of glass is -excited by friction with the cushions. It is the most recent type of -frictional machine and has superseded the old cylinder machines. In its -turn it is superseded by influence machines, really plate machines, but -not so termed in practice. - - -Plate, Ground. -In a lightning arrester, the plate connected to the earth. - - -Plate, Negative. -In a voltaic battery, either primary or secondary, the plate which is -unattacked by the oxygen or negative radical or element of the fluid. It -corresponds to the carbon plate in the ordinary voltaic battery, and is -the one charged with positive electricity. - - -Plate, Positive. -In a voltaic battery, either primary or secondary, the plate which is -dissolved or attacked by the oxygen or negative radical or element of -the fluid. It is the plate corresponding to the zinc plate in the -ordinary voltaic battery, and is the one charged with negative -electricity. - - -Plating Balance. -A balance or scales to which articles in an electroplater's bath are -suspended. A weight exceeding by a known amount that of the article as -immersed overbalances the article. When the plating is being deposited -as soon as it exceeds the excess of weight of the counterpoise the -balance tips, the article descends a little, the electric circuit is -broken and the plating ceases. Thus the plating is automatically stopped -when a predetermined amount of metal is deposited. - - -418 STANDARD ELECTRICAL DICTIONARY. - - -Plating Bath. -A vessel of solution for the deposition of metal by electrolysis as used -in electro-plating. - - -Plating, Electro-. -The deposition of metal by electrolysis so as to coat the conducting -surface of objects therewith. The full details of the many processes are -very lengthy and cannot be given here. - -The general principle includes a battery or source of electric current. -The object to be plated is connected to the negative terminal and is -immersed in the solution. Thus with a battery the object is in -electrical connection with the zinc plate. To the other terminal a -metallic plate is connected. The object and the plate termed the anode -being introduced into a suitable bath, the metal whose solution is in -the bath is deposited upon the surface of the object. - -The bath is a solution of the metal in some form that will lend itself -to the electrolytic action. The anode is often a plate of the metal of -the bath, so that it dissolves as fast as metal is deposited on the -object, thus keeping up the strength of the solution. - -The objects to be plated must be scrupulously clean, and great care must -be taken to keep the bath uncontaminated. - -When the object has a non-conducting surface, it is made conducting by -being brushed over with plumbago q.v. In addition iron dust is sometimes -dusted over it. This acts by precipitating the metal of the bath -directly and thus giving a conducting basis for the metal to deposit on. -To avoid getting iron in a bath the object may be dipped in copper -sulphate solution. This precipitates copper in place of the iron and -leaves the article in good shape for silver or other plating. - -Electro-plating, if made thick enough, gives a reverse of the article -when separated therefrom. A direct copy can be got by a second plating, -on the first plating after separation, or a wax impression can be -employed. - -Under the different metals, formulae for the baths will be found. (See -also Quicking-- -Steeling--Plating Balance.) - - -Platinoid. -An alloy of copper, nickel, zinc in the proportions of German silver -with 1 or 2 per cent of tungsten. It is used for resistances. It has a -specific resistance (or resistance per centimeter cube) of about 34 -microhms. Its percentage variation in resistance per degree C. (1.8° F.) -is only about .021 per cent., or less than half that of German silver. -This is its most valuable feature. - - -419 STANDARD ELECTRICAL DICTIONARY. - - -Platinum. -A metal; one of the elements; symbol, Pt; atomic weight, 197.4; -equivalent, 49.35; valency, 4; specific gravity, 21.5. -It is a conductor of electricity. -The following data refer to the annealed metal at 0° C. (32° F.) - Relative Resistance (Silver annealed = 1), 6.022 - Specific Resistance, 9.057 microhms. - Resistance of a wire, - (a) 1 foot long, weighing 1 grain, 2.779 ohms. - (b) 1 foot long, 1/1000 inch thick, 54.49 " - (c) 1 meter long, weighing 1 gram, 1.938 " - (d) 1 meter long, 1 millimeter thick, .1153 " -Resistance of a 1 inch cube, 3.565 -Electro-chemical equivalent (Hydrogen = .0105), 0.5181. - -The coefficient of expansion by heat is almost the same as that of -glass. It can be passed through holes in glass and the latter can be -melted about it so as to hermetically seal its place of passage through -the glass. It is used in incandescent lamps for leading-in wires and -other similar uses. - - -Platinum Black. -Finely divided platinum. It is made by boiling a solution of platinic -chloride with excess of sodium carbonate and a quantity of sugar, until -the precipitate is perfectly black and the supernatant liquid is -colorless. It seems to possess a great power of occluding oxygen gas. -When heated to redness it becomes spongy platinum. The negative plates -of a Smee battery are coated with platinum black. - - -Platinum-silver Alloy. -An alloy of 1 part platinum and 2 parts silver, used for resistance coils. - - Relative Resistance (silver annealed = 1 ), 16.21 microhms. - Specific Resistance at 0°C. (32° F.), 24.39 - Resistance of a wire, - (a) 1 foot long, weighing 1 grain, 4.197 ohms. - (b) 1 foot long, 1/1000 inch diameter, 146.70 " - (c) 1 meter long weighing 1 gram, 2.924 " - (d) 1 meter long, 1 millimeter diameter, 0.3106 " - Resistance of a 1 inch cube, 9.603 microhms. - Percentage Variation per degree C. (1.8° F.) - at about 20° C. (68° F.), 0.031 per cent. - -Synonym--Platinum Alloy. - - -Platinum Sponge. -Finely divided platinum obtained by igniting platinum black, q.v., and -also by igniting salts of platinum. It has considerable power of -condensing or occluding oxygen. It will, if in good condition, set fire -to a jet of hydrogen impinging upon it. - - -Plow. -Contact arms projecting downwards from the motors, trucks, or bodies of -electric street cars, which enter the underground conduit through the -slot and carry contact pieces or brushes, to take the current for -driving the motors from the leads within the conduit. - - -420 STANDARD ELECTRICAL DICTIONARY. - - -Plücker Tubes. -A special form of Geissler tube designed for the production of -stratification and for observing the effects produced in the space -surrounding the negative electrode. - - -Plug. -(a) A piece of metal with a handle and a somewhat tapered end, used to -make connections by insertions between two plates or blocks of metal -slightly separated and with grooves to receive it. - -(b) A plug or wedge with two metallic faces, insulated from each other -with a separate wire connected to each one. It is used in spring-jacks -q. v., to introduce a loop in a circuit. - -Synonym--Wedge. - - -Plug. v. -To connect by inserting a plug, as in a resistance box. - - -Fig. 265. PLUGS FOR RESISTANCE COIL BOX. - - -Fig. 266. PLUG SWITCH. - - -Plug, Double. -A spring-jack plug or wedge with two pairs of insulated faces, one -behind the other, so as to simultaneously introduce two loops into a -circuit. - - -Plug, Grid. -A piece or mass of lead oxide, inserted into the holes in the lead -plates of storage batteries. The holes are often dovetailed or of uneven -section to better retain the plugs. - - -Plug Infinity. -In a box-bridge or resistance box, a plug whose removal from between two -disconnected discs opens the circuit. All the other discs are connected -by resistance coils of various resistance. - - -Plug Switch. -A switch composed of two contact blocks, not touching each other and -brought into electrical connection by the insertion of a metallic plug. -The latter is usually provided with an insulating handle, and a seat is -reamed out for it in the two faces of the contact blocks. - - -421 STANDARD ELECTRICAL DICTIONARY. - - -Plumbago. -Soft lustrous graphite, a native form of carbon; sometimes chemically -purified. It is used in electro-plating to give a conducting surface to -non-conducting objects, such as wax moulds. The surface, after coating -with plumbago, is sometimes dusted over with iron dust, which -precipitates the metal of the bath and starts the plating. It is -sometimes plated with copper, silver or gold, and is then termed -coppered, silvered, or gilt plumbago. It is gilded by moistening with -etherial solution of gold chloride and exposing to the air, and drying -and igniting. - - -Plunger. -A movable core which is used in connection with a so-called solenoid -coil, to be drawn in when the coil is excited. (See Coil and Plunger.) - - -Fig. 267 COIL AND PLUNGER WITH SCALES TO SHOW ATTRACTION. - - -P. O. -Abbreviation for Post Office, q.v. - - -Poggendorf's Solution. -An acid depolarizing and exciting fluid for zinc-carbon batteries. The -following is its formula: Water, 100 parts; potassium bichromate, 12 -parts; concentrated sulphuric acid, 25 parts. All parts by weight. Use -cold. - - -Point, Neutral. -(a) On a commutator of a dynamo the points at the ends of the diameter -of commutation, or where the brushes rest upon the surface of the -commutator, are termed neutral points. At these points there is no -generation of potential, they marking the union of currents of opposite -direction flowing from the two sides of the armature into the brushes. - -(b) In electro-therapeutics, a place in the intra-polar region of a -nerve so situated with reference to the kathode and electrode as applied -in treatment, that its condition is unaffected. - -Synonym--Indifferent Point. - -(c) In a magnet the point of no attraction, situated between the two -poles, at about an equal distance from each, so as to mark the centre of -a magnet of even distribution of polarity. - -(d) In thermo-electricity the point of temperature where the -thermo-electric powers of two metals are zero; in a diagram the point -where the lines representing their thermo-electric relations cross each -other; if the metals are arranged in a thermo-electric couple, one end -at a temperature a given amount above, the other at a temperature the -same amount below the neutral point, no current or potential difference -will be produced. - - -422 STANDARD ELECTRICAL DICTIONARY. - - -Point, Null. -A nodal point in electrical resonators; a point where in a system of -waves or oscillations, there is rest, the zero of motion being the -resultant of oppositely directed and equal forces. In electrical -resonators it is to be sought for in a point symmetrically situated, -with reference to the spark gap, or in a pair of points, which pair is -symmetrically placed. - -The null point in resonators is found by connecting a lead from one of -the secondary terminals of an induction coil to different parts of the -resonator. The null point is one where the connection does not give rise -to any sparks between the micrometer knobs or spark gap, or where the -sparks are of diminished size. - -The whole is exactly comparable to loops and nodes in a vibrating string -or in a Chladni plate as described in treatises on sound and acoustics. -(See Resonance, Electrical--Resonator, Electrical.) - -Synonym--Nodal Point. - - -Point Poles. -Magnet poles that are virtually points, or of no magnitude. A long thin -magnet with little leakage except close to the ends may be supposed to -have point poles within itself a short distance back from the ends. - - -Points, Consequent. -In a magnet with consequent poles, the points where such poles are -situated. - - -Points, Corresponding. -In bound electrostatic charges the points of equal charges of opposite -potentials; the points at opposite extremities of electrostatic lines of -force. This definition implies that the bound charges shall be on equal -facing areas of conductors, as otherwise the spread or concentration of -the lines of force would necessitate the use of areas of size -proportionate to the spreading or concentrating of the lines of force. -At the same time it may figuratively be applied to these cases, the -penetration of the surface by a single line of force including the area -fixed by its relation to the surrounding lines. - - -Points, Isoelectric. -In electro-therapeutics, points of equal potential in a circuit. - - -423 STANDARD ELECTRICAL DICTIONARY. - - -Points of Derivation. -The point where a single conductor branches into two or more conductors, -operating or acting in parallel with each other. - - -Polar Angle. -The angle subtended by one of the faces of the pole pieces of the field- -magnet of a dynamo or motor. The centre of the circle of the angle lies -in the axis of the armature. - -Synonym--Angle of Polar Span. - - -Polar Extension. -An addition made of iron to the poles of magnets. Various forms have -been experimented with. The pole pieces of dynamo field magnets are -polar extensions. - -Synonyms--Pole Piece--Polar Tips. - - -Polarity, Diamagnetic. -The induced polarity of diamagnetic substances; it is the reverse of -paramagnetic polarity, or of the polarity of iron. A bar of diamagnetic -material held parallel with the lines of force in a magnetic field has a -like pole induced in the end nearest a given pole of the field magnet, -and vice versa. This theory accounts for the repulsion by a magnet of a -diamagnetic substance. The existence of this polarity is rather an -assumption. It originated with Faraday. - - -Polarity, Paramagnetic. -The induced polarity of paramagnetic substances, such as iron, nickel, -or cobalt. - -When such a substance is brought into a magnetic field the part nearest -a specific pole of a magnet acquires polarity opposite to that of such -pole and is thereby attracted. - -Another way of expressing it, in which the existence of a pole in or -near to the field is not implied, is founded on the conventional -direction of lines of force. Where these enter the substance a south -pole is formed and where they emerge a north pole is formed. - -Such polarity tends always to be established in the direction of -greatest length, if the body is free to rotate. - - -424 STANDARD ELECTRICAL DICTIONARY. - - -Polarization. -(a) The depriving of a voltaic cell of its proper electro-motive force. -Polarization may be due to various causes. The solution may become -exhausted, as in a Smee battery, when the acid is saturated with zinc -and thus a species of polarization follows. But the best definition of -polarization restricts it to the development of counter-electro-motive -force in the battery by the accumulation of hydrogen on the negative -(carbon or copper) plate. To overcome this difficulty many methods are -employed. Oxidizing solutions or solids are used, such as solution of -chromic acid or powdered manganese dioxide, as in the Bunsen and -Leclanché batteries respectively; a roughened surface of platinum black -is used, as in the Smee battery; air is blown through the solution to -carry off the hydrogen, or the plates themselves are moved about in the -solution. - -(b) Imparting magnetization to a bar of iron or steel, thus making a -permanent magnet, is the polarization of the steel of which it is made. -Polarization may be permanent, as in steel, or only temporary, as in -soft iron. - -(c) The strain upon a dielectric when it separates two oppositely -charged surfaces. The secondary discharge of a Leyden jar, and its -alteration in volume testify to the strain put upon it by charging. - -(d) The alteration of arrangement of the molecules of an electrolyte by -a decomposing current. All the molecules are supposed to be arranged -with like ends pointing in the same direction, positive ends facing the -positively-charged plate and negative ends the negatively-charged one. - -(e) The production of counter-electro-motive force in a secondary -battery, or in any combination capable of acting as the seat of such -counter-electro-motive force. (See Battery, Secondary--Battery, Gas.) -The same can be found often in organized cellular tissue such as that of -muscles, nerves, or of plants. If a current is passed through this in -one direction, it often establishes a polarization or potential -difference that is susceptible of giving a return current in the -opposite direction when the charging battery is replaced by a conductor. - - -Polarization Capacity. -A voltaic cell in use becomes polarized by its negative plate -accumulating hydrogen, or other cause. This gradually gives the plate a -positive value, or goes to set up a counter-electro-motive force. The -quantity of electricity required to produce the polarization of a -battery is termed its Polarization Capacity or Capacity of Polarization. - - -Polarization of the Medium. -The dielectric polarization, q. v., of a dielectric, implying the -arrangement of its molecules in chains or filaments; a term due to -Faraday. He illustrated it by placing filaments of silk in spirits of -turpentine, and introduced into the liquid two conductors. On -electrifying one and grounding (or connecting to earth) the other one, -the silk filaments arranged themselves in a chain or string connecting -the points of the conductors. - - -Polar Region. -That part of the surface of a magnet whence the internal magnetic lines -emerge into the air. (S. P. Thompson.) As such lines may emerge from -virtually all parts of its surface, the polar regions are indefinite -areas, and are properly restricted to the parts whence the lines emerge -in greatest quantity. - - -Polar Span. -A proportion of the circle which represents the transverse section of -the armature space between the pole pieces of the field magnet in a -dynamo or motor; it is the proportion which is filled by the faces of -the pole pieces. - - -425 STANDARD ELECTRICAL DICTIONARY. - - -Pole, Analogous. -The end of a crystal of a pyroelectric substance, such as tourmaline, -which end when heated become positively electrified. On reduction of -temperature the reverse effect obtains. - - -Pole, Antilogous. -The end of a crystal of a pyroelectric substance, such as tourmaline, -which end, while increasing in temperature, becomes negatively -electrified. During reduction of its temperature the reverse effect -obtains. - - -Pole Changer. -(a) An automatic oscillating or vibrating switch or contact-breaker -which in each movement reverses the direction of a current from a -battery or other source of current of fixed direction, as such current -goes through a conductor. - -(b) A switch moved by hand which for each movement effects the above -result. - - -Pole, Negative. -(a) In a magnet the south pole; the pole into which the lines of force -are assumed to enter from the air or outer circuit. - -(b) In a current generator the pole or terminal into which the current -is assumed to flow from the external circuit. It is the negatively -charged terminal and in the ordinary voltaic battery is the terminal -connected to the zinc or positive plate. - - -Pole Pieces. -The terminations of the cores of field or other electro-magnets, or of -permanent magnets. These terminations are variously shaped, sometimes -being quite large compared to the core proper of the magnet. - -They are calculated so as to produce a proper distribution of and -direction of the lines of force from pole to pole. As a general rule the -active field should be of uniform strength and the pole pieces may be of -contour calculated to attain this end. - - -Pole, Positive. -(a) In a magnet the north pole; the pole from which lines of force are -assumed to emerge into the air. - -(b) In a current generator the pole or terminal whence the current is -assumed to issue into the outer circuit. It is the positively charged -terminal, and in the ordinary voltaic battery is the terminal connected -to the copper or carbon plate, termed the negative plate. - - -Poles. -(a) The terminals of an open electric circuit, at which there -necessarily exists a potential difference, produced by the generator or -source of electro-motive force in the circuit. - -(b) The terminals of an open magnetic circuit; the ends of a magnetized -mass of steel, iron or other paramagnetic substance. - -(c) The ends in general of any body or mass which show electric or -magnetic properties more developed than those of the central sections of -the body. - - -426 STANDARD ELECTRICAL DICTIONARY. - - -Pole, Salient. -In dynamo and motor field magnets, salient poles are those projecting -from the base or main body of the field magnet, as distinguished from -consequent poles formed by coils wound on the main body itself. - - -Fig. 268. SALIENT POLES OF FIELD MAGNET. - - -Poles, Compensating. -A device for avoiding the cross-magnetizing effect on the commutator -core due to the lead of the brushes. It consists in maintaining a small -bar electro-magnet perpendicularly between the pole pieces. This -compensates the cross-magnetizing effect. - - -Poles of Intensity. -The locus of highest magnetic force on the earth's surface. One such -pole is in Siberia, another is about lat. 52° N., long. 92° W. - -[Transcriber's note: 52° N., long. 92° W is about 250 miles Northeast of -Winnipeg.] - - -Poles of Verticity. -The magnetic poles of the earth. (See Magnetic Poles.) - -Pole Tips. -The extreme ends of the expanded poles of a field magnet. In some -machines some of the pole tips are made of cast iron, to alter the -distribution of the lines of force and resulting magnetic pull upon the -armatures. This is done to take off the weight of the armature from its -bearings. - - -Pole, Traveling. -A term applied to the poles produced in the action of a rotatory field, -whose poles constantly rotate around the circle of the field. (See -Field, Rotatory.) - - -417 STANDARD ELECTRICAL DICTIONARY. - - -Porous Cup. -A cup of pipe clay, unglazed earthenware or other equivalent material -used in voltaic cells to keep two liquids separate and yet to permit -electrolysis and electrolytic conduction. - -They are necessarily only an expedient, as their porous nature permits -considerable diffusion, and were they not porous electrolytic action -would be impossible. - -Synonym--Porous Cell. - - -Porret's Phenomenon. -In electro-physiology, an increase in the diameter of a nerve produced -by the positive pole of a voltaic circuit, when placed in contact with -the tissue and near to the nerve in question, the other pole being -connected to a more or less remote part of the body. - - -Portelectric Railroad. -A railroad worked by solenoidal attraction, the car forming the core of -the solenoids. It includes a series of solenoids or hollow coils of -copper wire distributed all along the road and inclosing within -themselves the track. On this a cylindrical car with pointed ends moves -on wheels. Current is supplied to the solenoid in advance of the car, -and attracts it. As it advances it breaks the contacts of the attracting -solenoid and turns the current into the one next in advance. This -operation is repeated as the car advances. - -The solenoids are placed close together, each including in the trial -track 630 turns of No. 14 copper wire. The car was of wrought iron, 12 -feet long, 10 inches in diameter and weighing 500 lbs. It was proposed -to employ the system for transportation of mail matter and similar uses. - - -Position Finder. -An instrument for determining the position of objects which are to be -fired at from forts. It is designed for use from forts situated on the -water. - -Fiske's position finder may be thus generally described. On a chart the -channel is divided into squares, and the position finder determines the -square in which a vessel lies. For each square the direction and -elevation of the guns is calculated beforehand. The enemy can therefore -be continuously located and fired at, although from smoke or other cause -the object may be quite invisible to the gunner. - -It comprises two telescopes situated at distant extremities of as long a -base line as is obtainable. These telescopes are kept directed upon the -object by two observers simultaneously. The observers are in constant -telephonic communication. As each telescope moves, it carries a contact -over an arc of conducting material. Below each telescope is an arm also -moving over an arc of conducting material. These arcs enter into a -Wheatstone bridge and are so connected that when the arm and the distant -telescope are at the same angle or parallel a balance is obtained. Thus -each observer has the power of establishing a balance. A chart is -provided for each of them, and over it the arm connected with the -distant telescope and an arm or indicator attached to the telescope at -that station move so that as long as both telescopes point at the object -and each observer maintains the electric balance, the intersection of -the arms shows the position on the chart. - -The Position Finder is a simplification and amplification of the Range -Finder, q. v. In practice the observers may be placed far from the -forts, and may telephone their observations thereto. It has been found -accurate within one-third of one per cent. - - -428 STANDARD ELECTRICAL DICTIONARY. - - -Positive Direction. -The direction which lines of force are assumed to take in the air or -outer circuit from a positive to a negative region. It applies to -electrostatic, to magnetic and to electro-magnetic lines of force. - - -Positive Electricity. -The kind of electricity with which a piece of glass is charged when -rubbed with silk; vitreous electricity. - -In a galvanic cell the surface of the copper or carbon plate is charged -with positive electricity. (See Electrostatic Series.) - -According to the single fluid theory positive electrification consists -in a surplus of electricity. - -[Transcriber's note: "Positive electricity" is a deficiency of electrons.] - - -Post Office. adj. -Many pieces of electric apparatus of English manufacture are thus -qualified, indicating that they are of the pattern of the apparatus used -by the British Post Office in its telegraph department. - -Potential. -Potential in general may be treated as an attribute of a point in space, -and may express the potential energy which a unit mass would have if -placed at that point. - -This conception of potential is that of a property attributable to a -point in space, such that if a unit mass were placed there the forces -acting upon it would supply the force factor of energy, while the body -would supply the mass factor. This property is expressible in units, -which produce, if the supposed mass is a unit mass, units of work or -energy, but potential itself is neither. - -Thus taking gravitation, a pound mass on the surface of the earth -(assuming it to be a sphere of 4,000 miles radius) would require the -expenditure of 21,120,000 foot pounds to remove it to an infinite -distance against gravity. The potential of a point in space upon the -surface of the earth is therefore negative and is represented by --21,120,000*32.2 foot poundals (32.2 = acceleration of gravity). (See -Poundal.) In practice and conventionally all points on the earth's -surface are taken as of zero potential. - -[Transcriber's note; 21,120,000 foot pounds is about 8 KWh.] - - -429 STANDARD ELECTRICAL DICTIONARY. - - -Potential, Absolute. -The absolute electrical potential at a point possesses a numerical value -and measures the tendency which the existing electric forces would have -to drive an electrified particle away from or prevent its approach to -the point, if such a particle, one unit in quantity, were brought up to -or were situated at that point. It is numerically equal to the number of -ergs of work which must be done to bring a positive unit of electricity -from a region where there is absolutely no electric force up to the -point in question. (Daniell.) Two suppositions are included in this. The -region where there is an electric force has to be and only can be at an -infinite distance from all electrified bodies. The moving of the -particle must take place without any effect upon the distribution of -electricity on other particles. - - -Potential, Constant. -Unchanging potential or potential difference. - -The ordinary system of incandescent lighting is a constant potential -system, an unvarying potential difference being maintained between the -two leads, and the current varying according to requirements. - - -Potential Difference, Electric. -If of any two points the absolute potentials are determined, the -difference between such two expresses the potential difference. -Numerically it expresses the quantity of work which must be done to -remove a unit of electricity from one to the other against electric -repulsion, or the energy which would be accumulated in moving it the -other way. - -A positively charged particle is driven towards the point of lower -potential. A negatively charged body is driven in the reverse direction. - - -Potential Difference, Electro-motive. -A difference of potential in a circuit, or in part of a circuit, which -difference produces or is capable of producing a current, or is due to -the flow of such current. - -It may be expressed as the fall in potential or the electro-motive force -included between any two points on a circuit. The current in an active -circuit is due to the total electro-motive force in the circuit. This is -distributed through the circuit in proportion to the resistance of its -parts. Owing to the distribution of electro-motive force throughout a -circuit including the generator, the terminals of a generator on closed -circuit may show a difference of potential far lower than the -electro-motive force of the generator on closed circuit. Hence potential -difference in such a case has been termed available electro-motive -force. - - -Potential, Electric Absolute. -The mathematical expression of a property of a point in space, measuring -the tendency which existing electric forces would have to drive an -electrified unit particle away from or prevent its approach to the point -in question, according to whether the point was situated at or was at a -distance from the point in question. - -Potential is not the power of doing work, although, as it is expressed -always with reference to a unit body, it is numerically equal to the -number of ergs of work which must be done in order to bring a positive -unit of electricity from a region where there is no electric -force--which is a region at an infinite distance from all electrified -bodies--up to the point in question. This includes the assumption that -there is no alteration in the general distribution of electricity on -neighboring bodies. (Daniell.) - -In practice the earth is arbitrarily taken as of zero electric potential. - - -430 STANDARD ELECTRICAL DICTIONARY. - - -Potential, Fall of. -The change in potential between any two points on an active circuit. The -change in potential due to the maintenance of a current through a -conductor. - -The fall in potential multiplied by the current gives work or energy -units. - -The fall of potential in a circuit and its subsequent raising by the -action of the generator is illustrated by the diagram of a helix. In it -the potential fall in the outer circuit is shown by the descent of the -helix. This represents at once the outer circuit and the fall of -potential in it. The vertical axis represents the portion of the circuit -within the battery or generator in which the potential by the action of -the generator is again raised to its original height. - -In a circuit of even resistance the potential falls evenly throughout -it. - -A mechanical illustration of the relation of fall of potential to -current is shown in the cut Fig. 269. A vertical wire is supposed to be -fixed at its upper end and a lever arm and cord at its lower end, with -weight and pulley imparts a torsional strain to it. The dials and -indexes show a uniform twisting corresponding to fall of potential. For -each unit of length there is a definite loss of twisting, corresponding -to fall of potential in a unit of length of a conductor of uniform -resistance. The total twisting represents the total potential -difference. The weight sustained by the twisting represents the current -maintained by the potential difference. For a shorter wire less twisting -would be needed to sustain the weight, as in a shorter piece of the -conductor less potential difference would be needed to maintain the same -current. - - -Fig. 269. MECHANICAL ILLUSTRATION OF FALL OF POTENTIAL AND CURRENT -STRENGTH. - - -431 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 270. ILLUSTRATION OF THE FALL AND REDEVELOPMENT OF POTENTIAL IN AN -ELECTRIC CIRCUIT. - - -The fall of potential in a circuit in portions of it is proportional to -the resistance of the portions in question. This is shown in the -diagram. The narrow lines indicate high and the broad lines low -resistance. The fall in different portions is shown as proportional to -the resistance of each portion. - - -Fig. 271. DIAGRAM OF FALL OF POTENTIAL IN A CONDUCTOR OF UNEVEN -RESISTANCE. - - -Potential, Magnetic. -The magnetic potential at any point of a magnetic field expresses the -work which would be done by the magnetic forces of the field on a -positive unit of magnetism as it moves from that point to an infinite -distance therefrom. The converse applies to a negative unit. - -It is the exact analogue of absolute electric potential. - -The potential at any point due to a positive pole m at a distance r is -m/r;. that due to a negative pole - m at a distance r' is equal to --m/r';. that due to both is equal to m/r - m/r' or m(1/r - 1/r'). - -Like electric potential and potential in general, magnetic potential -while numerically expressing work or energy is neither, although often -defined as such. - - -432 STANDARD ELECTRICAL DICTIONARY. - - -Potential, Negative. -The reverse of positive potential. (See Potential, Positive.) - - -Potential, Positive. -In general the higher potential. Taking the assumed direction of lines -of force, they are assumed to be directed or to move from regions of -positive to regions of negative potential. The copper or carbon plate of -a voltaic battery is at positive potential compared to the zinc plate. - - -Potential, Unit of Electric. -The arbitrary or conventional potential--or briefly, the potential of a -point in an electric field of force--is, numerically, the number of ergs -of work necessary to bring a unit of electricity up to the point in -question from a region of nominal zero potential--i. e., from the -surface of the earth. (Daniell.) This would give the erg as the unit of -potential. - - -Potential, Zero. -The potential of the earth is arbitrarily taken as the zero of electric -potential. - -The theoretical zero is the potential of a point infinitely distant from -all electrified bodies. - - -Fig. 272. DIAGRAM OF POTENTIOMETER CONNECTIONS. - - -Potentiometer. -An arrangement somewhat similar to the Wheatstone Bridge for determining -potential difference, or the electro-motive force of a battery. In -general principle connection is made so that the cell under trial would -send a current in one direction through the galvanometer. Another -battery is connected, and in shunt with its circuit the battery under -trial and its galvanometer are connected, but so that its current is in -opposition. By a graduated wire, like that of a meter bridge, the -potential of the main battery shunt can be varied until no current -passes. This gives the outline of the method only. - - -433 STANDARD ELECTRICAL DICTIONARY. - - -In the cut A B is the graduated potentiometer wire through which a -current is passed in the direction of the arrow. E is the battery under -trial, placed in opposition to the other current, with a galvanometer -next it. Under the conditions shown, if the galvanometer showed no -deflection, the E. M. F. of the battery would be to the E. M. F. between -the ends of the potentiometer wire, 1 . . . . .10, as 1.5 the distance -between the points of connection, A and D of the battery circuit, is to -10, the full length of the potentiometer wire. - - -Poundal. -The British unit of force; the force which acting on a mass of one pound -for one second produces an acceleration of one foot. - -[Transcriber's note: The force which acting on a mass of one pound -produces an acceleration of ONE FOOT PER SECOND PER SECOND.] - - -Power. Activity; -the rate of activity, of doing work, or of expending energy. The -practical unit of electric power is the volt-ampere or watt, equal to -1E7 ergs per second. The kilowatt, one thousand watts or volt-amperes, -is a frequently adopted unit. - - -Power, Electric. -As energy is the capacity for doing work, electric energy is represented -by electricity in motion against a resistance. This possesses a species -of inertia, which gives it a species of kinetic energy. To produce such -motion, electro- motive force is required. The product of E. M. F. by -quantity is therefore electric energy. (See Energy, Electric.) - -Generally the rate of energy or power is used. Its dimensions are - ( ( (M^.5)*(L^.5) ) / T ) * ( ( (M^.5) *(L^1.5) )/( T^2) ) - (intensity or current rate) * (electro-motive force or potential) - = (M * (L^2) ) / (T^3), -which are the dimensions of rate of work or activity. The practical unit -of electric rate of energy or activity is the volt-ampere or watt. By -Ohm's law, q. v., we have C = E/R (C = current; E = potential difference -or electro-motive force; R = resistance.) The watt by definition = C*E. -By substitution from Ohm's formula we deduce for it the following -values: ((C^2) * R) and ((E^2) /R). From these three expressions the -relations of electric energy to E.M.F., Resistance, and Current can be -deduced. - - -Power of Periodic Current. -The rate of energy in a circuit carrying a periodic current. In such a -circuit the electro-motive force travels in advance of the current it -produces on the circuit. Consequently at phases or intervals where, -owing to the alternations of the current, the current is at zero, the -electro-motive force may be quite high. At any time the energy rate is -the product of the electro-motive force by the amperage. To obtain the -power or average rate of energy, the product of the maximum -electro-motive force and maximum current must be divided by two and -multiplied by the cosine of the angle of lag, which is the angle -expressing the difference of phase. - -[Transcriber's note; The voltage phase will lead if the load is -inductive. The current phase will lead if the load is capacitive. -Capacitors or inductors may be introduced into power lines to correct -the phase offset introduced by customer loads.] - - -434 STANDARD ELECTRICAL DICTIONARY. - - -Pressel. -A press-button often contained in a pear-shaped handle, arranged for -attachment to the end of a flexible conductor, so as to hang thereby. By -pressing the button a bell may be rung, or a distant lamp may be -lighted. - - -Pressure. -Force or stress exerted directly against any surface. Its dimensions are -force/area or ((M*L)/(T^2)) / (L^2) = M/(L* (T^2)). - - -Pressure, Electric. -Electro-motive force or potential difference; voltage. An expression of -metaphorical nature, as the term is not accurate. - - -Pressure, Electrification by. -A crystal of Iceland spar (calcium carbonate) pressed between the -fingers becomes positively electrified and remains so for some time. -Other minerals act in a similar way. Dissimilar substances pressed -together and suddenly separated carry off opposite charges. This is -really contact action, not pressure action. - - -Primary. -A term used to designate the inducing coil in an induction coil or -transformer; it is probably an abbreviation for primary coil. - - -Primary Battery. -A voltaic cell or battery generating electric energy by direct -consumption of material, and not regenerated by an electrolytic process. - -The ordinary voltaic cell or galvanic battery is a primary battery. - - -Prime. vb. -To impart the first charge to one of the armatures of a Holtz or other -influence machine. - - -Fig. 273. PRIME CONDUCTOR AND PROOF PLANE. - - -435 STANDARD ELECTRICAL DICTIONARY. - - -Prime Conductor. -A metal or metal coated sphere or cylinder or other solid with rounded -ends mounted on insulating supports and used to collect electricity as -generated by a frictional electric machine. - -According to whether the prime conductor or the cushions are grounded -positive or negative electricity is taken from the ungrounded part. -Generally the cushions are grounded, and the prime conductor yields -positive electricity. - - -Probe, Electric. -A surgeon's probe, designed to indicate by the closing of an electric -circuit the presence of a bullet or metallic body in the body of a -patient. - -Two insulated wires are carried to the end where their ends are exposed, -still insulated from each other. In probing a wound for a bullet if the -two ends touch it the circuit is closed and a bell rings. If a bone is -touched no such effect is produced. The wires are in circuit with an -electric bell and battery. - - -Projecting Power of a Magnet. -The power of projecting its lines of force straight out from the poles. -This is really a matter of magnetic power, rather than of shape of the -magnet. In electromagnets the custom was followed by making them long to -get this effect. Such length was really useful in the regard of getting -room for a sufficient number of ampere turns. - - -436 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 274. PRONY BRAKE. - - -Prony Brake. -A device for measuring the power applied to a rotating shaft. It -consists of a clamping device to be applied more or less rigidly to the -shaft or to a pulley upon it. To the clamp is attached a lever carrying -a weight. The cut shows a simple arrangement, the shaft A carries a -pulley B to which the clamp B1 B2 is applied. The nuts C1 C2 are used -for adjustment. - -A weight is placed in the pan E attached to the end of the lever D. The -weight and clamp are so adjusted that the lever shall stand horizontally -as shown by the index E. If we call r the radius of the pulley and F the -friction between its surface and the clamp, it is evident that r F, the -moment of resistance to the motion of the pulley, is equal to the weight -multiplied by its lever arm or to W*R, where W indicates the weight and -R the distance of its point of application from the centre of the pulley -or r*F = R*W. The work represented by this friction is equal to the -distance traveled by the surface of the wheel multiplied by the -frictional resistance, or is 2*PI*r*n*F, in which n is the number of -turns per minute. But this is equal to 2*PI*R*W. These data being known, -the power is directly calculated therefrom in terms of weight and feet -per minute. - - -Proof-plane. -A small conductor, usually disc shaped, carried at the end of an -insulating handle. It is used to collect electricity by contact, from -objects electrostatically charged. The charge it has received is then -measured (see Torsion Balance) or otherwise tested. (See Prime -Conductor.) - - -Proof-sphere. -A small sphere, coated with gold-leaf or other conductor, and mounted on -an insulated handle. It is used instead of a proof-plane, for testing -bodies whose curvature is small. - - -Fig. 275. BOX BRIDGE. - - -437 STANDARD ELECTRICAL DICTIONARY. - - -Proportionate Arms. In general terms the arms of a Wheatstone bridge -whose proportion has to be known to complete the measurement. There is a -different system of naming them. Some designate by this title the two -arms in parallel with each other branching at and running from one end -of the bridge to the two galvanometer connections. In the cut of the Box -Bridge, A C and A B are the proportionate arms. The third arm is then -termed the Rheostat arm. (Stewart & Gee.) - -Others treat as proportionate arms the two side members of the bridge in -parallel with the unknown resistance and third or rheostat arm. - -Synonym--Ratio Arms. - - -Prostration, Electric. -Too great exposure to the voltaic arc in its more powerful forms causes -symptoms resembling those of sunstroke. The skin is sometimes affected -to such a degree as to come off after a few days. The throat, forehead -and face suffer pains and the eyes are irritated. These effects only -follow exposure to very intense sources of light, or for very long -times. - -[Transcriber's note: Arcs emit ultraviolet rays.] - - -Protector, Comb. -A lightning arrester, q. v., comprising two toothed plates nearly -touching each other. - - -Protector, Electric. -A protective device for guarding the human body against destructive or -injurious electric shocks. In one system, Delany's, the wrists and -ankles are encircled by conducting bands which by wires running along -the arms, back and legs are connected. A discharge it is assumed -received by the hands will thus be short circuited around the body and -its vital organs. India rubber gloves and shoe soles have also been -suggested; the gloves are still used to some extent. - - -Pull. -A switch for closing a circuit when pulled. It is used instead of a push -button, q.v., in exposed situations, as its contacts are better -protected than those of the ordinary push button. - - -Pump, Geissler. -A form of mercurial air pump. It is used for exhausting Geissler tubes, -incandescent lamp bulbs and similar purposes. - -Referring to the cut, A is a reservoir of mercury with flexible tube C -connected to a tube at its bottom, and raised and lowered by a windlass -b, the cord from which passes over a pulley a. When raised the mercury -tends to enter the chamber B, through the tube T. An arrangement of -stopcocks surmounts this chamber, which arrangement is shown on a larger -scale in the three figures X, Y and Z. To fill the bulb B, the cocks are -set in the position Z; n is a two way cock and while it permits the -escape of air below, it cuts off the tube, rising vertically from it. -This tube, d in the full figure connects with a vessel o, pressure gauge -p, and tube c, the latter connecting with the object to be exhausted. -The bulb B being filled, the cock m is closed, giving the position Y and -the vessel A is lowered until it is over 30 inches below B. - -438 STANDARD ELECTRICAL DICTIONARY. - -This establishes a Torricellian vacuum in B. The cock n is now turned, -giving the position X, when air is at once exhausted from the vessel -connected to C. This process is repeated until full exhaustion is -obtained. In practice the first exhaustion is often effected by a -mechanical pump. By closing the cock on the outlet tube c but little air -need ever find its way to the chambers o and B. - - -Fig. 276. GEISSLER AIR PUMP. - - -439 STANDARD ELECTRICAL DICTIONARY. - - -Pumping. -In incandescent lamps a periodical recurring change in intensity due to -bad running of the dynamos, or in arc lamps to bad feeding of the -carbons. - - -Fig. 277. SPRENGEL AIR PUMP. - - -Pump, Sprengel. -A form of mercurial air pump. A simple form is shown in the cut. Mercury -is caused to flow from the funnel A, through c d to a vessel B. A side -connection x leads to the vessel R to be exhausted. As the mercury -passes x it breaks into short columns, and carries air down between -them, in this way exhausting the vessel R. In practice it is more -complicated. It is said to give a better vacuum than the Sprengel pump, -but to be slower in action. - - -440 STANDARD ELECTRICAL DICTIONARY. - - -Pump, Swinburne. -A form of mechanical air pump for exhausting incandescent lamp bulbs. -Referring to the cut, A is a bulb on the upper part of a tube G; above A -are two other bulbs C and D. From the upper end a tube runs to the bulb -E. Through the cock L, and tube F connection is made with a mechanical -air pump. The tube H leads to a drying chamber I, and by the tube J -connects with the lamp bulbs or other objects to be exhausted. The tube -G enters the bottle B through an airtight stopper, through which a -second tube with stopcock K passes. In use a vacuum is produced by the -mechanical pumps, exhausting the lamp bulbs to a half inch and drawing -up the mercury in G. The bent neck in the bulb E, acts with the bulb as -a trap to exclude mercury from F. When the mechanical pumps have -produced a vacuum equal to one half inch of mercury, the cock L is -closed and K is opened, and air at high pressure enters. This forces the -mercury up to the vessel D, half filling it. The high pressure is now -removed and the mercury descends. The valve in D closes it as the -mercury falls to the level G. Further air from the lamps enters A, and -by repetition of the ascent of the mercury, is expelled, through D. The -mercury is again lowered, producing a further exhaustion, and the -process is repeated as often as necessary. - - -Fig. 278. SWINBURNE'S AIR PUMP. - - -Push-Button. -A switch for closing a circuit by means of pressure applied to a button. -The button is provided with a spring, so that when pushed in and -released it springs back. Thus the circuit is closed only as long as the -button is pressed. The electric connection may be made by pressing -together two flat springs, each connected to one of the wires, or by the -stem of the button going between two springs, not in contact, forcing -them a little apart to secure good contact, and thereby bridging over -the space between them. - - -441 STANDARD ELECTRICAL DICTIONARY. - -Pyro-electricity. -A phenomenon by which certain minerals when warmed acquire electrical -properties. (Ganot.) The mineral tourmaline exhibits it strongly. It was -originally observed in this mineral which was found to first attract and -then to repel hot ashes. - -The phenomenon lasts while any change of temperature within certain -limits is taking place. In the case of tourmaline the range is from -about 10º C. (50º F.) to 150º C. (302º F.) Above or below this range it -shows no electrification. - -The effect of a changing of temperature is to develop poles, one -positive and the other negative. As the temperature rises one end is -positive and the other negative; as the temperature becomes constant the -polarity disappears; as the temperature falls the poles are reversed. - -If a piece of tourmaline excited by pyro-electricity is broken, its -broken ends develop new poles exactly like a magnet when broken. - -The following minerals are pyro-electric: Boracite, topaz, prehnite, -zinc silicate, scolezite, axenite. The following compound substances are -also so: Cane sugar, sodium- ammonium racemate and potassium tartrate. - -The list might be greatly extended. - -The phenomenon can be illustrated by sifting through a cotton sieve upon -the excited crystal, a mixture of red lead and flowers of sulphur. By -the friction of the sifting these become oppositely electrified; the -sulphur adheres to the positively electrified end, and the red lead to -the negatively electrified end. (See Analogous Pole-Antilogous Pole.) - - -Pyromagnetic Motor. -A motor driven by the alternation of attraction and release of an -armature or other moving part, as such part or a section of it is -rendered more or less paramagnetic by heat. - -Thus imagine a cylinder of nickel at the end of a suspension rod, so -mounted that it can swing like a pendulum. A magnet pole is placed to -one side to which it is attracted. A flame is placed so as to heat it -when in contact with the magnet pole. This destroys its paramagnetism -and it swings away from the magnet and out of the flame. It cools, -becomes paramagnetic, and as it swings back is reattracted, to be again -released as it gets hot enough. This constitutes a simple motor. - -A rotary motor may be made on the same lines. Nickel is particularly -available as losing its paramagnetic property easily. - - -442 STANDARD ELECTRICAL DICTIONARY. - - -Various motors have been constructed on this principle, but none have -attained any practical importance. Owing to the low temperature at which -it loses its paramagnetic properties nickel is the best metal for -paramagnetic motors. - -In Edison's motor, between the pole pieces of an electro-magnet a -cylinder made up of a bundle of nickel tubes is mounted, so as to be -free to rotate. A screen is placed so as to close or obstruct the tubes -farthest from the poles. On passing hot air or products of combustion of -a fire or gas flame through the tubes, the unscreened ones are heated -most and lose their paramagnetism. The screened tubes are then attracted -and the armature rotates, bringing other tubes under the screen, which -is stationary. Then the attracted tubes are heated while the others -cool, and a continuous rotation is the result. - - -Fig. 279. EDISON'S PYROMAGNETIC MOTOR. - - -Pyromagnetic Generator. -A current generator producing electric energy directly from thermal -energy by pyromagnetism. - -Edison's pyromagnetic generator has eight electro-magnets, lying on -eight radii of a circle, their poles facing inward and their yokes -vertical. Only two are shown in the cut. On a horizontal iron disc are -mounted eight vertical rolls of corrugated nickel representing -armatures. On each armature a coil of wire, insulated from the nickel by -asbestus is wound. The coils are all in series, and have eight -connections with a commutator as in a drum armature. There are two main -divisions to the commutator. Each connects with an insulated collecting -ring, and the commutator and collecting rings are mounted on a spindle -rotated by power. Below the circle of vertical coils is a horizontal -screen, mounted on the spindle and rotating with it. - -A source of heat, or a coal stove is directly below the machine and its -hot products of combustion pass up through the coils, some of which are -screened by the rotating screen. The effect is that the coils are -subjecting to induction owing to the change in permeability of the -nickel cores, according as they are heated, or as they cool when the -screen is interposed. The two commutator segments are in constant -relation to the screen, and current is collected therefrom and by the -collecting rings is taken to the outside circuit. - - -443 STANDARD ELECTRICAL DICTIONARY. - - -Pyromagnetism. -The development of new magnetic properties or alteration of magnetic -sensibility in a body by heat. Nickel and iron are much affected as -regards their paramagnetic power by rise of temperature. - - -Fig. 280. PYROMAGNETIC GENERATOR. - - -Pyrometer, Siemens' Electric. -An instrument for measuring high temperatures by the variations in -electric resistance in a platinum wire exposed to the heat which is to -be measured. - - -Q. -Symbol for electric quantity. - - -Quad. -(a) A contraction for quadrant, used as the unit of inductance; the henry. - -(b) A contraction for quadruplex in telegraphy. - -[Transcriber's note: A modern use of "quad" is a unit of energy equal to -1E15 (one quadrillion) BTU, or 1.055E18 joules. Global energy -production in 2004 was 446 quad.] - - -Quadrant. -A length equal to an approximate earth quadrant, equal to 1E9 -centimeters. It has been used as the name for the unit of inductance, -the henry, q. v. - -Synonym--Standard Quadrant. - - -444 STANDARD ELECTRICAL DICTIONARY. - - -Quadrant, Legal. -The accepted length of the quadrant of the earth, 9.978E8 instead of 1E9 -centimeters; or to 9,978 kilometers instead of 10,000 kilometers. - - -Quadrature. -Waves or periodic motions the angle of lag of one of which, with -reference to one in advance of it, is 90°, are said to be in quadrature -with each other. - -[Transcriber's note: If the voltage and current of a power line are in -quadrature, the power factor is zero (cos(90°) = 0) and no real power -is delivered to the load.] - - -Qualitative. -Involving the determination only of the presence or absence of a -substance or condition, without regard to quantity. Thus a compass held -near a wire might determine qualitatively whether a current was passing -through the wire, but would not be sufficient to determine its quantity. -(See Quantitative.) - - -Quality of Sound. -The distinguishing characteristic of a sound other than its pitch; the -timbre. - -It is due to the presence with the main or fundamental sound of other -minor sounds called overtones, the fundamental note prevailing and the -other ones being superimposed upon it. The human voice is very rich in -overtones; the telephone reproduces these, thus giving the personal -peculiarities of every voice. - -Synonym--Timbre. - - -Quantitative. -Involving the determination of quantities. Thus a simple test would -indicate that a current was passing through a wire. This would be a -qualitative test. If by proper apparatus the exact intensity of the -current was determined, it would be a quantitative determination. (See -Qualitative.) - - -Quantity. -This term is used to express arrangements of electrical connections for -giving the largest quantity of current, as a quantity armature, meaning -one wound for low resistance. - -A battery is connected in quantity when the cells are all in parallel. -It is the arrangement giving the largest current through a very small -external resistance. - -The term is now virtually obsolete (Daniell); "in surface," "in -parallel," or "in multiple arc" is used. - - -Quantity, Electric. -Electricity may be measured as if it were a compressible gas, by -determining the potential it produces when stored in a defined -recipient. In this way the conception of a species of quantity is -reached. It is also measured as the quantity of current passed by a -conductor. - -Thus a body whose surface is more or less highly charged with -electricity, is said to hold a greater or less quantity of electricity. - -It may be defined in electrostatic or electro-magnetic terms. (See -Quantity, Electrostatic--Quantity, Electro-magnetic.) - - -445 STANDARD ELECTRICAL DICTIONARY. - - -Quantity. -Electro-magnetic. Quantity is determined electro-magnetically by the -measurement of current intensity for a second of time: its dimensions -are therefore given by multiplying intensity or current strength by -time. The dimensions of intensity are - ( (M^.5) * (L^.5) ) / T -therefore the dimensions of electro-magnetic quantity are - ( ( (M^.5) * (L^.5) ) / T ) * T = ( (M^.5) * (L^.5) ) - - -Quantity, Electro-magnetic, Practical Unit of. -The quantity of electricity passed by a unit current in unit time; the -quantity passed by one ampere in one second; the coulomb. - -It is equal to 3E9 electrostatic absolute units of quantity and to 0.1 -of the electro- magnetic absolute unit of quantity. - -One coulomb is represented by the deposit of - .00111815 gram, or .017253 grain of silver, - .00032959 gram, or .005804 grain of copper, - .0003392 gram, or .005232 grain of zinc. - -If water is decomposed by a current each coulomb is represented by the -cubic centimeters of the mixed gases (hydrogen and oxygen) given by the -following formula. - ( 0.1738 * 76 * (273 + Cº ) ) / ( h * 273 ) -in which Cº is the temperature of the mixed gases in degree centigrade -and h is the -pressure in centimeters of mercury column; or by - ( 0.01058 * 30 (491 + Fº - 32) ) / (h * 491 ) -for degrees Fahrenheit and inches of barometer. - -[Transcriber's note: 6.24150962915265E18 electrons is one coulomb.] - - -Quantity, Electrostatic. -Quantity is determined electro-statically by the repulsion a charge of -given quantity exercises upon an identical charge at a known distance. -The force evidently varies with the product of the two quantities, and -by the law of radiant forces also inversely with the square of the -distance. The dimensions given by these considerations is Q * Q/(L*L). -This is the force of repulsion. The dimensions of a force are -(M * L) /(T^2). Equating these two expressions we have: - (Q^2)/(L^2) = (M*L)/(T^2) - or - Q = ((M^.5)*(L^1.5)) / T -which are the dimensions of electrostatic quantity. - - -Quantity, Meter. -An electric meter for determining the quantity of electricity which -passes through it, expressible in coulombs or ampere hours. All -commercial meters are quantity meters. - - -446 STANDARD ELECTRICAL DICTIONARY. - - -Quartz. -A mineral, silica, SiO2. It has recently been used by C. V. Boys and -since by others in the making of filaments for torsion suspensions. The -mineral is melted, while attached to an arrow or other projectile. It is -touched to another piece of quartz or some substance to which it adheres -and the arrow is fired off from the bow. A very fine filament of -surpassingly good qualities for galvanometer suspension filaments is -produced. - -As a dielectric it is remarkable in possessing but one-ninth the -residual capacity of glass. - - -Quicking. -The amalgamating of a surface of a metallic object before silver -plating. It secures better adhesion of the deposit. It is executed by -dipping the article into a solution of a salt of mercury. A solution of -mercuric nitrate 1 part, in water 100 parts, both by weight, is used. - - -R. -(a) Abbreviation and symbol for Reamur, as 10º R., meaning 10º by the -Reamur thermometer. (See Reamur Scale.) - -(b) Symbol for resistance, as in the expression of Ohm's Law C=E/R. -(rho, Greek r) Symbol for specific resistance. - - -Racing of Motors. -The rapid acceleration of speed of a motor when the load upon it is -removed. It is quickly checked by counter-electro-motive force. (See -Motor, Electric.) - - -Radian. -The angle whose arc is equal in length to the radius; the unit angle. - - -Radiant Energy. -Energy, generally existing in the luminiferous ether, kinetic and -exercised in wave transmission, and rendered sensible by conversion of -its energy into some other form of energy, such as thermal energy. - -If the ether waves are sufficiently short and not too short, they -directly affect the optic nerve and are known as light waves; they may -be so short as to be inappreciable by the eye, yet possess the power of -determining chemical change, when they are known as actinic waves; they -may be also so long as to be inappreciable by the eye, when they may be -heat-producing waves, or obscure waves. - -Other forms of energy may be radiant, as sound energy dispersed by the -air, and gravitational energy, whose connection with the ether has not -yet been demonstrated. - - -Radiation. -The traveling or motion of ether waves through space. - -[Transcriber's note: The modern term corresponding to this definition is -photons. The modern concept of radiation also includes particles-- -neutrons, protons, alpha (helium) and beta (electrons) rays and other -exotic items.] - - -Radicals. -A portion of a molecule, possessing a free bond and hence free to -combine directly. A radical never can exist alone, but is only -hypothetical. An atom is a simple radical, an unsaturated group of atoms -is a compound radical. - - -447 STANDARD ELECTRICAL DICTIONARY. - - -Radiometer. -An instrument consisting of four vanes poised on an axis so as to be -free to rotate, and contained in a sealed glass vessel almost perfectly -exhausted. The vanes of mica are blackened on one side. - -On exposure to light or a source of heat (ether waves) the vanes rotate. -The rotation is due to the beating back and forth of air molecules from -the surface of the vanes to the inner surface of the glass globe. - - -Radiometer, Electric. -A radiometer in which the motion of the molecules of air necessary for -rotation of the vane is produced by electrification and not by heating. - - -Radio-micrometer. -An instrument for detecting radiant energy of heat or light form. It -consists of a minute thermopile with its terminals connected by a wire, -the whole suspended between the poles of a magnet. A minute quantity of -heat produces a current in the thermopile circuit, which, reacted on by -the field, produces a deflection. A convex mirror reflecting light is -attached so as to move with the thermopile. The instrument is of -extraordinary sensitiveness. It responds to .5E-6 of a degree Centigrade -or about 1E-6 degree Fahrenheit. - - -Radiophony. -The production of sound by intermittent action of a beam of light upon a -body. With possibly a few exceptions all matter may produce sound by -radiophouy. - - -Range Finder. -An apparatus for use on shipboard to determine the distance of another -ship or object. It is designed for ships of war, to give the range of -fire, so as to set the guns at the proper elevation. The general -principle involved is the use of the length of the ship if possible, if -not of its width, as a base line. Two telescopes are trained upon the -object and kept trained continuously thereon. The following describes -the Fiske range finder. - -The range finder comprises two fairly powerful telescopes, each mounted -on a standard, which can be rotated round a vertical axis, corresponding -with the center of the large disc shown in the engraving. One-half of -the edge of this disc is graduated to 900 on either side of a zero -point, and below the graduation is fixed a length of platinum silver -wire. This wire only extends to a distance of 81.10 on either side of -zero, and is intended to form two arms of a Wheatstone bridge. The -sliding contact is carried by the same arm as the telescope standards, -so that it moves with the telescope. The two instruments are mounted at -a known distance apart on the ship, as shown diagrammatically in the -cut. Here A and B are the centers of the two discs, C and D the arms -carrying the telescopes, and E and F the platinum silver wires. Suppose -the object is at T, such that A B T is a right angle, then -AT=AB/sin(ATB). - - -448 STANDARD ELECTRICAL DICTIONARY. - - -If the two sectors are coupled up as shown, with a battery, h, and a -galvanometer, by the wires, a b and c d, then since the arm, e, on being -aligned on the object takes the position c1 while d remains at zero, the -Wheatstone bridge formed by these segments and their connections will be -out of balance, and a current will flow through the galvanometer, which -may be so graduated as to give the range by direct reading, since the -current through it will increase with the angle A T B. - - -Fig. 281. RANGE FINDER. - - -In general, however, the angle A B T will not be a right angle, but some -other angle. In this case AT = AB / sin(A T B) * sin( A B T), and hence -it will only be necessary to multiply the range reading on the -galvanometer by the sine of the angle A B T, which can be read directly -by the observer at B. This multiplication is not difficult, but by -suitably arranging his electrical appliances Lieutenant Fiske has -succeeded in getting rid of it, so that the reading of the galvanometer -always gives the range by direct reading, no matter what the angle at B -may be. To explain this, consider the two telescopes shown in the cut in -the positions C and D; the whole current then has a certain resistance. - - -449 STANDARD ELECTRICAL DICTIONARY. - - -Next suppose them, still remaining parallel, in the positions C1 and D1. -The total resistance of the circuit is now less than before, and hence -if C1, one of the telescopes, is moved out of parallel to the other, -through a certain angle, the current through the galvanometer will be -greater than if it were moved through an equal angle out of a parallel -when the telescopes were in the positions C and D. The range indicated -is, therefore, decreased, and by properly proportioning the various -parts it is found that the range can always be read direct from the -galvanometer, or in other words the multiplication of A B/sin( A T B ) -by sin( A B T ) is to all intents and purposes performed automatically. -There is, it is true, a slight theoretical error; but by using a small -storage battery and making the contents carefully it is said to be -inappreciable. Each telescope is fitted with a telephone receiver and -transmitter, so that both observers can without difficulty decide on -what point to align their telescopes. It will be seen that it is -necessary that the lines of sight of two telescopes should be parallel -when the galvanometer indicates no current. It has been proposed to -accomplish this by sighting both telescopes on a star near the horizon, -which being practically an infinite distance away insures the -parallelism of the lines of sight. - - -Rate Governor. -An apparatus for securing a fixed rate of vibration of a vibrating reed. -It is applied in simultaneous telegraphy and telephoning over one wire. -The principle is that of the regular make and break mechanism, with the -feature that the contact is maintained during exactly one-half of the -swing of the reed. The contact exists during the farthest half of the -swing of the reed away from the attracting pole. - - -Fig. 282. LANGDON DAVIRS' RATE GOVERNOR. - - -In the left hand figure of the cut, K is the key for closing the -circuit. A is the base for attachment of the reed. V is the -contact-spring limited in its play to the right by the screw S. C is the -actuating magnet. By tracing the movements of the reed, shown on an -exaggerated scale in the three right hand figures, it will be seen that -the reed is in electric contact with the spring during about one-half -its movement. The time of this connection is adjustable by the screw S. - -Synonym--Langdon Davies' Rate Governor or Phonophone. - - -450 STANDARD ELECTRICAL DICTIONARY. - - -Ray, Electric. Raia torpedo. -The torpedo, a fish having the same power of giving electric shocks as -that possessed by the electric eel, q. v. (See also Animal Electricity.) - - -Fig. 283. TORPEDO OR ELECTRIC RAY - - -Reaction of Dynamo, Field and Armature. -A principle of the dynamo current generator, discovered by Soren Hjorth -of Denmark. - -When the armature is first rotated it moves in a field due to the -residual magnetism of the field magnet core. This field is very weak, -and a slight current only is produced. This passing in part or in whole -through the field magnet cores slightly strengthens the field, whose -increased strength reacts on the armature increasing its current, which -again strengthens the field. In this way the current very soon reaches -its full strength as due to its speed of rotation. - -The operation is sometimes termed building up. - -Sometimes, when there is but a trace of residual magnetism, it is very -hard to start a dynamo. - - -Reading Telescope. -A telescope for reading the deflections of a reflecting galvanometer. - -A long horizontal scale is mounted at a distance from the galvanometer -and directly below or above the centre of the scale a telescope is -mounted. The telescope is so directed that the mirror of the -galvanometer is in its field of view, and the relative positions of -mirror, scale and telescope are such that the image of the scale in the -galvanometer mirror is seen by the observer looking through the -telescope. - -Under these conditions it is obvious that the graduation of the scale -reflected by the mirror corresponds to the deflection of the -galvanometer needle. - -The scale may be straight or curved, with the galvanometer in the latter -case, at its centre of curvature. - - -Reamur Scale. -A thermometer scale in use in some countries of Continental Europe. The -temperature of melting ice is 0°; the temperature of condensing steam -is 80°; the degrees are all equal in length. For conversion to -centigrade degrees multiply degrees Reamur by 5/4. For conversion to -Fahrenheit degrees multiply by 9/4 and add 32 if above 0° R., and if -below subtract 32. Its symbol is R., as 10° R. - - -451 STANDARD ELECTRICAL DICTIONARY. - - -Recalescence. -A phenomenon occurring during the cooling of a mass of steel, when it -suddenly emits heat and grows more luminous for an instant. It is a -phase of latent heat, and marks apparently the transition from a -non-magnetizable to a magnetiz able condition. - - -Receiver. -In telephony and telegraphy, an instrument for receiving a message as -distinguished from one used for sending or transmitting one. - -Thus the Bell telephone applied to the ear is a receiver, while the -microphone which is spoken into or against is the transmitter. - - -Receiver, Harmonic. -A receiver including an electro-magnet whose armature is an elastic -steel reed, vibrating to a particular note. Such a reed responds to a -series of impulses succeeding each other with the exact frequency of its -own natural vibrations, and does not respond to any other rapid series -of impulses. (See Telegraph Harmonic.) - - -Reciprocal. -The reciprocal of a number is the quotient obtained by dividing one by -the number. Thus the reciprocal of 8 is 1/8. - -Applied to fractions the above operation is carried out by simply -inverting the fraction. Thus the reciprocal of 3/4 is 4/3 or 1-1/3. - - -Record, Telephone. -Attempts have been made to produce a record from the vibrations of a -telephone disc, which could be interpreted by phonograph or otherwise. - - -Fig. 284. MORSE RECORDER OR EMBOSSER. - - -452 STANDARD ELECTRICAL DICTIONARY. - - -Recorder, Morse. -A telegraphic receiving apparatus for recording on a strip of paper the -dots and lines forming Morse characters as received over a telegraph -line. Its general features are as follows: - -A riband or strip of paper is drawn over a roller which is slightly -indented around its centre. A stylus or blunt point carried by a -vibrating arm nearly touches the paper. The arm normally is motionless -and makes no mark on the paper. An armature is carried by the arm and an -electro-magnet faces the armature. When a current is passed through the -magnet the armature is attracted and the stylus is forced against the -paper, depressing it into the groove, thus producing a mark. When the -current ceases the stylus is drawn back by a spring. - - -Fig. 285. INKING ROLLER MECHANISM OF MORSE RECORDER. - - -In some instruments a small inking roller takes the place of the stylus, -and the roller is smooth. The cut, Fig. 285, shows the plan view of the -ink-roller mechanism. J is the roller, L is the ink well, Cl is the arm -by which it is raised or lowered by the electro-magnet, as in the -embosser. S S is the frame of the instrument, and B the arbor to which -the arm carrying the armature is secured, projecting to the right. A -spring is arranged to rub against the edge of the inking roller and -remove the ink from it. - -The paper is fed through the apparatus by clockwork. At the present day -sound reading has almost entirely replaced the sight reading of the -recorder. - - -Recorder, Siphon. -A recording apparatus in which the inked marks are made on a strip of -paper, the ink being supplied by a siphon terminating in a capillary -orifice. - -In the cut N S represents the poles of a powerful electro-magnet. A -rectangular coil bb of wire is suspended between the coils. A stationary -iron core a intensifies the field. The suspension wire f f 1 has its -tension adjusted at h. This wire acts as conductor for the current. - - -453 STANDARD ELECTRICAL DICTIONARY. - - -The current is sent in one or the other direction or is cut off in -practice to produce the desired oscillations of the coil b b. A glass -siphon n l works upon a vertical axis l. One end l is immersed in an ink -well m. Its longer end n touches a riband of paper o o. The thread k -attached to one side of the coil pulls the siphon back and forth -according to the direction of current going through the electro-magnet -cores. A spiral spring adjusted by a hand-screw controls the siphon. In -operation the siphon is drawn back and forth producing a zigzag line. -The upward marks represent dots, the downward ones dashes. Thus the -Telegraphic Code can be transmitted on it. To cause the ink to issue -properly, electrification by a static machine has been used, when the -stylus does not actually touch the paper, but the ink is ejected in a -series of dots. - - -Fig. 286. SIPHON RECORDER. - - -Reducteur for Ammeter. -A resistance arranged as a shunt to diminish the total current passing -through an ammeter. It is analogous to a galvanometer shunt. (See -Multiplying Power of Shunt.) - - -Reducteur for Voltmeter. -A resistance coil connected in series with a Voltmeter to diminish the -current passing through it. Its resistance being known in terms of the -resistance of the voltmeter it increases the range of the instrument so -that its readings may cover double or more than double their normal -range. - - -Reduction of Ores, Electric. -Treatment of ores by the electric furnace (see Furnace, Electric.) The -ore mixed with carbon and flux is melted by the combined arc and -incandescent effects of the current and the metal separates. In another -type the metal is brought into a fusible compound which is electrolyzed -while fused in a crucible. Finally processes in which a solution of a -salt of the metal is obtained, from which the metal is obtained by -electrolysis, may be included. Aluminum is the metal to whose extraction -the first described processes are applied. - - -454 STANDARD ELECTRICAL DICTIONARY. - - -Refraction, Electric Double. -Double refraction induced in some materials by the action of either an -electrostatic, magnetic or an electro-magnetic field. - -The intensity or degree of refracting power is proportional to the -square of the strength of field. - - -Refreshing Action. -In electro-therapeutics the restoration of strength or of nerve force by -the use of voltaic alternatives, q. v. - - -Region, Extra-polar. -In electro-therapeutics the area or region of the body remote from the -therapeutic electrode. - - -Region, Polar. -In electro-therapeutics the area or region of the body near the -therapeutic electrode. - - -Register, Electric. -There are various kinds of electric registers, for registering the -movements of watchmen and other service. Contact or press buttons may be -distributed through a factory. Each one is connected so that when the -circuit is closed thereby a mark is produced by the depression of a -pencil upon a sheet or disc of paper by electro-magnetic mechanism. The -paper is moved by clockwork, and is graduated into hours. For each -push-button a special mark may be made on the paper. The watchman is -required to press the button at specified times. This indicates his -movements on the paper, and acts as a time detector to show whether he -has been attending to his duty. - - -Register, Telegraphic. -A term often applied to telegraph recorders, instruments for producing -on paper the characters of the Morse or other alphabet. - - -Regulation, Constant Current. -The regulation of a dynamo so that it shall give a constant current -against any resistance in the outer circuits, within practical limits. -It is carried out in direct current machines generally by independent -regulators embodying a controlling coil with plunger or some equivalent -electro-magnetic device inserted in the main circuit and necessarily of -low resistance. In some regulators the work of moving the regulator is -executed mechanically, but under electrical control; in others the -entire work is done by the current. - -A typical regulator or governor (Golden's) of the first class comprises -two driven friction wheels between which is a driving friction wheel, -which can engage with one driven wheel only at once. It is brought into -engagement with one or the other by a solenoid and plunger. - - -455 STANDARD ELECTRICAL DICTIONARY. - - -As it touches one wheel it turns it in one direction. This moves a -sliding contact in one direction so as to increase a resistance. This -corresponds to a motion of the plunger in one direction. As the driving -wheel moves in the opposite direction by a reverse action it diminishes -the resistance. Thus the increase and decrease of resistance correspond -to opposite movements of the solenoid plunger, and consequently to -opposite variations in the current. The whole is so adjusted that the -variations in resistance maintain a constant amperage. The resistance is -in the exciting circuit of the dynamo. - -In Brush's regulator, which is purely mechanical, a series dynamo is -made to give a constant current by introducing across the field magnets -a shunt of variable resistance, whose resistance is changed by an -electro-magnet, whose coils are in circuit with the main current. Carbon -resistance discs are used which the electro-magnet by its attraction for -its armature, presses with varying intensity. This alters the -resistance, decreasing it as the current increases and the reverse. As -the connection is in shunt this action goes to maintain a constant -current. - - -Regulation, Constant Potential. -The regulation of constant potential dynamos is executed on the same -lines as that of constant current dynamos. If done by a controlling -coil, it must for constant potential regulation be wound with fine wire -and connected as a shunt for some part of the machine. - - -Regulation of Dynamos. -The regulation of dynamos so that they shall maintain a constant -potential difference in the leads of their circuit for multiple arc -systems or shall deliver a constant current in series systems. Hence two -different systems of regulation are required, (a) constant potential -regulation--(b) constant current regulation. The first named is by far -the more important, as it concerns multiple arc lighting, which is the -system universally used for incandescent lighting. - -S. P. Thompson thus summarizes the methods of governing or regulating -dynamos. Premising that alteration of the magnetic flux is the almost -universal way of control, it can be done in two ways; first, by varying -the excitation or ampere turns of the field, and second by varying the -reluctance of the magnetic circuit. The excitation or magnetic flux may -be varied - -(a) by hand, with the aid of rheostats and commutators in the exciting -circuit; - -(b) automatically, by governors, taking the place of the hand; - -(c) by compound windings. The magnetic circuit may have its reluctance -caused to vary in several ways; - -(d) by moving the pole pieces nearer to or further from the armature; - -(e) by opening or closing some gap in the magnetic circuit (field-magnet -core); - -(f) by drawing the armature endways from between the pole pieces; - -(g) by shunting some of the magnetic lines away from the armature by a -magnetic shunt. - -The latter magnetic circuit methods d, e, f, and g, have never met with -much success except on small machines or motors. Method e is adopted in -the Edison motor, the yoke being withdrawn or brought nearer the cores -of the coils. (See Regulation, Constant Current-Regulation, constant -Potential.) - - -456 STANDARD ELECTRICAL DICTIONARY. - - -Reguline. adj. -Having the characteristics of a piece of metal, being flexible, -adherent, continuous, and coherent. Applied to electrolytic deposits. - - -Relative. -Indicating the relation between two or more things without reference to -absolute value of any one of them. Thus one lamp may be of relatively -double resistance compared to another, but this states nothing of the -resistance in ohms of either lamp. - - -Relay. -A receiving instrument which moves in accordance with impulses of -currents received, and in so moving opens and closes a local circuit, -which circuit may include as powerful a battery as required or -desirable, while the relay may be on the other hand so delicate as to -work with a very weak current. - - -Fig. 287. RELAY. - - -The typical relay includes an electro-magnet and armature. To the latter -an arm is attached and the lower end of the arm works in pivots. As the -armature is attracted the arm swings towards the magnet. When the -current is cut off, the armature and arm are drawn back by a spring. -When the arm swings towards the magnet its upper end touching a contact -screw closes the local circuit. When it swings back it comes in contact -with a second screw, with insulated point, and opens the circuit as it -leaves the first named screw. - -One terminal connects with the arm through the pivots and frame. The -other connects with the contact screw through the frame carrying it. - -Synonym--Relay Magnet. - - -457 STANDARD ELECTRICAL DICTIONARY. - - -Relay Bells. -Bells connected by relay connection to a main line for acoustic -telegraphy. A stroke on one bell indicates a dot and on the other a -dash. The system is now nearly extinct. - - -Relay, Box-sounding. -A relay which is surrounded by or mounted on a resonator or wooden box -of such proportions and size as to reinforce the sound. This enables a -relay to act as a sounder, its weak sounds being virtually magnified so -as to be audible. - - -Relay Connection. -A connection used in telegraphy, including a local battery, with a short -circuit normally open, but closed by a switch and a sounder or other -appliance. The latter is made very sensitive so as to be worked by a -feeble current, and is connected to the main line. A very slight current -closes the switch and the local battery comes into operation to work a -sounder, etc. When the current ceases on the main line the switch opens -and throws the local battery out of action. The switch is termed a -relay, q. v. A long main line may thus produce strong effects at distant -stations, the intensity of action depending on the local battery. - - -Fig. 288. RELAY OR LOCAL CIRCUIT. - - -Relay, Differential. -A relay containing two coils wound differentially, and of the same -number of turns and resistance. If two equal currents pass through the -coils they counteract each other and no action takes place. If there is -a difference in the currents the relay acts as one coil preponderates. -The coils may be wound for uneven currents with different resistance and -number of turns. - - -Relay, Microphone. -A relay connection applied to a telephone circuit. It consists of a -microphone mounted in front of the diaphragm of a telephone receiver. In -circuit with the microphone is a battery and second telephone receiver. -The microphone is supposed to intensify the sounds of the first -telephone. - - -458 STANDARD ELECTRICAL DICTIONARY. - - -Relay, Polarized. -A relay whose armature is of steel, and polarized or permanently -magnetized, or in which a permanent magnet is used as the basis for the -electro-magnets. In the relay shown in the cut the coils shown are -mounted on cores carried on the end of a powerful bent permanent magnet. -Thus when no current passes their upper poles are both of the same sign, -and the horizontally vibrating tongue is held by the magnetic attraction -against one or the other pole piece. If a current is sent through the -electro-magnet it gives opposite polarity to the two polar extensions. -As the end of the vibrating tongue is of polarity determined by the -permanent magnet it is attracted to one pole and repelled from the -other. On cessation of current it remains attached by the permanent -magnetism. If now a current is sent in the opposite direction the two -poles again acquire opposite polarity, the reverse of the former, and -the tongue flies across to the opposite side. On cessation of current it -remains attached as before by the permanent magnetism. - -In its movements to and fro the relay tongue opens and closes a contact, -so as to work a sounder or other apparatus. The polarized relay is of -high sensibility, and requires little or no change of adjustment. - - -Fig. 288. POLARIZED RELAY - - -Reluctance. -In a magnetic circuit or portion thereof, the resistance offered to the -flow of lines of force. The magnetic circuit as has already been stated -is treated like an electric circuit, and in it reluctance occupies the -place of resistance in the electric circuit. It is the reciprocal of -permeance. S. P. Thompson expresses the law thus: - -Total number of magnetic lines = (magneto-motive force) / (magnetic -reluctance) - -Synonyms--Magnetic Reluctance-Magnetic Resistance. - - -Reluctance, Unit of. -The reluctance of a circuit through which unit magnetizing power -(magneto-motive force) can produce a unit of induction or one line of -force. This value is very high; the reluctance of ordinary magnetic -circuits ranges from 1E-5 to 1E-8 unit of reluctance. - - -Reluctivity. -Specific reluctance; the reluctance of a cube of material whose edge -measures one centimeter in length. It is a quality bearing the same -relation to reluctance that permeability does to permeance. - -It is defined as the reciprocal of magnetic permeability. (Kenelly.) If -plotted as a curve for different values of the magnetizing force it is -found to be nearly a straight line, a linear function of the magnetizing -force, H with the equation a + b H. Reluctivity is the property of a -substance; reluctance is the property of a circuit. - - -459 STANDARD ELECTRICAL DICTIONARY. - - -Remanence. -The residual magnetism left after magnetic induction, expressed in lines -of force per square centimeter. - - -Repeater. -In telegraphy an instrument for repeating the signals through a second -line. It is virtually a relay which is operated by the sender, and which -in turn operates the rest of the main line, being situated itself at -about the middle point of the distance covered. In the simpler forms of -repeater two relays are used, one for transmission in one direction the -other for transmission in the other. An attendant switches one or the -other in as required. - -Thus a common relay is virtually a repeater for its local circuit. If -such a relay is placed half way down a line, and if the line beyond it -is connected as its local, it becomes a repeater. - -Some forms of repeaters are automatic, and repeat both ways without the -need of an attendant. - -It is the practice to somewhat prolong the signals sent through a -repeater. - - -Replenisher, Sir William Thomson's. -A static accumulating influence machine contained in Thomson's quadrant -electrometer and used to change the quadrants. The cut shows the -horizontal section and construction of the apparatus. - -It contains two gilt brass inductors A B, and two eccentric sectors or -carriers, C, D, which are mounted on an ebonite spindle, which is spun -around by the fingers. The springs s s1 connect each with its inductor; -the springs S S1 connect only each other, and touch the sectors as they -turn around. - -One of the inductors may be always assumed to be of slightly higher -potential than that of the other one. When the carriers are in contact -with the springs S S1 they are each charged by induction with -electricity opposite in sign to that of the nearest quadrant. As they -leave the springs S S1 in their rotation, they next touch the springs s -s1, but of the recently opposite inductor. They share each a portion of -its charge with the inductors building up their charges. The action is -repeated over and over again as they rotate. - - -Fig. 290. THOMSON'S REPLENISHER. - - -460 STANDARD ELECTRICAL DICTIONARY. - - -Reservoir, Common. -A term applied to the earth, because all electrified bodies discharge -into it if connected thereto. - - -Fig. 289. DIAGRAM OF THOMSON'S REPLENISHER. - - -Residual Atmosphere. -The air left in a receiver after exhaustion by an air pump. The -quantity, where good air pumps are used, is very minute. - - -Residue, Electric. -The residual charge of a condenser. (See Charge, Residual.) - - -Resin. -(a) The product obtained by non-destructive distillation of the juice of -the pitch pine. It is the solid residue left after the turpentine has -been evaporated or distilled. It is a mixture of abietic acid C44 H64 O5 -and pinic acid C20 H30 O2. It is an insulator; its specific inductive -capacity is 2.55. (Baltzmann.) - -Synonyms--Colophony--Rosin. - -(b) The name is also generally applied to similar substances obtained -from the sap of other trees; thus shellac is a resin. The resins are a -family of vegetable products; the solid portions of the sap of certain -trees. Common resin, lac, dragons blood, are examples. They are all -dielectrics and sources of resinous or negative electricity when rubbed -with cotton, flannel, or silk. (See Electrostatic Series.) - - -461 STANDARD ELECTRICAL DICTIONARY. - - -Resinous Electricity. -Negative electricity; the electricity produced upon the surface of a -resinous body by rubbing it; such a body is shellac or sealing wax; -flannel and other substances may be used as the rubbing material. (See -Electrostatic Series.) - - -Resistance. -(a) The quality of an electric conductor, in virtue of which it opposes -the passage of an electric current, causing the disappearance of -electro-motive force if a current passes through it, and converting -electric energy into heat energy in the passage of a current through it. -If a current passes through a conductor of uniform resistance there is a -uniform fall of potential all along its length. If of uneven resistance -the fall in potential varies with the resistance. (See Potential, Fall -of.) - -The fall of potential is thus expressed by Daniell. "In a conductor, say -a wire, along which a current is steadily and uniformly passing, there -is no internal accumulation of electricity, no density of internal -distribution; there is, on the other hand, an unequally distributed -charge of electricity on the surface of the wire, which results in a -potential diminishing within the wire from one end of the wire to the -other." - -Resistance varies inversely with the cross section of a cylindrical or -prismatic conductor, in general with the average cross-section of any -conductor, and in the same sense directly with its true or average or -virtual length. It varies for different substances, and for different -conditions as of temperature and pressure for the same substance. A rise -of temperature in metals increases the resistance, in some bad -conductors a rise of temperature decreases the resistance. - - -462 STANDARD ELECTRICAL DICTIONARY. - - -Approximately, with the exception of iron and mercury, the resistance of -a metallic conductor varies with the absolute temperature. This is very -roughly approximate. - -Except for resistance energy would not be expended in maintaining a -current through a circuit. The resistance of a conductor may be supposed -to have its seat and cause in the jumps from molecule to molecule, which -the current has to take in going through it. If so a current confined to -a molecule would, if once started, persist because there would be no -resistance in a molecule. Hence on this theory the Ampérian currents -(see Magnetism, Ampere's Theory of) would require no energy for their -maintenance and Ampére's theory would become a possible truth. - -When metals melt their resistance suddenly increases. - -Light rays falling on some substances, notably selenium, q. v., vary the -resistance. - -Longitudinal stretching of a conductor decreases it, it increases with -longitudinal compression, and increases in iron and diminishes in tin -and zinc when a transverse stress tends to widen the conductor. - -(b) The term resistance is used to express any object or conductor used -in circuit to develop resistance. - -[Transcriber's note: At room temperatures, the thermal motion of ions in -the conductor's crystal lattice scatters the electrons of the current. -Imperfections of the lattice contribute slightly. At low temperatures -superconductivity (zero resistance) can occur because an energy gap -between the electrons and the crystal lattice prevents any interaction. -At the time of this book, none of this was known. "Jumps from molecule -to molecule" is a good guess.] - - -Resistance, Apparent. -Impedance; the virtual resistance of a circuit including the spurious -resistance due to counter-electromotive force. It may be made up of true -resistance and partly of an inductive reaction, as it represents the net -factor, the entire obstruction to the passage of a current, and not -merely a superadded resistance or counter-electro-motive force. - -Synonym--Impedance. - -[Transcriber's note: Impedance can also have a component due to -capacitance.] - - -Resistance, Asymmetrical. -Resistance which varies in amount in different directions through a -conductor. It implies a compound or composite conductor such as the -human system. The presence of counter-electro-motive force in different -parts of a conductor may bring about asymmetrical resistance. - - -Resistance, B. A. Unit of. -The British Association Ohm. (See Ohm, B. A.) - - -463 STANDARD ELECTRICAL DICTIONARY. - - -Resistance Box. -A box filled with resistance coils. The coils are connected in series so -that a circuit including any given number has their aggregate resistance -added to its own. The terminals of consecutive coils are connected to -short blocks of brass which are secured to the top of the box, lying -flatwise upon it, nearly but not quite in contact with each other. Plugs -of brass are supplied which can go in between pairs of blocks, which -have a pair of grooves reamed out to receive them. Such plugs short -circuit the coil below them when in position. The cut shows how such -coils are connected and the use of plugs to short circuit them. The -diagram shows the top of a Wheatstone bridge, q. v., resistance box with -connections for determining resistances. - - -Fig. 291. RESISTANCE BOX. - - -Resistance Box, Sliding. -A resistance box whose coils are set in a circle. Two metal arms with -handles are pivoted at the centre of the circle and by moving them -around they make and break contacts so as to throw the coils in and out -of circuit. The object is to permit an operator to adjust resistance -without looking at the box--an essential in duplex telegraphy. - - -Resistance, Breguet Unit of. -The same in origin as the Digney Unit. (See Resistance, Digney Unit of.) - -It is equal to 9.652 Legal Ohms. - - -Resistance, Carbon. -A resistance, a substitute for a resistance coil; it is made of carbon, -and is of various construction. In the Brush dynamo regulator a set of -four vertical piles of plates of retort carbon, q. v., is used as a -resistance, whose resistance is made to vary by changing the pressure. -This pressure automatically increases as the current strength increases, -thus reducing the resistance. - - -464 STANDARD ELECTRICAL DICTIONARY. - - -Resistance Coil, Standard. -A standard or resistance issued by the Electric Standard Committee of -Great Britain. The cut shows the standard ohm. It is formed either of -German silver, or of an alloy of silver, 66.6 per cent. and platinum, -33.4 per cent. The wire is insulated and doubled before winding as -described before. (See Coil, Resistance.) The two ends of the wire are -soldered, each one to a heavy copper wire or rod r. The whole coil is -enclosed in a brass case, and is enclosed with paraffine melted in at A. -A place for a thermometer is provided at t. By immersing the lower part -of the case B in water of different degrees of heat any desired -temperature can be attained. - - -Fig. 292. STANDARD OHM COIL. - - -Resistance, Combined. -The actual resistance of several parallel conductors starting from the -same point and ending at the same point. If the individual resistance be -a b c d .. and the combined resistance be x then we have -x = 1 / (( 1/a) + (1/b) + (1/c) + (1/d) + …) - -Synonym--Joint Resistance. - - -Resistance, Critical. -In a series wound dynamo the resistance of the outer circuit above which -the machine will refuse to excite itself. - - -Resistance, Dielectric. -The mechanical resistance of a dielectric to the tendency to perforation -or to the strains due to electrification. This is a phase of mechanical -resistance, and is distinct from the electrical or ohmic resistance of -the same substance. - - -Resistance, Digney Unit of. -The resistance of an iron wire, 1 kilometer long, 4 millimeters -diameter, temperature unknown. - -It is equal to 9.163 legal ohms. - - -Resistance, Electrolytic. -The resistance of an electrolyte to the passage of a current decomposing -it. It is almost entirely due to electrolysis and is added to by -counter- electro-motive force, yet it is not treated specifically as -such, but as an actual resistance. When a current of a circuit of too -low voltage to decompose an electrolyte is caused by way of immersed -terminals to pass through an electrolyte the resistance appears very -high and sometimes almost infinite. If the voltage is increased until -the electrolyte is decomposed the resistance suddenly drops, and what -should be termed electrolytic resistance, far lower than the true -resistance, appears. - - -465 STANDARD ELECTRICAL DICTIONARY. - - -Resistance, English Absolute or Foot-Second Unit of. -A unit based on the foot and second. It is equal to (( foot / second ) * -1E7) , being based on these dimensions. - -It is equal to 0.30140 legal ohm. - - -Resistance, Equivalent. -A resistance equivalent to other resistances, which may include -counter-electro-motive force. - - -Resistance, Essential. -The resistance of the generator in an electric circuit; the same as -internal resistance. - - -Resistance, External. -In an electric circuit the resistance of the circuit outside of the -generator, or battery. - -Synonym--Non-essential Resistance. - - -Fig. 293. RESISTANCE FRAME. - - -Resistance Frame. -An open frame filled with resistance coils of iron, or German silver -wire. It is used as a resistance for dynamos and the larger or working -class of plant. The coils are sometimes connected so that by a switch -moving over a row of studs one or more can be thrown into series -according to the stud the switch is in contact with. - - -Resistance, German Mile Unit of. -The resistance of 8,238 yards of iron wire 1/6 inch in diameter. It is -equal to 56.81 legal ohms. - - -466 STANDARD ELECTRICAL DICTIONARY. - - -Resistance, Hittorf's. -A high resistance, often a megohm, composed of Hittorf's solution, q. v. -It is contained in a vertical glass tube near whose upper and lower ends -are electrodes of metallic cadmium attached to platinum wires. The -cadmium is melted in glass tubes, the platinum wire is inserted into the -melted metal and the tube is broken after all is solid. The resistance -should show no polarization current. - - -Fig. 294. HITTORF'S RESISTANCE - - -Resistance, Inductive. -A resistance in which self-induction is present; such as a coil of -insulated wire wound around an iron core. - - -Resistance, Insulation. -The resistance of the insulation of an insulated conductor. It is stated -in ohms per mile. It is determined by immersing a section of the line in -water and measuring the resistance between its conductor and the water. -The section must be of known length, and its ends must both be above the -liquid. - - -Resistance, Internal. -The resistance of a battery, or generator in an electric circuit as -distinguished from the resistance of the rest of the circuit, or the -external resistance. - -Synonym--Essential Resistance. - - -Resistance, Jacobi's Unit of. -The resistance of a certain copper wire 25 feet long and weighing 345 -grains. - -It is equal to 0.6296 legal ohm. - - -Resistance, Matthiessen's Meter-gram Standard. -The resistance of a pure hard drawn copper wire of such diameter that -one meter of it weighs one gram. It is equal to .1434 Legal Ohms at 0º -C. (32º F.) - - -Resistance, Matthiessen's Unit of. -The resistance of a standard mile of pure annealed copper wire 1/16 inch -diameter, at a temperature of 15.5º C. (60º F.). - -It is equal to 13.44 legal ohms. - - -467 STANDARD ELECTRICAL DICTIONARY. - - -Resistance, Meter-millimeter Unit of. -The resistance of a wire of copper one meter long and one square -millimeter in section. It is equal to .02057 ohms at 0º C. (32º F.) The -term may also be applied to the resistance of similar sized wire of -other metals. - - -Resistance, Mil-foot Unit of. -The resistance of a foot of copper wire one-thousandth of an inch in -diameter. It is equal to 9.831 ohms at 0º C. (32º F.) The term may also -be applied to the resistance of similar sized wire of other metals. - - -Resistance, Non-essential. -The resistance of the portion of an electric circuit not within the -generator; the same as external resistance. - -Synonym--External Resistance. - - -Resistance, Non-inductive. -A resistance with comparatively little or negligible self-induction. - -Resistance of Human Body. -The resistance of the human body is largely a matter of perfection of -the contacts between its surface and the electrodes. It has been -asserted that it is affected by disease. From 350 to 8,000 ohms have -been determined as resistances, but so much depends on the contacts that -little value attaches to the results. - - -Resistance, Ohmic. -True resistance measured in ohms as distinguished from -counter-electro-motive force, q. v. The latter is called often spurious -resistance. - -Synonym--True Resistance. - -[Transcriber's note: "True" vs. "spurious" are interesting terms, -considering that today we define impedance as a combination of "real" -resistance and "imaginary" capacitive and inductive reactance.] - - -Resistance, Reduced. -The resistance of a conductor reduced to ohms, or to equivalent lengths -of a column of mercury, 1 square millimeter in cross area. - - -Resistance, Siemen's Unit of. -The resistance of a column of mercury 1 meter long and 1 square -millimeter cross-sectional area at 0º C. (32º F.) - -It is equal to .9431 legal ohm. - - -Resistance, Specific. -The relative resistance of a substance. It is expressed as the actual -resistance of a cube of the substance which is one centimeter on each -edge. For metals it is usually expressed in microhms, for liquids in -ohms. - -The resistances of a specified length of wire of specified diameter of -different substances is often given, and is really a particular way of -stating specific resistances. - -Synonym--Specific Conduction Resistance. - - -Resistance, Spurious. -The counter-electro-motive force, q. v., operating to prevent a current -being produced of what should be its full strength were the true -resistance and actuating electro-motive force only concerned. Such -counter-electro-motive force may be treated as a spurious resistance and -such a value in ohms assigned to it as would correspond to its proper -effect. - - -468 STANDARD ELECTRICAL DICTIONARY. - - -In its effect on opposing a current and in resisting its formation it -differs from true resistance. The latter in diminishing current strength -absorbs energy and develops heat; spurious resistance opposes and -diminishes a current without absorption of energy or production of heat. - -[Transcriber's note: "Spurious resistance" is now called reactance, -consisting of capacitive reactance and inductive reactance. The -combination of reactance and (Ohmic/true) resistance is called -impedance. The calculation of impedance requires complex algebra, not -just real values used in DC circuit analysis.] - - -Resistance, Steadying. -When arc lamps are connected in parallel or multiple arc a small -resistance coil is sometimes placed in series with each lamp for -steadying purposes. It reduces the percentage of variation of resistance -in each lamp, which may be caused by a change in the position of the -carbons. - - -Resistance, Swiss Unit of. -A unit constructed by the "Administration Suisse," based on the same -data as the Breguet and the Digney Units. (See Resistance, Digney Unit -of) - -It is equal to 10.30 legal ohms. - - -Resistance, Thomson's Unit of. -A unit of resistance based on the foot and second. - -It is equal to 0.3166 legal ohm. - - -Resistance, Unit. -Unit resistance is that of a conductor in which unit current is produced -by unit electro-motive force. - - -Resistance, Varley's Unit of. -The resistance of a standard mile of a special copper wire 1/16 inch -diameter. - -It is equal to 25.33 ohms. - - -Resistance, Weber's Absolute Unit. -A metric system unit; (meter / second) * 1E7 - -It is equal to 0.9089 legal ohm. - - -Resonance, Electric. -A set of phenomena known as the Hertz experiments are grouped under this -title, which phenomena are incidents of and depend on the propagation of -electric waves through wires or current conductors, as well as through -the ether. Ordinarily a wire is only a seat of current, and is in its -nature inconsistent with wave propagation through its mass. Such waves -are virtually confined to the exterior of the wire. The point is that -the current-producing force is supposed to enter the wire at all points -from without, the current not being produced by an end-push. Hence in -rapidly recurring waves which are produced by a rapidly pulsatory or -alternating current, no time is afforded for the current-producing -force, in this case the wave-producing force, to penetrate into the -substance of the wire. In one of his experiments Dr. Hertz surrounded a -wire by a glass tube chemically silvered. The coating was so thin as to -be translucent. Through this metallic layer a current could be induced -in the wire in its interior. Any mechanical layer of metal took up the -induction itself, and protected the central wire. This gave a clue to -the thickness of metal penetrated by the rapid induced waves used by Dr. -Hertz. - - -469 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 295. ELECTRICAL RESONANCE EXCITER. - - -The method used for the production of rapid oscillations is the -following. To the terminals of an induction coil two metal spheres AA1 -are connected as shown. This apparatus is termed the exciter; in its -discharge a series of isochronous discharges takes place, alternating in -direction. The period of duration T of a single one is given by the -formula T= 2* PI * squareRoot( LC ), in which C is the capacity and L -is the self-induction. The spheres may be 30 centimeters (11.8 inches) -in diameter, connected each to conductors 0.5 centimeter (.2 inch) in -diameter and 40 centimeters (15.7 inches) long each. For the length of -an undulation the formula gives for this apparatus 4.8 meters (15.75 -feet) as the length of a wave, assuming for them the velocity of -propagation equal to that of light. The exciter may have 10,000 times -the rate of oscillation possessed by the plain induction coil. - -When this apparatus is worked it produces induced waves in every -neighboring conductor. The resonance effects appear in the size of the -spark induced. Thus a wire bent into a circle with its ends nearly -touching will give a spark, but if made of proper electrostatic -capacity, corresponding with the particular waves employed, the spark -will be very much larger. The ring, with its spark gap is termed a -resonator. It is used as an explorer to trace the waves. - -Waves thus produced are transmitted by stone walls and nonconductors in -general. A plate of zinc reflects part and transmits part. The reflected -waves can be traced by the resonator, their angle of reflection being -equal to their angle of incidence. They can be received by one parabolic -reflector, reflected to another and brought to a focus. They can be -reflected so as to produce interference or loops and nodes, and the -loops and nodes can be traced by the resonator. By a prism of asphalt -they are refracted exactly like light. - -From all this it is concluded that an additional proof is furnished of -the identity of light and electro-magnetic waves, and a very strong -experimental proof of Maxwell's theory of light is furnished. - -Synonym--Hertz's Experiments. - - -470 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 296. ELECTRICAL RESONATOR. - - -Resonator, Electric. -A small open electric circuit, with ends nearly touching. When exposed -to electric resonance, or to a sympathetic electric oscillatory -discharge, a spark passes from across the gap. The production of this -spark is altogether a matter of the inductance of the resonator. The -simplest form is a circle of copper wire with its ends nearly touching. -The length of the gap is adjustable by bending. A screw adjustment may -also be provided. Another form is shown in the cut, Fig. 296. Here -sheets of tinfoil are used to regulate the electrostatic capacity, while -at m is shown the finger piece for regulating the size of the spark gap -a. - -Synonym--Spark Micrometer. - - -Resultant. -The line indicating the result of the application of two or more forces -to a point. Its direction and length give the elements of direction and -intensity. (See Forces, Resolution of Forces, Composition of -Components.) - - -Resultant Polarity. -The magnetic polarity imparted to a mass of iron acted on by two or more -separate inducing forces or currents. It appears in dynamos and motors. -The final polarity is the resultant of the inducing effect of the field -magnet poles and of the windings. - - -Retardation. -In telegraphy a retardation of the rate of transmission of signals. It -is due to several causes. - -(a) The self-induction of the circuit, especially if it includes many -electro-magnets, produces extra currents (see Currents, Extra.) These -are opposed to the main current on closing it and hence retard the -action. They are in the same direction on opening it and hence again -retard the action. - -(b) Every line has a certain static capacity. This is affected by the -proximity of the lines to the earth. For each signal electricity has to -be charged upon the line until the line is charged to its end with a -certain proportion of the initial density. This charging takes time and -hence introduces retardation. - -(c) The cores of the electro-magnets of the relays or sounders are not -instantly magnetized and demagnetized. This magnetic lag, q. v., -introduces retardation. - - -471 STANDARD ELECTRICAL DICTIONARY. - - -Retardation of Phase. -The fractional lagging behind of waves or alternating currents; by -lagging behind a portion of a wave length the corresponding phases, as -of full amplitude, are kept back or retarded. The phase of current -intensity may be retarded with reference to the electro-motive force by -the introduction of transformers of high capacity with high resistance -on open secondary circuits. - -[Transcriber's note: Capacitors are used to correct current phase lag.] - - -Retentivity. -Coercitive or coercive force; by virtue of which steel retains its -magnetism. It is the more modern name, "coercive force" as a term being -rejected by many. - -Synonyms--Coercive Force--Coercitive Force. - - -Retort Carbon. -Carbon deposited in coal gas retorts from decomposition of the -hydrocarbons. It is a very hard, pure form, and is of graphitic -modification. Owing to its great hardness it is little used for -electrical purposes, the molded carbons being easier to make. The -deposition occurs in the regular gas-making process, and is a -disadvantage to the working. - - -Return. -A line or conductor which is supposed to carry current back to its -starting point, after it has traversed a line. It may be a wire or the -grounding of the ends of a line [or] may make the earth act as a return, -termed ground- or earth-return. The best distinction of a return is to -so term the portion of a circuit on which no apparatus is placed. - - -Reversibility. -The principal in virtue of which a device for producing a given form of -energy can absorb the same and do work. The reversibility of the dynamo -is its quality in virtue of which it can act as a current generator, -thereby converting mechanical energy into electric energy, or if a -current is passed through it, it rotates, doing work, and thereby -converting electric energy into mechanical energy. The knowledge of this -principle can be traced back to Jacobi in 1850. - - -Reversible Bridge. -A form of Wheatstone's Bridge adapted for reversal of the positions or -interchange of the proportionate arms, v., so that the accuracy of the -coils can be tested. - - -Rheochord. -An apparatus by means of which variable quantities of wire are thrown -into the circuit; a rheostat using wire. (See Rheostat, Wheatstone's.) - - -Rheometer. -A galvanometer. (Obsolete.) - - -472 STANDARD ELECTRICAL DICTIONARY. - - -Rheomotor. -A source of current; a current generator; a producer of potential -difference. (Obsolete.) - - -Rheophore. -The portion of an active circuit capable of deflecting a magnetic -needle. This properly includes all of the metallic conductor of a -circuit. (Obsolete.) - - -Rheoscope. -A galvanoscope; an instrument for qualitatively detecting potential -difference, fall or rise. (See Galvanoscope.) - - -Rheostat. -An adjustable resistance; an apparatus for changing the resistance -without opening the circuit. Its action may depend on the introduction -of variable lengths of mercury column, of some other liquid, or of wire -into a circuit. (See Rheostat, Wheatstone's.) - - -Rheostat Arm. -The third arm of known resistance in a Wheatstone bridge. (See -Proportionate Arms.) - - -Rheostatic Machine. -An apparatus for increasing potential difference. It consists of a -number of static condensers. They are charged in multiple arc or in -parallel, and are discharged in series. Secondary batteries may be used -for the charging; thus a static effect is produced from a galvanic -battery. - - -Rheostat, Wheatstone's. -This apparatus consists of two cylinders, one, A, made of brass, the -other, B, of wood, with a spiral groove. At its end is a copper ring a. -A fine brass wire has one end attached to this ring. Its other end is -fastened at e, and it is wound as shown; n and o are binding screws -connected, one with the cylinder-ring a, the other with the brass -cylinder, A. The current entering at o, traverses the wire on B, as -there the windings are insulated by the grooves, thence it passes to m -and by A, whose metal short circuits all the wire on it, to the -binding-post n. The handle, d, is turned one way or the other to -regulate the length of the wire through which the current must pass. On -each cylinder there is a square head, one of which is shown at c, so -that the handle can be shifted from one to the other as required; to A -if the wire is to be wound on that cylinder, to B if the reverse is -desired. - - -Fig. 297. WHEATSTONE'S RHEOSTAT. - - -473 STANDARD ELECTRICAL DICTIONARY. - - -Rheotome. -An automatic circuit breaker, one which rapidly opens and closes a -circuit, as in the case of the primary of an induction coil an -interrupter. (Obsolete.) - - -Rheotrope. -A pole changer, current reverser, or commutator, g., such as the -commutator of an induction coil. (Obsolete.) - - -Rhigolene. -A petroleum product; a hydrocarbon of low boiling point. Its vapor is -used in flashing (q. v.) carbon filaments for incandescent lamps. - - -Rhumbs. -In a mariners' compass, the thirty-two points, designated, north, north -by east, north north east, etc. (See Compass Mariner's-Compass, Points -of the.) - - -Rhumkorff Coil. -The induction coil, q. v. - - -Rigidity, Molecular. -The tendency of molecules to resist rotation or change of position; the -assumed cause of magnetic coercive force, or retentivity. - - -Ring Contact. -A contact formed by a terminal clip in the shape of a ring, split or cut -at one point so that its ends tend to spring together. The other -terminal is a bar which passes into the cut and is tightly pressed by -the elastic ring. - - -Fig. 298. SWITCH WITH RING CONTACTS. - - -474 STANDARD ELECTRICAL DICTIONARY. - - -Ring, Faraday. -A closed ring of iron used as the core of a transformer or induction -coil. The term is derived from Faraday's classic experiment with such an -apparatus when he produced a spark by induction in a secondary circuit. - - -Roaring. -A term applied to the noise sometimes produced in a voltaic arc, when -the electrodes are close together and a heavy current is passing. - - -Rocker. -In a dynamo the movable piece, mounted concentrically with the -commutator, and carrying the rocker-arms and brush-holders. By moving it -the brushes are adjusted for proper lead. - - -Rocker Arms. -The arms projecting from a rocker and each carrying one of the -brush-holders. - - -Roget's Spiral. -An experimental apparatus for illustrating the mutual attraction of -currents going in like direction. A cylindrical helix or spiral of wire -is suspended by one end. Its lower end just dips into a mercury cup. An -active circuit is connected, one terminal to the upper end, the other -terminal to the mercury cup, bringing the apparatus in series into the -circuit. The current as it passes causes the coil to shorten, each -spiral attracting its neighbors. This breaks the circuit by drawing the -lower end out of the mercury cup. The current being cut off the coils -cease to attract each other, and the end dips into the mercury cup -again. This closes the circuit, the coils again attract each other and -the same sequence follows and is repeated over and over again. A bright -spark is produced at each break of the mercury contact. - - -Rotation of Liquids, Electro-dynamic. -By passing a current through a liquid, such as dilute sulphuric acid, it -rotates if exposed to the induction of a current flowing at right angles -to it. The condition resolves itself into a liquid traversed by -horizontal currents from centre to circumference or vice versa, rotated -by a current passing through a circular conductor below it. - - -475 STANDARD ELECTRICAL DICTIONARY. - - -Rotation of Liquids, Electro-magnetic. -The rotation produced in a liquid carrying centripetal or centrifugal -currents by an electromagnet. It is practically an intensification of -electro-dynamic rotation. (See Rotation of Liquids, Electro-dynamic.) - - -Rubber. -In a frictional electric machine the cushion of leather which is pressed -against the plate as it rotates. - - -S. -(a) Symbol for second. - -(b) Symbol for space, or length; L is preferable. - -(c) Symbol for south-seeking pole of a magnet. - - -Saddle Bracket. -A bracket carried on the top of telegraph poles, carrying an insulator -for the upper wire. - - -Safety Device. -(a) A device to prevent overheating of any portion of a circuit by -excess of current. It generally consists of a slip of fusible metal -which if the current attains too much strength melts and opens the -circuit. To ensure its breaking a weight is sometimes suspended from the -strip. In one form an insulated German silver wire is wrapped around the -end of the fusible strip a number of times and its end is connected to -it. The other end of the German silver wire connects with the main lead, -so that all the current goes through both in series. If the German -silver wire becomes heated from excess of current the coil wrapped -tightly around the end of the fusible strip melts it and opens the -circuit. - -(b) Lightning arresters, q. v., may be cited under this heading. - -Synonyms--Automatic Cut Out--Safety Fuse, Plug, or Strip. - - -Fig. 299. COCKBURN SAFETY FUSE. - - -Safety Fuse. -A strip of metal inserted so as to form part of a circuit and of such -size that a smaller current [than] would heat the regular wire of the -circuit dangerously, so as to cause a conflagration for instance, would -melt the fuse and open the circuit. As it sometimes happens that a -safety fuse melts without parting a weight is sometimes hung upon it, so -as to break it as it softens. - - -Salt. -A salt is a chemical compound containing two atoms of two radicals,. -which saturate each other. One atom or radical is electro-positive -referred to the other, which is electro-negative. By electrolysis salts -are decomposed, the atoms or radicals separating and uniting to form new -molecules. - - -476 STANDARD ELECTRICAL DICTIONARY. - - -Saturated. adj. -A liquid is saturated with a substance when it has dissolved all that it -can, while an excess is present in the liquid. It is possible, by -dissolving some salts in hot water and allowing the solution to cool -without access of air, to obtain a supersaturated solution. On -introduction of a crystal of the salt, or often on mere access of air, -the solution forms crystals and the liquid left is saturated. - - -Saw, Electric. -A platinum coated steel wire mounted and connected to be raised to -incandescence for cutting purposes. - - -Schweigger's Multiplier. -An old term for the galvanometer as invented by Schweigger soon after -Oerstedt's discovery. - - -Scratch Brushes. -Brushes for cleaning the surface of articles to be electroplated to give -a good metallic surface suitable for deposition. They have often wire -instead of bristles. - - -477 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 300. WIRE GAUZE ELECTRIC SCREEN. - - -Screen, Electric. -A large plate or a hollow case or cage of conducting material connected -with the earth, and used to protect any body placed within it from -electrostatic influences. - -If within a hollow conducting sphere an electrified body is placed, the -inner surface of the sphere will be charged with electricity of opposite -kind to that of the sphere, and the outer surface with the same kind as -that of the sphere. Thus the sum of the electricities called into action -by induction is zero. The two inner charges are bound to each other. The -induced charge on the outer surface of the sphere is all that has any -effect on objects in the outer air. - -If the outer surface is connected to the earth it becomes discharged, -and however highly electrified the body introduced into the sphere and -the inner surface of such sphere may be, they produce no external -effects, as they are bound one to the other. - -If the sphere is connected to the earth and an unelectrified object is -placed within it, such object will be perfectly shielded from the -effects of an outer electrostatic field. Perforated tinfoil or wire -gauze has just as good a result. A large plate of metal connected to the -earth has the same effect. The screen whether plane or hollow simply -retains a bound charge due to the field of force, thereby neutralizing -it, and the electricity of the opposite sign escapes to the earth. Thus -a true shielding or screening effect is produced. - -In the cut an experiment is shown in which an electric screen is carried -by a Leyden jar. Pith balls are suspended outside and inside of it. By -the approach of an electrified body the outer pith balls will diverge, -while no effect is produced upon the inner ones. - - -Secondary Actions. -In electrolysis the direct products of the electrical decomposition are -not always obtained at the electrodes, but products due to their -reaction on the water and other chemicals may appear. These constitute -secondary actions. Thus if a solution of copper sulphate is electrolyzed -with platinum electrodes, metallic copper appears at one pole and -sulphuric acid and oxygen gas at the other. But the products of -electrolysis by the current are copper (Cu) and sulphion (SO4). The -latter reacting on water sets free oxygen gas and forms sulphuric acid. -The latter is a secondary action. - - -Secondary Generator. -(a) An alternating current converter generating a so-called secondary -current. - -(b) A secondary battery, q. v., may be thus termed. - - -Secondary, Movable. -The term movable secondaries has been applied to rings, spheres and -discs of conducting material, such as copper, whose behavior when near -the pole of an electro-magnet traversed by an alternating current, have -been studied by Elihu Thomson. Such masses are subjected to very -peculiar movements and mutual reactions. As the phenomena are due to -induced currents the above term has been applied to the masses in which -the currents are induced. - - -478 STANDARD ELECTRICAL DICTIONARY. - - -Secondary Plates, Colors of. -In a secondary battery of the lead plate type, the color of the plates -is a good indication of the condition of the battery. The negative plate -should be brown or deep-reddish, the other should be slate-colored. - - -Secondary Poles. -Poles sometimes found in magnets existing in positions intermediate -between the end or true poles. - -Synonym--Consequent Poles. - - -Seebeck Effect. -The production of a current by heating the junction of two different -metals forming part of a circuit, or the thermo-electric production of -current, is stated as the Seebeck effect, having been discovered by that -investigator. - - -Selenium. -A non-metallic element. It is interesting electrically on account of the -changes its electric resistance undergoes when it is subjected to light. - -In one set of experiments it was found that diffused light caused the -resistance to fall in the ratio of 11 to 9. Full sunlight reduced it to -one-half. Of the spectrum colors red was most powerful and the ultra red -region still more strongly affected its resistance. - -The effect produced by exposure to light is instantaneous, but on -removal to the dark only slowly disappears. - -A vessel of hot water was found to have no effect, showing that short -ether waves are essential to the effect. - - -Selenium Cell. -A selenium resistance box. Vitreous selenium is made by keeping ordinary -selenium for some hours at a temperature of about 220º C. (428º F.) -after fusing. It is placed in an electric circuit as part of the -conductor. - -Its resistance can then be determined. It decreases in sunlight to about -one-half its resistance in the dark. - -The selenium cell is used in the Photophone, q. v. Otherwise it is -little more than a subject of experiment. - - -Selenium Eye. -A model eye in which selenium in circuit with a battery and galvanometer -takes the place of the retina of the human eye. - - -Self-repulsion. -When a body is electrified each molecule repels its neighbor and the -condition in question is thus designated. An electrified soap-bubble -expands in virtue of self-repulsion. - - -Semi-conductors. -Substances which conduct static electricity poorly, but quite -appreciably and beyond the extent of leakage. The following are -examples: Alcohol and ether, powdered glass, flowers of sulphur, dry -wood, paper, ice at 0º C. (32º F.) - - -479 STANDARD ELECTRICAL DICTIONARY. - - -Sensibility. -The measure of the effect of a current upon a galvanometer, or any -similar case. - - -Sensitiveness, Angle of Maximum. -Every galvanometer has its angle of maximum sensitiveness, which is the -angle of deflection at which a small increment of current will produce -the greatest deflection. For every tangent galvanometer 45° is the angle -in question. In using a galvanometer for direct reading methods it is an -object to have it work at its angle of maximum sensitiveness. - - -Separately Excited Dynamo. -A dynamo-electric machine whose field magnet is excited from an outside -source, which may be another dynamo or a battery. Alternating current -dynamos are often of this description. - - -Separate Touch. -In magnetism a method of inducing magnetism in a steel bar. The opposite -poles of two magnets are applied at the center of the bar to be -magnetized, but without touching each other, and are drawn apart to its -ends. They are returned through the air and the process is repeated a -number of times and on both sides of the bar if necessary. - - -Separation of Electricities. -Under the double fluid theory of electricity the action of -electrification in accumulating positive electricity in one conductor -and negative on the other of the excited surfaces of two conductors. - - -Separator. -India rubber bands or other forms used in batteries to keep the plates -from touching in the cell; especially applied to secondary batteries, -where the plates are so near together as to require separators to -prevent short circuiting. - - -Fig. 301. SERIES CONNECTION. - - -Series. -(a) Arranged in succession as opposed to parallel. Thus if a set of -battery jars are arranged with the zinc of one connected to the carbon -of the next one for the entire number, it is said to be arranged in -series. When incandescent lamps are arranged in succession so that the -current goes through one after the other they are arranged in series. - -The opposite of parallel, q. v., or multiple arc, q. v.; it may be used -as a noun or as an adjective. - -(b) See Electro-Chemical Series; - -(c) Thermo-Electric Series - -(d) Electrostatic Series; - -(e) Electro-motive Series. - -Synonym--Cascade Connection (but little used.) - - -480 STANDARD ELECTRICAL DICTIONARY. - -Series-multiple. -Arrangement of electric apparatus, in which the parts are grouped in -sets in parallel and these sets are connected in series. It is used as a -noun, as "arranged in series-multiple," or as an adjective, as "a -series-multiple circuit or system." - - -Fig. 302. SERIES-MULTIPLE CONNECTION. - - -Service Conductors. -In electric distribution the equivalents of service pipes in the -distribution of gas; wires leading from the street mains to the houses, -where current is to be supplied. - - -Serving. -The wrapping or winding of a cable composed of small size wire, laid -closely and smoothly with a tool called a serving mallet, or serving -block, or by machinery. It serves to protect the cable from wear. - - -Shackle. -In telegraph lines a swinging insulator bracket for use where wires make -an angle with the pole. A journal box is attached to the pole, like half -of a gate hinge. To this a short iron arm is pivoted so as to be free to -swing through a considerable angle. At its end an insulator is carried -to which the wire is attached. The shackle swings into line with the -wire, or takes a position for two wires corresponding to the resultant -of their directions of pull. - - -Fig. 303. DOUBLE SHACKLE - - -Shadow. Electric. -A term applied to a phenomenon of high vacua. If an electric discharge -is maintained in a Crookes' tube the glass opposite the negative -electrode tends to phosphoresce. A plate of aluminum, used also as the -positive electrode, protects the glass directly behind it so as to -produce the effect of a shadow. - -Synonym--Molecular Shadow. - -[Transcriber's note: The effect is due to the "shadowing" of the -electrons streaming past the plate.] - - -481 STANDARD ELECTRICAL DICTIONARY. - - -Sheath for Magnet Coils. -In 1867 C. E. Varley proposed the use of a copper sheath surrounding a -magnet core to diminish self-induction. It has since been used by Brush -and others. Sometimes metallic foil is laid between the successive coils -of wire. - -Synonym--Mutual Induction Protector. - - -Sheath for Transformers. -A protective sheath of copper, interposed between the primary and -secondary circuits of an alternating current transformer. It is -connected to the earth. If the primary coil loses its insulation before -it can leak to the secondary it is grounded. This protects the secondary -circuit from the high electro-motive force of the primary circuit. - - -Shellac. -A resin; produced as an exudation upon the branches of certain Asiatic -trees, such as the banyan (Ficus religiosa). It is due to punctures in -the bark of the trees in question, which punctures are made by the -female of the insect coccus ficus or c. lacca. - -Commercial shellac contains about 90 per cent. of resinous material, the -rest is made up of wax, gluten, coloring matter and other substances. - -Shellac is soluble in alcohol, and in aqueous solutions of ammonium -chloride, of borax and in strong ammonia solution. Long standing is -required in the case of the last named solvent. Dilute hydrochloric and -acetic acids dissolve it readily; nitric acid slowly; strong sulphuric -acid is without action on it. Alkalies dissolve it. - -In electric work it is used as an insulator and dielectric. Its -alcoholic solution is used to varnish glass plates of influence -machines, for the coils of induction coils and similar purposes. - -Resistance in ohms per centimeter cube at 28° C. (82.4 F.)--(Ayrton), -9.0E15 - -Specific Inductive Capacity (Wüllner), 2.95 to 3.73 - -The same substance in less pure forms occurs in commerce, as stick lac, -lump lac, seed lac, button lac. - - -Shellac Varnish. -Solution of shellac in alcohol; methylic alcohol (wood alcohol or wood -naphtha) is often used as solvent. - -Dr. Muirhead recommends button lac, dissolved in absolute alcohol, and -the top layers decanted. For highest insulation he dissolves the lac in -ordinary alcohol, precipitates by dropping into water, collects the -precipitate, dries and dissolves in absolute alcohol. - - -Shielded. adj. -An electric measuring instrument of the galvanometer type is shielded -when it is so constructed that its indications are not seriously -affected by the presence of neighboring magnets or by fields of force. -Shielding can be effected by using a very strong permanent magnet to -produce a field within which the magnetic needle moves and which reacts -upon it, or by enclosing the instrument in a thick iron box. - - -482 STANDARD ELECTRICAL DICTIONARY. - - -S. H. M. -Symbol or abbreviation for "simple harmonic motion." - - -Shock, Break. -A term in electro-therapeutics; the shock received when an electric -circuit, including the patient in series, is broken or opened. - -Synonym--Opening Shock. - - -Shock, Electric. -The effect upon the animal system of the discharge through it of -electricity with high potential difference. Pain, nervous shock, violent -muscular contortions accompany it. Of currents, an alternating current -is reputed worse than a direct current; intermediate is the pulsatory -current. - -The voltage is the main element of shock, amperage has also some direct -influence. - - -Shock, Static. -A term in electro-therapeutics. The application of static discharges -from small condensers or Leyden jars to a patient who is insulated from -the ground with one electrode applied to the conducting surface on which -he rests, while the other, a spherical electrode, is brought near the -body so as to produce a disruptive or spark discharge. - - -Short Circuit. -A connection between two parts of a circuit, which connection is of low -resistance compared to the intercepted portion. The term is used also as -a verb, as "to short circuit a lamp." - - -Fig. 304. DIAGRAM ILLUSTRATING SHORT CIRCUIT WORKING. - - -Short Circuit Working. -A method of working intermittently an electro-magnet so as to avoid -sparking. It consists in providing a short circuit in parallel with the -magnetic coils. This short circuit is of very low resistance. To throw -the magnet into action the short circuit is opened; to throw it out of -action the short circuit is closed. The shunt or short circuit must be -of negligibly small resistance and inductance. - - -483 STANDARD ELECTRICAL DICTIONARY. - - -Shovel Electrodes. -Large plate electrodes used in a medical bipolar bath. (See Bath, -Bipolar.) - - -Shunt. -In a current circuit a connection in parallel with a portion of the -circuit. Thus in a dynamo a special winding for the field may have its -ends connected to the bushes, from which the regular external circuit -also starts. The field is then wound in shunt with the armature. In the -case of a galvanometer a resistance coil may be put in parallel with it -to prevent too much current going through the galvanometer; this -connection is a shunt. - -The word is used as a noun, as "a shunt," or "a connection or apparatus -in shunt with another," and as an adjective, as "a shunt connection," or -as a verb, as "to shunt a battery." - - -Shunt Box. -A resistance box designed for use as a galvanometer shunt. (See Shunt, -Galvanometer.) The box contains a series of resistance coils which can -be plugged in or out as required. - - -Shunt, Electro-magnetic. -In telegraphy a shunt for the receiving relay consisting of the coils of -an electro-magnet. It is placed in parallel with the relay. Its poles -are permanently connected by an armature. Thus it has high -self-induction. - -On opening and closing the circuit by the sending key, extra currents -are produced in the shunt. The connections are so arranged that on -making the circuit the extra current goes through the relay in the same -direction as the principal current, while on breaking the circuit the -induced current goes in the opposite direction. - -Thus the extra currents accelerate the production and also the cessation -of signalling currents, tending to facilitate the operations of sending -despatches. - - -Shunt, Galvanometer. -A resistance placed in parallel with a galvanometer, so as to short -circuit its coils and prevent enough current passing through it to -injure it. By knowing the resistance of the shunt and of the -galvanometer coils, the proportion of current affecting the galvanometer -is known. This gives the requisite factor for calculation. (See -Multiplying Power of Shunt.) - - -Shunt Ratio. -The coefficient expressing the ratio existing between the current in a -shunt and in the apparatus or conductor in parallel with it. (See -Multiplying Power of/ Shunt.) - - -Shunt Winding. -A dynamo or motor is shunt-wound when the field magnet winding is in -shunt or in parallel with the winding of the armature. - - -Shuttle Current. -A current alternating in direction; an alternating current. - - -484 STANDARD ELECTRICAL DICTIONARY. - - -Side-Flash. -A bright flashing lateral discharge from a conductor conveying a current -due to a static discharge. - - -Sighted Position. -In an absolute electrometer (see Electrometer, Absolute) the position of -the balanced arm carrying the movable disc or plate, when the disc and -guard plate are in one plane. The cross-hair on the lever-end is then -seen midway between two stops, or some other equivalent position is -reached which is discerned by sighting through a magnifying glass or -telescope. - - -Silver. -A metal; one of the elements; symbol Ag.; atomic weight, 108; valency, 1; -equivalent, 108; specific gravity, 10.5. It is a conductor of electricity. - Relative resistance, annealed, 1.0 - Specific Resistance, annealed, at 0° C. (32° F.) 1.504 microhms. - Resistance of a wire at 0° C. (32° F.), Annealed. Hard Drawn. - (a) 1 foot long, weighing 1 grain, .2190 ohms .2389 ohms. - (b) 1 foot long, 1/1000 inch thick, 9.048 " 9.826 " - (c) 1 meter long, weighing 1 gram, .1527 " .1662 " - (d) 1 meter long, 1 millimeter thick, .01916 " .02080 " - - Resistance annealed of a 1-inch cube, at 0° C. (32°F.) .5921 microhms. - - Percentage increase in resistance per degree C. - (1.8 F.) at about 20° C. (68° F.), annealed, 0.377 per cent. - - Electro-chemical equivalent, (Hydrogen = .0105) .1134 mgs. - - -Silver Bath. -A solution of a salt of silver for deposition in the electroplating -process. - -The following is a typical formula: - Water, 10.0 parts by weight. - Potassium Cyanide, 5 " " - Metallic Silver, 2.5 " " - -The silver is first dissolved as nitrate and converted into cyanide and -added in that form, or for 2.5 parts metallic silver we may read: - Silver cyanide, 3 parts by weight. - -While many other formulas have been published the above is -representative of the majority. Other solvents for the silver than -potassium cyanide have been suggested, such as sodium hyposulphite, but -the cyanide solution remains the standard. - - -Silver Stripping Bath. -Various baths are used to remove silver from old electroplated articles. -Their composition depends upon the base on which the metal is deposited. -Silvered iron articles are placed as anodes in a solution of 1 part -potassium cyanide in 20 parts of water. As kathode a silver anode or a -copper one lightly oiled may be used. From the latter the silver easily -rubs off. For copper articles a mixture of fuming sulphuric acid and -nitric acid (40º Beaumé) may be used. The presence of any water in this -mixture will bring about the solution of the copper. Or fuming sulphuric -acid may be heated to between 300º and 400º F., some pinches of dry -pulverized potassium nitrate may be thrown in and the articles at once -dipped. These methods effect the solution of the silver, leaving the -copper unattacked. - - -485 STANDARD ELECTRICAL DICTIONARY. - - -Simple Substitution. -A method of obtaining a resistance equal to that of a standard. The -standard is put in circuit with a galvanometer and the deflection is -noted. For the standard another wire is substituted and its length -altered until the same deflection is produced. The two resistances are -then evidently identical. The standard can be again substituted to -confirm the result. - - -Sine Curve. -If we imagine a point moved back and forth synchronously with a -pendulum, and if such point made a mark upon paper, it would trace the -same line over and over again. If now the paper were drawn steadily -along at right angles to the line of motion of the point, then the point -would trace upon it a line like the profile of a wave. Such line is a -sine curve. It derives its name from the following construction. Let a -straight line be drawn, and laid off in fractions, such as degrees, of -the perimeter of a circle of given diameter. Then on each division of -the line let a perpendicular be erected equal in height to the sine of -the angle of the circle corresponding to that division; then if the -extremities of such lines be united by a curve such curve will be a sine -curve. - -In such a curve the abscissas are proportional to the times, while the -ordinates are proportional to the sines of angles, which angles are -themselves proportional to the times. The ordinates pass through -positive and negative values alternately, while the abscissas are always -positive. - -Any number of sine curves can be constructed by varying the diameter of -the original circle, or by giving to the abscissas a value which is a -multiple of the true length of the divisions of circle. If the pendulum -method of construction were used this would be attained by giving a -greater or less velocity to the paper as drawn under the pendulum. - -A species of equation for the curve is given as follows: y = sin( x ) - -In this x really indicates the arc whose length is x, and reference -should be made to the value of the radius of the circle from which the -curve is described. It will also be noticed that the equation only -covers the case in which the true divisions of the circle are laid off -on the line. If a multiple of such divisions are used, say n times, or -1-n times, then the equation should read -y = n sin( x ) or y = sin( x ) / n - -Synonyms--Curve of Sines--Sinusoidal Curve--Harmonic Curve. - - -486 STANDARD ELECTRICAL DICTIONARY. - - -Sine Law. -The force acting on a body is directly proportional to the sine of the -angle of deflection when-- - -I. The controlling force is constant in magnitude and direction; and - -II. The deflecting force, although variable in its direction in space, -is fixed in direction relatively to the deflecting body. - - -Single Fluid Theory. -A theory of electricity. Electricity, as has been said, being -conveniently treated as a fluid or fluids, the single fluid theory -attributes electrical phenomena to the presence or absence of a single -fluid. The fluid repels itself but attracts matter; an excess creates -positive, a deficiency, negative electrification; friction, contact -action or other generating cause altering the distribution creates -potential difference or electrification. The assumed direction (see -Direction) of the current and of lines of force are based on the single -fluid theory. Like the double fluid theory, q. v., it is merely a -convenience and not the expression of a truth. (See Fluid, Electric, and -Double Fluid Theory.) - -Synonym--Franklin's Theory. - - -Single Fluid Voltaic Cell. -A galvanic couple using only a single fluid, such as the Smee or Volta -cell. - - -Simple Harmonic Motion. -Motion of a point or body back and forth along a line; the motion of a -pendulum, as regards its successive swings back and forth, is an example -of harmonic motion. - - -Sinistrotorsal. adj. -The reverse of dextrotorsal, q. v. A helix with left-handed winding, the -reverse of an ordinary screw, such as a wood-screw or corkscrew. - - -Skin Effect. -A current of very brief duration does not penetrate the mass of a -conductor. Alternating currents for this reason are mainly conducted by -the outer layers of a conductor. The above is sometimes called the skin -effect. - - -Sled. -A contact for electric cars of the conduit system. It is identical with -the plow, q.v., but is drawn after the cars instead of being pushed -along with them. - - -Slide Meter Bridge. -A name for a Slide Bridge one meter long. There are also slide half -meter and slide quarter meter bridges and others. (See Meter Bridge.) - - -S. N. Code. -Abbreviation for single needle code, the telegraphic alphabet used with -the single needle system. - - -Soaking-in-and-out. -A term for the phenomena of the residual electrostatic charge; the -gradual acquirement or loss by a condenser of a portion of its -electrostatic charge. - - -487 STANDARD ELECTRICAL DICTIONARY. - - -Soldering, Electric. -(a) Soldering in which the solder is melted by means of electricity; -either current incandescence or the voltaic arc may be used. It is -identical in general with electric welding. (See Welding, Electric.) - -(b) The deposition by electric plating of a metal over the ends of two -conductors held in contact. This secures them as if by soldering. It is -used in connecting the carbon filament of an incandescent lamp with the -platinum wires that pass through the glass. Copper is the metal usually -deposited. - - -Solenoid. -The ideal solenoid is a system of circular currents of uniform -direction, equal, parallel, of equal diameter of circle, and with their -centers lying on the same straight line, which line is perpendicular to -their planes. - - -Fig. 305. EXPERIMENTAL SOLENOID. - - -The simple solenoid as constructed of wire, is a helical coil, of -uniform diameter, so as to represent a cylinder. After completing the -coil one end of the wire is bent back and carried through the centre of -the coil, bringing thus both ends out at the same end. The object of -doing this is to cause this straight return member to neutralize the -longitudinal component of the helical turns. This it does approximately -so as to cause the solenoid for its practical action to correspond with -the ideal solenoid. - -Instead of carrying one end of the wire through the centre of the coil -as just described, both ends may be bent back and brought together at -the centre. - -A solenoid should always have this neutralization of the longitudinal -component of the helices provided for; otherwise it is not a true -solenoid. - -Solenoids are used in experiments to represent magnets and to study and -illustrate their laws. When a current goes through them they acquire -polarity, attract iron, develop lines of force and act in general like -magnets. - -A solenoid is also defined as a coil of insulated wire whose length is -not small as compared with its diameter. - - -488 STANDARD ELECTRICAL DICTIONARY. - - -Sonometer, Hughes'. -A sound measurer; a modification of a portion of Hughes' induction -balance, used for testing the delicacy of the ear or for determining the -relative intensity of sounds. (See Hughes' Induction Balance.) It is the -arrangement of three coils, two mounted one at each of the ends of a -graduated bar, and the third one between them and free to slide back and -forth thereon. - - -Sonorescence. -The property of producing sounds under the influence of momentary light -radiations rapidly succeeding each other. It is the property utilized in -the photophone, q. v. - - -Fig. 306. MORSE SOUNDER. - - -Sounder. -In telegraphy an instrument consisting of an electromagnet with armature -attached to an oscillating bar, the range of whose movements is -restricted by adjusting screws. The armature is drawn away from the -magnet by a spring. When a current is sent through the magnet the -armature is drawn towards the poles and produces a sound as the bar -strikes a striking piece or second adjusting screw. When the current -ceases the bar and armature are drawn back, striking the first mentioned -screw with a distinct sound, the back stroke. - -The sounder is used to receive Morse and analogous character messages. -The forward strokes correspond to the beginnings of the dots or dashes -of the code, the back strokes to beginnings of the intervals. The -distinction between dots and dashes is made by observing the interval -between forward and back stroke. - -Various devices are used to increase the sound. Sometimes a resonance -box is used on which the sounder is mounted. - -In practice sounders are generally placed on local circuits and are -actuated by relays. - - -489 STANDARD ELECTRICAL DICTIONARY. - - -Sound Reading. -The art or method of receiving telegraph messages by ear. It is now -universally used by all expert Morse operators. It can only be applied -to telegraph systems producing audible sounds; in some cases, as in -needle telegraphy, it may be quite inapplicable. - - -Space, Clearance. -The space between faces of the pole pieces and the surface of the -armature in a dynamo. It is really the air gap, but in calculating -dynamo dimensions the thickness of the insulated copper wire windings of -the commutator are counted in as part of the air gap, because copper is -almost the same as air in impermeability. Clearance space is a -mechanical factor; the air gap is an electric or magnetic factor. - -Synonym--Inter-air Space. - - -Space, Crookes' Dark. -In an exhausted tube, through which an electric discharge is caused to -pass, the space surrounding the negative electrode of the tube. This -space is free from any luminous effect, and by contrast with the light -of the discharge appears dark. The vacuum may be made so high that the -dark space fills the whole space between the electrodes. It is less for -a less vacuum and varies for other factors, such as the temperature of -the negative electrode from which it originates, the kind of residual -gas present, and the quality of the spark. - - -Space, Faraday's Dark. -The space in an exhausted tube between the luminous glows about the two -electrodes. - - -Space, Interferric. -A term for the air-gap in a magnetic circuit. It is etymologically more -correct than air-gap, for the latter is often two-thirds or more filled -with the insulating material and copper wire of the armature windings. -(See Space, Clearance.) - - -Spark Arrester. -A screen of wire netting fitting around the carbons of an arc lamp above -the globe to prevent the escape of sparks from the carbons. - - -Spark Coil. -A coil for producing a spark from a source of comparatively low -electro-motive force. It consists of insulated wire wound round a core -of soft iron, best a bundle of short pieces of wire. Such a coil may be -eight inches long and three inches thick, and made of No. 18-20 copper -wire, with a core one inch in diameter. On connecting a battery -therewith and opening or closing the circuit, a spark is produced by -self-induction, q. v. It is used for lighting gas. - - -490 STANDARD ELECTRICAL DICTIONARY. - - -Spark, Duration of Electric. -Wheatstone determined the duration of the spark given by a Leyden jar as -1/24000 second. Feddersen by interposing a tube of water 9 millimeters -(.36 inch) long in its path found that it lasted 14/10000 second, and -with one 180 millimeters (7.2 inches) long, 188/10000 second. Lucas and -Cazin for a 5 millimeter (.2 inch) spark, with different numbers of -Leyden jars, found the following: -Number of jars. Duration of Spark. - 2 .000026 second - 4 .000041 " - 6 .000045 " - 8 .000047 " - -The duration increases with the striking distance, and is independent of -the diameter of the balls between which it is produced. - - -Spark Gap. -The space left between the ends of an electric resonator (see Resonator, -Electric) across which the spark springs. Its size may be adjustable by -a screw, something like the arrangement of screw calipers. - - -Sparking. -In dynamo-electric machines, the production of sparks at the commutator -between the brushes and commutator sections. The sparks are often true -voltaic arcs, and in all cases are injurious if in any quantity, wearing -out the commutator and brushes. - - -Sparking, Line or Points of Least. -In a dynamo or electric motor the diameter of the commutator -determining, or the points on the commutator marking the position of the -brushes where the sparking is a minimum. Field magnets powerful in -proportion to the armature are a preventative cause. The direction of -the line fixes the angle of lead to be given to the brushes. - - -Sparking, Resistance to. -The resistance to disruptive discharge through its substance offered by -a dielectric or insulator. It does not depend on its insulating -qualities, but on its rigidity and strength. - - -Spark, Length of. -The length of the spark accompanying the disruptive discharge is counted -as the distance from one electrode to the other in a straight line. It -is longer for an increased potential difference between the two -electrodes. If the gas or air between the electrodes is exhausted the -length increases, until the vacuum becomes too high, when the length -begins to decrease, and for a perfect vacuum no spark however small can -be produced. The shape of the conductor which is discharged, the -material of the electrodes, and the direction of the current are all -factors affecting the length of spark producible. - - -491 STANDARD ELECTRICAL DICTIONARY. - - -Spark Tube. -A tube used as a gauge or test to determine when the exhaustion of the -vacuum chamber or bulb of an incandescent lamp is sufficiently high. - -The interior of the tube is connected with the interior of the bulb or -chamber of the lamps in process of exhaustion, and hence shares their -degree of exhaustion. From time to time connections with an induction -coil are made. When the exhaustion is carried far enough no discharge -will take place through the vacuum. As long as the tube acts like a -Geissler tube the exhaustion is not considered perfect. - - -Specific Heat of Electricity. -The heat absorbed or given out by a fluid in passing from one -temperature to another depends on its specific heat. In the Peltier and -the Thomson effects. q. v., the electric current acts as the producer of -a change of temperature, either an increase or decrease as the case may -be. This suggests an absorption of and giving out of heat which amount -of heat corresponding to a current of known amount is determinable, and -may be referred to any unit of quantity such as the coulomb. This or -some equivalent definite quantity of heat it has been proposed (Sir -William Thomson) to term the Specific Heat of Electricity. - - -Spent Acid. -Acid which has become exhausted. In a battery the acid becomes spent -from combination with zinc. It also loses its depolarizing power, if it -is a chromic acid solution or of that type, and then may be said to be -spent. - - -Spent Liquor. -The liquor of a plating bath which has become exhausted from use, the -metal it contained being all or partly deposited. - - -Sphygmograph, Electric. -An electric apparatus for recording the beat of the pulse, both as -regards its rate and strength. - - -Sphygmophone. -An apparatus for examination of the pulse by the microphone and -telephone. - - -Spiders. -Core-discs of a dynamo or motor armature are sometimes perforated with a -large central aperture, are fastened together with insulated bolts, and -the whole mass is secured to the shaft by three- or four-armed spiders. -These are like rimless wheels, the ends of their arms being secured to -the hollow cylinder constituting the armature core, and a central -aperture in their hub receiving the shaft. - - -492 STANDARD ELECTRICAL DICTIONARY. - - -Spiral. -This term is sometimes used instead of coil, as the primary spiral or -secondary spiral of an induction coil or transformer. - - -Spiral Winding. -The winding used on ring armatures. This may diagrammatically be -represented by a spiral carried around the ring shaped core. With two -field poles it gives two collecting points, positive and negative, with -four field poles it gives four collecting points, alternately positive -and negative. - - -Splice Box. -A box in which the splices in underground cables and electric lines are -contained. The splicing is generally done in the boxes with the cables -in place. They may be two-way for straight lines, or be four-way for two -side or lateral connections. - - -Spluttering. -A term applied to a sound sometimes produced in a voltaic arc, perhaps -caused by impure or insufficiently baked electrodes. (Elihu Thomson.) - - -Spring Control. -Control of or giving the restitutive force to the needle of a -galvanometer, core of a solenoid ammeter or moving part of any similar -instrument by a spring. As an example see Ammeter, Ayrton's. - - -Fig. 307. SPRING JACKS. - - -Spring Jack. -An arrangement for effecting, at one insertion of a species of plug, the -opening or breaking of a circuit and for the simultaneous connection to -the terminals formed by the breaking of two terminals of another system -or loop. Thus let a line include in its circuit two springs pressing -against each other, thereby completing the circuit. If a plug or wedge -of insulating material were inserted between the springs so as to press -them apart it would break the circuit and the whole would constitute a -spring jack cut-out. If each side of the plug had a strip of brass or -copper attached to it, and if the ends of another circuit were connected -to these strips, then the insertion of the plug would throw the new line -into the circuit of the other line. - - -493 STANDARD ELECTRICAL DICTIONARY. - - -Spring Jack Cut-out. -A cut-out, of the general construction of a spring jack, q. v., except -that a simple insulating plug or wedge is used in place of the -metal-faced wedge with its connections of the regular spring jack. The -insertion of an insulating wedge opens the circuit, which on its removal -is closed. The regular spring jack wedge will operate in the same way, -if its connections are kept open. - - -Spurious Voltage. -The voltage in excess of that developed by a secondary battery which is -required in the charging process. It is about .25 volt. - - -Square Wire. -Wire whose cross-section is a square. It has been used of iron for -building up the cores of armatures for dynamos or motors, for which it -is peculiarly suitable, and also of copper as a winding for armatures. - - -Staggering. adj. -When the brushes of a dynamo are set, one a little in advance of the -other on the surface of the commutator, they are said to be set -staggering. It is used to get over a break in the armature circuit. - - -State, Electrotonic. -A term expressing an abandoned theory. Faraday at one time proposed the -theory that a wire had to be in the electrotonic state to produce -electro-motive force by movement through an electric field. Any such -idea was ultimately abandoned by Faraday. - - -Static Breeze. -The electric breeze obtained by the silent discharge of high tension -electricity. - - -Static Electricity. -Electricity at rest or not in the current form ordinarily speaking. The -term is not very definite and at any rate only expresses a difference in -degree, not in kind. The recognition of the difference in degree has now -to a great extent also disappeared. - - -Station, Central. -The building or place in which are placed electrical apparatus, steam -engines and plant supplying a district with electric energy. - - -Station, Distant. -The place at the further end of a telegraph line, as referred to the -home station. - - -Station, Home. -The end of a telegraph line where the operators using the expression are -working. - - -494 STANDARD ELECTRICAL DICTIONARY. - - -Station, Transforming. -In alternating current distribution, a building or place where a number -of transformers are worked, so that low potential or secondary circuits -are distributed therefrom. - - -Steel. -A compound of iron with carbon. The carbon may range from a few -hundredths of one per cent. up to two per cent. For magnets, tool steel -drawn to a straw color or a little lower is good. All shaping and filing -should be done before magnetization. - - -Steeling. -The deposition of iron on copper plates by electrolysis. In -electrotyping a thin deposit of iron is thus given the relief plates -before printing from them. The deposit is very hard and exceedingly -thin, so that it does not interfere with the perfection of the -impression in the printing process. As the iron becomes worn it can be -dissolved off with hydrochloric acid, which does not dissolve the -copper, and a new deposit can be given it. Thus the plate may last for -an indefinite number of impressions. - -The iron bath may be prepared by immersing in a solution of ammonium -chloride, two plates of iron, connected as anode and kathode in a -circuit. One plate dissolves while hydrogen is given off from the other. -The solution thus produced is used for a bath. - -The hardness of the deposit, which is really pure iron, gives the name -of "steeling." - -Synonym--Acierage. - - -St. Elmo's Fire. -Luminous static discharge effects sometimes seen on objects elevated in -the air. They are especially noticed on ships' masts. The sailors term -them corpusants (holy bodies). They resemble tongues or globes of fire. - - -Step-by-step Telegraphy. -A system of telegraphy in which in the receiving instrument a hand is -made to move step-by-step, with an escape movement around a dial. For -each step there is a letter and the hand is made to stop at one or the -other letter until the message is spelled out. (See Dial Telegraph.) - - -Step-down. adj. -A qualification applied to a converter or transformer in the alternating -current distribution, indicating that it lowers potential difference and -increases current from the secondary. - - -Step-up. adj. -The reverse of step-down; a qualification of a transformer or converter -indicating that it raises the potential and decreases the current in the -secondary. - - -Sticking. -The adherence, after the current is cut off, of the armature to the -poles of a magnet. In telegraphy it is a cause of annoyance and -obstructs the working. It may, in telegraphy, be due to too weak a -spring for drawing back the armature, or to imperfect breaking of the -contact by the despatcher's key or by the receiver's relay. - - -495 STANDARD ELECTRICAL DICTIONARY. - - -Stopping Off. -In electroplating the prevention of deposition of the plating metal on -any desired portions of the object. It is effected by varnishing the -places where no coating is desired. An article can be plated with -silver, stopped off in any desired design, and the unvarnished portions -may then be plated with gold in another bath. Various effects can be -produced by such means. - - -Storage Capacity. -A term for the ampere-hours of electricity, which can be taken in -current form from a storage battery. - - -Storage of Electricity. -Properly speaking electricity can only be stored statically or in static -condensers, such as Leyden jars. The term has been popularly applied to -the charging of secondary or storage batteries, in which there is really -no such thing as a storage of electricity, but only a decomposition and -opposite combination brought about, which leave the battery in a -condition to give a current. - - -Storms, Electric. -Wide-spread magnetic and electric disturbances, involving the -disturbance of the magnetic elements and other similar phenomena. (See -Magnetic Storms.) - - -Strain. -The condition of a body when subjected to a stress. Various consequences -may ensue from strain in the way of disturbance of electric and other -qualities of the body strained. - - -Stratification Tube. -A Geissler tube, q. v., for showing the stratification of the electric -discharge through a high vacuum. - -The stratifications are greatly intensified by the presence of a little -vapor of turpentine, alcohol, bisulphide of carbon and other substances. - - -Stray Field. -In a dynamo or motor the portion of the field whose lines of force are -not cut by the armature windings. - - -Stray Power. -The proportion of the energy wasted in driving a dynamo, lost through -friction and other hurtful resistances. - - -Streamlets, Current. -A conception bearing the same relation to an electric current that lines -of force do to a field of force; elementary currents. If evenly -distributed the current is of uniform density; if unevenly distributed, -as in alternating currents, the current density varies in different -parts of the cross section of the conductor. This evenness or unevenness -may be referred to the number of streamlets per unit of area of -cross-section. - -[Transcriber's note: Streamlets per unit of area is redundant with -current density.] - - -Stress. -Force exercised upon a solid tending to distort it, or to produce a -strain. - - -496 STANDARD ELECTRICAL DICTIONARY. - - -Stress, Dielectric. -The condition of a dielectric when maintaining a charge; its two -extremities are in opposite states of polarity, or are under permanent -potential difference. As the two opposite polarities tend to unite a -condition of stress is implied in the medium which separates them. - - -Stress, Electro-magnetic. -The stress produced upon transparent substances in an electro-magnetic -field of force. It is shown in the modified optical properties of glass -and similar substances placed between the poles of a strong -electro-magnet. - - -Stress, Electrostatic. -The stress produced upon substances in an electrostatic field of force; -the exact analogue of electro-magnetic stress, and affecting transparent -substances in the same general way. - - -Striae, Electric. -In Geissler tubes the light produced by the electric discharge is filled -with striae, bright bands alternating with dark spaces; these may be -termed electric striae. - - -Striking Distance. -The distance that separates two conductors charged with electricity of -different potential, when a spark starts between them. - - -Striking Solution. -In silver-plating a bath composed of a weak solution of silver -cyanide-with a large proportion of free potassium cyanide. It is used -with a strong current and a large silver anode. This gives an -instantaneous deposition of metallic silver over the surface of the -article which goes to insure a perfect coating in the silver bath -proper. After a few seconds in the striking solution, the article is at -once removed to the plating bath. - - -Stripping. -The removal of electroplating from an object. It may be effected in -several ways. An object whose plating is to be removed is placed in a -plating bath of the solution of the metal with which it is coated. It is -connected as the anode to the positive plate of the battery or -corresponding terminal of the generator. A kathode connected to the -other terminal being placed in the bath, the coating is dissolved by -electrolytic action. Sometimes simple treatment with acid is employed. -Different stripping baths are described under the heads of the different -metals. - - -S. U. -Symbol or abbreviation for Siemens' Unit of Resistance. (See Resistance, -Siemens' Unit of.) - - -Sub-branch. -A branch or lead of wire taken from a branch lead: a term used in -electric distribution. - - -Sub-main. -In electric distribution a conductor connected directly to a main; a -branch. - - -497 STANDARD ELECTRICAL DICTIONARY. - - -Subway, Electric. -A subterranean system of conduits for electric cables. As generally -constructed in this country it includes manholes, q. v., at the street -corners connected by ducts or pipes. These pipes are large enough to -hold a cable. To introduce a cable into a duct, which latter may be two -or three inches in diameter, and from two hundred to six or seven -hundred feet long, a wire or rope is first passed through the duct. This -is done by a set of short wooden rods with screws at the end so as to be -screwed together. Each rod must be shorter than the diameter of the -manhole. A rod is thrust in, another is screwed to it and thrust in, and -thus a set of rods is made to extend as far as desired. In pulling them -out a rope is attached and drawn through. This rope or a larger one is -used in drawing the cable through the duct. A windlass is employed to -draw the rope with cable attached through the ducts. - - -Sulphating. -In storage battery cells, the formation of a hard white basic lead -sulphate, Pb2 S05. Its formation is due to over-exhaustion of the cells. -As long as the voltage is not allowed to fall below 1.90 volts per cell -little of it forms. As it accumulates it is apt to drop off the plate -and fall to the bottom, thus weakening the plate possibly, and depriving -it of active material, and clogging up the cell. If it carries a film of -metallic lead with it, there is danger of short circuiting the cell. - -The presence of some sodium sulphate in the solution is said to tend to -prevent sulphating, or to diminish it. - -Sulphur Dioxide. -A compound gas, S O2; composed of - Sulphur, 32 - Oxygen, 32 - Molecular weight, 64 - Specific gravity, 2.21. - -It is a dielectric of about the same resistance as air. Its specific -inductive capacity at atmospheric pressure is: 1.0037 (Ayrton). - -Synonyms--Sulphurous Acid--Sulphurous Acid Gas. - - -Sunstroke, Electric. -Exposure to the arc light sometimes produces the effects observed in -cases of sunstroke. It is said that, in the case of workmen at electric -furnaces, these effects are very noticeable. (See Prostration, -Electric.) - -[Transcriber's note: Effects are due to ultraviolet light.] - - -Supersaturated. adj. -A liquid is supersaturated when it has dissolved a substance at a -temperature favorable to its solubility and its temperature has been -allowed to change, the liquid being kept free from agitation or access -of air, provided crystallization or precipitation has not taken place. -It expresses the state of a liquid when it holds in solution more than -the normal quantity of any substance soluble in it. - - -Surface. -A galvanic battery is arranged in surface when all the positive plates -are connected together and all the negative plates are also connected. -This makes it equivalent to one large cell, the surface of whose plates -would be equal to the aggregate surface of the plates of the battery. It -is also used as an adjective, as "a surface arrangement of battery." - - -498 STANDARD ELECTRICAL DICTIONARY. - - -Surface Density. -The relative quantity of an electric charge upon a surface. - - -Surface, Equipotential. -A surface over all of which the potential is the same. In a general -sense equipotential surfaces are given by planes or surfaces which cut -lines of force at right angles thereto, or which are normal to lines of -force. The conception applies to electrostatic and electro-magnetic -fields of force, and for current conductors the planes normal to the -direction of the current are equipotential surfaces. - -The contour of an equipotential surface of a field of force which is -drawn or represented by delineations of its lines of force can be -obtained by drawing a line normal thereto. This line will ordinarily be -more or less curved, and will be a locus of identical potentials. - -An electric equipotential surface may be described as electro-static, -electro- magnetic, or magnetic; or may be an equipotential surface of a -current conductor. Besides these there are mechanical and physical -equipotential surfaces, such as those of gravitation. - - -Surface Leakage. -Leakage of current from one part of an insulating material to another by -the film of moisture or dirt on the surface. - - -Suspension. -This term is applied to methods of supporting galvanometer needles, -balance beams, magnetic compass needles and similar objects which must -be free to rotate. (See Suspension, Bifilar--Fibre and Spring -Suspension--Fibre Suspension--Knife Edge Suspension--Pivot -Suspension--Suspension, Torsion.) - - -308. DIAGRAM OF BIFILAR SUSPENSION. - - -Suspension, Bifilar. -Suspension by two vertical parallel fibres, as of a galvanometer needle. -The restitution force is gravity, the torsion being comparatively slight -and negligible. Leaving torsion out of account the restitution force is -(a) proportional to the distance between the threads;. (b) inversely -proportional to their length; (c) proportional to weight of the needle -or other object suspended; (d) proportional to the angle of -displacement. - - -499 STANDARD ELECTRICAL DICTIONARY. - - -Assume two masses A and B at the end of a weightless rod, suspended by -the parallel cords a A, b B. Let the rod be rotated through an angle -theta. Consider the cord a A. Its lower end is swung through the angle -theta, as referred to the center O; the cord is deflected from the -vertical by an angle psi, such that a A tang(psi)= O A 2 sin (theta/2). -The component of gravitation tending to restore A to A, acting towards A -is equal to m g tan(psi). Its moment around O is equal to (m g tan(psi)) -* (O A cos(theta/2). The whole moment of the couple is 2 m g tan(psi). -0 A. cos(theta/2) = 2 m g (O A2/ a A) 2 sin(theta/2). Cos(theta/2) = -2mgl(OA2/aA) sin(theta). The moment of the restoring force is thus -proportional to the sine of the angle of deflection, and the -oscillations of such a system are approximately simple harmonic. -(Daniell.) - -If the twisting is carried so far as to cause the threads to cross and -come in contact with each other the suspension ceases to be a bifilar -suspension, but assumes the nature of a torsional suspension. - -[Transcriber's note: This is the image of the first paragraph.] - - -Swaging, Electric. -Mechanical swaging in which the objects to be swaged are heated by an -electric current as in electric welding. - - -S. W. G. -Abbreviation for Standard Wire Gauge. - - -Fig. 309. SIMPLE SWITCH. - - -Switch. -A device for opening and closing an electric circuit. - -A simple type is the ordinary telegrapher's switch. A bar of metal is -mounted horizontally by a pivot at one end, so as to be free to rotate -through an arc of a circle. In one position its free end rests upon a -stud of metal. One terminal of a circuit is attached to its journal, the -other to the stud. Resting on the stud it closes the circuit, in other -positions it opens the circuit. - - -500 STANDARD ELECTRICAL DICTIONARY. - - -Switch, Automatic. -A switch opened and closed by the electric current. It is used for -lighting distant incandescent lamps. It includes one or two -electro-magnets operated by two push buttons. In the usual arrangement -one button is black and the other white, for extinguishing and lighting -respectively. When the white button is pushed it causes a current to -pass through one of the electro-magnets. This attracts its armature, -thereby making a contact and throwing the lamps into the lighting -circuit. Then they remain lighted until the black button is pressed. -This excites the other magnet, which attracts its armature, breaks the -contact and extinguishes the lights. - -The object of the automatic switch is to enable distant lamps to be -lighted without the necessity of carrying the electric leads or wires to -the place whence the lighting is to be done. A very small wire will -carry enough current to operate the magnets, and open circuit batteries, -such as Leclanché batteries, may be used as the source of current for -the switch, but generally the lighting current is used for the purpose. - -A single magnet may do the work. When the lighting button is pressed the -magnet is excited, attracts its armature and holds it attracted, until -by pressing the black button the current is turned off from it. In this -case the lighting current is used to excite the magnet. - - -Switch Board. -A board or tablet to which wires are led connecting with cross bars or -other switching devices, so as to enable connections among themselves or -with other circuits to be made. - - -Switch, Circuit Changing. -A switch whose arm in its swing breaks one contact and swinging over -makes another. It is employed to change the connections of circuits from -one dynamo to another. - -Synonyms--Changing Switch--Changing Over Switch. - - -Switch, Double Break. -A form of switch in which double contact pieces are provided to give a -better contact. One form consists of a hinged bar whose end swings down -between two pairs of springs. Both pairs are connected to one terminal, -and the bar to the other terminal of a circuit. - - -Switch, Double Pole. -A heavy switch for central station work, that connects and disconnects -two leads simultaneously. - - -Switch, Feeder. -A heavy switch, often of double contact type, for connecting and -disconnecting feeders from bus bars in central stations. - - -501 STANDARD ELECTRICAL DICTIONARY. - - -Switch, Knife. -A switch whose movable arm is a narrow, deep bar of copper or brass, and -which in making contact is forced in edgeways between two springs -connected to one terminal. The bar is connected to the other terminal. - -Synonyms--Knife Break Switch--Knife Edge Switch. - - -Switch, Multiple. -A switch which in the swing of its bar connects one by one with a number -of contacts so that ultimately the end of its bar is in contact with all -at once. It is used to throw lights in and out in succession, and it -can, if the multiple contacts connect with resistances, make them -operate as a rheostat. - - -Switch, Pole Changing. -A switch for changing the direction of the current in a circuit. - - -Switch, Reversing. -A switch, often of the plug type (see Plug Switch) for changing the -direction of current passing through a galvanometer. - - -Switch, Snap. -A switch constructed to give a quick, sharp break. It has a spiral -spring interposed between the handle and arm. As the handle is drawn -back to open it the spring is first extended, the bar being held by the -friction of the contacts, until the spring suddenly jerks it up, thus -breaking the contact. - - -Switch, Storage Battery Changing. -A switch for changing storage battery connections from series to -multiple and back again. - - -Switch, Three Way. -A switch, so constructed that by turning its handle connection can be -made from one lead to either of two other leads, and also so that -connection can be completely cut off. - - -Sympathetic Vibration. -The establishment of periodic movement in one body by impulses of the -same period communicated to it from another body in motion. Thus if two -tuning forks are of the same pitch and one is sounded the other will -begin to sound by sympathy, the sound waves communicating the necessary -periodic impulses to it. - -Sympathetic vibrations are utilized in harmonic telegraphy. (See -Harmonic Receiver--Telegraph, Harmonic.) - - -T. -Symbol of time. - - -Tailings. -(a) In high speed transmission of telegraph signals by the automatic -system, the definiteness of the signal marks is sometimes interfered -with by retardation. Wrong marks are thus produced called tailings. - -(b) The prolongation of the current at the distant receiving station of -a telegraph line due to the discharge of the line and to self-induction. - -Synonyms--Tailing--Tailing Current. - - -502 STANDARD ELECTRICAL DICTIONARY. - - -Tamidine. -Reduced nitro-cellulose. Nitro-cellulose is dissolved in a proper -solvent and is obtained by evaporation as a translucent solid mass. By -ammonium sulphide or other reagent it is reduced so as to be virtually -cellulose. It is cut into shape for filaments of incandescent lamps, -which shapes are carbonized and flashed. - - -Tangent Law. -In a galvanometer the tangents of the angles of deflection of the needle -are proportional to the deflecting force-- - -I. When the controlling force is unaltered in absolute magnitude and -direction by the motion of the needle. - -II. When the deflecting force acts at right angles always to the -controlling force. - -These conditions are usually secured by having the actuating coil -through which the current passes flat and of large diameter compared to -the length of the needle; by using the uniform field of the earth as the -control; by having a short needle; by placing the coil with its plane in -the magnetic meridian. - -For best proportions of tangent galvanometer coils see Bobbins. - - -Fig. 310. GRAPHIC CONSTRUCTION OF TANGENT SCALE. - - -Tangent Scale. -An arc of a circle in which the number of graduations in any arc -starting from zero are proportional to the tangent of the angle -subtended by such arc. The system is for use with tangent galvanometers. -Thus if for 45° a value of 100 is taken and marked on the scale then for -the arc 26° 33' + a value of 50 should be marked on the scale because -such are the relative values of the tangents. - -Thus the scale instead of being divided into degrees is divided into -arcs of varying length, growing shorter as they are more distant from -the zero point, of such length that the first division being subtended -by a tangent of length 1, the first and second divisions added or taken -together as one arc are subtended by a tangent of length 2, and so on. - -In the cut a simple method of graphically laying out a tangent scale is -shown. In it C is the centre of the arc, and H the radius running to the -zero of the instrument. From C a circle is described and on H a vertical -line tangent to the arc is erected. Taking any part of the tangent, as -the length shown ending at D, it is divided into any number of equal -parts. Radii of the circle are now drawn whose prolongations pass -through the divisions on the tangent. These radii, where they intersect -the arc of the circle, determine equal divisions of the tangent scale, -which, as is evident from the construction, are unequal angular -divisions of the arc. - - -503 STANDARD ELECTRICAL DICTIONARY. - - -Tanning, Electric. -The tanning of hides in the manufacture of leather by the aid of -electrolysis. A current of electricity is maintained through the tanning -vats in which regular tanning liquor is contained. Very extraordinary -claims are made for the saving of time in the tanning process. What is -ordinarily a process of several months, and sometimes of a year, is said -to be reduced to one occupying a few days only. The action of -electrolysis is the one relied on to explain the results. - - -Tapper. -The key used in single needle telegraph transmitters. It comprises two -flat springs L, E, each with a handle, normally pressed upward against -one contact bar Z, and when pressed down by the operator making contact -against a lower bar C when messages are to be transmitted. A double -tapper, such as shown, is used for each instrument. - -Synonyms--Double Tapper Key--Pedal Key. - - -Fig. 311. TAPPER. - - -Target, Electric. -A target registering or indicating electrically upon an annunciator the -point of impact of each bullet. - - -Taste, Galvanic. -The effect produced upon the gustatory nerves by the passage of an -electric current, or by the maintenance of potential difference between -two portions of the tongue. It is very simply produced by placing a -silver coin above, and a piece of zinc below the tongue, or the reverse, -and touching their edges. A sour, peculiar taste is at once perceived. -It cannot be due to any measurable quantity of current or of -electrolytic decomposition, because the couple can do little more than -establish a potential difference. With a strong current the taste -becomes too strong for comfort, and if on a telegraph line the extra -currents produced by the signaling make the operation of tasting the -current a very unpleasant one. It is said that messages have been -received in this way, the receiver placing one terminal of the line on -his tongue, and a terminal attached to a grounded wire below it, and -then receiving the Morse characters by taste. - - -504 STANDARD ELECTRICAL DICTIONARY. - - -Teazer. -Originally a fine wire coil wound on the field magnets of a dynamo in -shunt with the regular winding to maintain the magnetism. It was -originally used in electroplating machines to prevent inversion of the -magnetism, but has since developed into a component part of the winding -of the compound dynamo. (See Dynamo, Compound.) - - -Tee, Lead. -A lead pipe of T shape used for connecting branches to electric cables. -The tee is soldered by wiped joints to the lead sheathings of the cable -and branches after the wires have been connected, and the junctions -coated with insulating tape or cement, or both. - -It is sometimes made in two halves, and is known as a split tee. - - -Tel-autograph. -A telegraph for reproducing the hand-writing of the sender at the -receiving end of the line. To save time a special spelling is sometimes -used. - - -Teleautograph. -The special spelling used with the Tel-Autograph telegraph. - - -Tele-barometer, Electric. -A barometer with electric attachment for indicating or recording at a -distance the barometric readings. - - -Telegraph, ABC. -This term is applied to alphabet telegraphs indicating the message by -the movements of a pointer on a dial marked with the characters to be -sent. In England the Wheatstone ABC system is much employed. - - -Telegraph, Automatic. -A telegraph system based on the operation of the transmitting instrument -by a perforated strip of paper drawn through it. The perforations made -by an apparatus termed a perforator, are so arranged as to give -telegraphic characters of the Morse or International Code in the -transmitting instrument. (See Perforator.) Bain in the year 1846 was the -originator of the system. He punched a fillet of paper with dots and -dashes, and drew it between two terminals of the line, thus sending over -the line a corresponding series of short and long currents which were -received by his chemical receiver. (See Chemical Receiver.) The method -was not successful. Its modern development, the Wheatstone Automatic -Telegraph, is highly so. The perforated paper by its perforations -controls the reciprocating movement of two rods, which pass through each -hole in two rows, corresponding to the two rods respectively as the -holes come opposite to the ends of the rods. The rods are kept -constantly moving up and down. If unperforated paper is above them their -upward motion is limited. This gives three positions for the rods, (a) -both down, (b) one up and the other down, (c) both up. These positions -of the rods work a pole changing key by which dots, spaces, and dashes -are transmitted to the receiving instrument, which is an exceedingly -delicate ink-printer. The latter can have its speed adjusted to receive -from 200 to 450 words per minute. - - -505 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Dial. -A telegraph in which as receiver a dial instrument is used. A pointer or -index hand moves around a dial. The dial is marked with letters of the -alphabet. The movements of the pointer are controlled by the -transmitting operator at a distant station. He by the same actions moves -a pointer on a duplicate instrument before him and the two are -synchronized to give identical indications. Thus a message is spelled -out letter by letter on both dials simultaneously. The motions of the -index are generally produced by what is virtually a recoil escapement. -The scape wheel is carried by the axle of the index, and a pallet or -anchor is vibrated by an electro-magnet whose armature is attached to -the stem of the pallet. As the pallet is vibrated it turns the wheel and -index one tooth for each single movement. There are as many teeth in the -wheel as there are characters on the dial. The two instruments being in -duplicate and synchronized, the pallets move exactly in unison, so that -identical readings of the dials are given. The pallets may be moved by -any kind of make and break mechanism, such as an ordinary telegraph key. -The index moves by steps or jerks, so that the system is sometimes -called step-by-step telegraphy. - - -Fig. 312. DIAL TELEGRAPH. - - -In the cut the make and break transmitter is shown at v v, with its -handle and contacts g and t. This mechanism sends impulses of current by -F and Z to the receiving magnet l. This attracts and releases its -armature K from contact into the position indicated by the dotted lines. -This works the rocker n on the pin o, and actuates the double or anchor -pawl s r, which turns the pallet or scrape wheel m. - -The system is dropping into disuse, being supplanted by the telephone. - -Synonym--Step-by-step Telegraph. - - -506 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Double Needle. -A telegraph system in which the message is read by the motions of two -vertical needles on the face of the instrument in front of the receiving -operator. An identical instrument faces the transmitting operator. By -two handles, one for each hand, the needles are caused by electric -impulses to swing to right and to left so as to give a telegraphic code. -It has been generally superseded by the single needle telegraph. - - -Telegraph, Duplex. -A telegraph capable of transmitting simultaneously two messages over one -wire. The methods of effecting it are distinct from those of multiplex -telegraphy. This term is used as a distinction from diode multiplex -telegraphy, in which the work is done on other principles. There are two -systems of duplex telegraphy, the differential and the bridge systems. - - -Telegraph, Duplex Bridge. -A system of duplex telegraphy employing the principle of the Wheatstone -bridge. The other or differential system depends on equality or -difference of currents; the bridge method on equality or difference of -potentials. The cut shows the system known as Steam's Plan. - -At the ends of the line wire are two cross connections like duplicate -galvanometer connections in a Wheatstone bridge, each including a -receiving relay. The rest of the connections are self-explanatory. - -When A depresses his key the current splits at the point indicating the -beginning of the bridge. One portion goes through the line to B and to -earth, the other goes to earth at A through the rheostats indicated by -the corrugated lines. - -On reaching B's end the current divides at the cross-connection and part -goes through the receiving relay shown in the center of that -cross-connection. - -Thus if A sends to B or B to A it is without effect on the home -receiving instrument. Now suppose that both simultaneously are sending -in opposite directions. If the connections be studied it will be seen -that every movement of the transmitting key will affect the balance of -the distant or receiving end of the bridge and so its instrument will -record the signals as they are sent. - -As shown in the cut the sending keys are on local circuits, and work -what are known as duplex transmitters. These are instruments which send -line signals without breaking the connection. - - -Fig. 313. STEARN'S PLAN OF DUPLEX BRIDGE TELEGRAPHY. - - -In Stearn's plan condensers are introduced as shown. By this plan -different receiving instruments can be used. The inventor once worked a -Morse instrument at one end of the line, and a Hughes' instrument at the -other end. - - -507 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Duplex, Differential. -A system of duplex telegraphy employing the differential action of two -exciting or magnetizing coils. The general principles are the following. -Suppose that at each of two stations, there is a magnet working as a -sounder or relay. Each magnet is differentially wound, with two coils of -opposite direction, of identical number of turns. - -When the sending key at a station A is depressed two exactly equal -currents go through the magnet in opposite directions. One called the -compensation current goes to the earth at the stations. The other called -the line current goes through the line, through the line coil of the -distant station E, thereby actuating the relay or sounder armature. - -The instrument of the sender A is unaffected because he is sending -opposite and equal currents through its two coils. A special resistance -is provided on the compensation circuit for keeping the currents exactly -equal in effect. Nothing the sender at A does affects his own -instrument. - -Now suppose E desires to telegraph back at the same time that A is -telegraphing to his station. He works his key. This does not affect his -own instrument except by sending the equal and opposite currents through -its coils. When his key is depressed and A's key is untouched, he works -A's receiving instrument. - - -508 STANDARD ELECTRICAL DICTIONARY. - - -When A's key is depressed simultaneously with B's key, the two line -currents are in opposition and neutralize each other. This throws out -the balance in the instruments and both armatures are attracted by the -compensation currents left free to act by the neutralization of the line -currents. - - -Fig. 314. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM - - -Suppose that B is sending a dash, and it begins while A's key is raised. -The line and compensation currents in B's receiving instrument -neutralize each other and no effect is produced, while A's receiving -instrument begins to register or indicate a dash. Now suppose A starts -to send a dash while B's is half over. He depresses his key. This sends -the two opposite currents through his magnet. His line current -neutralizes B's working current so that the compensation currents in -both receiving instruments hold the armatures attracted for the two -dashes. Meanwhile A's dash ends and he releases his key. At once his -line current ceases to neutralize B's line current, his receiving -instrument is actuated now by B's line current, while B's receiving -instrument ceases to be actuated by the compensation current. - -Two assumptions are made in the above description. The line currents are -assumed to be equal in strength and opposite in direction at each -station. Neither of these is necessary. The line current received at a -station is always weaker than the outgoing line current, and it is the -preponderance of the compensation current over the partly neutralized -line current that does the work. As this preponderance is very nearly -equal to the line current received from the distant station, the signals -are actuated by almost the same current, whether it is compensation or -line current. - - -509 STANDARD ELECTRICAL DICTIONARY. - - -Both line currents may coincide in direction. Then when the two keys are -depressed, a line current of double strength goes through both receiving -instruments and both work by preponderance of the double line current -over the compensation current. In other respects the operation is the -same as before described. - - -Fig. 315. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM. - - -Fig. 316. DIFFERENTIAL DUPLEX TELEGRAPH CONNECTIONS. - - -The cut shows a diagram of the operation of one end of the line. R and R -are resistances, E and E are earth contacts, and the two circles show -the magnet of the receiving instrument wound with two coils in -opposition. The battery and key are also shown. It also illustrates what -happens if the key of the receiver is in the intermediate position -breaking contact at both 1 and 2. The sender's line current then goes -through both coils of the receiving instrument magnet, but this time in -series, and in coincident direction. This actuates the instrument as -before. Owing to the resistance only half the normal current passes, but -this half goes through twice as many coils or turns as if the receiver's -key was in either of the other two positions. - -In actual practice there are many refinements. To compensate for the -varying resistance of the line a rheostat or resistance with sliding -connection arm is connected in the compensation circuit so that the -resistance can be instantly changed. As the electro-static capacity of -the line varies sectional condensers are also connected in the -compensation circuits. - - -510 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Facsimile. -A telegraph for transmitting facsimiles of drawing or writing. The -methods employed involve the synchronous rotation of two metallic -cylinders, one at the transmitting end, the other at the receiving end. - -On the transmitter the design is drawn with non-conducting ink. A tracer -presses upon the surface of each cylinder and a circuit is completed -through the two contacts. In operation a sheet of chemically prepared -paper is placed over the surface of the receiving cylinder. The two -cylinders are rotated in exact synchronism and the tracers are traversed -longitudinally as the cylinders rotate. Thus a number of makes and -breaks are produced by the transmitting cylinder, and on the receiving -cylinder the chemicals in the paper are decomposed, producing marks on -the paper exactly corresponding to those on the transmitting cylinder. - -Synonyms--Autographic Telegraph--Pantelegraphy. - - -Telegraph, Harmonic Multiplex. -A telegraph utilizing sympathetic vibration for the transmission of -several messages at once over the same line. It is the invention of -Elisha Gray. The transmitting instrument comprises a series of vibrating -reeds or tuning-forks, each one of a different note, kept in vibration -each by its own electro-magnet. Each fork is in its own circuit, and all -unite with the main line so as to send over it a make and break current -containing as many notes superimposed as there are tuning forks. At the -other end of the line there are corresponding tuning forks, each with -its own magnet. Each fork at this end picks up its own note from the -makes and breaks on the main line, by the principle of sympathetic -vibration. - -To each pair of operators a pair of forks of identical notes are -assigned. As many messages can be transmitted simultaneously as there -are pairs of forks or reeds. - -The movements of a telegraph key in circuit with one of the transmitting -reeds sends signals of the Morse alphabet, which are picked out by the -tuning fork of identical note at the other end of the line. - - -511 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Hughes'. -A printing telegraph in very extensive use in continental Europe. Its -general features are as follows: - -The instruments at each end of the line are identical. Each includes a -keyboard like a piano manual, with a key for each letter or character. -On each machine is a type wheel, which has the characters engraved in -relief upon its face. With the wheel a "chariot" as it is termed also -rotates. The type wheels at both stations are synchronized. When a key -is depressed, a pin is thrown up which arrests the chariot, and sends a -current to the distant station. This current causes a riband of paper to -be pressed up against the face of both type wheels so as to receive the -imprint of the character corresponding to the key. The faces of the -wheels are inked by an inking roller. - - -Fig. 317. ELECTRO-MAGNET OF HUGHES' PRINTING TELEGRAPH. - - -The most characteristic feature is the fact that the current sent by -depressing a key does not attract an armature, but releases one, which -is then pulled back by a spring. The armature is restored to its -position by the mechanical operation of the instrument. The magnet used -is a polarized electro-magnet. Coils are carried on the ends of a strong -powerful magnet. The coils are so connected that a current sent through -them by depressing a key is in opposition to the magnetism of the -permanent magnet so that it tends to release the armature, and in -practice does so. This release permits the printing mechanism to act. -The latter is driven by a descending weight, so that very slight -electric currents can actuate the instruments. - -Synonym--Hughes' Type Printer. - - -Telegraphic Code. -(a) The telegraphic alphabet, as of the Morse System. (See Alphabet, -Telegraphic.) - -(b) A code for use in transmitting messages either secretly, or -comprising several words or short sentences in one word, in order to -economize in transmission. Such codes are extensively used in commercial -cable messages. - - -512 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Magneto-electric. -A telegraph in which the current is produced by magneto-electric -generators. It has been applied to a considerable extent in England. The -Wheatstone ABC or dial telegraph is operated by a magneto-generator -turned by hand. - -In this country the magneto-electric generator by which the calling bell -of a telephone is rung is an example. The magneto-electric key (See Key, -Magneto-electric) is for use in one kind of magneto-electric -telegraphing. - - -Telegraph, Morse. -A telegraph, characterized by the use of a relay, working a local -circuit, which circuit contains a sounder, or recorder for giving dot -and dash signals constituting the Morse alphabet. The signals are sent -by a telegraph key, which when depressed closes the circuit, and when -released opens it. The two underlying conceptions of the Morse Telegraph -system are the use of the dot and dash alphabet, and the use of the -local circuit, which circuit includes a receiving instrument, and is -worked by a relay, actuating a local battery. It would be difficult to -indicate any invention in telegraphy which has had such far-reaching -consequences as the one known as the Morse telegraph. - -In other places the principal apparatus of the system will be found -described. The cut Fig. 318, repeated here gives the general disposition -of a Morse system. (See Circuit, Local.) - - -Fig. 318. DIAGRAM OF MORSE SYSTEM. - - -513 STANDARD ELECTRICAL DICTIONARY. - - -The key by which the messages are transmitted is shown in Fig. 319. M is -a base plate of brass. A is a brass lever, mounted on an arbor G carried -between adjustable set screws D. C is the anvil where contact is made by -depressing the key by the finger piece B of ebonite. E, Fl are adjusting -screws for regulating the vertical play of the lever. H is the switch -for opening or closing the circuit. It is opened for transmission, and -closed for receiving. By screws, L L, with wing nuts, K K, the whole is -screwed down to a table. - - -Fig. 319. MORSE TELEGRAPH KEY. - - -In the United States the simplest disposition of apparatus is generally -used. The main line is kept on closed circuit. In it may be included a -large number of relays at stations all along the line, each with its own -local circuit. There may be fifty of such stations. Battery is generally -placed at each end of the line. Very generally gravity batteries are -used, although dynamos now tend to supplant them in important stations. - -As relays the ordinary relay is used. Its local circuit includes a -sounder and local battery. The latter is very generally of the gravity -type, but oxide of copper batteries (See Battery, Oxide of Copper) are -now being introduced. At main or central offices, the terminals of the -lines reach switch boards, where by spring-jacks and plugs, any desired -circuits can be looped into the main circuit in series therewith. - -In European practise the main line is kept on open circuit. Polarized -relays are used to work the local circuits. The currents for these have -to be alternating in direction. When the line is not in use its ends are -connected to earth at both ends, leaving the battery out of circuit. -Each intermediate station has its own main, or line battery for use when -it desires to send a message. In the American system as first described, -it will be seen that the main batteries are at most two in number. - -For the details of the different apparatus, the following definitions -may be consulted: Embosser, Telegraphic--Recorder, Morse--Relay--Relay -Connection--Sounder. - - -514 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Multiplex. -A system of telegraphy by which a number of messages can be transmitted -in both directions over a single wire. The principles underlying the -systems are the following: - -Suppose that at the two extremities of a telegraph line two arms are -kept in absolute synchronous rotation. Let the arms in their rotation, -press upon as many conducting segments as there are to be transmissions -over the line. A transmitting and receiving set of instruments may be -connected to one segment at one end of the line, and another set to the -corresponding segment at the distant station. For each pair of segments -two sets can be thus connected. Then if the arm rotates so rapidly that -the contacts succeed each other rapidly enough each pair of sets of -instruments can be worked independently of the others. In practice this -rapid succession is effected by having a number of contacts made for -each pair during a single rotation of the arm or equivalent. - -The multiplex system has been perfected by the use of La Cour's phonic -wheel (see Phonic Wheel), and brought into a practical success by -Patrick B. Delany, of New York. - -Two phonic wheels rotate at each end of the line. They are kept in -synchronous motion by two vibrating steel reeds of exactly the same -fundamental note, and the axle of each wheel carries an arm whose end -trails over the contacts or distributor segments already spoken of. The -reeds are adjusted to vibrate at such speed that the trailer is in -contact with each segment about 1/500 second. The number of groups of -segments required for each working is determined by the retardation of -the signals owing to the static capacity of the line. To convert the -rapidly recurring impulses of current into practically a single current, -condensers are connected across the coils of the relay. One battery -serves for all the arms. - -Multiplex telegraphy can effect from two to six simultaneous -transmissions over one wire. For two or four transmissions the method -only distinguishes it from duplex or quadruplex telegraphy. The terms -diode, triode, tetrode, pentode and hexode working are used to indicate -respectively the simultaneous transmission of two, three, four, five, or -six messages over one wire. - -It will be seen that the multiplex process really assigns to each -transmission separate times, but divides these times into such short and -quickly recurring intervals that the work is executed as if there was -continuous contact. In no case is there the popular conception of the -sending of several messages actually simultaneously over one wire. Each -signal in reality has its own time assigned it, divided into short -periods of high frequency, and only utilizes the line when it is free. - - -515 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Over-house. -An English term for telegraph lines led over houses and supported on -standards on the roofs. - - -Telegraph Pole Brackets. -Arms for carrying insulators, which arms are attached to telegraph poles -or other support. They vary in style; sometimes they are straight bars -of wood gained into and bolted or spiked in place; sometimes they are of -iron. - - -Telegraph, Printing. -Various telegraphs have been invented for printing in the ordinary -alphabet the messages at the receiving end of the line. - -Representative instruments of this class are used for transmitting -different market and stock reports to business offices from the -exchanges. The type faces are carried on the periphery of a printing -wheel, which is rotated like the hand of a dial telegraph, and against -whose face a paper riband is pressed whenever the proper letter comes -opposite to it. As each letter is printed the paper moves forward the -space of one letter. Spacing between words is also provided for. In the -recent instruments two lines of letters are printed on the paper one -above the other. - -In England, and on the continent of Europe, printing instruments have -received considerable use for ordinary telegraphic work. Hughes' type -printer and Wheatstone's ABC telegraph meet with extensive use there for -ordinary transmission. - - -Telegraph, Quadruplex. -Duplex telegraphy is the sending of two messages in opposite directions -simultaneously through the same wire. Duplex telegraphy is the sending -of two messages simultaneously in the same direction. The two combined -constitute quadruplex telegraphy. [SIC] - -The system was suggested by Stark of Vienna and Bosscha of Leyden in -1855; the successful problem was solved by Edison in 1874. - -The principle is based on the two orders of difference in electric -currents; they may vary in strength or in direction. Thus we may have -one instrument which works with change of strength of current only, the -other with change of direction only. The two can be worked together if -the direction of the current can be altered without alteration of -strength, and if strength can be altered without alteration of -direction. Double current and single current working are so combined -that one relay works by one system of currents and another relay by the -other system. A current is constantly maintained through the line. The -relay operated by change in direction is a simple polarized relay which -works by change of direction of current. The relay operated by change in -strength is the ordinary unpolarized relay. - - -516 STANDARD ELECTRICAL DICTIONARY. - - -For the following description and the cuts illustrating it we are -indebted to Preece and Sivewright. The cut shows the arrangement of the -apparatus and connections for terminal offices. - -"Sufficient table room is provided to seat four clerks. The apparatus is -arranged for the two senders to sit together in the centre, the messages -to be forwarded being placed between them. The section on the left of -the switch Q is known as the 'A' side, that on the right as the 'B' side -of the apparatus. - -K1 the reversing key, reverses the direction of the current. K2 is a -simple key, known as the increment key; it is used simply to increase -the strength of the current. - - -Fig. 320. QUADRUPLEX TELEGRAPH CONNECTIONS. - - -The way in which the keys K1 and K2 combine their action is shown by -Fig. 321. E1 and E2 are the line batteries, the one having two and -one-third (2-1/3) the number of cells of the other, so that if E1 be the -electro-motive force of the smaller, that of the whole combined battery -will be 3.3 E1. The negative pole of E1 is connected to z and z1 of K1 -and the positive pole of E2 to a of K2 through a resistance coil s. A -wire, called the 'tap' wire, connects the positive pole of E1 and the -negative pole of E2 to b of K2. This wire has in it a resistance coil -r2. The springs c and c1 of Kl are connected to the lever L of K2. Now, -when both keys are at rest, the negative pole of E1 is to line through -z, and the positive pole of E1 to earth through b of K2 and c of K1; the -positive pole of E2 being insulated at a of K2. - - -517 STANDARD ELECTRICAL DICTIONARY. - - -There is thus a weak negative current flowing to line. When K1 alone is -worked, the current of E1 is reversed. When K2 is worked alone, c of K1 -is transferred from b to a, and the strength of the negative current -going to line is increased through the increase of the electro-motive -force from E1 to 3.3 E1 for the whole battery is brought into play. When -K1 and K2 are depressed together, then the negative pole of E1 goes to -earth through Z1; and the positive pole of E2 to line through a of K2 -and c1 of K1 and a positive current, due to the whole electro-motive -force 3.3 E1 goes to line. Hence the effect of working K1 is simply to -reverse the current, whatever its strength, while that of K2 is to -strengthen it, whatever its direction. - -The resistance coil s, of 100° resistance, is called a spark coil, -because it prevents the high electro-motive force of the whole battery -from damaging the points of contact by sparking or forming an arc across -when signals are sent; and the resistance r2 is made approximately equal -to the combined resistance of E2 and the spark coil, so that the total -resistance of the circuit may not be altered by the working of the -apparatus. - - -Fig. 321. QUADRUPLEX TELEGRAPH. - - -A1 and B1 (Fig. 320) are the relays which are used to respond to the -changes in the currents sent by the keys K1 and K2 at the distant -station. - -A, is a simple polarized relay wound differentially, each wire having a -resistance of 200 [omega], and so connected up as to respond to the working of -the reversing key K1 of the distant station. It acts independently of -the strength of the current, and is therefore not affected by the -working of the increment key K2. It is connected up so as to complete -the local circuit of the sounder S1 and the local battery l1 and forms -the receiving portion of the 'A' side. - -B, is a non-polarized relay also wound differentially, each coil having -a resistance of 200 [omega]. It responds only to an increase in the -strength of the current, and therefore only to the working of the -increment key K2 of the distant station. - -[Transcriber's note: In current usage upper case omega indicates ohms and -lower case omega denotes angular frequency, 2*PI*f.] - - -518 STANDARD ELECTRICAL DICTIONARY. - - -The relay spring is so adjusted that the armatures are not actuated by -the weak current sent from E by the key K1. - -In its normal position this relay completes the circuit of the local -battery through the sounder S. This sounder S, called the uprighting -sounder, acts as a relay to a second sounder, S2, called the reading -sounder, which is worked by another local battery, l2. Of course, -normally, the armature of S is held down and that of S2 is up, but when -the tongue t moves, as it does when the increment key K2 is depressed so -as to send the whole current to line, then the current from l is -interrupted, and the circuit of l2 is completed by the rising of the -armature of S, causing the reading sounder S2 to work. This is the 'B' -side. - -R is a rheostat for balancing the resistance of the line, as used in -duplex working. - -C is a condenser used for compensating the static charge of the line. It -is provided with an adjustable retardation coil, R1, to prolong the -effect of the compensating current from the condenser. - -G is a differential galvanometer, used for testing, and for facilitating -adjustment and balancing. - -Q is a switch for putting the line to earth, either for balancing, or -for any other purpose. There is on the earth wire leading from Q a -resistance coil, r1, equalling approximately the resistance of the whole -battery, 3.3 E1, and the resistance s. - -The connections shown in Fig. 321, are for an 'up' office. At a 'down' -office it is necessary to reverse the wires on the two lower terminals -of the galvanometer and the two battery wires on the reversing key K1. - -The keys K1 and K2 are, for repeaters, replaced by transmitters. - -The adjustment of this apparatus requires great care and great accuracy. -Its good working depends essentially on technical skill that can only be -acquired by patience and perseverance. - -Faults in working generally arise from careless adjustments, dirty -contacts, loose connections, battery failures, and the ordinary line -interruptions, but there are no troubles that are beyond the reach of -ordinary skill, and it can be safely said that, within moderate -distances, wherever and whenever duplex working is practicable, then -quadruplex working is so too." - -The above is a typical quadruplex bridge system. There is also a -differential system, the full description of which, in addition to what -has been given, is outside of the scope of this work. - - -519 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph Repeater. -An extension of the relay system, adopted for long lines. A repeating -station comprises in general terms duplicate repeating apparatus. One -set is connected for messages in one direction, the other for messages -in the opposite direction. The general operation of a repeating set is -as follows. The signals as received actuate a relay which by its local -circuit actuates a key, which in ordinary practise would be the sounder, -but in the repeater its lever opens and closes a circuit comprising a -battery and a further section of the line. - -Repeaters are placed at intervals along the line. Each repeater repeats -the signals received for the next section of line with a new battery. It -represents an operator who would receive and repeat the message, except -that it works automatically. - -The Indo-European line from London to Teheran, 3,800 miles long, is -worked directly without any hand retransmission, it being carried out by -five repeaters. This gives an average of over 500 miles for each -repeater. -[Transcriber's note: … 650 miles for each repeater.] - -Repeaters introduce retardation, and each repeater involves a reduction -in the rate of working. Yet in many cases they increase the speed of a -line greatly, as its speed is about equal to that of its worst section, -which may be far greater than that of the whole line in one. - -Synonym--Translater. - - -Telegraph Signal. -In the telegraph alphabet, a dot, or dash; the signal or effect produced -by one closing of the circuit. A dash is equal in length to three dots. -The space between signals is equal to one dot; the space between letters -to three dots; and the space between words to six dots. - - -Telegraph, Single Needle. -A telegraph system in which the code is transmitted by the movements of -a needle shaped index which oscillates to right and left, the left hand -deflection corresponding to dots, the right hand deflection to dashes. -The instruments for sending and receiving are combined into one. The -needles are virtually the indexes of vertical galvanometers. In one form -by a tapper key (see Tapper), in another form by a key worked by a -drop-handle (the drop handle instrument), currents of opposite -directions are sent down the line. These pass through both instruments, -affecting both needles and causing them to swing to right or left, as -the operator moves his key. - -As galvanometer needle or actuating needle a soft iron needle is -employed, which is polarized by the proximity of two permanent magnets. -This avoids danger of reversal of polarity from lightning, a trouble -incident to the old system. - - -520 STANDARD ELECTRICAL DICTIONARY. - - -The cut, Fig. 322, shows a single needle telegraph instrument of the -tapper form. The action of the tapper can be understood from the next -cut. - - -Fig. 322. SINGLE NEEDLE TELEGRAPH INSTRUMENT, DOUBLE -TAPPER FORM. - - -Fig. 323. DOUBLE TAPPER KEY FOR SINGLE NEEDLE TELEGRAPH. - - -C and Z are two strips of metal to which the positive and negative poles -of the battery are respectively connected. E and L are two metallic -springs; E is connected to earth, L is connected to the line; at rest -both press against Z. If L is depressed so as to touch C, the current -from the battery goes to the line by the key L, goes through the coils -of the distant instrument and deflects the needle to one side, and then -goes to the earth. If the key E is depressed, L retaining its normal -position, the direction of the current is reversed, for the other pole -of the battery is connected to the earth and the reverse current going -through the coils of the distant instrument deflects the galvanometer -needle to the other side. - -In the drop-handle type an analogous form of commutator worked by a -single handle produces the same effects. - - -521 STANDARD ELECTRICAL DICTIONARY. - - -Telegraph, Wheatstone, A. B. C. -A magneto-electric telegraph of the dial system. An alternating current -magneto-generator is turned by hand and by depressing keys its current -is admitted to or cut off from the line and receiver's instrument. The -message is received by a dial instrument working by the escapement -motion described under Telegraph, Dial. - - -Telegraph, Writing. -A telegraph in which the message is received in written characters. The -transmitter includes a stylus which is held in the hand and whose point -bears against the upper end of a vertical rod. The rod is susceptible of -oscillation in all directions, having at its base a spring support -equivalent to a universal joint. - -The stylus is moved about in the shape of letters. As it does this it -throws a series of resistances in and out of the circuit. - -At the receiving end of the line the instrument for recording the -message includes two electro-magnets with their cores at right angles to -each other and their faces near together at the point of the angle. An -armature is supported between the faces and through it a vertical rod -carried by a spring at its bottom rises. These magnets receive current -proportional to the resistances cut in and out by the motions of the -other rod at the transmitting end of the line. These resistances are -arranged in two series at right angles to each other, one for each -magnet. Thus the movements of the transmitting stylus and rod are -repeated by the end of the rod in the receiving instrument. A species of -pen is carried at the end of the rod of the receiving instrument, which -marks the letters upon a riband of paper which is fed beneath it. - - -Telemanometer. Electric. -A pressure gauge with electric attachment for indicating or recording -its indications at a distance. - -It is applicable to steam boilers, so as to give the steam pressure in -any desired place. - - -Telemeter, Electric. -An apparatus for electrically indicating or recording at a distance the -indications of any instrument such as a pressure gauge, barometer or -thermometer, or for similar work. The telemanometer applied to a boiler -comes into this class of instrument. - - -Telephotography. -The transmission of pictures by the electric current, the requisite -changes in the current being effected by the action of light upon -selenium. The picture is projected by a magic lantern. Its projection is -traversed by a selenium resistance through which the current passes. -This is moved systematically over its entire area, thus constituting the -transmitter, and synchronously with the motion of the selenium a contact -point at the other end of the line moves systematically over a sheet of -chemically prepared paper. The paper, which may be saturated with a -solution of potassium ferrocyanide and ammonium nitrate, is stained by -the passage of the current, and by the variation in intensity of -staining, which variation is due to variations in the current, produced -by the effects of the light upon the selenium, the picture is -reproduced. - - -522 STANDARD ELECTRICAL DICTIONARY. - - -Telepherage. -An electric transportation system, hitherto only used for the carrying -of ore, freight, etc. Its characteristic feature is that the electric -conductors, suspended from poles, supply the way on which carriages -provided with electric motors run. The motors take their current -directly from the conductors. - -There are two conducting lines, running parallel with each other, -supported at the opposite ends of transverse brackets on a row of -supporting poles. At each pole the lines cross over so that right line -alternates with left, between consecutive pairs of poles. - -The cars are suspended from pulleys running on one or the other of the -conductors. A train of such cars are connected and the current is taken -in near one end and leaves near the other end of the train. These -current connections are so distant, their distance being regulated by -the length of the train, that they are, for all but an instant at the -time of passing each of the poles, in connection with segments of the -line which are of opposite potential. To carry out this principle the -distance between contacts is equal to the distance between poles. Owing -to the crossing over of the lines the contacts are in connection as -described and thereby the actuating current is caused to go through the -motors. - -Cars running in one direction go on the electric conductors on the one -side, those running in the other direction go on the other conductor. - -A great many refinements have been introduced, but the system has been -very little used. - - -Telephone. -An instrument for the transmission of articulate speech by the electric -current. The current is defined as of the undulatory type. (See Current, -Undulatory.) - -The cut shows what may be termed the fundamental telephone circuit. A -line wire is shown terminating in ground plates and with a telephone in -circuit at each end. The latter consists of a magnet N S with a coil of -insulated wire H surrounding one end. Facing the pole of the magnet is a -soft iron diaphragm D, held in a frame or mouthpiece T. Any change of -current in the line affects the magnetism of the magnet, causing it to -attract the diaphragm more or less. The magnet and diaphragm really -constitute a little electric motor, the diaphragm vibrating back and -forth through an exceedingly short range, for changes in the magnetic -attraction. - -The principle of the reversibility of the dynamo applies here. If the -magnet is subjected to no change in magnetism, and if the diaphragm is -moved or vibrated in front of its poles, currents will be induced in the -wire bobbin which surrounds its end. If two such magnets with bobbins -and diaphragms are arranged as shown, vibrations imparted to one -diaphragm will send currents through the line which, affecting the -magnetism of the distant magnet, will cause its diaphragm to vibrate in -exact accordance with the motions of the first or motor diaphragm. In -the combination one telephone represents a dynamo, the other a motor. - -If the vibrations of the diaphragm are imparted by the voice, the voice -with all its modulations will be reproduced by the telephone at the -distant end of the line. - - -523 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 324. DIAGRAM OF BELL TELEPHONES AND LINE WITH EARTH CONNECTIONS. - - -Fig. 325. SECTION OF BELL TELEPHONE. - - -The above gives the essential features of the Bell telephone. In -practice the telephone is used only as the receiver. As transmitter a -microphone is employed. To give the current a battery, generally of the -open circuit type, is used, and the current in the line is an induced or -secondary one. - -The microphone which is talked to, and which is the seat of the current -variations which reproduce original sound, is termed the transmitter, -the telephone in which the sounds are produced at the distant end of the -line is termed the receiver. - -Fig. 325 shows the construction of the Bell telephone in universal use -in this country as the receiver. M is a bar magnet, in a case L L. B B -is a bobbin or coil of insulated wire surrounding one end of the magnet. -D is the diaphragm of soft iron plate (ferrotype metal), and E is the -mouthpiece. The terminals of the coil B B connect with the binding -screws C C. The wire in the coil is No. 36, A. W. G., and is wound to a -resistance of about 80 ohms. - - -524 STANDARD ELECTRICAL DICTIONARY. - - -As typical transmitter the Blake instrument may be cited. It is a carbon -microphone. It is shown in section in the cut; a is the mouthpiece and e -is a diaphragm of iron plate, although other substances could be used; f -is a steel spring, with a platinum contact piece at its end. One end -bears against the diaphragm, the other against a carbon block k. The -latter is carried by a brass block p, and pressure is maintained between -these contacts by the spring g and weight of the piece c, which by -gravity tends to press all together. The current passes by way of the -spring f, carbon button k and spring g through the circuit indicated. - -A battery is in circuit with these parts. If a telephone is also in -circuit, and the transmitter is spoken against, the diaphragm vibrating -affects the resistance of the carbon-platinum contact, without even -breaking the contact, and the telephone reproduces the sound. The heavy -piece of metal C acts by its inertia to prevent breaking of the contact. -The position of this piece c, which is carried by the brass plate m, is -adjusted by the screw n. - - -Fig. 326. SECTION OF BLAKE TRANSMITTER. - - -In practice the transmitter and battery are usually on a local circuit, -which includes the primary of an induction coil. The line and distant -receiving telephone are in circuit with the secondary of the induction -coil, without any battery. - -Telephone, Bi-. -A pair of telephones carried at the ends of a curved bar or spring so -that they fit the head of a person using them. One telephone is held -against each ear without the use of the hands. - - -525 STANDARD ELECTRICAL DICTIONARY. - - -Telephone, Capillary. -A telephone utilizing electro-capillarity for the production of -telephonic effects. The following describes the invention of Antoine -Breguet. - -The point of a glass tube, drawn out at its lower end to a capillary -opening dips vertically into a vessel. This vessel is partly filled with -mercury, over which is a layer of dilute sulphuric acid. The end of the -immersed tube dips into the acid, but does not reach the mercury. One -line contact is with mercury in the tube, the other with the mercury in -the vessel. The arrangement of tube and vessel is duplicated, giving one -set for each end of the line. On introducing a battery in the circuit -the level of the mercury is affected by electro-capillarity. The tubes -are closed by plates or diaphragms at their tops, so as to enclose a -column of air. It is evident that the pressure of this air will depend -upon the level of the mercury in the tube, and this depends on the -electro-motive force. On speaking against the diaphragm the sound waves -affect the air pressure, and consequently the level, enough to cause -potential differences which reproduce the sound in the other instrument. - - -Fig. 327. BREGURT'S CAPILLARY TELEPHONE. - - -Telephone, Carbon. -A telephone transmitter based on the use of carbon as a material whose -resistance is varied by the degree of pressure brought to bear upon it. -Undoubtedly the surface contact between the carbon and the other -conducting material has much to do with the action. Many carbon -telephones have been invented. Under Telephone the Blake transmitter is -described, which is a carbon telephone transmitter. The Edison carbon -transmitter is shown in section in the cut. E is the mouth piece and D -the diaphragm. I is a carbon disc with adjusting screw V. A platinum -plate B B, with ivory button b, is attached to the upper surface of the -carbon disc. C C is an insulating ring. The wire connections shown bring -the disc into circuit. It is connected like a Blake transmitter. It is -now but little used. - - -Fig. 328. SECTION OF EDISON CARBON TRANSMITTER. - - -526 STANDARD ELECTRICAL DICTIONARY. - - -Telephone, Chemical. -A telephone utilizing chemical or electrolytic action in transmitting or -receiving. The electro-motograph is an example of a chemical receiver. -(See Electro-motograph.) - - -Telephone, Electrostatic. -A telephone utilizing electrostatic disturbances for reproduction of the -voice. In the cut D and C are highly charged electrophori. The -diaphragms A and B when spoken to affect the potential of the -electrophorus so as to produce current variations which will reproduce -the sound. Dolbear and others have invented other forms of transmitters -based on electrostatic action. Receivers have also been constructed. A -simple condenser may be made to reproduce sound by being connected with -a powerful telephone current. - - -Fig. 329. DIAGRAM OF EDISON'S ELECTROSTATIC TELEPHONE. - - -Telephone Induction Coil. -The induction coil used in telephone circuits for inducing current on -the main line. It is simply a small coil wound with two separate -circuits of insulated wire. In the Edison telephone the primary coil, in -circuit with the transmitter, is of No. 18 to 24 wire and of 3 to 4 ohms -resistance. The secondary in circuit with the line and receiving -instrument is of No. 36 wire and of 250 ohms resistance. The Bell -telephone induction coil has its primary of No. 18 to 24 wire wound to a -resistance of 1/2 ohm, and its secondary of No. 36 wire, and of 80 ohms -resistance. - - -527 STANDARD ELECTRICAL DICTIONARY. - - -Telephone, Reaction. -A form of telephone containing two coils of insulated wire, one of which -is mounted on the disc, and the other on the magnet pole in the usual -way. These coils react upon each other so as to strengthen the effect. - - -Telephone, Thermo-electric. -A telephone transmitter including a thermo-electric battery, placed in -circuit with the line. A plate of vulcanite faces it. When the sound -waves strike the vulcanite they move it backward and forward. These -movements, owing to the elasticity of the vulcanite, produce minute -changes of temperature in it, which affecting the thermo-electric pile -produce in the circuit currents, which passing through a Bell telephone -cause it to speak. This type of instrument has never been adopted in -practice. - - -Telephote. -An apparatus for transmitting pictures electrically, the properties of -selenium being utilized for the purpose. - -Synonym--Pherope. - - -Teleseme. -An annunciator, displaying on a dial the object wanted by the person -using it. It is employed to transmit messages from rooms in a hotel to -the office, or for similar functions. - - -Tele-thermometer. -A thermometer with electric attachment for indicating or recording its -indications at a distance. - - -Tempering, Electric. -A process of tempering metals by electrically produced heat. The article -is made part of an electric circuit. The current passing through it -heats it, thereby tempering it. For wire the process can be made -continuous. The wire is fed from one roll to another, and if required -one roll may be immersed in a liquid bath or the wire between the rolls -may be led therein. The current is brought to one roll and goes through -the wire to the other. As it does this the wire is constantly fed from -one roll to another. The bath may be used as described to cool it after -the heating. The amount of heating may be regulated by the rate of -motion of the wire. - - -528 STANDARD ELECTRICAL DICTIONARY. - - -Ten, Powers of. -This adjunct to calculations has become almost indispensable in working -with units of the C. G. S. system. It consists in using some power of 10 -as a multiplier which may be called the factor. The number multiplied -may be called the characteristic. The following are the general -principles. - -The power of 10 is shown by an exponent which indicates the number of -ciphers in the multiplier. Thus 10^2 indicates 100; 10^3 indicates 1,000 -and so on. - -The exponent, if positive, denotes an integral number, as shown in the -preceding paragraph. The exponent, if negative, denotes the reciprocal -of the indicated power of 10. Thus 10^-2 indicates 1/100; 10^-3 indicates -1/1000 and so on. - -The compound numbers based on these are reduced by multiplication or -division to simple expressions. Thus: 3.14 X 10^7 = 3.14 X 10,000,000 = -31,400,000. 3.14 X 10^-7 = 3.14/10,000,000 or 314/1000000000. Regard must -be paid to the decimal point as is done here. - -To add two or more expressions in this notation if the exponents of the -factors are alike in all respects, add the characteristics and preserve -the same factor. Thus: - - (51X 10^6) + (54 X 10^6) = 105 X 10^6. - (9.1 X 10^-9) + (8.7 X 10^-9) = 17.8 X 10^-9. - -To subtract one such expression from another, subtract the -characteristics and preserve the same factor. Thus: - - (54 X 10^6) - (51 X 10^6) = 3 X 10^6. - -If the factors have different exponents of the same sign the factor or -factors of larger exponent must be reduced to the smaller exponent, by -factoring. The characteristic of the expression thus treated is -multiplied by the odd factor. This gives a new expression whose -characteristic is added to the other, and the factor of smaller exponent -is preserved for both, - -Thus: - (5 X 10^7) + (5 X10^9) = (5 X 10^7) + (5 X 100 X 10^7) = 505 X 10^7. - -The same applies to subtraction. Thus: - (5 X 10^9) - (5 X 10^7) = (5 X 100 X 10^7) - (5 X 10^7) = 495 X 10^7. - -If the factors differ in sign, it is generally best to leave the -addition or subtraction to be simply expressed. However, by following -the above rule, it can be done. Thus: - -Add - 5 X 10^-2 and 5 X 10^3. - 5 X 10^3 = 5 X 10^5 X 10^-2 - (5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2 - -This may be reduced to a fraction 500000/100 = 5000.05. - -To multiply add the exponents of the factors, for the new factor, and -multiply the characteristics for a new characteristic. The exponents -must be added algebraically; that is, if of different signs the -numerically smaller one is subtracted from the other one, and its sign -is given the new exponent. - -Thus; - (25 X 10^6) X (9 X 10^8) = 225 X 10^14. - (29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1 - (9 X 10^8) X (98 X 10^2) = 882 X 10^1 - - -529 STANDARD ELECTRICAL DICTIONARY. - - -To divide, subtract (algebraically) the exponent of the divisor from -that of the dividend for the exponent of the new factor, and divide the -characteristics one by the other for the new characteristic. Algebraic -subtraction is effected by changing the sign of the subtrahend, -subtracting the numerically smaller number from the larger, and giving -the result the sign of the larger number. -(Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2.) - -Thus; - (25 X 10^6) / (5 X 10^8) = 5 X 10^-2 - (28 X 10^-8) / (5 X 10^3) = 5.6 X 10^-11 - -[Transcriber's note: I have replaced ordinary exponential notation by -the more compact and simpler "programming" representation. The last two -example would be: - 25E6 / 5E8 = 5E-2 - 28E-8 / 5E3 = 5.6E-11 -] - - -Tension. -Electro-motive force or potential difference in a current system is -often thus termed. It is to be distinguished from intensity or current -strength, which word it too greatly resembles. - - -Tension, Electric. -(a) The condition an electrified body is brought into by -electrification, when each molecule repels its neighbor. The condition -is described as one of self-repulsion. - -(b) The voltage or potential difference of a circuit is also thus -termed. - - -Terminal. -The end of any open electric circuit, or of any electric apparatus; as -the terminals of a circuit, dynamo, or battery. - - -Terminal Pole. -In telegraph line construction the last pole of a series; one beyond -which the line is not carried. Such pole, as the pull of the wires is -all in one direction, requires special staying or support. The regular -line poles are free from this strain, as the wire pulls in both -directions. - - -Tetanus, Acoustic. -A term in electro-therapeutics. An effect produced on a nerve by very -rapidly alternating induced currents. The currents are produced by an -induction coil with a vibrator giving a musical note. This is a species -of gauge of proper frequency of alternations. - - -Theatrophone. -An apparatus worked by automatic paying machinery by which a telephone -connection is made with a theatre or opera by the deposition of a coin -in a slot. - - -Therm. -A unit of heat. It has been proposed by the British Association and -amounts to a redefinition of the smaller calorie. It is the amount of -heat required to raise the temperature of one gram of water one degree -centigrade, starting at the temperature of maximum density of water. - - -530 STANDARD ELECTRICAL DICTIONARY. - - -Thermaesthesiometer. -An electro-therapeutic instrument for testing the sensitiveness of the -surface of the body to changes of temperature. Vessels of mercury are -provided with thermometers to indicate their temperature. One vessel is -surrounded by an electric conductor wound in a number of turns. The -temperature is raised by passing a current through this. By successive -applications of the vessels to the same spot upon the skin the power of -differentiating temperatures is determined. - - -Thermo Call. -(a) An electric alarm or call bell operated by thermo-electric currents. -It may serve as a fire alarm or heat indicator, always bearing in mind -the fact that differential heat is the requisite in a thermo-electric -couple. - -(b) See Thermo-electric Call. - - -Thermo-chemical Battery. -A voltaic battery in which the electro-motive force is generated by -chemical action induced by heat. - -The chemical used generally is sodium nitrate or potassium nitrate. The -positive plate is carbon. On heating the battery the nitrate attacks the -carbon, burning it and produces potential difference. For negative plate -some metal unattacked by the nitrate may be employed. - - -Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY. - - -Thermo-electric Battery or Pile. -A number of thermo-electric couples q. v., connected generally in -series. - -In Nobili's pile the metals are bismuth and antimony; paper bands -covered with varnish are used to insulate where required. In Becquerel's -pile copper sulphide (artificial) and German silver, (90 copper, 10 -nickel) are the two elements. The artificial copper sulphide is made -into slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about). -Water is used to keep one set of junctions cool, and gas flames to heat -the other set. In Fig. 331, c, d represent the binding screws. The -couples are mounted on a vertical standard, with adjusting socket and -screw B, so that its lower end can be immersed in cold water, or raised -therefrom as desired. - - -531 STANDARD ELECTRICAL DICTIONARY. - - -FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES. - - -Fig. 332 shows one couple of the battery. S is artificial antimony -sulphide; M is German silver; m is a protecting plate of German silver -to save the sulphide from wasting in the flame. - - -Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES. - - -Clamond's pile has been used in practical work. The negative element is -an alloy of antimony, 2 parts, zinc, 1 part. The positive element is tin -plate. Mica in some parts, and a paste of soluble glass and asbestus in -other parts are used as insulators. They are built up so as to form a -cylinder within which the fire is maintained. The air is relied on to -keep the outer junctions cool. The temperature does not exceed 200° C. -(392° F.) - -Sixty such elements have an electro-motive force of 300 volts and an -internal resistance of 1.5 ohms. Such a battery requires the consumption -of three cubic feet of gas per hour. (See Currents, Thermo-electric. ) - - -532 STANDARD ELECTRICAL DICTIONARY. - - -Thermo-electric Call. -A thermostat arranged to ring a bell or to give some indication when the -temperature rises or falls beyond certain points. It may be a compound -bar of brass and steel fixed at one end and free for the rest of its -length. Its end comes between two adjustable contacts. As the -temperature rises it bends one way (away from the brass side) and, if -hot enough, touching a contact gives one signal. If the temperature -falls it curves the other way, and if cold enough touches the other -contact, giving another signal. (See Thermostat, Electric.) - - -Thermo-electric Couple. -If two dissimilar conductors form adjacent parts of a closed circuit, -and their junction is at a different temperature than that of the rest -of the circuit, a current will result. Such pair of conductors are -called a thermo-electric couple. They may be joined in series so as to -produce considerable electro-motive force. (See Thermo-electricity and -other titles in thermo-electricity.) - -The efficiency of a thermo-electric couple according to the second law -of thermo-dynamics is necessarily low--not over 10 per cent. - - -Thermo-electric Diagram. -A diagram indicating the change in potential difference for a fixed -difference of temperature between different metals at different -temperatures. It is laid out with rectangular co-ordinates. On one axis -temperatures are laid off, generally on the axis of abscissas. On the -other axis potential differences are marked. Different lines are then -drawn, one for each metal, which show the potential difference, say for -one degree centigrade difference of temperature between their junctions, -produced at the different temperatures marked on the axis of abscissas. - - -Fig. 333· THERMO-ELECTRIC DIAGRAM, GIVING POTENTIAL DIFFERENCE IN -C. G. S. UNITS. - - -Thus taking copper and iron we find at the temperature 0° C. (32° F.) a -difference of one degree C. (1.8° F.) in their junctions will produce a -potential difference of 15.98 micro volts, while at 274.5° C. (526.1° -F.) the lines cross, and zero difference of potential is indicated. -Taking the lead line on the same diagram it crosses the iron line a -little above 350° C. (662° F.), indicating that if one junction is -heated slightly above and the other is heated slightly below this -temperature no potential difference will be produced. Lead and copper -lines, on the other hand, diverge more and more as the temperature -rises. - - -533 STANDARD ELECTRICAL DICTIONARY. - - -Thermo-electric Inversion. -The thermo-electric relations of two conductors vary at different -temperatures. Sometimes at a definite point they have no electro-motive -force and after passing this point the positive plate becomes a negative -one and vice versa. This is inversion, or reversal. (See Thermo-electric -Diagram.) - -Synonym-- Thermo-electric Reversal. - - -Thermo-electricity. -Electric energy, electro-motive force or electrification produced from -heat energy by direct conversion. It is generally produced in a circuit -composed of two electric conductors of unlike material, which circuit -must possess at least two junctions of the unlike substances. By heating -one of these to a higher temperature than that of the other, or by -maintaining one junction at a different temperature from that of the -other a potential difference is created accompanied by an electric -current. - -In many cases differential application of heat to an identical material -will develop potential difference. This effect, the converse of the -Thomson effect, is not used to produce currents, as in a closed circuit -the potential differences due to differential heating would neutralize -each other. - - -Thermo-electric Junction. -A junction between two dissimilar conductors, which when heated or -cooled so as to establish a differential temperature, as referred to the -temperature of the other junction, produces potential difference and an -electric current. - - -Thermo-electric Pile, Differential. -A thermo-electric pile arranged to have opposite faces subjected to -different sources of heat to determine the identity or difference of -temperature of the two sources of heat. It corresponds in use to a -differential air thermometer. - - -Thermo-electric Power. -The coefficient which, multiplying the difference of temperature of the -ends of a thermo-electric couple, gives the potential difference, -expressed in micro-volts. It has always to be assigned to a mean or -average temperature of the junctions, because the potential difference -due to a fixed difference of temperature between two metals varies with -the average temperature of the two junctions. (See Thermo-electric -Diagram.) - -For bismuth and antimony at 19.5° C. (67.1° F.) it is 103 microvolts per -degree Centigrade (1.8° F.). This means that if one junction is heated -to 19° C. and the other to 20° C. (66.2° F. and 68.0° F.) a potential -difference of 103 micro-volts will be produced. - -The potential difference is approximately proportional to the difference -of temperature of the two junctions if such difference is small. Hence -for large differences of potential the thermo-electric power coefficient -does not apply. - -As a differential function it is thus deduced by Sir William Thomson, -for expressing the E. M. F. in a thermo-electric circuit: If a circuit -is formed of two metals with the junctions at indefinitely near -temperatures, t and t + dt, and dE is the E. M. F. of the circuit, then -the differential coefficient dE/dt is called the thermo-electric power -of the two metals for the temperature t. - - -534 STANDARD ELECTRICAL DICTIONARY. - - -Thermo-electric Series. -The arrangement of possible thermoelectric elements, q. v., in a table -in the order of their relative polarity. Bismuth and antimony form a -couple in which when their junction is heated the bismuth acts as the -positive or negatively charged element and antimony as the negative or -positively charged. Between these two extremes according to Seebeck the -series runs as follows: - - Antimony, Silver, Copper, - Arsenic, Gold, Platinum, - Iron, Molybdenum, Palladium, - Steel, Tin, Cobalt, - Cadmium, Lead, Nickel, - Tungsten, Mercury, Bismuth. - Zinc, Manganese, - -A differential temperature of 1° C. (1.8° F.) in a bismuth-antimony -couple maintains a potential difference of 103 micro-volts. - -Matthiessen gives a different series; it is arranged in two columns; the -first column has positive coefficients annexed the second has negative. -On subtracting the greater one from the lesser, which, if the two -elements are in different columns, of course amounts to adding after -changing the negative sign, the relative potential difference due to the -combination is obtained. - + - - Bismuth 25 Gas Coke 0.1 - Cobalt 9 Zinc 0.2 - Potassium 5.5 Cadmium 0.3 - Nickel 5 Strontium 2.0 - Sodium 3. Arsenic 3.8 - Lead 1.03 Iron 5.2 - Tin 1 Red Phosphorous 9.6 - Copper 1 Antimony 9.8 - Silver 1 Tellurium 179.9 - Platinum 0.7 Selenium 290 - -Thus the relative E. M. F. of a bismuth-nickel couple, as both are in -the + column, would be 25 - 5 = 20; that of a cobalt-iron couple, one -being in the + column the other in the - column, would be 9 + 5.2 = -14.2. Alloys are not always intermediate to their constituents, and -small amounts of impurities affect the results largely. This may account -for the discrepancies of different observers. Other compounds could be -introduced into the series. - -Artificial silver sulphide has been used by Becquerel in a -thermo-electric battery. - - -535 STANDARD ELECTRICAL DICTIONARY. - - -Thermo-electric Thermometer. -A species of differential thermometer. It consists of two -thermo-electric junctions connected in opposition with a galvanometer in -the circuit. Any inequality of temperature in the two ends or junctions -produces a current shown by the galvanometer. It may be used to -determine the temperature of a distant place, one of the junctions being -located there and the other being under control of the operator. If the -latter junction is heated until no current is produced its temperature -is evidently equal to that of the distant couple or junction. The -heating may be done with hot water or mercury, or other melted metal. -The temperature of the water, or other substance, gives the temperature -of the distant place. - - -Thermolysis. -Decomposition by heat; dissociation. All compound bodies are -decomposable by heat if it is intense enough. Hence at very elevated -temperatures there can be no combustion. - -Synonym--Dissociation. - - -Thermometer. -An instrument for indicating the intensity of heat. Three scales of -degrees of heat are used in practise, the Fahrenheit, Réamur, and -Centigrade, each of which is described under its own title. (See Zero, -Thermometric-Zero, Absolute.) The ordinary thermometer depends on the -expansion of mercury; in some cases alcohol is used. Besides these the -compound bar principle as used in the thermostat (see Thermostat, -Electric) is employed. - - -Thermometer, Electric. -(a) A thermometer whose indications are due to the change of resistance -in conductors with change of temperature. Two exactly similar resistance -coils maybe electrically balanced against each other. On exposing one to -a source of heat, its resistance will change and it will disturb the -balance. The balance is restored by heating the other coil in a vessel -of water when the temperature of the water gives the temperature of both -coils. The coils are enclosed in water-tight metallic cases. - -Synonym--Electric Resistance Thermometer. - -(b) A differential thermometer may be made by connecting with a pair of -conductors, two thermo-electric couples in opposition to each other, and -including a galvanometer in series. On heating the junction of one -couple more than that of the other a current at once goes through the -galvanometer. - -(c) (See Thermometer, Kinnersley's.) - -Synonym--Thermo-electrometer. - - -536 STANDARD ELECTRICAL DICTIONARY. - - -Fig. 334. KINNERSLEY'S THERMOMETER. - - -Thermometer, Kinnersley's. -A thermo-electrometer. A large glass tube is mounted on a standard and -communicates with a small tube parallel to it. Water is poured in so as -to rise in the small tube. Two wires terminating in bulbs enter the -large tube by its top and bottom. The upper wire can be adjusted by -moving up and down through a stuffing box. On discharging a Leyden jar -through the space between the knobs on the two wires the water for a -moment rises in the small tube. There is little or no accuracy in the -instrument. It is allied to the electric mortar (see Mortar, Electric) -as a demonstrative apparatus. - -Synonyms--Electric Thermometer--Thermo-electrometer. - - -Thermo-multiplier. -A thermo-electric battery including a number of couples. The term is -generally applied to a small battery with its similar junctions facing -in one direction and used for repeating Melloni's experiments on radiant -energy, or so-called radiant heat. - - -537 STANDARD ELECTRICAL DICTIONARY. - - -Thermophone. -An apparatus for reproducing sounds telephonically by the agency of -heat; a receiving telephone actuated by heat. Thus a wire may be -attached to the centre of a diaphragm and kept in tension therefrom, and -the transmitting telephone current may be caused to pass through it. The -wire changes in temperature and consequently in length with the pulses -of current going through it and vibrates the diaphragm, reproducing the -sound. It is to be distinguished from the thermo-electric telephone -which involves the action of potential difference produced by -thermo-electric action. - - -Thermostat, Electric. -A thermostat or apparatus, similar to a thermometer in some cases, for -closing an electric circuit when heated. It is used in connection with -automatic fire alarms to give warning of fire. For this use a -temperature of 52° C. (125° F.) is an approved one for setting one at, -to complete the circuit. It is also applied to regulation of -temperature, as in incubators. - -(a) One kind of thermostat consists of a compound bar wound into a -spiral and fastened at one end, to which a terminal of a circuit is -connected. The bar may be made of two strips of brass and iron riveted -together, and wound into a spiral. When such a bar is submitted to -changes of temperature it bends in different directions, because brass -expands and contracts more under changes of temperature than does iron. -A contact point, to which the other terminal is connected, is arranged -to make contact with the spiral at any desired degree of temperature, -thus closing an electric circuit and ringing a bell, opening or closing -a damper, or doing anything else to notify an attendant or to directly -change the temperature. - -If the brass forms the outside of the spiral, increase of temperature -makes the bending of the spiral bring the coils still closer. If the -brass forms the inside, increase of temperature makes the spiral tend to -become less close. As shown in the cut, the brass should lie along the -inside of the spiral. - -Sometimes a straight compound bar is used, one of whose ends is fastened -and the other is free. As the temperature changes such a bar curves more -or less, its free end moving to and fro. Two contact screws are -provided, one on each side of its free end. If the temperature falls it -makes contact with one of these; if the temperature rises, it makes -contact with the other. Thus it may close one of two circuits, one for a -fall and the other for a rise in temperature. - -It is well to introduce a third bar between the brass and iron ones, -made of some material of intermediate coefficient of expansion. - -(b) Another kind of thermostat comprises a vessel of air or other gas, -which, expanding by heat, actuates a piston or other device and closes -an electric circuit. Synonym--Electro-pneumatic Thermostat. - -(c) Another form utilizes the expansion of mercury. The mercury is made -part of an open electric circuit. As it expands it comes in contact with -the other terminal of the circuit, thus completing it, when the current -gives an alarm or does as is provided for in the apparatus employed. - -Thermostats may be worked on either open or closed circuits; normally -the circuit may be open as described and may close on rise of -temperature, or it may be normally closed and open as the temperature -rises. - - -Fig. 335. ELECTRIC THERMOSTAT. - - -538 STANDARD ELECTRICAL DICTIONARY. - - -Thomson Effect. -In an unequally heated conductor the differential heating is either -increased as in iron, or diminished as in copper by a current. In lead -the phenomenon does not occur. It is termed the Thomson effect. It is -intimately related to the Peltier effect. - -In a thermo-electric couple a heated junction is the source of -electro-motive force, if heated more than other parts of the circuit. -The current in a copper-iron junction flows from the copper to the iron -across the heated junction. A hot section of an iron conductor next to a -cold section of the same is a source of thermoelectricity, in the sense -that the hot section is negative to the colder. A current passing from -the hot to the cold iron travels against rising potentials, and cools -the iron in the cooler parts. As it passes to the hotter parts it -travels against falling potentials and hence heats the iron in these -parts. In this way a current intensifies differential heating in an iron -conductor. - -In copper the reverse obtains. In it the thermo-electric relations of -hot and cold copper are the reverse of those of iron, and a current -tends to bring all parts of a differentially heated copper conductor to -an identical temperature. - -As a current travels in iron from hot to cold it absorbs heat; in copper -traveling from cold to hot it absorbs heat. - -The convection of heat by a current of electricity in unequally heated -iron is negative, for it is opposed to that convection of heat which -would be brought about by the flow of water through an unequally heated -tube. In copper, on the other hand, the electric convection of heat is -positive. (Daniell.) - -The above effects of the electric current upon an unequally heated -conductor are termed the Thomson effects. In iron, at low red heat, they -are reversed and are probably again reversed at higher temperatures. - - -539 STANDARD ELECTRICAL DICTIONARY. - - -Three Wire System. -A system of distribution of electric current for multiple arc or -constant potential service. It is the invention of Thomas A. Edison. - -It includes three main wires which start from the central station or -generating plant, and ramify with corresponding reduction in size, -everywhere through the district or building to be lighted. As ordinarily -carried out when dynamos are used, the dynamos are arranged in groups of -two. One lateral lead starts from the negative binding post of one -dynamo. The positive terminal of this dynamo connects to the negative of -the other. Between the two dynamos the central or neutral lead is -connected. The other lateral lead starts from the positive binding post -of the second dynamo. - -The lamps or other appliances are calculated for the potential -difference of a single dynamo. They are arranged between the neutral -wire and the laterals, giving as even a disposition as possible to the -two laterals. - - -Fig. 336. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE. - - -If evenly arranged and all burning or using current, no current goes -through the neutral wire. If all the lamps situated on one lateral are -on open circuit all the current goes through the neutral wire. In other -cases the neutral wire receives the excess of current only. - -The advantages of the system are that it uses smaller wire than the two -wire system for lamps of the same voltage. If lamps of double the -voltage were used the two wire system would be most economical. - - -540 STANDARD ELECTRICAL DICTIONARY. - - -Four wire and five wire systems have been more or less used, based on -identical considerations, and involving in each case the coupling of -three or of four dynamos respectively, or else employing a dynamo with -special armature connections to give the requisite three-fold or -four-fold division of total potential. In the five wire system the total -voltage is four times that of a single lamp, the lamps are arranged four -in series across the leads and the central wire is the only one that can -be considered a neutral wire. When lamps are burning entirely from three -side-leads they constitute a sort of three wire system by themselves, -and their central wire may for the time be a neutral wire. - -In some of the three wire mains, especially in the larger sizes, the -neutral wire is made of much smaller section than that of a lateral -conductor, because in extensive districts it is practically impossible -that the current should be concentrated in the neutral wire. - - -Throw. -In a galvanometer the instantaneous deflection of the needle when the -contact or closing of the circuit is instantaneous, or when the -discharge is completed before the needle begins to move. The throw of -the needle is the datum sought when the ballistic galvanometer is used. - -Synonym--Elongation. - - -Throw-back Indicator. -A drop annunciator, whose shutter or drop is electrically replaced. - - -Thrust-bearings. -Bearings to support the end-thrust or push of a shaft. In disc armatures -where the field-magnets attract the armatures in the direction of their -axis of rotation, thrust-bearings have to be provided. In ordinary -cylinder or drum armatures end-thrust is not applied, as a little end -motion to and fro is considered advantageous as causing more even wear -of the commutator surface. - - -Thunder. -The violent report which, as we hear it, succeeds the lightning flash in -stormy weather. It is really produced simultaneously with the lightning -and is supposed to arise from disturbance of the air by the discharge. -The rolling noise has been attributed to successive reflections between -clouds and earth, and to series of discharges reaching the ear from -different distances and through air of varying density. The subject is -obscure. By timing the interval from lightning flash to the report of -the thunder an approximate estimate of the distance of the seat of -discharge can be made. The first sound of the thunder should be timed. -An almost concurrence of thunder and lightning indicates immediate -proximity of the discharge. - -[Transcriber's note: The speed of sound at sea level is about 5 seconds -per mile.] - - -Ticker. -A colloquial name for a stock or market report automatic printing -telegraph, which prints its quotations and messages on a long tape. - - -541 STANDARD ELECTRICAL DICTIONARY. - - -Time Constant. -(a) When current is first turned into a circuit of considerable -self-induction it is resisted rather by the inductance than by the -resistance. It is governed by the ratio of resistance and self-induction -and this factor represents the time which it takes for the current to -reach a definite fraction of its final strength. This fraction is -(2.7183 - 1)/2.7183 or 0.63. 2.7183 is the base of the Napierian system -of logarithms. Thus if in any circuit we divide the inductance in -henries by the resistance in ohms, the ratio gives the time-constant of -the circuit, or it expresses the time which it will take for the current -to reach 0.63 of its final value. - -(b) In a static condenser the time required for the charge to fall to -1/2.7183th part of its original value. - - -Time Cut-outs. -Cut-outs which automatically cut storage batteries out of the charging -circuit when they are sufficiently charged. - - -Time-fall. -In a secondary battery the decrease with use of electromotive force -maintained by a primary or secondary battery. As the battery becomes -spent its voltage falls. The conditions of the fall are represented by -its discharging curve. (See Curve, Discharging.) - - -Time-reaction. -A term in electro-therapeutics; the period of time occupied in the -passage of the effects of an electric current from nerve to muscle. - - -Time-rise. -In a secondary battery the increase of electromotive force produced -during the charging process. Its rate and conditions are graphically -shown in the charging curve. (See Curve, Charging.) - - -Tin. -A metal; one of the elements; symbol, Sn; atomic weight, 117.8; -equivalent, 58.9 and 29.5; valency, 2 and 4; specific gravity, 7.3. -It is a conductor of electricity. - - Relative resistance, compressed, (Silver = 1) 8.784 - Specific resistance at 0° C. (32° F.), 13.21 microhms. - Resistance of a wire at 0° C. (32° F.), - (a) 1 foot long, weighing 1 grain, 1.380 ohms. - (b) 1 foot long, 1/1000 inch thick, 79.47 " - (c) 1 meter long, weighing 1 gram, .9632 " - (d) 1 meter long, 1 millimeter thick, .1682 " - Resistance of a 1 inch cube at 0° C. (32° F.), 5.202 microhms. - Percentage of variation in resistance - per degree C. (1.8° F.), at about 20° C. (68° F.), .0365 - Electro-chemical equivalent (hydrogen = .0105), .619 mgs. - .310 " - -542 STANDARD ELECTRICAL DICTIONARY. - - -Tinnitus, Telephone. -A nervous affection of the ear, of the order of professional cramp; it -is attributed to too much use of the telephone. - - -Tin Sounders. -A recent addition to the single needle telegraph. (See Telegraph, Single -Needle.) It consists of small tin plates, cut and bent, and so fitted in -pairs to the instrument, that the needle as deflected strikes one or the -other on its right and left hand movements. The sounders can be made to -give sufficiently distinctive sounds to make sound-reading, q. v., -possible. Commercial tin plate, which is really tinned iron, seems to -give the best results. - - -Fig. 337. TIN SOUNDERS. - - -Tissandier's Solution. -A solution for bichromate batteries. It is composed as follows: - Water, 100 parts by weight - potassium bichromate, 16 parts - 66° sulphuric acid, 37 parts. - - -Tongue of Polarized Relay. -The German silver extension of the vibrating or oscillating member of a -polarized relay, corresponding to the armature of an ordinary relay. - - -Tongue of Polarized Relay, Bias of. -In a Siemens' polarized relay the pole pieces are adjustable so that -they may be brought nearer to or withdrawn from the tongue. One of the -poles is adjusted so as to be nearer the tongue. This one-sided -adjustment is the bias. Its effect is that when the relay is unexcited -this pole attracts the armature so that it normally is drawn towards it. -This ensures the normal contact of the tongue either with the contact -point, or with the insulated stop piece or adjustment screw. Without -bias the armature remains in contact with or drawn towards whichever -pole it was last attracted to. In its usual use a bias is given it. - - -Top, Magnetic. -A toy illustrating magnetic attraction. It consists of a disc or body of -lead or other material, through which a magnetized steel spindle pointed -at its lower end is thrust. A number of short pieces of iron wire are -used with it. It is spun like an ordinary top upon the point of the -spindle and one of the pieces of iron wire is laid by the side of its -point. As it turns the magnetic adherence causes the piece of wire to be -carried along in one direction by the rotation of the spindle, until the -end is reached, when it goes over to the other side of the spindle and -travels back again. - -By using bent pieces of wire of various shapes the most curious effects -are produced. Circles and S shaped pieces give good effects. To increase -the mysterious effect covered iron wire (bonnet wire) may be employed. - - -Fig. 338. MAGNETIC TOP. - - -543 STANDARD ELECTRICAL DICTIONARY. - - -Torpedo, Electric. -(a) A fish, the Raia Torpedo, which possesses the power of giving -electric shocks. (See Ray, Electric.) - -(b) An instrument of war; a torpedo whose operations include electrical -discharge or other electric function or factor of operation. - - -Torpedo, Sims-Edison. -A torpedo driven by an electric motor, and also steered by electricity. -Its motions are all controlled from the shore. The torpedo proper is -carried some distance below the surface of the water by a vessel -immediately above it, from which it is suspended by two rigid bars. In -the torpedo is a cable reel on which the conducting cable is disposed. -An electric motor and controlling gear are also contained within the -torpedo. In its front the explosive is placed. It is driven by a screw -propeller actuated by the electric motor. As it moves it pays out cable -so that it has no cable to draw after it through the water, the cable -lying stationary in the water behind it. This avoids frictional -resistance to its motion. The maintenance of the torpedo at a proper -depth is one of the advantages of the system. - - -544 STANDARD ELECTRICAL DICTIONARY. - - -Torque. -A force tending to produce torsion around an axis. An example is the -pulling or turning moment of an armature of an electric motor upon its -shaft. It is often expressed as pounds of pull excited at the end of a -lever arm one foot long. - -The expression is due to Prof. James Thompson, then of the University of -Glasgow. - -"Just as the Newtonian definition of force is that which produces or -tends to produce motion (along a line), so torque may be defined as that -which produces or tends to produce torsion (around an axis). It is -better to use a term which treats this action as a single definite -entity than to use terms like 'couple' and 'moment,' which suggest more -complex ideas." (S. P. Thompson.) - -A force, acting with radius r gives a torque equal to f X r ; f and r -may be expressed in any units. S. P. Thompson gives the following -equivalents : - -To reduce - dyne-centimeters to gram centimeters, divide by 981 - dyne-centimeters to meter-kilograms divide by 981E5 - dyne-centimeter, to pound-feet divide by 13.56E6 - pound-feet to meter-kilograms divide by 7.23 - -In each of these compound units the first unit is the force and the -second unit is the radius or lever arm of the torque. - -Synonyms--Turning Moment--Moment of Couple--Axial Couple--Angular -Force--Axial Force. - - -Torsion Balance, Coulomb's. -Originally an apparatus in which electrostatic attraction or repulsion -is measured against the torsion of a filament, often of silk-worm cocoon -fibre. It consists in one form of a cylindrical glass vessel in which a -light shellac needle is suspended horizontally by a fibre. This needle -carries at one end a gilded disc or sphere and is suspended by a fine -wire, or filament. A proof plane, q. v., is excited by touching it to -the body under trial; it is then inserted in the case. The disc on the -needle is first attracted and then repelled. The position finally taken -by the needle is noted. The force of torsion thus produced is determined -by twisting the filament by the torsion head on the top of the apparatus -so as to move the needle a certain distance towards the proof plane. The -more the torsion-head has to be turned to carry the needle through a -specified arc the greater is the torsion effected or the greater is the -repulsion exerted, The torsional force of a wire is proportional to the -angle of torsion; this gives the basis for the measurement. - -With magnetic needle it is used to measure magnetic repulsion and -attraction. The best material for the filament is quartz, but the -instrument is not very much used. - - -Torsion Galvanometer. -A galvanometer in which the torsion required to bring the index back to -zero, when the current tends to displace it, is made the measure of the -current strength or of the electro-motive force. It involves the use of -a torsion head, q. v., or its equivalent. - - -545 STANDARD ELECTRICAL DICTIONARY. - - -Torsion Head. -The handle and disc from whose undersurface the filament depends to -which the needle or magnet is attached. It is turned to measure the -torsional effect, the edge of the disc being marked or graduated so as -to give the angle of deflection required to overcome the effect of the -torque of the needle. - - -Torsion Suspension. -Suspension by one or more wires, fibres, or ribands, involving the -restitutive force of torsion. Thus fibre suspension, q. v., is a variety -of torsion suspension. - -Often a single riband of steel stretched horizontally and secured at -both ends is used, the suspended object, e. g., a balance beam, being -attached at its own centre to the centre of the stretched riband. Quite -sensitive balances are constructed on this principle. It is peculiarly -available where an electric current is to be transmitted, as absolute -contact is secured, as in William Thomson's ampere balances. - - -Touch. -A term applied to methods of magnetization, as "single touch," "double -touch," or "separate touch," indicating how the poles of the inducing -magnet or magnets are applied to the bar to be magnetized. Under the -titles of Magnetization the different methods are described. - - -Tourmaline. -A mineral; a subsilicate; characterized by the presence of boric -trioxide, which replaces aluminum oxide. It is notable for possessing -pyro-electric properties. (See Pyro-electricity.) - - -Tower, Electric. -The tower used in the tower system, q. v., of arc light illumination. - - -Tower System. -In electric lighting the system of lighting extended areas by powerful -arc lamps placed on high towers, generally of iron or steel frame-work. -The lights are thus maintained at a high elevation, giving greater -uniformity of illumination than if they were lower, but at the expense -of considerable light which is lost. Sometimes wooden masts are employed -instead of towers. - -The principle involved is that the intensity of light at any place given -by a source of illumination varies with the square of its distance from -the place in question. Hence in using strong arc lights it is an object -to have the distances of all parts of the area illuminated at as nearly -uniform distances from the light as possible. An approximation to -uniformity is secured by placing the lamps at a very high elevation. - - -546 STANDARD ELECTRICAL DICTIONARY. - - -Transformer. -In alternate current lighting the induction coil by which the primary -current with high initial electro-motive force is caused to produce a -secondary current with low initial electromotive force. - -A typical transformer consists of a core of thin iron sheets. The -primary is of comparatively thin wire and often of ten or more times as -many turns as the secondary. The latter is of thicker wire. Where the -ratio of 10 to 1 as regards number of turns in the primary and secondary -obtains, the initial E. M. F. of the secondary is one-tenth that of the -primary circuit. - -The cores are laminated, as described, to avoid the formation of -Foucault currents. - -The counter-electro-motive force of the transformer when the secondary -circuit is open, prevents any but the slightest current from passing -through the primary. In proportion as the secondary is closed and its -resistance diminished, as by lighting more lamps in parallel, the -counter-electro-motive force of the transformer falls and more current -passes through the primary. - - -Fig. 339. FERRANTI'S TRANSFORMER. - -The economy of the apparatus is in the fact that counter-electromotive -force reduces current through a conductor without absorbing any energy. -A resistance coil cuts down a current, but absorbs energy equal to the -current multiplied by the potential difference between the terminals of -the coil. This electric energy is converted into heat energy and is -wasted. But the counter-electromotive force of a transformer is exerted -to reduce current without production of heat and with little waste of -energy. This is one of the advantages of the alternating current system -of distribution of electric energy. - -The object of a transformer being to secure safety to the person or to -life by the separation of the high potential primary or street circuit, -and the low potential house circuit, any contact of the two circuits in -the converter is a source of danger. Special care should be taken to -ensure absence of leakage, as it is termed. Mica or other insulation is -sometimes employed to prevent the wires from coming in contact by -piercing or sparking with the core and with each other. - - -547 STANDARD ELECTRICAL DICTIONARY. - - -Transformer, Commuting. -A type of continuous current transformer, resembling a dynamo with -armature and field both stationary, but with revolving commutator, by -which the magnetic polarity of a double wound armature is made to -rotate. This secures the desired action, of a change or lowering of -potential. - - -Transformer, Continuous Alternating. -An apparatus for transforming a continuous into an alternating current -or the reverse. The combination of a continuous current dynamo with an -alternating current one is sometimes employed. It is a form of motor -dynamo. - -Another type is a regular dynamo with ordinary commutator and with, in -addition thereto, two, three or four contact rings, connecting to as -many symmetrically disposed points in the winding of the armature. This -will give out or receive alternating currents of two, three or four -phases according to the number of collecting rings. One winding serves -for both alternating and continuous currents. - - -Transformer, Continuous Current. -A machine of the dynamo type for changing the potential of a circuit. In -one form two armatures are mounted on one shaft in a single field or in -separate fields; one is a motor armature driven by the original current; -the other generates the new current. This is a motor dynamo. In 1874 -Gramme constructed a machine with ring armature with two windings, of -coarse and fine wire respectively, and with independent commutators. -Such dynamo could transform currents up or down. - -Continuous current transformers have attained an efficiency of 83 per -cent. at full load, and of 75 per cent. at half load. Owing to the -balancing of the self-inductions of the two windings these machines do -not spark. As the driven and driving parts are contained in one rotating -part their friction is very slight. - - -Transformer, Core. -A transformer wound upon an enclosed core, such as the hedgehog -transformer (see Transformer, Hedgehog), or common induction coil. - - -548 STANDARD ELECTRICAL DICTIONARY. - - -Transformer, Hedgehog. -An induction coil transformer whose iron core is composed of a bundle of -iron wires, which after the wire windings are in place have their ends -spread out to reduce to some extent the reluctance of the circuit, which -at the best is high, as the air acts as the return circuit. - -This transformer has a low degree of hysteresis; and its efficiency for -very small loads or for no load is superior to that of the closed -magnetic circuit transformer. - - -Fig. 340. SWINBURNE'S HEDGEHOG TRANSFORMER. - - -Transformer, Multiple. -A transformer connected in parallel with others between the two leads of -the primary circuit. The term refers to the connection only and not to -any peculiarity of the transformer itself. - - -Transformer, Oil. -A transformer with oil insulation. The advantage of this insulation is -that if pierced it at once closes, so that no permanent injury ensues. -It is a self-healing form of insulation. - - -Transformer, Series. -Transformers connected in series upon the primary circuits. The term, -like "multiple transformers," only applies to the connection, not to the -transformer. Series transformers are but little used. - - -Transformer, Shell. -A transformer with its iron core entirely outside of and enclosing the -primary and secondary winding. It may be made by the use of outer iron -wire windings as core. - - -Transformer, Welding. -The transformer used for electric welding. (See Welding, Electric.) It -is a transformer with very long primary and exceedingly short and thick -secondary. It is used with the alternating current in the primary, and -produces in the secondary circuit which includes the bars to be welded a -very low potential difference. - -Owing to the very low resistance of the secondary circuit this low -electro-motive force produces a very strong current, which develops the -requisite heat. The same type of transformer is used for brazing and -similar purposes. - - -549 STANDARD ELECTRICAL DICTIONARY. - - -Transmitter. -In general electric phraseology, any instrument which produces signals -to be transmitted through a line or circuit is a transmitter. Thus the -Morse key in telegraphy or the Blake transmitter in telephony are -examples of such. - - -Transmitter, Carbon. -A form of microphone used as a telephone transmitter. (See Carbon -Telephone.) - - -Transposing. -A method of laying metallic circuits for telephoning. The wires at short -intervals are crossed so that alternate sections lie on opposite sides -of each other. It is done to avoid induction. - - -Transverse Electro-motive Force. -Electro-motive force in a substance in which electric displacement is -taking place, produced by a magnetic field. It is sometimes assigned as -the cause of the Hall effect, q. v. - - -Trimmer, Brush. -A shears for cutting off evenly and squarely the ends of copper dynamo -brushes. The brushes when uneven from wear are removed from the brush -holders, and their ends are sheared off in the trimmer. - - -Trolley. -A grooved metallic pulley or set of pulleys which runs along an active -wire of a circuit, a lead from which trolley goes to earth or connects -with another wire, so that the trolley takes current generally for -operating a street car motor placed upon the circuit leading from it; a -rolling contact with an electric lead. - -Trolleys are principally used on electric railroads, and are now -universally of the sub-wire system, being at the end of a pole which is -inclined backward and forced upward by springs, so as to press the -trolley against the bottom of the wire. Thus the trolley does not -increase the sagging of the wire, but tends to push it up a little in -its passage. - - -Trolley, Double. -A trolley with two rollers or grooved wheels, placed side by side, and -running on two parallel leads of wire. It is adapted to systems -employing through metallic trolley lines with the motors in multiple -arc, connecting or across the two leads. - - -Trolley Section. -An unbroken or continuous section of trolley wire. - - -Trouvé's Solution. -An acid exciting and depolarizing solution for a zinc-carbon battery. -Its formula is as follows: Water, 80 parts; pulverized potassium -bichromate, 12 parts; concentrated sulphuric acid, 36 parts; all parts -by weight. The pulverized potassium bichromate is added to the water, -and the acid is added slowly with constant stirring. As much as 25 parts -potassium bichromate may be added to 100 parts of water. The heating -produced by the acid and water dissolves nearly all the potassium salt. -Use cold. - - -550 STANDARD ELECTRICAL DICTIONARY. - - -True Contact Force. -A species of electro-motive force whose existence is supposed to be -proved by the Peltier effect. The lowering in temperature of a contact -of dissimilar metals is attributed to a force that helps the current on -its way if in the direction of thermo-current proper to the junction and -opposing it if in the reverse. The true contact force is taken to -explain this phenomenon; thermo-electric force cannot, as there is no -heat or cold applied to the junction. - - -Trumpet, Electric. -An apparatus consisting of a vibrating tongue, kept in motion by -electricity as in the buzzer, q. v., placed in the small end of a -trumpet-shaped tube. - - -Trunking Switchboard. -A telephone switchboard arranged in sections, which sections are -connected by trunk lines, through which trunk lines the desired -connections -are made. - - -Trunk Lines. -In telephone distribution systems, the lines connecting different -stations, or different sections of a switch-board and used by anyone -requiring such connections; one trunk line answers for a number of -subscribers. - - -Tube, Electric. -A tube of glass around which is pasted a series of tinfoil circles, -diamonds, or little squares, or other form of interrupted conductor. The -pieces generally are placed in the line of a spiral. When a static -discharge of electricity takes place along the conductor a row of bright -sparks is produced at the breaks in the conductor. These by reflection -are multiplied apparently, and a beautiful effect of intersecting or -crossing spirals of sparks is presented. - -The experiment is in line with the luminous pane and lightning jar, and -is used merely as a demonstration, or lecture experiment. - -Synonym--Luminous Tube. - - -Tubular Braid. -A braid woven of tissue or worsted, and tubular or hollow. Its object is -to provide a covering which can be drawn over joints in covered wires. -In making the joint the ends of the wires are necessarily bared, and a -short piece of tubular braid is used for covering them. It is drawn by -hand over the joint. - - -Turns. -An expression applied to the convolutions of wire in a solenoid, -electro-magnet, or other apparatus or construction of that kind. A turn -indicates a complete encircling of the core or axis of the object. Thus -a wire wound five times around a bar gives five turns. - -While this is its primary meaning the term if compounded may refer to -virtual turns. Thus an ampere-turn means one ampere passing through one -turn. But ten ampere-turns may mean ten amperes passing through ten -turns, five amperes passing through two turns, and so on. This use is -analogous to a dimension of length in a compound word, as foot-pound. - -[Transcriber's note: "But ten ampere-turns may mean ten amperes passing -through ONE turn or one ampere through ten turns, and so on."] - -There may be a number of kinds of turns qualified by descriptive -adjectives, as series-turns, the turns of wire in a series circuit of a -compound dynamo. In the same way there are shunt-turns. If series -ampere-turns or shunt ampere-turns are meant the word ampere should be -included. - - -551 STANDARD ELECTRICAL DICTIONARY. - - -Turns, Dead, of a Dynamo. -The rotations of a dynamo armature while it is building itself up or -exciting itself. The expression is a bad one, as it is likely to be -confounded with the dead turns of armature wire. - - -Turns, Primary Ampere-. -The ampere-turns in a primary circuit of an induction coil or -transformer. In an electric welding transformer, or in the transformer -used in the alternating current system, where efficiency is an important -element, the ampere-turns in primary and secondary for an efficiency of -100 per cent. should be equal. In the case of an experimental induction -coil other considerations outweigh that of mere efficiency. Insulation, -including security from piercing, and the production of as long a spark -as possible, are, in these cases, the controlling consideration. - -[Transcriber's note: A 100 per cent efficient transformer is impossible, -but over 99 per cent is common. At room temperature there is always some -lost flux, eddy currents and resistive losses.] - - -Turns, Secondary Ampere-. -The ampere-turns on the secondary circuit of an induction coil or -transformer. These depend on the path provided for the current. If of -negligible inductance, such as a number of incandescent lamps would -provide, the ampere-turns should be equal to those of the primary coil. -(See Turns, Primary Ampere.) - - -Typewriter, Electric. -A typewriter in which the work of printing or of pressing the type faces -against the paper, or printing ribbon, is done by electro-magnetic -attraction. The keys close electric circuits, throwing the -electro-magnetic action into play. This involves the use of electricity -for what is ordinarily only a mechanical process. The strength of the -impression, however, is independent of the touch of the operator. It has -not come into very extensive use. - -[Transcriber's note: IBM introduced widely used electric typewriters in -1935.] - - -Ultra-gaseous Matter. -Gas so rarefied that its molecules do not collide or very rarely do so. - -Experiments of very striking nature have been devised by Crookes and -others to illustrate the peculiar phenomena that this matter presents. -The general lines of this work are similar to the methods used in -Geissler tube experiments, except that the vacua used are very much -higher. - -When the vacuum is increased so that but one-millionth of the original -gas is left the radiant state is reached. The molecules in their kinetic -movements beat back and forth in straight lines without colliding, or -with very rare collisions. Their motions can be guided and rendered -visible by electrification. A tube or small glass bulb with platinum -electrodes sealed in it, is exhausted to the requisite degree and is -hermetically sealed by melting the glass. The electrodes are connected -to the terminals of an induction coil or other source of high tension -electrification. The molecules which come in contact with a negatively -electrified pole are repelled from it in directions normal to its -surface. They produce different phosphorescent or luminous effects in -their mutual collisions. - -Thus if they are made to impinge upon glass, diamond or ruby, intense -phosphorescence is produced. A piece of platinum subjected to molecular -bombardment is brought to white heat. A movable body can be made to move -under their effects. Two streams proceeding from one negative pole repel -each other. The stream of molecules can be drawn out of their course by -a magnet. - -The experiments are all done on a small scale in tubes and bulbs, -resembling to a certain extent Geissler tubes. - -[Transcriber's note: These effects are caused by plasma--ionized gas and -electrons.] - - -552 STANDARD ELECTRICAL DICTIONARY. - - -Unbuilding. -The loss of its charge or excitation by a self-exciting dynamo. It is -the reverse of building-up. The latter indicates the exciting of the -field by the action of the machine itself; the former the spontaneous -loss of charge on open circuit or from other cause. - - -Underground Conductor. -An electric conductor insulated and placed under the surface of the -earth, as distinguished from aerial conductors. - - -Underground Electric Subway. -A subway for the enclosing of electric telegraph and other conductors -under the surface, generally in the line of streets, to do away with -telegraph poles and aerial lines of wire. Many systems have been -devised. The general type includes tubes called ducts in sets, called -conduits, bedded in concrete or otherwise protected. Every two or three -hundred feet the sets lead into a cistern-like cavity called a manhole. -The insulated wires or cables, generally sheathed with a lead alloy are -introduced into the tubes through the man-holes. A rope is first fed -through the tube. To do this short rods which screw together are -generally employed. One by one they are introduced, and each end one is -screwed to the series of rods already in the duct. When the end of the -duct is reached the rope is fastened to the last rod, and the rods are -then drawn through, unscrewed one by one and removed, the rope following -them. By means of the rope a windlass or capstan may be applied to draw -the cable into the duct. At least at every second man-hole the cables -have to be spliced. - -Each cable may contain a large number of conductors of small size for -telephoning, or a smaller number for electric light and power. The -tendency is now to separate the different classes of wires in important -lines, placing the heavier wires on one side of the street and the -telephone and telegraph wires on the other. This of course necessitates -two separate conduits. - -The advantage of underground distribution affects not only the -appearance of streets in doing away with unsightly telegraph poles, but -it also removes an element of danger at fires. Aerial wires interfere -greatly with the handling of ladders at fires, and expose the firemen -who attempt to cut them to danger to their lives from shock. - - -533 STANDARD ELECTRICAL DICTIONARY. - - -Unidirectional. adj. -Having one direction as a "unidirectional current" or "unidirectional -leak." The term is descriptive, and applicable to many cases. - - -Uniform. adj. -Unvarying; as a uniform potential difference, uniform current or -conductor of uniform resistance per unit of length. The term is -descriptive, and its application and meaning are obvious. - - -Uniform Field of Force. -A field of evenly distributed force; one in which the number of lines of -force per unit of area of any equipotential surface is the same. - - -Unipolar. adj. -Strictly speaking this term means having only one pole, and is applied -to magnets, armatures and the like. In its use a solecism is involved, -for there is no such condition possible as unipolar magnetism or -distribution of magnetism. An example of its use is shown in unipolar -magnets. (See Magnet, Unipolar.) - - -Unipolar Armature. -An armature of a unipolar dynamo; an armature whose windings -continuously cut the lines of force about the one pole, and hence whose -polarity is unchanged in its rotation. - - -Unipolar Current Induction. -Current induction produced by moving a conductor through a magnetic -field of force so that it always cuts the lines in similar relation to -itself. Thus it produces a constant current through its own circuit, if -a closed one, and no commutator is required. As this case always in -practice amounts to the cutting of lines of force in the neighborhood of -a single pole the term unipolar is employed to designate the action. - -The simplest representation of unipolar induction is the rotating of a -conductor around the end of a bar magnet, its axis of rotation -corresponding with the axis of the magnet. - - -Unipolar Dynamo. -A dynamo in which one part of the conductor slides on or around the -magnet, so as always to cut lines of force near the same pole of the -magnet. - - -Unit. -A directly or indirectly conventional and arbitrary quantity, in terms -of which measurements of things with dimensions expressible in the -chosen units are executed. - -Thus for length the c. g. s. unit is the centimeter; the B. E. unit is -the foot. - - -554 STANDARD ELECTRICAL DICTIONARY. - - -Unit, Absolute. -A unit based on the three fundamental units of length, mass and time. -These units are the centimeter, gram and second. Each one in itself may -be termed a fundamental absolute unit. The system of such units is -termed the centimeter-gram-second system. - - -Unit, Angle. -A factor or datum in angular velocity, q. v. It is the angle subtended -by a portion of the circumference equal in length to the radius of the -circle. It is equal very nearly to 57.29578° or 57° 17' 44.8". - - -Unit, B. A. -This term, while logically applicable to any of the British Association -units, is often restricted to the ohm as formerly defined by the British -Association, the B. A. Unit of Resistance, q. v. - - -Unit, Fundamental. -The three units of length, mass and time, the centimeter, gram and -second, are termed fundamental units. On them is based the absolute -system of units, and on multiples of them the practical system of units. - - -Unit Jar. -A Leyden jar which is used as a unit of measure of charge. - -It consists of a Leyden jar about 4 inches long and 3/4 inch diameter, -with about 6 square inches of its outer and the same of its inner -surface coated with tinfoil. It is placed between a source of -electricity and a larger jar or battery of jars which is to be charged. -The inner coating connects with the machine; the outer coating with the -jars to be charged. Short conductors terminating in knobs connect with -inner and outer coatings, and the knobs are adjusted at any desired -distance apart. - -By the charging operation the large jar or battery of jars receives a -charge by induction, and the charge of the small jar is at first equal -to this quantity. After a while a spark passes from knob to knob, -discharging the small jar. This indicates the reception by the large -jars of the quantity of electricity represented by the charge of the -small jar. The charging goes on, and for every spark approximately the -same quantity of electricity is received by the larger jars. - -The sparking distance m is directly proportional to the quantity of -electricity, and inversely proportional to the area of coated surface, -or is proportional to the potential difference of the two coats. This is -only true for short sparking distance, hence for accuracy the knobs -should be adjusted not too far from each other. - - -555 STANDARD ELECTRICAL DICTIONARY. - - -Unit of Supply. -A commercial unit for the sale of electric energy, as defined -provisionally by the English Board of Trade; 1,000 amperes flowing for -one hour under an E. M. F. of 1 volt; 3,600,000 volt-coulombs, or 1,000 -watt-hours, are its equivalent. It is equal to 1000/746 = 1.34 electric -horse power. - -Synonym--Board of Trade Unit. - -[Transcriber's note: Now called a kilowatt-hour.] - - -Units, Circular. -A system of units of cross-sectional area, designed especially for use -in describing wire conductors. The cross-sectional area of such is -universally a circle, and the areas of two wires of different sizes vary -with the square of their radii or diameters. Hence if the area of a -circle of known diameter is determined it may be used as a unit for the -dimensions of other circles. Any other circle will have an area -proportioned to the area of the unit circle, as the squares of the -diameters are to each other. - -In practise the commonest circular unit is the circular mil. This is the -area of a circle one mil, 1/1000 inch, in diameter and is equal to -.0000007854 square inch. A wire two mils in diameter has an area of four -circular mils; one ten mils in diameter has an area of one hundred -circular mils. - -Thus if the resistance of a given length of wire 1 mil in diameter is -stated, the corresponding resistance of the same length of wire of the -same material, but of other diameter, is given by dividing the first -wire's resistance by the square of the diameter in mils of the wire in -question. - -As it is a basic unit, most conveniently applied by multiplication, the -smaller units are used; these are the circular mil, and circular -millimeter. - - -Units, Derived. -Units derived by compounding or other processes, from the three -fundamental units. Such are the units of area, volume, energy and work, -momentum and electric units generally. In some cases the dimensions of -the derived unit may reduce to those of a simple unit as inductance -reduces to length, but the unit, as deduced from the fundamental ones, -is still a derived unit. - - -Units, Practical. -A system of units employed in practical computation. The absolute units, -especially in electricity, have been found too large or too small, and -the attempt to make them more convenient has resulted in this system. It -is based on exactly the same considerations as the absolute system of -units, except that multiples of the original fundamental units of -length, mass, and time have been taken as the base of the new system. -These basic units are multiples of the fundamental units. They are the -following: The unit of length is 1E9 centimeters; the unit of mass is -1E-11 gram; the unit of time remains 1 second. - -While this has conduced to convenience in giving better sized units, -micro- and mega-units and other multiples or fractions have to be used. -The following are the principal practical electric units: - - Electrostatic Electromagnetic - C. G. S Units. C. G. S. Units. -Intensity-Ampere equal to 3E9 1E-1 -Quantity-Coulomb " 3E9 1E-1 -Potential-Volt " (1/3)* E-2 1E8 -Resistance-Ohm " (1/9)* E-11 1E9 -Capacity-Farad " 9E11 1E-9 - - -556 STANDARD ELECTRICAL DICTIONARY. - - -Universal Battery System. -A term in telegraphy. If several equal and high resistance telegraphic -circuits are connected in parallel with each other from terminal to -terminal of a battery of comparatively low resistance each circuit will -receive the same current, and of practically the same strength as if -only one circuit was connected. This is termed the universal battery -system. It is a practical corollary of Ohm's law. The battery being of -very low resistance compared to the lines the joining of several lines -in parallel practically diminishes the total resistance of the circuit -in proportion to their own number. Thus suppose a battery of ten ohms -resistance and ten volts E. M. F. is working a single line of one -hundred ohms resistance. The total resistance of the circuit is then one -hundred and ten ohms. The total current of the circuit, all of which is -received by the one line is 10/110 = .09 ampere, or 90 milliamperes. Now -suppose that a second line of identical resistance is connected to the -battery in parallel with the first. This reduces the external resistance -to fifty ohms, giving a total resistance of the circuit of sixty ohms. -The total current of the circuit, all of which is received by the two -lines in equal parts, is 10/60 = .166 amperes. But this is equally -divided between two lines, so that each one receives .083 ampere or 83 -milliamperes; practically the same current as that given by the same -battery to the single line. It will be seen that high line resistance -and low battery resistance, relatively speaking, are required for the -system. For this reason the storage battery is particularly available. -The rule is that the resistance of the battery shall be less than the -combined resistance of all the circuits worked by it. - - -Unmarked End. -The south-seeking pole of a magnet, so called because the other end, -called the marked end, is usually marked with a scratch or notch by the -maker, while the south pole is unmarked. - - -V. -(a) Symbol for velocity. - -(b) Symbol or abbreviation for volume. - -(c) Symbol or abbreviation for volt. - - -557 STANDARD ELECTRICAL DICTIONARY. - - -V. A. -Symbol or abbreviation for voltaic alternatives, q. v. - - -Vacuum. -A space destitute of any substance. The great pervading substance is in -general sense the atmosphere. It is the gaseous mixture which surrounds -and envelopes the earth and its inhabitants. It consists of a simple -mixture of oxygen, 1 part, nitrogen, 4 parts, with 4 to 6 volumes of -carbonic acid gas in 10,000 volumes of air, or about one cubic inch to -one cubic foot. It presses with a force of about 14.7 lbs. per square -inch under the influence of the force of gravity. The term vacuum in -practise refers to any space from which air has been removed. It may be -produced chemically. Air may be displaced by carbonic acid gas and the -latter may be absorbed by caustic alkali or other chemical. The air may -be expelled and the space may be filled with steam which is condensed to -produce the vacuum. Of course in all cases the space must be included in -an hermetically sealed vessel, such as the bulb of an incandescent lamp. -But the universal method of producing a vacuum is by air pumps. An -absolute vacuum means the entire absence of gas or air, something almost -impossible to produce. A high vacuum is sometimes understood to mean one -in which the path of the molecules is equal in length to the diameter of -the containing vessels, as in Crookes' Radiometer and other apparatus -for illustrating the radiant condition of matter. The air left after -exhaustion is termed residual air or residual atmosphere. - -[Transcriber's note: Dry air is about .78 nitrogen, .21 oxygen, .01 -argon, .00038 carbon dioxide, and trace amounts of other gases. Argon -was suspected by Henry Cavendish in 1785. It was discovered in 1894 by -Lord Rayleigh and Sir William Ramsay.] - - -Vacuum, Absolute. -A space free of all material substance. It is doubtful whether an -absolute vacuum has ever been produced. - - -Vacuum, High. -An approximate vacuum, so nearly perfect that the molecules of the -residual gas in their kinetic motions rarely collide, and beat back and -forth between the walls of the containing vessel, or between any solid -object contained in the vessel and the walls of the vessel. The gas in -such a vacuum is in the radiant or ultra-gaseous state. (See -Ultra-gaseous Matter.) - - -Vacuum, Low. -A vacuum inferior to a high vacuum; a vacuum in which the molecules -collide with each other and do not move directly from side to side of -the containing vessel. - - -Vacuum, Partial. -A space partially exhausted of air so as to contain less than an equal -volume of the surrounding atmosphere. It really should come below a low -vacuum, but is often treated as synonymous therewith. - - -Vacuum, Torricellian. -The vacuum existing above the mercurial column in a barometer tube. The -principle of this vacuum is applied in the Geissler and other air pumps. -(See Pump, Geissler--Pump, Sprengel--Pump, Swinburne.) - - -558 STANDARD ELECTRICAL DICTIONARY. - - -Valency. -The relative power of replacing hydrogen or combining therewith -possessed by different elements; the number of atomic bonds belonging to -any element. Thus oxygen has a twofold valency, is bivalent or is a -dyad, and combines with two atoms of hydrogen because the latter has a -unitary atomicity, is monovalent or is a monad. - - -Valve, Electrically Controlled. -A valve which is moved by or whose movements are regulated by -electricity. - -In the block system of railroad signaling the semaphores are worked by -weights and pneumatic cylinders and pistons. The valves for admitting or -releasing the compressed air are operated by coil and plunger mechanism. -There are many other instances of the control of valves by the electric -current. - - -Vapor Globe. -A protecting glass globe surrounding an incandescent lamp, when the lamp -is to be used in an atmosphere of explosive vapor, as in mines or -similar places; or when in a place where it is exposed to dripping water -which would break the hot lamp bulb if it fell upon it. - - -Variable Period. -The period of adjustment when a current is started through a conductor -of some capacity. It is the period of duration of the variable state, q. -v., in a conductor. As indicated in the next definition in a cable of -high electrostatic capacity a variable period of nearly two minutes may -exist. This indicates the retardation in signaling to be anticipated in -cables and other lines of high capacity. - - -Variable State. -When an electric circuit is closed the current starts through the -conductor with its full strength from the point of closure, and advances -with a species of wave front so that some time elapses before it attains -its full strength in the most distant parts of the conductor, owing to -its having to charge the conductor to its full capacity at the given -potential. The state of the line while the current thus varies is called -the variable state. - -A long telegraph line when a message is being transmitted may be always -in the variable state. The current at the receiving end may never attain -its full strength. - -In the case of such a conductor as the Atlantic cable, 108 seconds would -be required for a current to attain 9/10 of its full strength at the -distant end, and but 1/5 second to attain 1/100 of its final value. -During the period of increase of current the variable state exists. - - -Variation of the Compass. -The declination of the magnetic needle. (See Elements, Magnetic.) As the -declination is subject to daily, annual and secular variations, it is -unfortunate that this term is synonymous with declination. Thus the -variation of the compass means its declination, while there is also the -variation of the declination and of other elements. The term variation -of the compass is more colloquial than the more definite expression -"declination," or "magnetic declination." - - -559 STANDARD ELECTRICAL DICTIONARY. - - -Variometer. -An apparatus used in determining the relative values of the horizontal -component of the earth's magnetic field in different places. - - -Varley's Condenser. -A static condenser whose conducting surfaces are platinum electrodes -immersed in dilute sulphuric acid. When the potential difference is -1/50th that of a Daniell's cell, two square inches of platinum have a -capacity equal to that of an air condenser whose plates have an area of -80,000,000 square inches, and separated 1/8th of an inch from each -other. As the E. M. F. increases the capacity also increases. - - -Varley's Resistances. -Variable resistances formed of discs of carbonized cloth, q. v., piled -up, and pressed together more or less firmly to vary the resistance as -desired. - - -Varnish. -A glossy transparent coating of the nature of paint, applied as a -protective, or ornamental coating to objects. - - -Varnish, Electric. -Alcoholic or etherial varnishes are the best for electrical apparatus. -They dry quickly and perfectly, and tend to form surfaces unfavorable to -the hygroscopic collection of water. Sealing wax dissolved in alcohol, -or shellac dissolved in the same solvent are used for electrical -apparatus, although the first is rather a lacquer than a varnish. -Etherial solution of gum-copal is used to agglomerate coils of wire. It -is well to bake varnished objects to harden the coating. - - -Varnish, Red. -A solution of sealing wax in 90 per cent. alcohol. It is best made thin -and applied in several coats, each coat being allowed to dry perfectly -before the next is applied. It is often seen on Leyden jars. It is a -protector from surface leakage. - - -Vat. -A vessel for chemical or other solutions. A depositing vat is one in -which a plating solution is worked, for the deposition of electroplate -upon articles immersed in the liquid, and electrolyzed by an electric -current. - - -Velocity. -The rate of motion of a body. It is usually expressed in distance -traversed per second of time. The absolute unit is one centimeter per -second or kine. The foot per second is very largely used also. - -The dimensions of velocity are length (L) divided by time (T) or L/T. - - -Velocity, Angular. -Velocity in a circle defined by the unit angle, or the angle which -subtends a circular arc equal in length to itself. The radius of the -circle traversed by the moving body does not enter into this definition, -as the real velocity of the object is not stated. If its angular -velocity and the radius of the path it travels are given its actual -velocity can be deduced. - - -560 STANDARD ELECTRICAL DICTIONARY. - - -Velocity of Signaling. -The speed of transmission of electric signals is affected by the nature -of the line, as regards its static capacity, and by the delicacy of the -receiving instruments, which may need a more or less strong current to -be affected. Thus of an original current one per cent. may suffice to -operate a sensitive instrument. This might give almost the velocity of -light, while if the instrument would only respond to the full current -nearly two minutes (see Variable State) might be required for the -production of a signal. - - -Velocity Ratio. -A term applied to the ratios existing between the electrostatic and -electro-magnetic units. If we take as numerators the dimensions of the -different qualities in the electrostatic system, and their dimensions in -the electro-magnetic system as denominators, the fractions thus obtained -reduce to expressions containing only velocity or V in some form. Thus -if we divide the dimensions of the electrostatic quantity by the -dimensions of electro-magnetic quantity the quotient is simply V or -velocity. A like division for potential, electrostatic and -electro-magnetic gives (1/V), and so on. - -The value of the velocity ratio is very nearly 3E10 (sometimes given as -2.98E10) centimeters per second. This is almost exactly that of light -(2.9992E10 centimeters per second.) This is one of the proofs of Clerk -Maxwell's magnetic theory of light. (See Maxwell's Theory of Light.) - -[Transcriber's note: The SI metre was defined in 1983 such that the -speed of light in a vacuum is exactly 299,792,458 metres per second or -about 186,282.397 miles per second.] - - -Ventilation of Armature. -In a dynamo or motor ventilation of the armature is often provided for -by apertures through it in order to prevent heating. This heating is -caused by Foucault currents. By proper disposition of the interior of -the armature with properly disposed vanes and orifices an action like -that of a fan blower can be produced, which by creating a current of air -cools the machine very efficiently. - - -Verticity, Poles of. -Points upon the earth's surface where the horizontal component of -magnetic force disappears, leaving only the vertical component active. -The term is derived from the verticity of the dipping needle when over -either of them. - - -561 STANDARD ELECTRICAL DICTIONARY. - - -Vibration Period. -In electrical resonance the period of a vibration in an electrical -resonator. The length of this period indicates the quality of the -resonator in responding to electrical oscillations by sympathetic -vibration. For conductors of small resistance the period is thus -calculated. Let T be the period of one-half a full vibration; L the -absolute coefficient of self-induction expressed in centimeters or in -henries X 10-9; C the electrostatic capacity of the terminals, also -expressed in the same unit; v the velocity of light in centimeters per -second. Then we have the formula - - T = PI * SquareRoot( L * C ) / v - -[Transcriber's note: If the inductance is in henries and the capacitance -in farads, frequency in hertz = 1/(2 * PI * squareRoot( L * C ) )] - - -Vibration, Sympathetic. -A vibration in a cord or other body susceptible of elastic vibration -produced by the vibrations of exactly the same period in a neighboring -vibrating body. Thus if two tuning forks are tuned to precisely the same -pitch, and are placed near each other, if one is sounded it will start -the other into vibration by sympathy. - -In electricity its application is found in electric resonance -experiments. The resonator has a definite period of electric resonance, -and is made to give a spark by the exciter of identical period. This is -by what may be called electric sympathetic vibration, and is exactly -analogous to the action of the tuning forks upon each other. - - -Vibrator, Electro-magnetic. -The make and break mechanism used on induction coils, or other similar -apparatus in which by alternate attractions by and releases from an -electro-magnet an arm or spring is kept in motion. In most cases the -work is done by a single magnet, whose armature is attracted to the -magnet, when the latter is excited, but against the action of a spring -which tends to pull it away from the magnet. In its motions a make and -break action is produced, to give the requisite alternations of -attraction and release. Two electro-magnets may be connected so as -alternately to be excited and keep an arm carrying a mutual armature in -vibration, or the same result may be attained by a polarized relay. The -make and break is illustrated under Bell, Electric--Coil, Induction-- -Anvil. - - -Villari's Critical Value. -Magnetization induced or residual in a wire is diminished on stretching, -provided that the magnetization corresponds to an inducing force above a -certain critical value, known as above; this being (Sir Wm. Thomson) -about 24 times the terrestrial intensity. Below that critical value -tension increases the magnetization of a magnetized wire. The effects of -transverse expansive stress are opposed to those of longitudinal -stretching. (Daniell.) - - -Viole's Standard of Illuminating Power. -A standard authorized by the International Congress of 1881. It is the -light given by one square centimeter of platinum, melted, but just at -the point of solidification. It is equal to 20 English standard candles -almost exactly. - -It has not been very widely accepted, the tendency among photometrists -being to adhere to the old standards, carcel or candle. It is obvious -that actual use of the Viole would be very inconvenient and would -involve expensive apparatus, difficult to work with. - -Synonym--Viole. - - -562 STANDARD ELECTRICAL DICTIONARY. - - -Vis Viva. -The kinetic energy of a body in motion; "mechanical energy." - - -Vitreous Electricity. -Positive electricity; the electricity produced on the surface of glass -by rubbing it with silk and other substances. (See Electrostatic -Series.) - -The term "positive electricity" should be allowed to supplant it. It is -the analogue and opposite of resinous electricity. - - -Vitriol, Blue. -A colloquial or trade name for copper sulphate (Cu SO4). - - -Vitriol, Green. -A colloquial or trade name for ferrous sulphate (Fe SO4). - - -Vitriol, White. -A colloquial or trade name for zinc sulphate (Zn SO4). - - -Volt. -The practical unit of electro-motive force or potential difference. It -may be referred to various data. - -An electro-motive force of one volt will cause a current of one ampere -to flow through a resistance of one ohm. - -A condenser of one farad capacity charged with one coulomb will have a -rise of potential of one volt. - -The cutting of 100,000,000 lines of force per second by a conductor -induces one volt E. M. F. - -A Daniell's battery gives an E. M. F. of 1.07 volts; about the most -familiar approximate standard that can be cited. - -It is equal to 1/300 absolute electrostatic unit. - -It is equal to 1E8 absolute electro-magnetic units. - -[Transcriber's note: The SI definition of a volt: The potential -difference across a conductor when a current of one ampere dissipates -one watt of power.] - - -Voltage. -Potential difference or electro-motive force expressed in volts; as a -voltage of 100 volts. Thus voltage may express the electro-motive force -absorbed in a conductor, while electro-motive force is a term generally -applied where it is produced, evolved or present in the object. The term -voltage of a lamp expresses simply the volts required, but does not -suggest the possession of electromotive force. - - -563 STANDARD ELECTRICAL DICTIONARY. - - -Voltage, Terminal. -The voltage or potential difference at the terminals of an electric -current generator, such as a dynamo, as distinguished from the total -electro-motive force of the dynamo or generator. - -In batteries the distinction is not generally made in practice; the -total electro-motive force of the battery is made the basis of -calculations. - - -Voltaic. adj. -This adjective is used to qualify a great many things appertaining to or -connected with current electricity. It is derived from Volta, the -inventor of the voltaic battery, and now tends to displace the term -"galvanic," formerly in general use. - - -Voltaic Alternatives. -A term used in electro-therapeutics or medical electricity to indicate -an alternating battery current. - -Synonym--Alternative current. - - -Voltaic Effect. -The potential difference developed by contact of different conductors. -It is the basis of the contact theory, q. v., of electricity, although -it may be accepted as the expression for a condition of things by those -who reject the above theory. This potential difference is slight when -the conductors are separated, but it is calculated that it would be -enormous could the metals be so quickly separated as to hold each its -own charge. - -Thus if a copper and a zinc plate are assumed to be in contact, really -1/20000000 centimeter or 1/50000000 inch apart, they may be treated as a -pair of condenser plates. Being so near, their density of charge, which -is a strongly bound charge, is enormous. If it were possible to separate -them without permitting any discharge, their potential would rise by the -separation, on the principle of Epinus' condenser, q. v., to such an -extent that they would spark through twenty feet of air. (See Volta's -Fundamental Experiment.) - - -Voltaic Electricity. -Electricity of low potential difference and large current intensity; -electricity such as produced by a voltaic battery; current or dynamic -electricity as opposed to static electricity. - - -Voltameter. -In general an apparatus for determining the quantity of electricity -passing through a conductor by measuring the electrolytic action it can -perform. - - -Voltameter, Copper. -An apparatus which may be of similar construction with the silver -voltameter (see Voltameter, Silver), but in which a copper anode and a -solution of copper sulphate are substituted for the silver anode and -silver nitrate solution. One coulomb corresponds to .329 milligram or -.005084 grain of copper deposited. It is not accepted as of as high a -standard as the silver voltameter. - -The electrodes should be placed half an inch from each other. Two square -plate electrodes may conveniently be used, and not less than two square -inches on each plate should be the area per ampere of current. - - -564 STANDARD ELECTRICAL DICTIONARY. - - -Voltameter, Differential, Siemens'. -A volume or gas voltameter with duplicate eudiometers and pairs of -electrodes. It is used for determining the resistance of the platinum -conductor used in his pyrometer. A current divides between the two -voltameters; in one branch of the circuit the platinum conductor is -placed, in the other a known resistance. The current strength varying -inversely with the resistance, the resistances of the two conductors are -inversely proportional to the gas evolved. - - -Voltameter, Gas. -A voltameter whose indications are based on the electrolysis of water, -made an electrolyte by the addition of sulphuric acid. The gases evolved -are measured. It may take several forms. - -In one form it is an apparatus consisting of a single eudiometer or -graduated glass tube with upper end closed and its lower end or mouth -open, collecting the mixture of hydrogen and oxygen. - -In the form shown in the cut three tubes are connected, the side tubes -representing eudiometers. For each side tube there is a platinum -electrode. In this apparatus the oxygen and hydrogen are connected in -opposite tubes. A is an open tube filled with dilute sulphuric acid. By -opening the cocks on B and C they can both be completely filled with -acid. As shown in the cut, this operation is not yet completed. The -hydrogen alone may in this case be measured. - -The mixed gas voltameter has only one eudiometer. - -The exact equivalents are only approximately known. The volume of mixed -gases per coulomb is given as .1738 cubic centimeters (Ayrton); .172 -cubic centimeters (Hospitalier); and other values by other authorities. -The hydrogen is equal to 1/3 of the mixed gases almost exactly. - -Synonyms--Volume Voltameter--Sulphuric Acid Voltameter. - -The gas is measured at 0º (32º F.) and 76 centimeters, or 30 inches -barometer. - - -Fig. 341. GAS VOLTAMETER. - - -565 STANDARD ELECTRICAL DICTIONARY. - - -If the gas is measured in cubic inches, the temperature in degrees F., -and the barometric height in inches, the following formula may be used -for reduction to standard pressure and temperature. It is the volume -corresponding to one coulomb. - ( .01058 * 30 * (491 + Fº - 32) ) / (h* 491) - -For the metric measurements and degrees C. - (.1738 * 76 * (273 + Cº)) / (h X 273) - - -Voltameter, Silver. -An apparatus consisting of a platinum vessel containing a solution of -silver nitrate into which solution a silver anode dips, whose end is -wrapped in muslin to prevent the detachment of any particles. When a -current is passed by connecting one terminal to the dish and the other -to the rod, securing a proper direction of current, silver will be -deposited on the dish and the same amount will be dissolved from the -rod. The dish is weighed before and after the test. Its increase in -weight gives the silver deposited. - - -FIG. 342. SILVER VOLTAMETER. - - -In the cut Ag is the silver anode, Pt is the platinum dish, r is the -conducting rod, p is a wooden standard, Cu is a copper plate on which -the dish rests and which also serves as a conductor and contact surface, -b is a muslin cloth to place over the silver plate to prevent detached -particles falling in the dish; s s' are the binding screws. - -The weight of silver corresponding to a coulomb is given variously by -different authorities. Ayrton and Daniell take 1.11815 milligrams or -.017253 grain of metallic silver. Other determinations are as follows: - 1.1183 milligrams (Kohlrausch). - 1.124 " (Merscart). - -The solution of silver nitrate should be from 15 to 30 per cent. of -strength. The current should not exceed one ampere per six square -inches; or in other words not more than about 3/1000 grain of silver -should be deposited per second on a square inch area of the dish. The -edge of the silver disc or anode should be about equidistant from the -side and bottom of the dish. The latter notes are due to Lord Rayleigh. - - -566 STANDARD ELECTRICAL DICTIONARY. - - -Voltameter, Weight. -A voltameter in which the amount of decomposition is determined by -weighing the products, or one of the products of the electrolysis. The -titles Voltameter, Copper, and Voltameter, Silver, may be cited. - - -Fig. 343. WEIGHT VOLTAMETERS. - - -In the cuts are shown examples of weight gas voltameters. These are -tubes light enough to be weighed when charged. Each contains a -decomposition cell T, with its platinum electrodes, and charged with -dilute sulphuric acid, while t is calcium chloride or other drying agent -to collect any water carried off as vapor or as spray by the escaping -gases; c are corks placed in position when the weighing is being -executed, so as to prevent the calcium chloride from absorbing moisture -from the air. - -In use the tubes are weighed. They are then connected to the circuit, -after removal of the corks, and the decomposition proceeds. After a -sufficient time they are removed, the corks put in place, and they are -weighed again. The loss gives the water decomposed. - -The water corresponding to one coulomb is - .09326 milligram .001430 grain, Ayrton, - .092 " Hospitalier, - .0935 " Daniell. - - -567 STANDARD ELECTRICAL DICTIONARY. - - -Voltametric Law. -The law on which voltameters are based. The amount of chemical -decomposition produced by an electric current in a given electrolyte is -proportional to the quantity of electricity passed through the solution. - - -Fig. 344. VOLTA'S FUNDAMENTAL EXPERIMENT. - - -Volta's Fundamental Experiment. -The moistened finger is placed on the upper plate of a condensing or -electrophorous electroscope. The other hand holds a plate of zinc z, -soldered to a plate of copper c. The lower plate is touched with the -copper. On removing the cover the gold leaves l diverge and with -negative electricity. Hence zinc is supposed to be positively -electrified when in contact with copper. The experiment is used to -demonstrate the contact theory of electricity. - - -568 STANDARD ELECTRICAL DICTIONARY. - - -Volta's Law of Galvanic Action. -The electro-motive force between any two metals in an electro-chemical -series (see Electro-Chemical Series) is equal to the sum of the -electro-motive forces between all the intervening metals. - - -Volta's Law of Thermo-electricity. -In a compound circuit, consisting of a number of different metals, all -points of which are at the same temperature, there is no current. - - -Volt, B. A. -The volt based on the B. A. ohm. It is equal to .9889 legal volt. - - -Volt, Congress. -The volt based upon the congress or legal ohm; the legal volt. - - -Volt-coulomb. -The unit of electric work; the watt-second; it is equivalent to - 1.0E7 ergs. - .24068 gram degree C. (calorie) - .737337 foot lbs., - .00134 horse power seconds. - - -Volt Indicator. -A form of easily read voltameter for use in electric light stations and -for similar work. - - -Volt, Legal. -The legal volt based upon the legal ohm. It is equal to 1.00112 B. A. -volt. - - -Voltmeter. -An instrument for determining the potential difference of any two -points. - -In many cases it is a calibrated galvanometer wound with a coil of high -resistance. The object to be attained is that it shall receive only an -insignificant portion of current and that such portion shall suffice to -actuate it. If connected in parallel with any portion of a circuit, it -should not noticeably diminish its resistance. - -The divisions into which ammeters range themselves answer for -voltmeters. In practice the same construction is adopted for both. The -different definitions of ammeters in disclosing the general lines of -these instruments are in general applicable to voltmeters, except that -the wire winding of the coils must be of thin wire of great length. The -definitions of ammeters may be consulted with the above understanding -for voltmeters. - -In the use made of voltmeters there is a distinction from ammeters. An -ammeter is a current measurer and all the current measured must be -passed through it. But while a voltmeter is in fact a current measurer, -it is so graduated and so used that it gives in its readings the -difference of potential existing between two places on a circuit, and -while measuring the current passing through its own coils, it is by -calibration made to give not the current intensity, but the -electro-motive force producing such current. - -In use it may be connected to two terminals of an open circuit, when as -it only permits an inconsiderable current to pass, it indicates the -potential difference existing between such points on open circuit. Or it -may be connected to any two parts of a closed circuit. Owing to its high -resistance, although it is in parallel with the intervening portion of -the circuit, as it is often connected in practice, it is without any -appreciable effect upon the current. It will then indicate the potential -difference existing between the two points. - - -569 STANDARD ELECTRICAL DICTIONARY. - - -Voltmeter, Battery. -A voltmeter for use in running batteries. In one form (Wirt's) it is -constructed for a low range of voltage, reading up to two and a half -volts and having exactly one ohm resistance, thus giving the battery -some work to do. - - -Voltmeter, Cardew. -A voltmeter in which the current passing through its conductor heats -such conductor, causing it to expand. Its expansion is caused to move an -index needle. By calibration the movements of the needle are made to -correspond to the potential differences producing the actuating currents -through it. The magnetic action of the current plays no part in its -operation. It is the invention of Capt. Cardew, R. E. - -The construction of the instrument in one of its most recent forms is -shown in the cut. On each side of the drum-like case of the instrument -are the binding screws. These connect with the blocks m and n. To these -the fine wire conductor is connected and is carried down and up over the -two pulleys seen at the lowest extremity, its centre being attached to -c. From c a wire is carried to the drum p, shown on an enlarged scale on -the left of the cut. A second wire from the same drum or pulley connects -to the spring S. The winding of the two wires is shown in the separate -figure of c, where it is seen that they are screwed fast to the -periphery of the little drum, and are virtually continuations of each -other. By the screw A the tension of the spring S is adjusted. - -On the shaft of the little drum p is a pinion, which works into the -teeth of the cog-wheel r. The shaft of r is extended through the dial -of the instrument, and carries an index. The dial is marked off for -volts; g g and h h are standards for carrying the pulleys. - - -570 STANDARD ELECTRICAL DICTIONARY. - - -The action of the instrument is as follows. The current passing through -the wire heats it. This current by Ohm's law is proportional to the -electro-motive force between the terminals. As it is heated it expands -and as it cools contracts, definite expanding and contracting -corresponding to definite potential differences. As the wire expands and -contracts the block or pin c moves back and forth, thus turning the drum -p and cogwheel r one way or permitting it to turn the other way under -the pull of the spring S. - - -Fig. 345. CARDEW VOLTMETER. - - -In this construction for a given expansion of the wire the piece c only -moves one half as much. The advantage of using a wire twice as long as -would be required for the same degree of movement were the full -expansion utilized is that a very thin wire can be employed. Such a wire -heats and cools more readily, and hence the instrument reaches its -reading more quickly or is more deadbeat, if we borrow a phraseology -properly applicable only to instruments with oscillating indexes. - -In the most recent instruments about thirteen feet of wire .0025 inch in -diameter, and made of platinum-silver alloy is used. - - -571 STANDARD ELECTRICAL DICTIONARY. - - -If the potential difference to be measured lies between 30 and 120 volts -the wire as described suffices. But to extend the range of the -instrument a resistance in series is required. If such resistance is -double that of the instrument wire, and remains double whether the -latter is hot or cold the readings on the scale will correspond to -exactly twice the number of volts. This is brought about in some -instruments by the introduction in series of a duplicate wire, precisely -similar to the other wire, and like it, carried around pulleys and kept -stretched by a spring. - -[Transcriber's note: If the series resistance is twice that of the -voltmeter, the indicated voltage will be ONE THIRD of the total -voltage.] - -Thus whatever ratio of resistance exists between the two wires cold, it -is always the same at any temperature, as they both increase in -temperature at exactly the same rate. Tubes are provided to enclose the -stretched wires and pulleys, which tubes are blackened. - -The voltmeter is unaffected by magnetic fields, and, as its -self-induction is very slight, it is much used for alternating currents. -The tubes containing the wire may be three feet long. - -Its disadvantages are thus summarized by Ayrton. It absorbs a good deal -of energy; it cannot be constructed for small potential differences, as -the wire cannot be made thicker, as it would make it more sluggish; -there is vagueness in the readings near the zero point and sometimes -inaccuracy in the upper part of the scale. - - -Volts, Lost. -The volts at the terminals of a dynamo at full load fall short of their -value on open circuit. The difference of the two values are termed lost -volts. - - -Voltmeter, Electrostatic. -A voltmeter based on the lines of the quadrant electrometer. It includes -two sets of quadrants, each oppositely excited by one of the two parts, -whose potential difference is to be determined. They attract each other -against a controlling force as of gravity. - -One form has the two sets poised on horizontal axes, bringing the parts -so that the flat quadrants move in vertical planes. - -In another form a number of quadrants are used in each set, the members -of the two sets alternating with each other. One set is fixed, the -others move and carry the index. - - -Vulcanite. -Vulcanized india rubber which by high proportion of sulphur and proper -vulcanization has been made hard. It is sometimes distinguished from -ebonite as being comparatively light in color, often a dull red, while -ebonite is black. For its electrical properties see Ebonite. - -Both substances have their defects, in producing surface leakage. -Washing with weak ammonia, or with dilute soda solution, followed by -distilled water, is recommended for the surface, if there is any trouble -with surface leakage. It may also be rubbed over with melted paraffine -wax. - - -572 STANDARD ELECTRICAL DICTIONARY. - - -W. -(a) A symbol or abbreviation for watt. - -(b) A symbol or abbreviation for work. - -(c) A symbol or abbreviation for weight. - - -Wall Bracket. -A telegraph bracket to be attached to the external walls of buildings to -which wires are attached as they come from the poles to reach -converters, or for direct introduction into a building. - - -Wall Sockets. -Sockets for incandescent lamps constructed to be attached to a wall. - - -Ward. -Direction in a straight line; a term proposed by Prof. James Thompson. -The words "backward" and "forward" indicate its scope. - - -Water. -A compound whose molecule consists of two atoms of hydrogen and one atom -of oxygen; formula, H2 O. - -Its specific gravity is 1, it being the base of the system of specific -gravities of solids and liquids. - -If pure, it is almost a non-conductor of electricity. If any impurity is -present it still presents an exceedingly high, almost immeasurable true -resistance, but becomes by the presence of any impurity an electrolyte. - - -Water Equivalent. -In a calorimeter of any kind the weight of water which would be raised -as much as is the calorimeter with its contents by the addition of any -given amount of heat received by the calorimeter. - - -Waterproof Lamp Globe. -An outer globe for incandescent lamps, to protect them from water. - - -Watt. -(a) The practical unit of electric activity, rate of work, or rate of -energy. It is the rate of energy or of work represented by a current of -one ampere urged by one volt electro-motive force; the volt-ampere. - -It is the analogue in electricity of the horse power in mechanics; -approximately, 746 watts represent one electric horse power. - -Ohm's law, taken as C = E/R, gives as values for current, C and E/R, and -for electro- motive force C R. In these formulas, C represents current -strength, R represents resistance and E represents electro-motive force. -Then a watt being the product of electro-motive force by current -strength, we get the following values for rate of electric energy, of -which the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R. - - -The equivalents of the watt vary a little according to different -authorities. Ayrton gives the following equivalents: 44.25 foot pounds -per minute--.7375 foot pounds per second--1/746 horse power. These -values are practically accurate. Hospitalier gives .7377 foot pounds per -second. Hering gives .737324 foot pounds per second, and 1000/745941 -horse power. - - -573 STANDARD ELECTRICAL DICTIONARY. - - -It is equal to 1E7 ergs per second. - -Synonym--Volt-ampere. - -(c) It has been proposed to use the term as the unit of energy, instead -of activity or rate of energy (Sir C. W. Siemens, British Association, -1882); this use has not been adopted and may be regarded as abandoned. - -[Transcriber's note; Watt is a unit of POWER--energy per unit of time.] - - -Watt-hour. -A unit of electric energy or work; one watt exerted or expended for one -hour. - -It is equivalent to : - 866.448 gram-degrees C. (calories) - 2654.4 foot lbs. - 3600 watt-seconds or volt-coulombs. - 60 watt-minutes. - - -Watt-minute. -A unit of electric energy or work; one watt exerted or expended for one -minute. - -It is equivalent to - 14.4408 gram-degrees C. (calories), - 44.240 foot pounds, - 60 watt seconds or volt-coulombs, - 1/60 watt hour. - - -Watts, Apparent. -The product in an alternating current dynamo of the virtual amperes by -the virtual volts. To give the true watts this product must be -multiplied by the cosine of the angle of lead or lag. (See Current, -Wattless.) - -[Transcriber's note: This is now called a volt-amp. The usual usage is -KVA, or kilovolt-ampere.] - - -Watt-second. -A unit of electric energy or work. One watt exerted or expended for one -second. - -It is equivalent to - .24068 gram degree C. (calorie), - .000955 lb. degree F., - .737337 foot lbs., - .0013406 horse power second (English), - .0013592 horse power second (metric). - -Synonym--Volt-coulomb. - - -Waves, Electro-magnetic. -Ether waves caused by electromagnetic disturbances affecting the -luminiferous ether. (See Discharge, Oscillatory--Maxwell's Theory of -Light--Resonance. Electric.) - -[Transcriber's note: The Michaelson-Morley experiment (1887) had already -called ether into question, but quantum theory and photons are decades -in the future.] - - -574 STANDARD ELECTRICAL DICTIONARY. - - -Weber. -(a.) A name suggested by Clausius and Siemens to denote a magnet pole of -unit strength. This use is abandoned. - -(b.) It has been used to designate the unit of quantity--the coulomb. -This use is abandoned. - -(c.) It has been used to designate the unit of current strength the -ampere. This use is abandoned. - -[Transcriber's note: Definition (a) is now used. One weber of magnetic -flux linked to a circuit of one turn produces an electromotive force of -1 volt if it is reduced to zero at a uniform rate in 1 second.] - - -Weber-meter. -An ampere-meter or ammeter. The term is not used since the term "weber," -indicating the ampere or coulomb, has been abandoned. - - -Welding, Electric. -Welding metals by heat produced by electricity. The heat may be produced -by a current passing through the point of junction (Elihu Thomson) or by -the voltaic arc. (Benardos & Olzewski.) - - -Fig. 346. ELECTRIC WELDING INDUCTION COIL. - - -The current process is carried out by pressing together the objects to -be united, while holding them in conducting clamps. A heavy current is -turned on by way of the clamps and rapidly heats the metals at the -junction, which is of course the point of highest resistance. As the -metal softens, it is pressed together, one of the clamps being mounted -with feed motion, flux is dropped on if necessary, and the metal pieces -unite. - -The most remarkable results are thus attained; almost all common metals -can be welded, and different metals can be welded together. Tubes and -other shapes can also be united. In many cases the weld is the strongest -part. - - -575 STANDARD ELECTRICAL DICTIONARY. - - -The alternating current is employed. A special dynamo is sometimes used -to produce it. This dynamo has two windings on the armature. One is of -fine wire and is in series with the field magnets and excites them. The -other is of copper bars, and connects with the welding apparatus, giving -a current of high intensity but actuated by low potential. - -Where the special dynamo is not used, an induction coil or transformer -is used. The primary includes a large number of convolutions of -relatively fine wire; the secondary may only be one turn of a large -copper bar. - -The cut shows in diagram an electric welding coil. P is the primary coil -of a number of turns of wire; S S is the secondary, a single copper bar -bent into an almost complete circle. It terminates in clamps D D for -holding the bars to be welded. B C, B' C are the bars to be welded. They -are pressed together by the screw J. The large coil I of iron wire -surrounding the coils represents the iron core. - -The real apparatus as at present constructed involves many -modifications. The diagram only illustrates the principle of the -apparatus. - -In welding by the voltaic arc the place to be heated is made an -electrode of an arc by connection with one terminal of an electric -circuit. A carbon is connected to the other terminal. An arc is started -by touching and withdrawal of the carbon. The heat may be used for -welding, soldering, brazing, or even for perforating or dividing metal -sheets. - - -Welding Transformer. -The induction coil or transformer used in electric welding. For its -general principles of construction, see Welding, Electric. - - -Wheatstone's Bridge. -A system of connections applied to parallel circuits, including -resistance coils for the purpose of measuring an unknown resistance. A -single current is made to pass from A through two parallel connected -branches, joining together again at C. A cross connection B D has a -galvanometer or other current indicator in circuit. In any conductor -through which a current is passing, the fall of potential at given -points is proportional to the resistance between such points. Referring -to the diagram a given fall of potential exists between A and C. The -fall between A and B is to the fall between A and C as the resistance r -between A and B is to the resistance r + r' between A and C. The same -applies to the other branch, with the substitution of the resistances s -and S' and the point D for r r' and B. Therefore, if this proportion -holds, r : r' : : s : S'. No current will go through B D , and the -galvanometer will be unaffected. Assume s' to be of unknown resistance, -the above proportion will give it, if r, r' and s are known, or if the -ratio of r to r' and the absolute value of s is known. - - -576 STANDARD ELECTRICAL DICTIONARY. - - -In use the resistances r, r', and s are made to vary as desired. To -measure an unknown resistance it is introduced at S', and one of the -other resistances is varied until the galvanometer is unaffected. Then -the resistance of S' is determined by calculation as just explained. The -artificial resistances may be resistance coils, q. v., or it is enough -to have one unknown resistance at s. Then if the length of wire ABC is -accurately known, the point B can be shifted along it until the balance -is attained. The relative lengths A B, and B C, will then give the ratio -r : r' needed for the calculation. This assumes the wire ABC to be of -absolutely uniform resistance. This is the principle of the meter-bridge -described below. The use of coils is the more common method and is -carried out by special resistance boxes, with the connections arranged -to carry out the exact principle as explained. The principle of -construction and use of a resistance box of the Wheatstone bridge type, -as shown in the cut, is described under Box Bridge, q. v. - - -FIG. 347. WHEATSTONE BRIDGE CONNECTIONS. - - -FIG. 348. TOP OF BOX BRIDGE. - - -577 STANDARD ELECTRICAL DICTIONARY. - - -The next cut shows the sliding form of bridge called the meter bridge, -if the slide wire is a meter long or a half- or a quarter-meter bridge, -etc., according to the length of this wire. It is described under Meter -Bridge, q. v. Many refinements in construction and in proper proportion -of resistances for given work apply to these constructions. - -Synonyms--Electric Balance--Resistance Bridge--Wheatstone's Balance. - - -Fig. 349. METER BRIDGE. - - -Whirl, Electric. -(a) A conductor carrying an electric current is surrounded by circular -lines of force, which are sometimes termed an electric whirl. - -(b) The Electric Flyer. (See Flyer, Electric.) - - -Wimshurst Electric Machine. -An influence machine for producing high potential or static electricity. - -Two circular discs of thin glass are mounted on perforated hubs or -bosses of wood or ebonite. Each hub has a groove turned upon it to -receive a cord. Each disc is shellacked. They are mounted on a -horizontal steel spindle so as to face and to be within one-eighth of an -inch of each other. On the outside of each disc sixteen or eighteen -sectors of tinfoil or thin metal are cemented. - - -578 STANDARD ELECTRICAL DICTIONARY. - - -Two curved brass rods terminating in wire brushes curved into a -semi-ellipse just graze the outer surfaces of the plates with their -brushes. They lie in imaginary planes, passing through the axis of the -spindle and at right angles from each other. - -Four collecting combs are arranged horizontally on insulating supports -to collect electricity from the horizontal diameters of the discs. These -lie at an angle of about 45° with the other equalizing rods. Discharging -rods connect with the collecting combs. - -The principle of the machine is that one set of sector plates act as -inductors for the other set. Its action is not perfectly understood. - -It works well in damp weather, far surpassing other influence machines -in this respect. On turning the handle a constant succession or stream -of sparks is produced between the terminals of the discharging rods. - - -Windage. -In a dynamo the real air gap between the armature windings and pole -pieces is sometimes thus termed. - - -Wind, Electric. -The rush of air particles from a point connected to a statically charged -condenser. - - -Winding, Compound. -A method of winding a generator or motor in which a shunt winding is -used for the field magnets and in which also a second winding of the -magnet is placed in series with the outer circuit. (See Winding, -Series--Winding, Shunt.) - - -Fig. 350. CHARACTERISTIC CURVES OF SHUNT AND SERIES WINDING. - - -The object of compound winding is to make a self-regulating dynamo and -this object is partly attained for a constant speed. - -The characteristic curves of shunt and series winding are of opposite -natures. The first increases in electro-motive force for resistance in -the outer circuit, the latter decreases under the same conditions. If -the windings are so proportioned that these conditions for each one of -the two windings are equal and opposite, it is evident that the -characteristic may be a straight line. This, however, it will only be at -a single speed of rotation. - - -579 STANDARD ELECTRICAL DICTIONARY. - - -Winding, Disc. -A winding which (S. P. Thompson) may be treated as a drum winding -extended radially, the periphery corresponding to the back end of the -drum. The magnet poles are generally placed so as to face the side or -sides of the disc. - - -Winding, Lap. -A method of winding disc and drum armatures. It consists in lapping back -each lead of wire towards the preceding lead upon the commutator end of -the armature. Thus taking the letter U as the diagrammatical -representation of a turn of wire in connecting its ends to the -commutator bars they are brought towards each other so as to connect -with contiguous commutator bars. This carries out the principle of -keeping the two members of the U moving in regions of opposite polarity -of field, so that the currents induced in them shall have opposite -directions, thus producing a total current in one sense through the bent -wire. - - -Winding, Long Shunt. -A system of compound winding for dynamos and motors. The field is wound -in series and, in addition thereto, there is a shunt winding connected -across from terminal to terminal of the machine, and which may be -regarded either as a shunt to the outer circuit, or as a shunt to the -series-field and armature winding. (See Winding, Short Shunt.) - -Synonyms--Series and Long Shunt Winding. - - -Winding, Multiple. -A winding of an electro-magnet, in which separate coils are wound on the -core, so that one or any number may be used as desired in parallel or in -series. For each coil a separate binding post should be provided. - - -Winding, Multipolar. -Winding adapted for armatures of multi-polar dynamos or motors. - - -Winding, Series. -A method of winding a generator or motor, in which one of the -commutator-brush connections is connected to the field-magnet winding; -the other end of the magnet winding connects with the outer circuit. The -other armature-brush connects with the other terminal of the outer -circuit. - - -Winding, Series and Separate Coil. -A method of automatic regulation applied to alternating current dynamos. - - -Winding, Short Shunt. -A method of compound winding for dynamos and motors. The field is wound -in series, and in addition thereto there is a shunt winding connected -from brush to brush only, thus paralleling the armature. (See Winding, -Long Shunt.) - -Synonyms--Series and Short Shunt Winding. - - -580 STANDARD ELECTRICAL DICTIONARY. - - -Winding, Shunt. -A method of winding a generator or motor. Each commutator-brush has two -connections. One set are the terminals of the outer circuit, the other -set are the terminals of the field-magnet windings. In other words, the -field-magnet windings are in shunt or in parallel with the outer -circuit. - - -Winding, Shuttle. -A method of dynamo or motor-armature winding. A single groove passes -longitudinally around the core and in this the wire is continuously -wound. The system is not now used. The old Siemens' H armature -illustrates the principle. - - -Winding, Wave. -A method of winding disc and drum armatures. It consists in advancing -the commutator ends of the U shaped turns progressively, so that as many -commutator bars intervene between any two consecutive commutator -connections of the wire as there are leads of wire on the drum between -consecutive leads of the wire. This is carried out with due regard to -the principle that taking the letter U as the diagrammatical -representation of a turn of wire, its two members must move through -regions of the field of opposite polarity. - - -Wire Finder. -A galvanometer or other instrument used for identifying the ends of a -given wire in a cable containing several. - - -Work. -When a force acts upon a body and the body moves in the direction of the -force, the force does work. Hence, work is the action of a force through -space against resistance. - -It is generally expressed in compound units of length and weight, as -foot-pounds, meaning a pound raised one foot. - - -Work, Electric, Unit of. -The volt-coulomb, q. v., or watt-second, as it is often termed. - - -Working, Diode. -In multiplex telegraphy the transmission of two messages, -simultaneously, over one wire. (See Telegraphy, Multiple.) - - -Working, Contraplex. -A variety of duplex telegraphy in which the messages are sent from -opposite ends of the line, simultaneously, so as to be transmitted in -opposite directions. (See Working, Diplex.) - - -Working, Diplex. -In duplex telegraphy the sending of two independent messages from the -same end of the line in the same direction. - - -581 STANDARD ELECTRICAL DICTIONARY. - - -Working, Double Curb. -A method of working telegraph lines. When a signal is sent the line is -charged. This has to be got rid of, and is an element of retardation. In -double curb working it is disposed of by sending a momentary current -first in the reverse, and then in the same, and finally in the reverse -direction. This is found to reduce the charge to a very low point. - - -Working, Hexode. -In multiplex telegraphy the transmission of six messages simultaneously -over one wire. (See Telegraphy, Multiplex.) - - -Working, Pentode. -In multiplex telegraphy the transmission of five messages simultaneously -over one wire. (See Telegraphy, Multiplex.) - - -Working, Reverse Current. -A method of telegraphy, in which the currents are reversed or alternated -in direction. - - -Working, Single Curb. -A simpler form of telegraph signaling than double curb working. It -consists in sending a reverse current through the line for each signal -by reversing the battery connection. - - -Working, Tetrode. -In multiplex telegraphy the transmission of four messages simultaneously -over the same line. (See Telegraphy, Multiplex.) - - -Working, Triode. -In multiplex telegraphy the transmission of three messages -simultaneously over the same wire. (See Telegraphy, Multiplex.) - - -Work, Unit of. -The erg, q. v. It is the same as the unit of energy, of which work is -the corelative, being equal and opposite to the energy expended in doing -it. There are many other engineering units of work, as the foot-pound -and foot-ton. - - -Yoke. -In an electro-magnet, the piece of iron which connects the ends furthest -from the poles of the two portions of the core on which the wire is -wound. - - -Zamboni's Dry Pile. -A voltaic pile or battery. It is made of discs of paper, silvered or -tinned on one side and sprinkled on the other with binoxide of -manganese. Sometimes as many as 2,000 of such couples are piled up in a -glass tube and pressed together with two rods which form the terminals. -They maintain a high potential difference, but having very high -resistance and slight polarization capacity, give exceedingly small -quantities. - -Zero. -(a) The origin of any scale of measurement. - -(b) An infinitely small quantity or measurement. - - -582 STANDARD ELECTRICAL DICTIONARY. - - -Zero, Absolute. -From several considerations it is believed that at a certain temperature -the molecules of all bodies would touch each other, their kinetic motion -would cease, and there would be no heat. This temperature is the -absolute zero. It is put at -273° C. (-459° F.) - -[Transcriber's note; The modern value is 0° Kelvin, -273.15° C, or --459.67° F. The lowest reported temperature observed is 1E-10° K.] - - -Zero, Potential. -Conventionally, the potential of the earth. True zero potential could -only exist in the surface of a body infinitely distant from other -electrified bodies. - - -Zero, Thermometric. -There are three thermometric zeros. In the Réaumur and centigrade -scales, it is at the temperature of melting ice; in the Fahrenheit -scale, it is 32° F. below that temperature, or corresponds to -17.78° C. - -The third is the absolute zero. (See Zero, Absolute.) - - -Zinc. -A metal; one of the elements; atomic weight, 65.1; -specific gravity, 6.8 to 7.2. - - microhms. -Resistance at 0° C. (32° F.), per centimeter cube, 5.626 -Resistance at 0° C. (32° F.), per inch cube, 2.215 - -Relative resistance (silver = 1), 3.741 - - ohms. -Resistance of a wire, 1 foot long, weighing 1 grain, .5766 - (a) 1 foot long, 1 millimeter diameter, 33.85 - (b) 1 meter long, weighing 1 gram, .4023 - (c) 1 meter long, 1 millimeter diameter, .07163 - -Zinc is principally used in electrical work as the positive plate in -voltaic batteries. - - -Zincode. -The terminal connecting with the zinc plate, or its equivalent in an -electric circuit; the negative electrode; the kathode. A term now little -used. - - -Zinc Sender. -An apparatus used in telegraphy for sending a momentary reverse current -into the line after each signal, thus counteracting retardation. - - -Zone, Peripolar. -In medical electricity, the region surrounding the polar zone, q. v. - - -Zone, Polar. -In medical electricity, the region surrounding the electrode applied to -the human body. - - -583-624 INDEX. - - Page -A 7 -Absolute 7 -Absolute Calibration 97 -Absolute Electric Potential 429 -Absolute Electrometer 222 -Absolute Galvanometer 266 -Absolute Measurement 8 -Absolute Potential 428 -Absolute Temperature 8 -Absolute Unit 554 -Absolute Unit Resistance, Weber's 468 -Absolute Vacuum 557 -Absolute Zero 581 -Abscissa 7 -Abscissas, Axis of 54 -Absorption, Electric 8 -A. C. C. 8 -Acceleration 8 -Accumulator 8 -Accumulator, Electrostatic 8 -Accumulator, Water Dropping 9 -Acetic Acid Battery 58 -Acheson Effect 208 -Acid, Carbonic 108 -Acid, Chromic, Battery 61 -Acid, Hydrochloric, Battery 66 -Acid, Spent 491 -Acid, Sulphuric 497 -Acidometer 10 -Acierage 494 -Aclinic Line 10 -Acoustic Telegraphy 10 -Acoutemeter 10, 53 -Action, Electrophoric 230 -Action, Local 331 -Action, Magne-crystallic 335 -Action, Refreshing 454 -Action, Secondary 477 -Actinic Photometer 411 -Actinic Rays. 11 -Actinism 11 -Actinometer, Electric 11 -Active Electric Circuit, 123 -Activity 11 -Actual Horse Power 290 -Adapter 11 -A. D. C., 11 -Adherence, Electro-magnetic 11 -Adherence, Magnetic 338 -Adjuster, Cord 152 -Adjustment of Brushes 90 -Admiralty Rules of Heating 12 -AEolotropic 34 -Aerial Cable 95 -Aerial Conductor 12 -Affinity 12 -Affinity, Molecular 380 -After Current,. 159 -Agglomerate Leclanché Battery 66 -Agir Motor 13 -Agone 13 -Agonic Line, 13 -Air 13 -Air Blast 13 -Air Condenser 14 -Air Field 252 -Air Gaps 15 -Air Line Wire 15 -Air Pump, Heated 15 -Air Pump, Mercurial 16 -Air Pumps, Short Fall 16 -Alarm, Burglar 16 -Alarm, Electric 17 -Alarm, Fire, Electric Automatic 257 -Alarm, Fire and Heat 17 -Alarm, Overflow 18 -Alarm, Water Level 18 -Alcohol, Electric Rectification of 18 -Alignment, 18 -Allotropy 18 -Alloy 18 -Alloy, Platinum 419 -Alloy, Platinum-Silver 419 -Alloys, Paillard 400 -Alphabet, Telegraphic 19 -Alternating 23 -Alternating Current 159 -Alternating Current Arc 23 -Alternating Current Dynamo 193 -Alternating Current Generator or Dynamo 24 -Alternating Current Meter 373 -Alternating Current System 23 -Alternating Field 252 -Alternative Current 563 -Alternative Path 24 -Alternatives, Voltaic 563 -Alternator 24 -Alternator, Constant Current 24 -Alternator, Dead Point of an 177 -Alternation 23 -Alternation, Complete 23 -Alternation, Cycle of 175 -Alum Battery 58 -Aluminum 24 -Aluminum Battery 58 -Amalgam 24 -Amalgamation 25 -Amber 25 -American Twist Joint 309 -Ammeter 26 -Ammeter, Ayrton 26 -Ammeter, Commutator 26 -Ammeter, Cunynghame's 26 -Ammeter, Eccentric Iron Disc 27 -Ammeter, Electro-magnetic 27 -Ammeter, Gravity 27 -Ammeter, Magnetic Vane 27 -Ammeter, Magnifying Spring 28 -Ammeter, Permanent Magnet 28 -Ammeter, Reducteur for 453 -Ammeter, Solenoid 28 -Ammeter, Spring 28 -Ammeter, Steel Yard 28 -Ammunition Hoist, Electric 29 -Amperage 29 -Ampere 29 -Ampere- and Volt-meter Galvanometer 274 -Ampere Arc 30 -Ampere Balance 56 -Ampere Currents 30 -Ampere Feet 30 -Ampere-hour 30 -Amperes, Lost 30 -Ampêre's Memoria Technica 30 -Ampere Meters 26, 30 -Ampere Meter, Balance 391 -Ampere Meter, Neutral Wire 391 -Ampere-minute 30 -Ampere Ring 30 -Ampere-second 30 -Ampere's Theory of Magnetism 354 -Ampere-turns 31 -Ampere-turns, Primary 31 -Ampere-turns, Secondary 31, 551 -Ampere Windings 31 -Ampérian Currents 165 -Amplitude of Waves 31 -Analogous Pole 31, 425 -Analysis 31 -Analysis, Electric 32 -Analysis, Electrolytic 214 -Analyzer, Electric 32 -Anelectrics 32 -Anelectrotonus 32 -Angle of Declination 32, 177 -Angle of the Polar Span 32 -Angle of Inclination or Dip 33 -Angle of Lag 33-318 -Angle of Lead 33 -Angle of Maximum Sensitiveness 479 -Angle of Polar Span 423 -Angle, Polar 423 -Angle, Unit 554 -Angular Currents 165 -Angular Currents, Laws of 165 -Angular Force 544 -Angular Velocity 32, 559 -Animal Electricity 33 -Animal System, Electric Excitability of 247 -Anion 33 -Anisotropic 34 -Annealing, Electric 34 -Annular Electro-magnet 216 -Annunciator 34 -Annunciator Clock 35 -Annunciator Clock, Electric 127 -Annunciator Drop 35 -Annunciator, Gravity Drop 35 -Annunciator, Needle 35 -Annunciator, Swinging or Pendulum 35 -Anodal Diffusion 35 -Anode 36 -Anodic Closure Contraction 36 -Anodic Duration Contraction 36 -Anodic Opening Contraction 36 -Anodic Reactions 36 -Anomalous Magnet 335 -Anti-induction Conductor 36, 145 -Anti-magnetic Shield 37 -Antilogous Pole, 425 -Antimony 37 -Anvil 37 -A. O. C. 38 -Aperiodic 38 -Aperiodic Galvanometer 266 -Apparent Coefficient of Magnetic Induction 346 -Apparent Resistance 297, 462 -Apparent Watts 573 -Arago's Disc 88 -Arc 39 -Arc, Ampere 30 -Arc, Compound. 39 -Arc, Electric Blow-pipe 84 -Arc, Metallic 39 -Arc, Micrometer 39, 376 -Arc, Multiple 387 -Arc, Simple 39 -Arc, Voltaic 39 -Arc Box, Multiple 387 -Arc Lamp 319 -Arc Lamp, Differential 320 -Arc Lamp, Double Carbon 191 -Areometer 41 -Areometer, Bead 41 -Argyrometry 41 -Arm 41 -Armature 41 -Armature, Bar 42 -Armature, Bipolar 42 -Armature Bore 42 -Armature Chamber 42 -Armature, Closed Coil 43 -Armature Coil, or Coils 43 -Armature Conductors, Lamination of 319 -Armature Core 43 -Armature, Cylinder 43 -Armature, Cylindrical 45 -Armature, Disc 43 -Armature, Drum 45 -Armature Factor 45 -Armature, Flat Ring 45 -Armature, Girder 49 -Armature, H 49 -Armature, Hinged 45 -Armature, Hole 45 -Armature, Intensity 45 -Armature Interference 45 -Armature, Load of 46 -Armature, Multipolar 46 -Armature, Neutral 46 -Armature, Neutral Relay 46, 390 -Armature, Non-polarized 46 -Armature of Influence Machine 46 -Armature of Leyden Jar or Static Condenser 46 -Armature, Open Coil 46 -Armature, Perforated 45 -Armature, Pivoted 47 -Armature Pockets 47 -Armature, Polarized 47 -Armature, Pole 47 -Armature, Quantity 47 -Armature, Radial 47 -Armature Reactions 41 -Armature, Revolving, Page's 47 -Armature, Ring 48 -Armature, Rolling 49 -Armatures, Gyrostatic Action of 288 -Armature, Shuttle 49 -Armature, Siemens' Old 49 -Armature, Spherical 49 -Armature, Stranded Conductor 49 -Armature, Unipolar 50, 553 -Armature, Ventilation of 560 -Armor of Cable 50 -Arm, Rheostat 472 -Arms, Proportionate 436 -Arms, Ratio 437 -Arms, Rocker 50-474 -Arrester, Lightning 328 -Arrester, Lightning, Counter-electro-motive Force 329 -Arrester, Lightning, Plates 329 -Arrester, Lightning, Vacuum. 329 -Arrester Plate 417 -Arrester, Spark 489 -Arrival Curve 168 -Articulate Speech 50 -Artificial Carbon 106 -Artificial Magnet 335 -Ascending Lightning 330 -Assymmetrical Resistance 462 -Astatic 50 -Astatic Circuit 12 -Astatic Couple 157 -Astatic Galvanometer 266 -Astatic Needle 50 -Astronomical Meridian, 372 -Asymptote 51 -Atmosphere 51 -Atmosphere, Residual 51, 460 -Atmospheric Electricity 51 -Atom 52 -Atomic Attraction 52 -Atomic Current 160 -Atomic Energy 238 -Atomic Heat 52-285 -Atomic Weight 53 -Atomicity 52 -Attracted Disc Electrometer 223 -Attraction 53 -Attraction, Atomic 52 -Attraction, Magnetic 338 -Attraction, Molar 380 -Attraction, Molecular 380 -Attraction and Repulsion, Electro-dynamic 211 -Attraction and Repulsion, Electro-magnetic 217 -Attraction and Repulsion, Electro-static 234 -Attraction and Repulsion, Electro-static, Coulomb's Law of 155 -Audiometer 53 -Aura, Electrical 53 -Aurora 53 -Austral Pole 54 -Autographic Telegraph 510 -Automatic Circuit Breaker 121 -Automatic Cut Out 175, 475 -Automatic Drop 192 -Automatic Electric Bell 78 -Automatic Electric Fire Alarm 257 -Automatic Switch 500 -Automatic Telegraph 504 -A. W. G., 54 -Axial Couple 514 -Axial Force 544 -Axial Magnet 336 -Axis, Electric 54 -Axis, Magnetic 338 -Axis of Abscissas 54 -Axis of Ordinates 54, 397 -Axis of X 54 -Axis of Y 54, 397 -Ayrton's Ammeter 26 -Azimuth 54 -Azimuth Circle 54 -Azimuth Compass 141 -Azimuth, Magnetic 338 - -B 55 -B. A. 55 -Back Electro-motive Force of Polarization 156 -Back Induction 55 -Back Shock or Stroke of Lightning 55 -Back Stroke 55 -Bagration Battery 59 -Balance 55 -Balance, Ampere 56 -Balance Ampere Meter 391 -Balance, Electric 577 -Balance, Inductance 293 -Balance, Plating 417 -Balance, Slide 374 -Balance, Thermic 85 -Balance, Torsion, Coulomb's 544 -Balance, Wheatstone's 577 -Balata 56 -Ballistic Galvanometer 567 -Balloon Battery 59 -B. and S. W. G. 56 -Banked Battery 59 -Bank of Lamps 323 -B. A. Ohm 394 -Barad 56 -Bar, Armature 42 -Bar, Bus 94 -Bar Electro-magnet 217 -Bar Magnet 336 -Barometer 56 -Bar, Omnibus 94 -Bar Photometer 411 -Bars, Commutator 56, 140 -Bath 57 -Bath, Bipolar Electric 57 -Bath, Copper 152 -Bath, Copper Stripping 152 -Bath, Electric Head 284 -Bath, Electric Shower 57 -Bath, Gold 279 -Bath, Gold Stripping 279 -Bath, Multipolar Electric 57 -Bath, Nickel 391 -Bath, Plating 418 -Baths, Electro-medical 222 -Bath, Silver 484 -Bath, Silver Stripping 484 -Bath, Stripping 57 -Bath, Unipolar Electric 57 -Batten 57-58 -Battery, Acetic Acid 58 -Battery, Alum 58 -Battery, Aluminum 58 -Battery, Bagration 59 -Battery, Balloon 59 -Battery, Banked 59 -Battery, Bichromate 59 -Battery, Bunsen 59 -Battery, Cadmium 60 -Battery, Callan 60 -Battery, Camacho's 60 -Battery, Carré's 60 -Battery, Cautery 61 -Battery Cell, Element of a 237 -Battery, Chloric Acid 61 -Battery, Chloride of Lime 61 -Battery, Chromic Acid 61 -Battery, Closed Circuit 61 -Battery, Column 61 -Battery, d'Arsonval's 62 -Battery, de la Rue .62 -Battery, de la Rive's Floating 179 -Battery, Dry 63 -Battery, Elements of 63 -Battery, Faradic 63 -Battery, Ferric Chloride 63 -Battery, Fuller's 63 -Battery, Gas 63 -Battery, Gas, Grove's 281 -Battery Gauge 64 -Battery, Gravity 64 -Battery, Grenet 65 -Battery, Grove's 65 -Battery, Hydrochloric Acid 66 -Battery, Lalande & Chaperon 69 -Battery, Lalande-Edison 69 -Battery, Lead Chloride 66 -Battery, Lead Sulphate 66 -Battery, Leclanché 66 -Battery, Leclanché Agglomerate 66 -Battery, Local 66, 831 -Battery, Magnetic 338 -Battery, Main 66 -Battery, Marié Davy's 67 -Battery, Maynooth's 67 -Battery, Medical 67 -Battery, Meidinger's 68 -Battery, Mercury Bichromate 63 -Battery Mud 68 -Battery, Multiple Connected 68 -Battery, Niaudet's 61 -Battery, Nitric Acid 68 -Battery of Dynamos 6S -Battery of Leyden Jars, 68 -Battery, Open Circuit 68 -Battery or Pile, Thermo-electric 530 -Battery, Oxide of Copper 68 -Battery, Peroxide of Lead 69 -Battery, Platinized Carbon 69 -Battery, Plunge 69 -Battery, Pneumatic 69 -Battery, Primary 69, 434 -Battery, Pulvermacher's Electro-medical 69 -Battery, Sal Ammoniac 69 -Battery, Salt, or Sea Salt 69 -Battery, Sand 70 -Battery, Secondary 70 -Battery, Secondary, Planté's 72 -Battery, Secondary, Real Efficiency of 205 -Battery, Sir William Thomson's 72 -Battery, Siemens and Halske's 72 -Battery, Skrivanow 72 -Battery, Smee's 73 -Battery Solutions, Chromic Acid 73 - 119, 178, 192, 232, 318, 421, 542, 549 -Battery, Spiral 73 -Battery, Split 73 -Battery, Sulphate of Mercury 67 -Battery System, Universal 556 -Battery, Thermo-chemical 530 -Battery, Trough 73 -Battery, Trouvé's Blotting Paper 73 -Battery, Tyer's 74 -Battery, Upward's 75 -Battery, Varley's 76 -Battery, Volta's 76 -Battery, Voltaic or Galvanic 76 -Battery Voltmeter 569 -Battery, Water 77 -Battery, Wollaston 78 -B. A. Unit, 554 -B. A. Unit of Resistance 78, 462 -B. A. Volt 568 -B. E. 78 -Bead Areometer 41 -Becquerel's Laws of Thermo-electricity 78 -Beaumé Hydrometer 78 -Bed-piece 78 -Bell, Automatic Electric 78 -Bell, Call 78, 98 -Bell Call 79 -Bell Call, Extension 248 -Bell, Circular 79 -Bell, Differentially Wound 79 -Bell, Electric 79 -Bell, Electro-mechanical 80 -Bell, Indicating 80, 297 -Bell, Magneto 80 -Bell, Magneto Call 361 -Bell, Night 392 -Bell-shaped Magnet, 336 -Bells, Relay 80, 457 -Bell, Trembling 78 -Bell, Vibrating. 78 -Belts, Joints in 311 -Bennett's Electroscope 233 -Bias 80 -Bias of Tongue of Polarized Relay 542 -Bichromate Battery 59 -Bichromate Mercury Battery 63 -Bifilar Suspension 498 -Bifilar Winding 81 -Binary Compound 81 -Binding 81 -Binding Posts or Screws 81 -Binnacle 81 -Biology, Electro- 208 -Bioscopy, Electric 82 -Bipolar Armature 42 -Bipolar Electric Bath 57 -Bisected Coils 132 -Bismuth 82 -Bi-telephone 82, 524 -Black, Platinum 419 -Blasting, Electric 83 -Bleaching, Electric 83 -Block, Branch 87 -Block, Cross-over 158 -Block System 83 -Block Wire 83 -Blotting Paper Battery, Trouvé's 73 -Blow-pipe 83 -Blow-pipe, Electric Arc 84 -Blue Magnetism 355 -Bluestone 84 -Blue Vitriol 562 -Board, Cross-connecting 157 -Board, Fuse 263 -Board, Hanger 284 -Board, Key 313 -Board, Multiple Switch 387 -Board of Trade Ohm 394 -Board of Trade Unit 555 -Board, Switch 500 -Boat, Electric 84 -Bobbins 84 -Body Protector 84 -Bohenberger's Electroscope 233 -Boiler Feed, Electric 84 -Boiling 84 -Boll 85 -Bolometer 85 -Bombardment, Molecular 380 -Bore, Armature 42 -Boreal Pole 85 -Bot 85 -Bound Charge 115 -Box Bridge 85 -Box, Cable 95 -Box, Cooling 151 -Box, Distributing 190 -Boxes, Flush 258 -Box, Fishing 311 -Box, Fuse 263 -Boxing the Compass 86 -Box, Junction 311 -Box, Multiple Arc 387 -Box, Resistance 462 -Box, Resistance, Sliding 463 -Box Sounding Relay 457 -Box, Splice 492 -Bracket, Saddle 475 -Bracket, Wall 572 -Braid, Tubular 550 -Brake, Electro-magnetic 86 -Brake, Magneto-electric 362 -Brake, Prony 435 -Branch 87 -Branch Block 87 -Branch Circuit 121 -Branch Conductor 87 -Branding, Electric 87 -Brassing 87 -Brazing, Electric 87 -Break 88 -Break, Circuit Loop 125 -Break-down Switch 88 -Breaker, Automatic Circuit 121 -Breaker, Circuit 121 -Breaker, Circuit, File 121 -Breaker, Contact 121, 146 -Break Induced Current 162 -Breaking Weight 89 -Break, Loop 332 -Break Shock 482 -Breath Figures, Electric 89 -Breeze, Electric 89 -Breeze, Static 493 -Breguet Unit of Resistance 463 -Bridge 89 -Bridge, Box 89 -Bridge, Inductance 293 -Bridge, Induction 293 -Bridge Key 313 -Bridge, Magnetic 338 -Bridge, Meter 373 -Bridge, Resistance 577 -Bridge, Reversible 472 -Bridge, Slide 374 -Bridge, Wheatstone . 575 -Bridge, Wheatstone, Commercial 36 -British Association Bridge 89 -Britannia Joint 309 -Broadside Method 89 -Broken Circuit 125 -Bronzing 89 -Brush 90 -Brush, Carbon 90 -Brush, Collecting 90 -Brush, Discharge 187 -Brushes, Adjustment of 90 -Brushes, Lead of 90 -Brushes, Negative Lead of 324 -Brushes, Scratch 476 -Brush, Faradic 251 -Brush Holders 91 -Brush, Pilot 91 -Brush, Rotating 91 -Brush, Third 91 -Brush Trimmer 549 -Brush, Wire Gauge 92 -Buckling 92 -Bug 92 -Bug Trap 92 -Bunched Cable 95 -Bunsen Battery 59 -Bunsen Disc 92 -Bunsen's Photometer 412 -Buoy, Electric 93 -Burglar Alarm 16 -Burner, Electric Gas 93 -Burning 94 -Bus Bar 94 -Bus Rod 94 -Bus Wire 94 -Butt Joint 310 -Button, Call 98 -Button, Press 94 -Button, Push 93, 98 -Buzzer 94 -B. W. G. 94 - -C 95 -C. C. 109 -Cable 95 -Cable, Aerial 95 -Cable, Armature of 50 -Cable, Armor of 50 -Cable Box 95 -Cable, Bunched 95 -Cable, Capacity of 95 -Cable Clip 97 -Cable Core 96 -Cable, Duplex 96 -Cable, Flat 96 -Cablegram 96 -Cable Grip 96 -Cable Hanger 96 -Cable Hanger Tongs 97 -Cable, Suspension Wire of 97 -Cable Tank 97 -Cadmium Battery 60 -Calamine 97 -Cal Electricity 208 -Calibration 97 -Calibration, Absolute 97 -Calibration, Invariable 97 -Calibration, Relative 98 -Call Bell 78, 79, 98 -Call Bell, Extension 248 -Call Bell, Magneto 361 -Call Button 98 -Call, Thermo 530 -Call, Thermo-electric 531 -Callan Battery 60 -Calling Drop 98 -Calorie or Calory 98 -Calorimeter 98 -Calorimetric Photometer 412 -Calory or Calorie 98 -Cam, Listening 330 -Camacho's Battery 60 -Candle 99 -Candle, Concentric 99 -Candle, Debrun 99 -Candle, Decimal 99 -Candle, Electric 99 -Candle-foot 259 -Candle, German Standard 99 -Candle Holder 99 -Candle, Jablochkoff 100 -Candle, Jamin 100 -Candle, Meter 374 -Candle Power 100 -Candle Power, Nominal 101 -Candle Power, Rated 101 -Candle Power, Spherical 101 -Candle, Standard 101 -Candle, Wilde 101 -Caoutchouc 101 -Cap, Insulator 306 -Capacity, Carrying 108 -Capacity, Dielectric 102 -Capacity, Electric or Electrostatic 102 -Capacity, Instantaneous 102 -Capacity, Magnetic Inductive 346, 349 -Capillarity, Electro- 209 -Capillary Electrometer 224 -Capacity of a Telegraph Conductor 103 -Capacity of Cable 95 -Capacity of Polarization of a Voltaic Cell 103 -Capacity, Polarization 424 -Capacity, Residual 103 -Capacity, Specific Inductive 103 -Capacity, Storage 105, 495 -Capacity, Unit of 105 -Capillarity 105 -Capillary Telephone 525 -Carbon 106 -Carbon, Artificial 106 -Carbon Brush 90 -Carbon, Concentric 107 -Carbon, Cored 107 -Carbon Dioxide 107 -Carbon Holders 107 -Carbonic Acid, 108 -Carbonic Acid Gas 108 -Carbonization 107 -Carbonized Cloth 107 -Carbon, Platinized, Battery 69 -Carbon Resistance 463 -Carbon, Retort 471 -Carbons, Lamp, Flashing of Incandescent 257 -Carbon, Telephone 525 -Carbon Transmitter 549 -Carbon, Volatilization of 108 -Carburetted Hydrogen, Heavy 397 -Carcel 108 -Carcel Gas Jet 108 -Carcel Lamp 108 -Card, Compass 142 -Cardew Voltmeter 569 -Carré's Battery 60 -Carrying Capacity 108 -Cascade 108 -Cascade, Charging and Discharging Leyden Jars in 108 -Cascade, Gassiot's 275 -Case-hardening, Electric 109 -Cataphoresis 109 -Catch, Safety 175 -Cathode, etc. See Kathode 312 -Caustry, Galvano 109 -Cautery Battery 61 -Cautery, Electric 109 -Cautery, Galvano 109 -Cautery, Galvano-electric 109 -Cautery, Galvano-thermal 109 -Cell, Battery, Element of a 237 -Cell, Constant 109 -Cell, Electrolytic 109 -Cell, Porous 427 -Cell, Selenium 478 -Cell, Standard Voltaic 109 -Cell, Standard Voltaic, Daniells' 109 -Cell, Standard Voltaic, Latimer Clark's 110 -Central Station 493 -Central Station Distribution or Supply 112 -Centre of Gravity 112 -Centre of Gyration 112 -Centre of Oscillation 112 -Centre of Percussion 112 -Centrifugal Force 112 -Centrifugal Governor 113 -C. G. S. 113 -Chain, Molecular 380 -Chamber, Armature 42 -Chamber of Incandescent Lamp 113 -Change, Chemical 116 -Changer, Pole 425 -Changing Over Switch 500 -Changing Switch 500 -Chaperon, Lalande &, Battery 69 -Characteristic 169 -Characteristic Curve 113, 168 -Characteristic Curve, External 171 -Characteristic Curve of Converter 169 -Characteristic, Drooping 114 -Characteristic, External 114 -Characteristic, Internal 114 -Characteristics of Sound 114 -Charge 114 -Charge and Discharge Key 313 -Charge, Bound 115 -Charge Current 160 -Charge, Density of 115, 180 -Charge, Dissipation of 115 -Charge, Distribution of 115 -Charge, Free 115 -Charge, Negative 389 -Charge, Residual 116 -Charging Curve 170 -Chatterton's Compound 116 -Chemical Change 116 -Chemical Electric Meter 375 -Chemical, Electro-, Equivalents 244 -Chemical Element 236 -Chemical Energy 239 -Chemical Equivalent 244 -Chemical, Cautery Galvano 265 -Chemical Recorder 117 -Chemical Telephone 526 -Chemical Equivalent, Thermo- 245 -Chemistry 118 -Chemistry, Electro- 209 -Cheval, Force de 260 -Chicle 56 -Chimes, Electric 118 -Chloric Acid Battery 61 -Chloride, Ferric, Battery 63 -Chloride, Lead, Battery 66 -Chloride of Lime Battery 61 -Chlorimeter 73 -Choking Coil 132 -Chronograph, Electric 118 -Chromic Acid Battery 61 -Chromic Acid Battery Solutions 73 -Chromoscope 119 -Chutaux's Solution 119 -Cipher Code 130 -Circle, Azimuth 54 -Circle, Delezenne's 133 -Circle, Galvanic or Voltaic 119 -Circle, Magic 119 -Circuit 120 -Circuit, Astatic 120 -Circuit, Branch 121 -Circuit Breaker 121 -Circuit Breaker, Automatic 121 -Circuit Breaker, File 121 -Circuit Breaker, Mercury 121 -Circuit Breaker, Pendulum 121 -Circuit Breaker, Tuning-fork 121 -Circuit, Broken 125 -Circuit Changing Switch 500 -Circuit, Closed, Battery 61 -Circuit, Derivative 123 -Circuit, Derived 123 -Circuit, Electrostatic 123 -Circuit, Electric, Active 123 -Circuit, External 123 -Circuit, Grounded 123 -Circuit, Incomplete 125 -Circuit Indicator 298 -Circuit Induction, Open 303 -Circuit, Leg of 325 -Circuit, Local 331 -Circuit, Loop 125 -Circuit, Loop Break 125 -Circuit, Magnetic 340 -Circuit, Magnetic Double 340 -Circuit, Main 125 -Circuit, Main Battery 125 -Circuit, Metallic 125 -Circuit, Negative Side of 125 -Circuit, Open 125 -Circuit, Positive Side of 125 -Circuit, Recoil 125 -Circuit, Return 125 -Circuits, Forked 126 -Circuit, Short 482 -Circuit, Shunt 123, 126 -Circuit, Simple 126 -Circuits, Parallel 123, 126 -Circuit, Voltaic 126 -Circuit Working, Short 482 -Circular Bell, 79 -Circular Current, 160 -Circular, Mil 379 -Circular Units 126, 555 -Circumflux 126 -Clamp 126 -Clark's Compound 126 -Cleansing, Fire 257 -Clearance Space, 489 -Cleat, Crossing 127 -Cleats 127 -Cleavage, Electrification by 127 -Clip, Cable 97 -Clock, Annunciator 35 -Clock, Controlled 127 -Clock, Controlling 127 -Clock, Electric Annunciator 127 -Clock, Electrolytic 128 -Clock, Master 127 -Clock, Secondary 127 -Clock, Self-winding, Electric 128 -Clockwork Feed 128 -Cloisons 128 -Closed Circuit Battery 61 -Closed Coil Armature 43 -Closure 128 -Closure Contraction, Kathodic 312 -Cloth, Carbonized 107 -Club-foot Electro-magnet 217 -Clutch 128 -Clutch, Electro-magnetic 128 -Coatings of a Condenser, or Prime Conductor 129 -Cockburn Fuse 263 -Code, Cipher 130 -Code, S. N. 486 -Code, Telegraphic 130, 511 -Coefficient 130 -Coefficient, Apparent, of Magnetic Induction 346 -Coefficient, Economic 130, 204, 205 -Coefficient of Electrical Energy 205 -Coefficient of Expansion 247 -Coefficient of Induced Magnetization 359, 354 -Coefficient of Magnetic Induction 346, 349 -Coefficient of Mutual Induction 301 -Coefficient of Self-induction 298 -Coercitive Force 471 -Coercive Force 471 -Coercive or Coercitive Force 131 -Coil and Plunger 131 -Coil and Coil Plunger 131 -Coil and Plunger, Differential 132 -Coil, Armature 43 -Coil, Choking 132 -Coil, Earth 133 -Coil, Electric 133 -Coil, Exploring 350 -Coil, Flat 133 -Coil, Induction 133 -Coil, Induction, Inverted 136 -Coil, Induction, Telephone 137 -Coil. Kicking 132 -Coil, Magnet 336 -Coil, Magnetizing 137 -Coil, Reaction 132 -Coil, Resistance 137 -Coil, Resistance, Standard 464 -Coil, Rhumkorff 138 -Coil, Ribbon 138 -Coils, Bisected 132 -Coils, Compensating 138 -Coils, Sectioned 138 -Coils, Henry's 138 -Coils, Idle 295 -Coil, Single, Dynamo 202 -Coil, Spark 489 -Coil, Sucking 132 -Collecting Brush 90 -Collecting Ring 139 -Collector 139 -Colombin, 139 -Colophony 460 -Colors of Secondary Plates 478 -Column Battery 61 -Column, Electric 139 -Comb 140 -Combined Resistance 464 -Comb Protector 437 -Commercial Efficiency 204 -Commercial Efficiency of Dynamo 195 -Commercial Wheatstone Bridge 86 -Common Reservoir 460 -Communicator 140 -Commutation, Diameter of 182 -Commutator 140 -Commutator Ammeter 26 -Commutator Bars 140, 56 -Commutator, Flats in 140 -Commutator, High Bars of 289 -Commutator, Neutral Line of 390 -Commutator, Neutral Point of 390 -Commutator of Current Generators and Motors 140 -Commutators, Bars of 56 -Commutator Segments 56 -Commutator, Split Ring 141 -Commuted Current 160 -Commuter 140 -Commuting Transformer 547 -Compass 141 -Compass, Azimuth 141 -Compass, Boxing the 86 -Compass Card, 142 -Compass, Declination 142 -Compass, Inclination 142 -Compass, Mariners' 142 -Compass, Points of the 143 -Compass, Spirit 143 -Compass, Surveyors 143 -Compass, Variation of the 32, 558 -Compensating Coils 138 -Compensating Magnet 336 -Compensating Poles 426 -Compensating Resistance 144 -Complementary Distribution 144 -Complete Alternation 23 -Component 144 -Components of Earth's Magnetism 356 -Composition of Forces 260 -Compound Arc 39 -Compound, Binary 81 -Compound, Chatterton's 116 -Compound, Clark's 126 -Compound Dynamo 195 -Compounding, Over- 399 -Compound Magnet 336 -Compound or Compound Wound Motor 382 -Compound Winding 578 -Concentration of Ores, Magnetic 340 -Concentrator, Magnetic 340 -Concentric Candle 99 -Concentric Carbon 107 -Condenser 144 -Condenser, Coatings of a, or Prime Conductor 129 -Condenser, Epinus' 242 -Condenser, Plate 417 -Condenser, Sliding 144 -Condenser, Varley's 559 -Condensing Electroscope 233 -Conductance 144 -Conductance, Magnetic 340 -Conduction 144 -Conduction, Electrolytic 215 -Conductive Discharge 187 -Conductivity 144 -Conductivity, Magnetic 340 -Conductivity, Specific 145 -Conductivity, Unit of 145 -Conductivity, Variable 145 -Conductor 145 -Conductor, Anti-induction 145 -Conductor, Branch 87 -Conductor, Capacity of a Telegraph 103 -Conductor, Conical 145 -Conductor, Imbricated 146 -Conductor, Interpolar 307 -Conductor, Leakage 325 -Conductor, Prime 146, 434 -Conductors, Equivalent 146 -Conductors, Lamination of Armature 319 -Conductors, Service 481 -Conductor, Underground 552 -Congress Ohm 395 -Congress Volt 568 -Conical Conductor 145 -Conjugate 146 -Connect 146 -Connection, Cross 158 -Connection, Relay 457 -Connector 146 -Consequent Points 422 -Consequent Poles 146, 478 -Conservation of Electricity 146 -Conservation of Energy 239 -Constant Current 160 -Constant Current Alternator 24 -Constant Current Regulation 454 -Constant, Dielectric 183 -Constant, Galvanometer 268 -Constant Potential 429 -Constant Potential Regulation 455 -Constant, Time 54l -Contact Breaker 121, 146 -Contact, Electric 147 -Contact Electricity 147 -Contact Faults 147 -Contact Key, Double 314 -Contact Key, Sliding 316 -Contact Lamp 320 -Contact, Line of 330 -Contact Point 147 -Contact Potential Difference 147 -Contact Ring 473 -Contact Spring 148 -Contact Series 147 -Contact Theory 148 -Continuity, Magnetic 340 -Continuous Alternating Transformer 547 -Continuous Current 161 -Continuous Current Transformer 384, 547 -Contraction, Anodic Closure 36 -Contraction, Anodic Duration 36 -Contraction, Anodic Opening 36 -Contraction, Kathodic Closure 312 -Contraction, Kathodic Duration 312 -Contractures 148 -Contraplex Working 580 -Control, Electro-magnetic 218 -Control, Gravity 281 -Controlled Clock, 127 -Controlling Clock 127 -Controlling Field 148 -Controlling Force 148 -Controlling Magnet 185, 336 -Control, Magnetic 341 -Control, Spring 492 -Convection, Electric 149 -Convection, Electrolytic 149, 214 -Convection of Heat, Electric 149 -Convective Discharge 187 -Conversion, Efficiency of 205 -Converter 149 -Cooling Box 151 -Co-ordinates, Origin of 391 -Co-ordinates, System of 150 -Copper 151 -Copper Bath 152 -Copper Stripping Bath 152 -Copper Voltameter 563 -Cord Adjuster 152 -Cord, Flexible 152 -Cord, Pendant 405 -Core 152 -Core, Armature 43 -Core, Cable 96 -Cored Carbon 107 -Core-discs 152 -Core-discs, Perforated 154 -Core-discs, Pierced 152 -Core-discs, Toothed 154 -Core, Laminated 154 -Core, Magnet 336 -Core Ratio 154 -Core, Ribbon 154 -Core, Ring 155 -Cores, Krizik's 318 -Core, Stranded 155 -Core, Tangentially Laminated 155 -Core Transformer 155 -Core, Tubular 155 -Corpusants 155 -Corresponding Points 422 -Coulomb 155 -Coulomb's Law of Electrostatic Attraction and Repulsion 155 -Coulomb's Law of Magnetic Attraction and Repulsion 338 -Coulomb's Torsion Balance 544 -Coulomb, Volt- 568 -Counter, Electric 156 -Counter Electro-motive Force 156, 228 -Counter-electro-motive Force Lightning Arrester 329 -Counter Inductive Effect 204 -Couple 156 -Couple, Astatic 157 -Couple, Axial 544 -Couple, Magnetic 341 -Couple, Moment of 544 -Couple, Thermo-electric 532 -Couple, Voltaic or Galvanic 156 -Coupling 259 -Coupling of Dynamo 201 -C. P. 157 -Crater 157 -Creep, Diffusion 184 -Creeping 157 -Creeping, Magnetic 341 -Creeping of Magnetism 356 -Crith 157 -Critical Current 161 -Critical Distance of Alternative Path 190 -Critical Resistance 464 -Critical Speed 157 -Critical Value, Villari's 561 -Crookes' Dark Space 489 -Cross 157 -Cross-connecting Board 157 -Cross Connection 158 -Cross Induction 298 -Crossing Cleat 127 -Crossing Wires 158 -Cross-magnetizing Effect 158, 298 -Cross-over Block 158 -Cross, Peltier's 405 -Cross Talk 158 -Crucible, Electric 158 -Crystallization, Electric 158 -Cube, Faraday's 249 -Culture. Electro- 209 -Cunynghame's Ammeter 26 -Cup, Mercury 371 -Cup, Porous 159, 426 -Current 159 -Current, After 159 -Current, Alternating 159 -Current, Alternating System 23 -Current, Alternative 563 -Current Arc, Alternating 23 -Current, Atomic 160 -Current, Break Induced 162 -Current, Charge 160 -Current, Circular 160 -Current, Commuted 160 -Current, Constant 160 -Current, Continuous 161 -Current, Continuous, Transformer 384 -Current, Critical 161 -Current, Daniel 161 -Current, U. S. or Siemens' Unit 161 -Current, Demarcation 161 -Current Density 161 -Current, Derived 164 -Current, Diacritical 161 -Current, Diaphragm 161 -Current, Direct 162 -Current, Direct Induced 162 -Current, Direction of 162 -Current, Displacement 162 -Current, Extra 162 -Current, Faradic 162 -Current, Field of Force of a 255 -Current, Foucault 163 -Current, Franklinic 163 -Current Generator 277 -Current, Induced 163 -Current Induction 163 -Current Induction, Unipolar 553 -Current Intensity 163 -Current, Inverse Induced 163 -Current, Jacobi's Unit of 163 -Current, Joint 163 -Current, Linear 164 -Current, Make and Break 164, 367 -Current, Make Induced 163 -Current Meter 164, 375 -Current Meter, Alternating 373 -Current, Negative 164 -Current, Nerve and Muscle 164 -Current, Opposed 164 -Current, Partial 164 -Current, Polarizing 164 -Current, Positive 164 -Current, Power of Periodic 433 -Current, Pulsatory 164 -Current, Rectified 164 -Current, Rectilinear 165 -Current, Redressed 165 -Current Regulation, Constant 454 -Current, Reverse Induced 163 -Current Reverser 165 -Currents, Ampere 30 -Currents, Ampérian 165 -Currents, Angular. 165 -Currents, Angular, Laws of 165 -Currents, Earth 166 -Current, Secondary 166 -Current, Secretion 166 -Currents, Eddy 163 -Currents, Eddy Displacement 162 -Currents in Parallel Circuits, Independence of 297 -Current, Sinuous 166 -Current, Sheet 166 -Current, Shuttle 483 -Currents, Local 163 -Currents, Local 331 -Currents, Multiphase 166 -Currents, Natural 166, 389 -Currents, Nerve 390 -Currents of Motion 167 -Currents of Rest 167 -Currents, Orders of 167 -Currents, Parasitical 163 -Currents, Polyphase 167 -Currents, Rotatory 167 -Currents, Thermo-electric 167 -Current Streamlets 495 -Current, Swelling 167 -Current, Tailing 501 -Current, Undulatory 167 -Current, Unit 167 -Current, Wattless 168 -Curve, Arrival 168 -Curve, Characteristic 113, 168 -Curve, Characteristic, of Converter 169 -Curve, Charging 170 -Curve, Discharging 170 -Curve, Elastic 206 -Curve, Electro-motive Force 170 -Curve, External Characteristic . 171 -Curve, Harmonic 174, 485 -Curve, Horse Power 171 -Curve, Isochasmen 171 -Curve, Life 171 -Curve, Load 172 -Curve, Magnetization 172 -Curve of Distribution of Potential in Armature 172 -Curve of Dynamo 173 -Curve of Saturation of Magnetic Circuit 174 -Curve of Sines 173, 485 -Curve of Torque 174 -Curve, Permeability Temperature 174 -Curve, Sine 174, 485 -Curve, Sinusoidal 174, 485 -Curves, Magnetic 341 -Cut In 174 -Cut Out 174 -Cut Out, Automatic 175, 475 -Cut Out, Magnetic 175 -Cut Out, Plug 175 -Cut Out, Safety 175 -Cut Out, Spring Jack 493 -Cut Outs, Time 541 -Cut Out, Wedge 175 -Cutting of Lines of Force 175 -Cycle of Alternation 175 -Cycle of Magnetization 360 -Cylinder, Armature 43 -Cylinder, Electric Machine 333 -Cylindrical Armature 45 -Cystoscopy 175 - -Damper 176 -Damping 176 -Damping Magnet 336 -Daniell's Standard Voltaic Cell 109 -Dark Space, Faraday's 249 -D'Arsonval's Battery 62 -Dash-pot 176 -Dead Beat 38, 176 -Dead Beat Discharge 187 -Dead Earth 176, 203 -Dead Point of an Alternator 177 -Dead Turns 177 -Dead Turns of a Dynamo 551 -Dead Wire 177 -Death, Electrical 177 -Debrun Candle 99 -Decalescence 177 -Decay of Magnetism 356 -Deci 177 -Decimal Candle 99 -Declination, Angle of 32-177 -Declination Compass 142 -Declination, Magnetic 342 -Declination Map 309 -Declination of the Magnetic Needle 178 -Decomposition 178 -Decomposition, Electrolytic 178 -Decrement 178 -De-energize 178 -Deflagration 178 -Deflagrator, Hare's 73 -Deflecting Field 178 -Deflection 178 -Deflection Method 178 -Deflection of Magnet 337 -Degeneration, Reaction of 179 -Degradation of Energy 239 -Deka 179 -De la Rive's Floating Battery 179 -De la Rue Battery 62 -Delaurier's Solution 179 -Delezenne's Circle 133 -Demarcation Current 161 -Demagnetization 179 -Density, Current 161 -Density, Electrical 115 -Density, Electric Superficial 180 -Density, Field 252 -Density, Magnetic 342 -Density of Charge 115, 180 -Dental Mallet, Electric 180 -Deposit, Electrolytic 180 -Deposit, Nodular 392 -Depolarization 180 -Depolarizing Fluid 258 -Derivation, Points of 180, 423 -Derivative Circuit 123 -Derived Circuit 123 -Derived Current 164 -Derived Units 555 -Desk Push 180 -Detector 180 -Detector, Lineman's 180 -Deviation of Discharge 188 -Deviation, Quadrantal 180 -Deviation, Semi-circular 181 -Device, Safety 475 -Dextrotorsal 181 -Diacritical 181 -Diacritical Current 161 -Diagometer 181 -Diagnosis, Electro- 181, 210 -Diagram, Thermo-electric 532 -Dial Telegraph 505 -Diamagnetic 181 -Diamagnetic Polarity 181, 423 -Diamagnetism 182 -Diameter of Commutation 182 -Diapason, Electric 182 -Diaphragm 182 -Diaphragm Current 161 -Dielectric, 182 -Dielectric Capacity 102 -Dielectric Constant 183 -Dielectric, Energy of 183 -Dielectric Polarization 183 -Dielectric Resistance 183, 464 -Dielectric Strain 183 -Dielectric Strength 183 -Dielectric Stress 496 -Differential Arc Lamp 320 -Differential Coil and Plunger 132 -Differential Galvanometer 268 -Differentially Wound Bell, 79 -Differential Magnetometer 365 -Differential Motor 382 -Differential Relay 457 -Differential Thermo-electric Pile 533 -Differential Winding Working 183 -Diffusion 184 -Diffusion, Anodal . 35 -Diffusion Creep 184 -Digney Unit of Resistance 464 -Dimensions and Theory of Dimensions 184 -Dimmer 185 -Diode Working 580 -Dioxide, Carbon 107 -Dioxide, Sulphur 497 -Dip, Magnetic 342, 346 -Dip of Magnetic Needle 185 -Dipping 185 -Dipping Needle 185 -Direct Current 162 -Direct Current Dynamo 197 -Direct Induced Current, . 162 -Direct Reading Galvanometer 269 -Directing Magnet 185 -Direction 185 -Direction of Current 162 -Direction, Positive 428 -Directive Power 187 -Disc, Arago's 38 -Disc, Armature 43 -Disc, Bunsen 92 -Disc, Dynamo 197 -Disc, Faraday's 249 -Discharge and Charge Key 313 -Discharge, Brush 187 -Discharge, Conductive 187 -Discharge, Convective 187 -Discharge, Dead Beat 187 -Discharge, Disruptive 187 -Discharge, Duration of 188 -Discharge, Glow 187 -Discharge, Impulsive 188 -Discharge Key, Kempe's 315 -Discharge, Lateral 188 -Discharge of Magnetism 356 -Discharge, Oscillatory 188 -Discharger 188 -Discharger, Henley's Universal 189 -Discharger, Universal 189 -Discharger, Universal, Henley's 189 -Discharge, Silent 187, 189, 206 -Discharge, Spark 189 -Discharge, Surging 188 -Discharging Curve 170 -Discharging Rod 189 -Discharging Tongs 189 -Disconnection 189 -Discontinuity, Magnetic 342 -Discovery, Oerstedt's 394 -Disc Winding 579 -Dispersion Photometer 412 -Displacement Current 162 -Displacement, Electric 188 -Displacement, Oscillatory 398 -Disruptive Discharge 187 -Disruptive Tension 189 -Dissimulated Electricity 189 -Dissipation of Charge 115 -Dissociation 189, 535 -Distance, Critical, of Alternative Path 190 -Distance, Explosive 190 -Distance, Sparking 190 -Distance, Striking 496 -Distant Station 493 -Distillation 190 -Distortion of Field 252 -Distributing Box 190 -Distributing Switches 190 -Distribution, Complementary 144 -Distribution, Isolated 309 -Distribution of Charge 115 -Distribution of Electric Energy, Systems of 190 -Distribution of Magnetism, Lamellar, 357 -Distribution of Magnetism, Solenoidal 358 -Distribution of Supply, Central Station 112 -Door Opener, Electric 190 -Dosage, Galvanic 190 -Double Break Switch 500 -Double Carbon Arc Lamp 191 -Double Contact Key 314 -Double Curb Working 581 -Double Fluid Theory 191 -Double Fluid Voltaic Cell 191 -Double Magnetic Circuit 340 -Double Needle Telegraph 506 -Double Plug 191 -Double Pole Switch 500 -Double Tapper Key 314 -Double Touch, Magnetization by 358 -Double Trolley 549 -Double Wedge 191 -Doubler 191 -D. P. 191 -Drag 191 -Drag of Field 254 -Dreh-Strom 191 -Drill, Electric 191 -Drip Loop 192 -Driving Horns 192 -Dronier's Salt 192 -Drooping Characteristic 114 -Drop, Annunciator 35 -Drop, Automatic 192 -Drop, Calling 98 -Drum Armature 45 -Drum, Electric 193 -Dry Battery 63 -Dry Pile, Zamboni's 581 -Dub's Laws 193 -Duct 193 -Duplex Bridge Telegraph 506 -Duplex Cable 96 -Duplex Differential Telegraph 507 -Duplex Telegraph, 506 -Duration Contraction, Kathodic 312 -Duration of Electric Spark 490 -Dyad 193 -Dyeing, Electric 193 -Dynamic Electricity 193 -Dynamic, Electro- 211 -Dynamic Induction, Magnetic 347 -Dynamo, Alternating Current 193 -Dynamo, Alternating Current Regulation of 195 -Dynamos, Battery of 68 -Dynamo, Commercial Efficiency of 195 -Dynamo, Compound 195 -Dynamo, Coupling of 201 -Dynamo, Curve of 173 -Dynamo, Dead Turns of a 551 -Dynamo, Direct Current 197 -Dynamo, Disc 197 -Dynamo-electric Machine 197 -Dynamo, Electroplating 198 -Dynamo, Equalizing 198 -Dynamo, Field and Armature Reaction of 450 -Dynamo, Far Leading 198 -Dynamo or Magneto-electric Generator, Flashing in a 257 -Dynamo, Inductor 199 -Dynamo, Interior Pole 199 -Dynamo, Iron Clad 200 -Dynamo, Ironwork Fault of a 308 -Dynamo, Motor 200 -Dynamo, Multipolar 200 -Dynamo, Non-polar 200 -Dynamo, Open Coil 200 -Dynamo, Overtype 399 -Dynamos, Regulation of 455 -Dynamo, Ring 200 -Dynamo, Self Exciting 201 -Dynamo, Separate Circuit 201 -Dynamo, Separately Excited 201, 479 -Dynamo, Series 201 -Dynamo, Shunt 202 -Dynamo, Single Coil 202 -Dynamo, Tuning Fork 202 -Dynamo, Unipolar 202, 553 -Dynamograph 199 -Dynamometer 200 -Dyne 203 - -Earth 203 -Earth Coil 133 -Earth Currents 166 -Earth, Dead 176, 203 -Earth, Magnetization by 359 -Earth, Partial 203, 404 -Earth Plate 203 -Earth Return 203 -Earth's Magnetism, Components of 356 -Earth, Solid 203 -Earth, Swinging 203 -Earth, Total 203 -Ebonite 203 -Eccentric Iron Disc Ammeter 27 -Economic Coefficient 130, 204, 205 -Eddy Currents 163 -Eddy Displacement Currents 162 -Ediswan 204 -Edison Effect 204 -Edison-Lalande Battery 69 -Eel, Electric 204 -Effect, Acheson 208 -Effect, Counter-inductive 204 -Effect, Cross-magnetizing 158, 298 -Effect, Edison 204 -Effect, Faraday 249 -Effect, Ferranti 251 -Effect, Hall 284 -Effect, Joule 311 -Effect, Kerr 235, 312 -Effect, Mordey 381 -Effect, Page 401 -Effect, Peltier 404 -Effect, Photo-voltaic 415 -Effect, Seebeck 478 -Effect, Skin 486 -Effect, Thomson 538 -Effect, Voltaic 563 -Efficiency 204 -Efficiency, Commercial 204 -Efficiency, Electrical 205 -Efficiency, Gross 205 -Efficiency, Intrinsic 205 -Efficiency, Net 205 -Efficiency of Conversion 205 -Efficiency of Secondary Battery Quantity 205 -Efficiency of Secondary Battery, Real 205 -Efflorescence 206 -Effluvium, Electric 206 -Egg, Philosopher's 409 -Elastic Curve 206 -Elasticity, Electric 206 -Electrepeter 206 -Electric, Absolute, Potential 429 -Electric Absorption 8 -Electric Actinometer 11 -Electric Alarm 17 -Electrical Classification of Elements 237 -Electrically Controlled Valve 558 -Electric Ammunition Hoist 29 -Electric Analysis 32 -Electric Analyzer 32 -Electric Annealing 34 -Electric Annunciator Clock 127 -Electric Arc Blow-pipe 84 -Electric Aura 53 -Electric Automatic Fire Extinguisher 257 -Electric Axis 54 -Electric Balance 577 -Electric Bath, Bipolar 57 -Electric Bath, Multipolar 57 -Electric Bath, Unipolar 57 -Electric Bell 79 -Electric Bell, Automatic 78 -Electric Bioscopy 82 -Electric Blasting 83 -Electric Bleaching 83 -Electric Boat 84 -Electric Boiler Feed 84 -Electric Branding 87 -Electric Brazing 87 -Electric Breath Figures 89 -Electric Breeze 89 -Electric Buoy 93 -Electric Candle 99 -Electric Case Hardening 109 -Electric Cautery 109 -Electric Chimes 118 -Electric Chronograph 118 -Electric Circuit, Active 123 -Electric Clock, Self-winding 128 -Electric Coil 133 -Electric Column 139 -Electric Contact 147 -Electric Convection 149 -Electric Convection of Heat 149, 286 -Electric Counter 156 -Electric Crucible 158 -Electric Crystallization 158 -Electric Death 177 -Electric Density 115 -Electric Dental Mallet 180 -Electric Diapason 182 -Electric Displacement 189 -Electric Door Opener 190 -Electric Double Refraction 454 -Electric Drill 191 -Electric Drum 193 -Electric Dyeing 193 -Electric Eel 204 -Electric Efficiency 205 -Electric Effluvium 206 -Electric Elasticity 206 -Electric Endosmose 238 -Electric Energy 239 -Electric Energy, Coefficient of 205 -Electric Energy, Systems of Distribution of 190 -Electric Engraving 245 -Electric Entropy 242 -Electric Etching 245 -Electric Evaporation 246 -Electric Excitability of Animal Systems 247 -Electric Exosmose 247 -Electric Expansion 247 -Electric Fire Alarm, Automatic 257 -Electric Floor Matting 369 -Electric Fluid 258 -Electric Fly or Flyer 259 -Electric Fog 259 -Electric Furnace 263 -Electric Fuse 264 -Electric Gas Burners 93 -Electric Headlight 285 -Electric Head Bath 284 -Electric Heat 285 -Electric Heater 286 -Electric Horse Power 290 -Electric Image 296 -Electric Incandescence 297 -Electric Influence 305 -Electric Insulation 305 -Electricities, Separation of 479 -Electricity 206 -Electricity, Animal 33 -Electricity, Atmospheric 51 -Electricity, Cal 208 -Electricity, Conservation of 146 -Electricity, Contact 147 -Electricity, Dissimulated 189 -Electricity, Dynamic 193 -Electricity, Frictional 262 -Electricity, Latent 323 -Electricity, Negative 389 -Electricity, Plant 317 -Electricity, Positive 428 -Electricity, Specific Heat of 491 -Electricity, Static 493 -Electricity, Storage of 495 -Electricity, Voltaic 563 -Electricity, Vitreous 562 -Electric Machine, Plate 417 -Electric Machine, Wimshurst 577 -Electric Mains 367 -Electric Mass 368 -Electric Matter 368 -Electric Meter, Chemical 375 -Electric Meter, Thermal 375 -Electric Meter, Time 375 -Electric Mortar 382 -Electric Motor 382 -Electric or Electrostatic Capacity 102 -Electric Organ 397 -Electric Oscillations 398 -Electric Osmose 398 -Electric Pen 405 -Electric Pendulum 405 -Electric Piano 415 -Electric Picture 415 -Electric Pistol 416 -Electric Popgun 282 -Electric Portrait 415 -Electric Potential Difference 429 -Electric Potential, Unit of 432 -Electric Power 433 -Electric Pressure 434 -Electric Probe 435 -Electric Prostration 437 -Electric Protector 437 -Electric Radiometer 447 -Electric Ray 450 -Electric Rectification of Alcohol 18 -Electric Reduction of Ores 453 -Electric Reduction of Phosphorous 410 -Electric Register 454 -Electric Residue 116, 460 -Electricity, Resinous 461 -Electric Resonance 468 -Electric Resonator 470 -Electric Rings 392 -Electrics 208 -Electric Saw 476 -Electric Screen, 476 -Electric Shadow 480 -Electric Shock 482 -Electric Shower Bath 57 -Electric Soldering 487 -Electric Spark, Duration of 490 -Electric Sphygmophone 491 -Electric Storms 495 -Electric Striae 496 -Electric Subway 496 -Electric Subway, Underground 552 -Electric Sunstroke 497 -Electric Superficial Density 180 -Electric Swaging 499 -Electric Tele-barometer 504 -Electric Telemanometer 521 -Electric Telemeter 521 -Electric Tempering 527 -Electric Tension 529 -Electric Thermometer 535 -Electric Thermostat 537 -Electric Torpedo 543 -Electric Tower 545 -Electric Transmission of Energy 240 -Electric Trumpet 550 -Electric Tube 550 -Electric Typewriter 551 -Electric Unit of Work 580 -Electric Varnish 559 -Electric Welding 574 -Electric Whirl 577 -Electric Wind 578 -Electrification 208 -Electrification by Cleavage 127 -Electrification by Pressure 434 -Electrified Body, Energy of an . 241 -Electrization 208 -Electro-biology 208 -Electro-capillarity 209 -Electro-chemical Equivalents 209, 244 -Electro-chemical Series 209 -Electro-chemistry 209 -Electro-culture 209 -Electrode 210 -Electrode, Indifferent 210 -Electrodes, Erb's Standard of 210 -Electrodes, Non-polarizable 210 -Electrodes, Shovel 483 -Electrode, Therapeutic 210 -Electro-diagnosis 181, 210 -Electro-dynamic 211 -Electro-dynamic Attraction and Repulsion, 211 -Electro-dynamic Rotation of Liquids 474 -Electro-dynamometer, Siemens' 212 -Electro-gilding 277 -Electro-kinetic 211 -Electrolier 212 -Electrolysis 212 -Electrolysis, Laws of 213 -Electrolyte 214 -Electrolytic Analysis 214 -Electrolytic Cell 109 -Electrolytic Clock 128 -Electrolytic Conduction 215 -Electrolytic Convection 149, 214 -Electrolytic Deposit 180 -Electrolytic Iron 308 -Electrolytic Resistance 464 -Electro-magnet 215, 337 -Electro-magnet, Annular 216 -Electro-magnet, Bar 217 -Electro-magnet, Club-foot 217 -Electro-magnet, Hinged 217 -Electro-magnet, Hughes' 291 -Electro-magnetic Ammeter 27 -Electro-magnetic and Magnetic Equipotential Surface 244 -Electro-magnetic Attraction and Repulsion 217 -Electro-magnetic Brake 86 -Electro-magnetic Clutch 128 -Electro-magnetic Control 218 -Electro-magnetic Eye 248 -Electro-magnetic Field of Force 218 -Electro-magnetic Force 260 -Electro-magnetic Gun 282 -Electro-magnetic Induction 218, 299 -Electro-magnetic Inertia 305 -Electro-magnetic Induction, Mutual 302 -Electro-magnetic Interrupter for Tuning Fork 307 -Electro-magnetic Leakage 219 -Electro-magnetic Lines of Force 219 -Electro-magnetic Liquids, Rotation of 475 -Electro-magnetic Meter 375 -Electro-magnetic Quantity 445 -Electro-magnetic Quantity, Practical Unit of 445 -Electro-magnetic Shunt .483 -Electro-magnetic Stress 219, 496 -Electro-magnetic Theory of Light 219 -Electro-magnetic Unit of Energy 220 -Electro-magnetic Vibrator 561 -Electro-magnetic Waves, 573 -Electro-magnet, Ironclad 219 -Electro-magnetism 220 -Electro-magnet, Joule's 337 -Electro-magnet, Long Range 220 -Electro-magnet, One Coil 219 -Electro-magnet, Plunger 220 -Electro-magnet, Polarized 220 -Electro-magnets, Interlocking 221 -Electro-magnets, Multiple Wire Method of Working 388 -Electro-magnet, Stopped Coil 221 -Electro-magnets, Surgical 222 -Electro-mechanical Bell 80 -Electro-mechanical Equivalent 244 -Electro-medical Baths 222 -Electro-medical Battery, Pulvermacher's 69 -Electro-metallurgy 222 -Electrometer 222 -Electrometer, Absolute 222 -Electrometer. Attracted Disc 223 -Electrometer, Capillary 224 -Electrometer Gauge 226 -Electrometer, Lane's 226 -Electrometer, Quadrant 226 -Electrometer, Thermo- 536 -Electrometer, Weight 223 -Electro-motive Force 227 -Electro-motive Force, Counter- 228 -Electro-motive Force Curve 170 -Electro-motive Force, Impressed 297 -Electro-motive Force, Motor 384 -Electro-motive Force. Oscillatory 398 -Electro-motive Force, Transverse 549 -Electro-motive Force, Unit 228 -Electro-motive Intensity 228 -Electro-motive Potential Difference 429 -Electro-motive Series 228 -Electro-motograph 229 -Electro-motor 229 -Electro-muscular Excitation 229 -Electro-negative 229 -Electro-optics 229 -Electrophoric Action 230 -Electrophorus 230 -Electro-physiology 231 -Electroplating 231, 418 -Electroplating Dynamo 198 -Electro-pneumatic Signals 231 -Electropoion Fluid 232 -Electro-positive 232 -Electro-puncture 232 -Electro-receptive 232 -Electroscope 232 -Electroscope, Bennett's 233 -Electroscope, Bohenberger's 233 -Electroscope, Condensing 233 -Electroscope, Gold Leaf 233 -Electroscope, Pith Ball 234 -Electrostatic Attraction and Repulsion 234 -Electrostatic Attraction and Repulsion. Coulomb's Law of 155 -Electrostatic Circuit 123 -Electrostatic Equipotential Surface 244 -Electrostatic Field of Force 254 -Electrostatic Force 260 -Electrostatic Induction 302 -Electrostatic Induction, Coefficient of 234 -Electrostatic Induction, Mutual 303 -Electrostatic Lines of Force 234 -Electrostatic Quantity 445 -Electrostatic Refraction 235 -Electrostatics 235 -Electrostatic Series 235 -Electrostatic Stress 236, 496 -Electrostatic Telephone 526 -Electrostatic Voltmeter 571 -Electro-thermal Equivalent 245 -Electro-therapeutics or Therapy 236 -Electrotonic State 493 -Electrotonus 236 -Electrotype 236 -Element, Chemical 236 -Element, Galvanic 264 -Element, Mathematical 237 -Element, Negative 390 -Element of a Battery Cell 237 -Element, Positive 277 -Elements, Electrical Classification of 237 -Elements, Magnetic 342 -Elements of Battery 63 -Elements, Thermo-electric 237 -Element, Voltaic 237 -Elias' Method of Magnetization 360 -Elongation 237, 540 -Elongation, Magnetic 344 -Embosser, Telegraph 237 -E. M. D. P. 238 -E. M. F. 238 -Energy 238 -Energy, Atomic 238 -Energy, Chemical 239 -Energy, Conservation of 239 -Energy, Degradation of 239 -Energy, Electric 239 -Energy, Electrical, Coefficient of 205 -Energy, Electric Transmission of 240 -Energy, Electro-magnetic, Unit of 220 -Energy, Kinetic 241 -Energy, Mechanical 241 -Energy Meter 375 -Energy, Molar 241 -Energy, Molecular 241 -Energy of an Electrified Body 241 -Energy of Dielectric 183 -Energy of Position 211 -Energy of Stress 241 -Energy, Physical 241 -Energy, Potential, or Static 241 -Energy, Radiant 446 -Energy, Thermal 242 -End-on Method 238 -End or Pole, Marked 368 -Endosmose, Electric 238 -End Play 238 -End, Unmarked 556 -English Absolute or Foot Second Unit of Resistance 465 -Engraving, Electric 245 -Entropy 242 -Entropy, Electric 242 -Epinus Condenser 242 -E. P. S. 243 -Equator, Magnetic 344 -Equator of Magnet 337 -Equipotential 244 -Equipotential Surface 498 -Equipotential Surface, Electrostatic 244 -Equipotential Surface, Magnetic and Electro-magnetic 244 -Equalizer 243 -Equalizer, Feeder 251 -Equalizing Dynamo 198 -Equivalent, Chemical 116, 244 -Equivalent Conductors 146 -Equivalent, Electro-thermal 245 -Equivalent, Joule's 311 -Equivalent Resistance 465 -Equivalents, Electro-chemical 209, 244 -Equivalent, Thermo-chemical 245 -Equivalent, Water 572 -Equivolt 245 -Erb's Standard of Electrodes 210 -Erg 245 -Erg-ten 245 -Error, Heating 286 -Escape 245 -Essential Resistance 465, 466 -Etching, Electric 245 -Ethene 397 -Ether 246 -Eudiometer 246 -Evaporation, Electric 246 -Ewing's Theory of Magnetism 356 -Exchange, Telephone 246 -Excitation, Electro-muscular 229 -Excitability, Faradic 246 -Excitability, Galvanic 247 -Excitability of Animal System, Electric 247 -Exciter 247 -Exosmose, Electric 247 -Expansion, Coefficient of 247 -Expansion, Electric 247 -Experiment, Franklin's 261 -Experiment, Hall's 284 -Experiment, Kerr's 312 -Experiment, Matteueci's 369 -Experiments, Hertz's 470 -Experiment, Volta's Fundamental 567 -Experiment with Frog, Galvani's 262 -Exploder 247 -Explorer 247 -Exploring Coil 350 -Explosive Distance 190 -Extension Bell Call 248 -Extension, Polar 423 -External Characteristic 114 -External Characteristic Curve 171 -External Circuit 123 -External Resistance 465, 467 -Extinguisher, Automatic Electric Fire 257 -Extra Current 162 -Extra-polar Region 454 -Eye, Electro-magnetic 248 -Eye, Selenium 478 - -Facsimile Telegraph 510 -Factor, Armature 45 -Fahrenheit Scale 248 -Fall of Potential 430 -False Poles, Magnetic 350 -Farad 248 -Faraday, Effect 249 -Faraday's Cube 249 -Faraday's Dark Space 249, 489 -Faraday's Disc 249 -Faraday's Net 250 -Faraday's Ring 473 -Faraday's Transformer 250 -Faraday's Voltameter 250 -Faradic 250 -Faradic Battery 63 -Faradic Brush 251 -Faradic Current 162 -Faradic Excitability 246 -Faradization 251 -Faradization, Galvano- 265 -Far Leading Dynamo 198 -Fault of a Dynamo, Ironwork 308 -Faults 251 -Faults, Contact 147 -Feed Clockwork 128 -Feeder 251 -Feeder, Equalizer 251 -Feeder, Main or Standard 251 -Feeder, Negative 251 -Feeder, Neutral 251 -Feeder, Positive 251 -Feeder, Switch 500 -Feet, Ampere 30 -Ferranti Effect 251 -Ferric Chloride Battery 63 -Ferro-magnetic 252 -Fibre and Spring Suspension 252 -Fibre Suspension 252 -Field, Air 252 -Field, Alternating 252 -Field and Armature Reaction of Dynamo, 450 -Field, Controlling 148 -Field, Deflecting 178 -Field Density 252 -Field, Distortion of 252 -Field, Drag of 254 -Field, Intensity of a Magnetic 306 -Field Magnet 337 -Field of Force . 254 -Field of Force, Electro-magnetic 218 -Field of Force, Electrostatic 254 -Field of Force, Magnetic 344 -Field of Force of a Current 255 -Field of Force, Uniform 553 -Field, Pulsatory 256 -Field, Rotating 256 -Field, Stray 256, 495 -Field, Uniform 256 -Field, Uniform Magnetic 345 -Field, Waste 256 -Figure of Merit 256 -Figures, Haldat's 284 -Figures, Lichtenberg's 327 -Figures, Magnetic 345 -Filament 256 -Filament, Magnetic 345 -Filaments, Paper 402 -File, Circuit Breaker 121 -Finder, Position 427 -Finder, Range 447 -Finder, Wire 580 -Fire Alarm, Electric Automatic 257 -Fire and Heat Alarm 17 -Fire Extinguisher, Electric Automatic 257 -Fire Cleansing 257 -Fire, St. Elmo's 494 -Fishing Box 311 -Flashing in a Dynamo or Magneto-Electric Generator 257 -Flashing of Incandescent Lamp Carbons 257 -Flashing Over 258 -Flash, Side 484 -Flat Cable 96 -Flat Coil 133 -Flat Ring Armature 45 -Flats 258 -Flats in Commutator 140 -Flexible Cord 152 -Floating Battery, De la Rive's 179 -Floating Magnets, Meyer's 370 -Floor Matting, Electric 369 -Floor Push 258 -Fluid, Depolarizing 258 -Fluid, Electric 258 -Fluid, Electropoion 232 -Fluid, Insulator. 306 -Fluid, North Magnetic 357 -Fluids, Magnetic 345 -Fluid, South Magnetic 356 -Fluid Theory, Single 486 -Fluorescence 258 -Flush Boxes 258 -Fluviograph 259 -Flux, Magnetic 345 -Fly or Flyer, Electric 259 -Foci Magnetic 259 -Fog, Electric 259 -Following Horns 259 -Foot-candle 259 -Foot, Mil- 379 -Foot-pound 259 -Foot-step 259 -Force 259 -Force, Annular 544 -Force, Axial 544 -Force, Centrifugal 112 -Force, Coercive or Coercitive 131-471 -Force, Controlling 148 -Force, Counter-electro-motive 156 -Force de Cheval 260 -Force, Electro-magnetic 260 -Force, Electro-motive 227 -Force, Electro-motive, Transverse 549 -Force, Electrostatic 260 -Force, Field of 254 -Force, Field of, of a Current 255 -Force, Field of, Electrostatic 254 -Force, Kapp Line of 312 -Force, Lines of 330 -Force, Magnetic 346 -Force, Magnetic Field of 344 -Force, Magnetic Lines of 348 -Force, Magneto-motive 365 -Force, Motor Electro-motive 384 -Force of Polarization, Back Electro-motive 156 -Force, Oscillatory, Electro-motive 398 -Force, Photo-electro-motive 410 -Forces, Composition of 260 -Forces, Parallelogram of 260 -Forces, Resolution of 261 -Force, True Contact 549 -Force, Tubes of 261 -Force, Unit of 261 -Forked Circuits 126 -Fork, Tuning, Dynamo 202 -Forming 261 -Formula of Merit 256 -Foucault Current 163 -Foundation Ring 261 -Fourth State of Matter 261 -Frame 261 -Frame, Resistance 465 -Franklinic Current 163 -Franklin's Experiment 261 -Franklin's Plate 262 -Franklin's Theory 262-486 -Free Charge 115 -Free Magnetism 356 -Frequency 262 -Frequency, High 289 -Frictional Electricity 262 -Frictional Electric Machine 333 -Frictional Heating 262 -Friction Gear, Magnetic 276 -Friction, Magnetic 295-346 -Fringe 262 -Frog, Galvani's Experiment with 262 -Frog, Rheoscopic 262 -Frying 263 -Fulgurite 263 -Fuller's Battery 63 -Fulminating Pane 262 -Fundamental Unit 554 -Furnace, Electric 263 -Fuse Block 175 -Fuse Board 263 -Fuse Box 263 -Fuse, Cockburn 263 -Fuse, Electric 264 -Fuse Links 330 -Fuse, Safety 175-475 - -Galvanic 264 -Galvanic Action, Volta's Law of 568 -Galvanic Dosage 190 -Galvanic Element 264 -Galvanic Excitability 247 -Galvanic or Voltaic Battery 76 -Galvanic or Voltaic Circle 119 -Galvanic or Voltaic Couple 156 -Galvanic Polarization 265 -Galvani's Experiment with Frog 262 -Galvanism 265 -Galvanization 265 -Galvanization, Labile 265 -Galvanized Iron 265 -Galvano-cautery 109 -Galvano-cautery, Chemical 265 -Galvano-electric Cautery 109 -Galvano-faradization 265 -Galvanometer 265 -Galvanometer, Absolute 266 -Galvanometer, Aperiodic 266 -Galvanometer, Astatic 266 -Galvanometer, Ballistic 267 -Galvanometer Constant 268 -Galvanometer, Differential 268 -Galvanometer, Direct Reading 269 -Galvanometer, Marine 269 -Galvanometer, Mirror 271 -Galvanometer, Potential 269 -Galvanometer, Proportional 269 -Galvanometer, Quantity 269 -Galvanometer, Reflecting 270 -Galvanometer, Shunt 271-483 -Galvanometer, Sine 271 -Galvanometer, Tangent 272 -Galvanometer, Torsion 273-544 -Galvanometer, Upright 274 -Galvanometer, Vertical 274 -Galvanometer, Volt and Ampere Meter 274 -Galvano-plastics 275 -Galvano-puncture 232-275 -Galvanoscope 275 -Galvano-thermal Cautery 100 -Gap, Spark 490 -Gas Battery 63 -Gas Battery, Grove's 281 -Gas Burner, Electric 93 -Gas, Carbonic Acid 108 -Gas, Electrolytic 275 -Gases, Magnetism of 357 -Gases, Mixed 275 -Gas Jet, Carcel 108 -Gas, Olefiant 397 -Gassing 275 -Gassiot s Cascade 275 -Gastroscope 275 -Gas Voltameter 564 -Gauge, Battery 64 -Gauge, Electrometer 226 -Gauss 275 -Gauss' Principle 276 -Gauss, Tangent Positions of 276 -Gauze Brush, Wire 92 -Gear, Magnetic 346 -Gear, Magnetic Friction 276 -Geissler Pump 437 -Geissler Tubes 276 -Generating Plate 277 -Generator, Current 277 -Generator Inductor 199 -Generator, Magneto-electric 362 -Generator, Magneto-electric, Flashing in a Dynamo or 257 -Generator, Motor 384 -Generator, Pyromagnetic. 442 -Generators and Motors, Commutator of Current 140 -Generator, Secondary 277-477 -Geographic Meridian 372 -German Mile Unit of Resistance 466 -German Silver 277 -German Standard Candle 99 -Gilding, Electro- 277 -Gilding Metal 277 -Gimbals 278 -Girder Armature 49 -Glass 278 -Globe or Globular Lightning 330 -Glow Discharge 187 -Gold 278 -Gold Bath 279 -Gold Leaf Electroscope 233 -Gold Stripping Bath 279 -Governor, Centrifugal 113 -Governor, Rate 449 -Graduator 279 -Gram 280 -Gram-atom 280 -Gram-molecule 280 -Graphite 280 -Gravitation 280 -Gravity, Acceleration of 280 -Gravity Ammeter 27 -Gravity Battery 64 -Gravity, Centre of 112 -Gravity Control 281 -Gravity Drop Annunciator 35 -Grease Spot 92 -Green Vitriol 562 -Grenet Battery 65 -Grid 281 -Grid Plug 420 -Grip, Cable 96 -Gross Efficiency 205 -Ground 281 -Grounded Circuit 123 -Ground Plate 417 -Ground Wire 281 -Grove's Battery 65 -Grove's Gas Battery 281 -Guard Ring 282 -Guard Tube 282 -Gun, Electro-magnetic 282 -Gutta Percha 282 -Gyration, Centre of 112 -Gyrostatic Action of Armatures 283 - -H 283 -H Armature 49 -Haarlem Magnet 337 -Hair, Removal of, by Electrolysis 283 -Haldat's Figures 284 -Hall Effect 284 -Hall Effect, Real 284 -Hall Effect, Spurious 284 -Halleyan Lines 308 -Hall's Experiment 284 -Halske's and Siemens' Battery 72 -Hand Hole 190 -Hanger Board 284 -Hanger, Cable 96 -Hanger, Cable, Tongs 97 -Harcourt's Pentane Standard 406 -Hare's Deflagrator 73 -Harmonic 23 -Harmonic Curve 174, 485 -Harmonic Motion, Simple 486 -Harmonic Receiver 284, 451 -Head Bath, Electric 284 -Head-light, Electric 285 -Head, Torsion 544 -Heat 285 -Heat and Fire Alarm 17 -Heat, Atomic 52, 285 -Heat, Electric 285 -Heat, Electric, Convection of 149, 286 -Heat, Irreversible. 286 -Heat, Mechanical Equivalent of 286 -Heat, Molecular 286 -Heat, Specific 286 -Heat, Specific, of Electricity 288 -Heat Units 288 -Heater, Electric 286 -Heating, Admiralty Rules of 12 -Heating Error 286 -Heating, Frictional 262 -Heating Magnet 286 -Heavy Carburetted Hydrogen, 397 -Hecto 288 -Hedgehog Transformer 548 -Heliograph 288 -Helix 288 -Henley's Universal Discharger 189 -Henry 288 -Henry's Coils 138 -Hermetically Sealed 289 -Hertz's Experiments 470 -Heterostatic Method 280 -Hexode Working 581 -High Bars of Commutator 289 -High Frequency 289 -High Vacuum 557 -Hinged Armature 45 -Hinged Electro-magnet 217 -Hissing 289 -Hittorf's Resistance 466 -Hittorf's Solution 289 -Hoffer's Method of Magnetization 360 -Hole Armature 45 -Hole, Hand 190 -Holders 289 -Holder, Brush 91 -Holder, Candle 99 -Holders, Carbon 107 -Holophote Lamp 321 -Holtz's Influence Machine 334 -Home Station 493 -Hood 290 -Horizontal Induction 302 -Horns 290 -Horns, Driving 132 -Horns, Following 259 -Horns, Leading 324 -Horns, Trailing 259 -Horse Power 290 -Horse Power, Actual 290 -Horse Power Curve 171 -Horse Power, Electric 290 -Horse Power Hour 290 -Horse Power, Indicated 290 -Horseshoe Magnet 337 -Hour, Ampere- 30 -Hour, Horse Power 290 -H. P. 290 -Hughes' Electro-magnet 291 -Hughes' Induction Balance 291 -Hughes' Sonometer 488 -Hughes' Telegraph 511 -Hughes' Theory of Magnetism 357 -Hughes' Type Printer 511 -Human Body, Resistance of 467 -Hydrochloric Acid Battery 66 -Hydro-electric 293 -Hydro-electric Machine 293 -Hydrogen 294 -Hydrogen, Carburetted, Heavy 397 -Hydrometer, Beaumé 78 -Hygrometer 294 -Hyperbolic Logarithms 389 -Hysteresis 295 -Hysteresis, Magnetic 294 -Hysteresis, Static 295 -Hysteresis, Viscous 295, 356 - -Idioelectrics 295 -Idiostatic Method 295 -Idle Coils 295 -Idle Poles 296 -Idle Wire 291 -Igniter 296 -I. H P. 296 -Illuminating Power 296 -Illuminating Power, Spherical 296 -Illuminating Power, Standard of, Viole's 561 -Illumination, Unit of 296 -Image, Electric 296 -Imbricated Conductor 146 -Immersion, Simple 185 -Impedance 297, 462 -Impedance, Impulsive 297 -Impedance, Oscillatory 297 -Impressed Electro-motive Force 297 -Impulse 297 -Impulsive Discharge 188 -Impulsive Impedance 297 -In-and-out, Soaking 486 -Incandescence, Electric 297 -Incandescent Lamp 321 -Incandescent Lamp Carbons, Flashing of 257 -Incandescent Lamp, Chamber of 113 -Incandescent Lamp, Life of 327 -Incandescent Lamp, Three Filament 322 -Inclination Compass 142 -Inclination, Magnetic 346 -Inclination Map 297 -Inclination or Dip, Angle of 33 -Incomplete Circuit 125 -Increment Key 314 -Independence of Currents in Parallel Circuits 297 -India Rubber 102 -Indicated Horse Power 290 -Indicating Bell 80, 297 -Indicator 298 -Indicator, Circuit 298 -Indicator, Throw-back 540 -Indicator, Volt 568 -Indifferent Electrode 210 -Indifferent Point 421 -Induced Current 163 -Induced Magnetization, Coefficient of 354, 359 -Inductance 298 -Inductance Balance 293 -Inductance Bridge 293 -Induction, Anti-, Conductor 36 -Induction, Back 55 -Induction Balance, Hughes 291 -Induction, Coefficient of Magnetic 349 -Induction, Coefficient of Mutual 301 -Induction, Coefficient of Self- 298 -Induction Coil 133 -Induction Coil, Inverted 136 -Induction Coil, Telephone 137, 526 -Induction, Cross 298 -Induction Current 163 -Induction, Electro-magnetic 218, 299 -Induction, Electrostatic 302 -Induction, Electrostatic, Coefficient of 234 -Induction, Horizontal 302 -Induction, Lateral 302 -Induction, Lines of 330 -Induction, Magnetic 302, 346 -Induction, Magnetic, Apparent Coefficient of 346 -Induction, Magnetic, Coefficient of 346 -Induction, Magnetic Dynamic 347 -Induction, Magnetic, Self- 352 -Induction, Magnetic Static 347 -Induction, Magnetic, Tube of 347 -Induction, Mutual, Electro-magnetic 302 -Induction, Mutual, Electrostatic 303 -Induction, Open Circuit 303 -Induction, Oscillatory 398 -Induction Protector, Mutual 481 -Induction, Self- 303 -Induction Sheath 303 -Induction. Unipolar 304 -Induction, Unit of Self- 304 -Induction, Vertical 304 -Inductive Capacity, Magnetic 346, 349 -Inductive Effect, Counter- 204 -Inductive Resistance 466 -Inductophone 304 -Inductor 305 -Inductor Dynamo 199 -Inductor Generator 199 -Inductor, Magneto- 363 -Inductor, Pacinotti's 400 -Inductorium 138 -Inertia 305 -Inertia, Electro-magnetic 305 -Inertia, Magnetic 347 -Infinity Plug 305, 420 -Influence, Electric 305 -Influence Machine 334 -Influence Machine, Armature of 46 -Influence Machine, Holtz 334 -Influence, Magnetic 346 -Installation 305 -Instantaneous Capacity 102 -Insulating Stool 305 -Insulating Tape 305 -Insulating Varnish 306 -Insulation, Electric 305 -Insulation, Magnetic 347 -Insulation, Oil 396 -Insulation Resistance 466 -Insulator 306 -Insulator Caps 306 -Insulator, Fluid 306 -Insulator, Line or Telegraph 306 -Intensity 306 -Intensity Armature 45 -Intensity Current 163 -Intensity, Electro-motive 228 -Intensity, Magnetic 348 -Intensity of a Magnetic Field 306 -Intensity of Magnetization 360 -Intensity, Poles of 426 -Inter-air Space 489 -Intercrossing 307 -Interference, Armature 45 -Interferric Space 489 -Interior Pole Dynamo 191 -Interlocking- Electro-magnets. 229 -Intermediate Metals, Law of 323 -Intermittent, 307 -Internal Characteristic 114 -Internal Resistance 466 -lnterpolar Conductor 307 -Interpolar Region 307 -Interpolation 307 -Interrupter, Electro-magnetic, for Tuning Fork 307 -Intrinsic Efficiency 205 -Invariable Calibration 97 -Inverse Induced Current 163 -Inverse Squares, Law of 323 -Inversion, Thermo-electric 533 -Ions 307 -Iron 308 -Ironclad Dynamo 200 -Ironclad Electro-magnet, 219 -Ironclad Magnet 356 -Iron Disc Ammeter, Eccentric 27 -Iron, Electrolytic 308 -Iron, Galvanized 265 -Ironwork Fault of a Dynamo 308 -Irreversible Heat 286 -Isochasmen Curve 171 -Isochronism 308 -Isoclinic Lines 308 -Isoclinic Map 308 -Isodynamic Lines 308 -Isodynamic Map 308 -Isoelectric Points 422 -Isogonal Lines 308 -Isogonic Map 309 -Isolated Distribution 309 -Isolated Plant 309 -Isolated Supply 309 -Isotropic 309 -Isthmus Method of Magnetization 360 -I. W. G., 309 - -J 309 -Jablochkoff Candle 160 -Jack. Spring- 492 -Jacketed Magnet 356 -Jacobi's Law 309 -Jacobi's Method of Magnetization 360 -Jacobi's Unit of Current 163 -Jacobi's Unit of Resistance 466 -Jamin Candle 100 -Jar, Leyden 325 -Jar, Lightning 330 -Jar, Luminous 332 -Jars, Leyden, Charging and Discharging 108 -Jar, Unit 554 -Jewelry 309 -Joulad 311 -Joule 311 -Joule Effect 311 -Joule's Electro-magnet 337 -Joule's Equivalent, 311 -Joint, American Twist 309 -Joint, Britannia 309 -Joint, Butt 310 -Joint Current 160 -Joint, Lap 310 -Joint, Marriage 310 -Joint, Resistance 464 -Joints in Belts 311 -Joint, Sleeve 310 -Joint, Splayed 311 -Junction Box 311 -Junction, Thermo-electric 533 - -K. 311 -Kaolin 311 -Kapp. Line of Force 312 -Kathelectrotonus 312 -Kathode 312 -Kathodic Closure Contraction 312 -Kathodic Duration Contraction 312 -K. C. C. 312 -K. D. C. 312 -Kempe's Discharge Key 315 -Keeper 312 -Kerr Effect 235, 312 -Kerr's Experiment 312 -Key 313 -Key Board 313 -Key, Bridge 313 -Key, Double Contact 314 -Key, Double Tapper 314 -Key, Charge and Discharge 313 -Key, Increment 314 -Key, Kempe's Discharge 315 -Key, Magneto-electric 315 -Key, Make and Break 316 -Key, Plug 316 -Key, Reversing 316 -Key, Sliding-contact 316 -Key, Telegraph 316 -Kicking Coil 132 -Kilo 316 -Kilodyne 316 -Kilogram 317 -Kilojoule 317 -Kilometer 317 -Kilowatt 317 -Kine 317 -Kinnersley's Thermometer 536 -Kinetics, Electro- 211 -Kinetic Energy 241 -Kirchoff's Laws 317 -Knife Break Switch 501 -Knife Edge Suspension 317 -Knife Edge Switch 501 -Knife Switch 501 -Knot 317 -Kohlrausch's Law 317 -Kookogey's Solution 318 -Krizik's Cores 318 - -L 318 -Lag, Angle of 33, 318 -Lag, Electric 332 -Lag, Magnetic 348 -Lalande & Chaperon Battery 69 -Lalande-Edison Battery 69 -Lamellar Distribution of Magnetism 357 -Laminated 318 -Laminated Core 154 -Laminated Core, Tangentially 155 -Lamination 318 -Lamination of Armature Conductors 319 -Lamination of Magnet 361 -Lamp, Arc 319 -Lamp, Arc, Double Carbon 191 -Lamp Carbons, Flashing of Incandescent 257 -Lamp, Carcel 108 -Lamp, Contact 320 -Lamp, Differential Arc 320 -Lamp Globe, Waterproof 572 -Lamp, Holophote 321 -Lamp-hour 321 -Lamp, Incandescent 321 -Lamp, Incandescent, Chamber of 113 -Lamp, Incandescent, Three Filament 322 -Lamp, Life of Incandescent 327 -Lamp, Lighthouse 322 -Lamp, Monophote 321 -Lamp, Pilot 323 -Lamp, Polyphote 323 -Lamp, Semi-Incandescent 323 -Lamp-socket 323 -Lamps, Bank of 323 -Lane's Electrometer 226 -Langdon Davies' Rate Governor or Phonophone 450 -Lenz's Law 325 -Lap Joint 310 -Lap Winding 570 -Latent Electricity 323 -Lateral Discharge 188 -Lateral Induction 302 -Latitude, Magnetic 348 -Law, Jacobi's 309 -Law, Kohlrausch's 317 -Law, Lenz's 325 -Law of Angular Currents 165 -Law of Electrolysis 213 -Law of Intermediate Metals 323 -Law of Inverse Squares 323 -Law of Magnetic Attraction and Repulsion. Coulomb's 338 -Law of Successive Temperatures 324 -Law, Magnus' 367 -Law, Ohm's 396 -Law, Pflüger's. 409 -Law, Right Handed Screw 324 -Law, Sine 486 -Laws, Kirchoff's 317 -Laws of Thermo-electricity, Becquerel's 78 -Law, Tangent 502 -Law, Voltametric 567 -Lead 324 -Lead, Angle of 33 -Lead Chloride Battery 66 -Lead of Brushes 90 -Lead of Brushes, Negative 324 -Lead, Peroxide of, Battery 69 -Lead Sulphate Battery 66 -Lead Tee 504 -Leading Horns 324 -Leading-in Wires 324 -Leak 324 -Leakage 324 -Leakage Conductor 325 -Leakage, Electro-magnetic 219 -Leakage, Magnetic. 348 -Leakage, Surface 498 -Leclanché Agglomerate Battery 66 -Leclanché Battery 66 -Leg of Circuit 325 -Legal Ohm 395 -Legal Quadrant 444 -Legal Volt 568 -Length of Spark 490 -Letter Boxes, Electric 325 -Leyden Jar 325 -Leyden Jar, Armature of 46 -Leyden Jars, Battery of 68 -Leyden Jars, Charging and Discharging 108 -Leyden Jars, Sir William Thomson's 326 -Lichtenberg's Figures 327 -Life Curve 171 -Life of Incandescent Lamp 327 -Light, Electro-magnetic, Theory of 219 -Light, Maxwell's Theory of 369 -Lighthouse Lamp 322 -Lightning 327 -Lightning Arrester 328 -Lightning Arrester, Counter-electro-motive Force 329 -Lightning Arrester Plates 329 -Lightning Arrester, Vacuum 329 -Lightning, Ascending 330 -Lightning, Globe or Globular 330 -Lightning Jar 330 -Lightning, Back Stroke or Shock of 55 -Lime, Chloride of, Battery 61 -Limit, Magnetic 348 -Limit of Magnetization 361 -Linear Current 164 -Lineman's Detector 180 -Line of Commutator, Neutral 300 -Line of Contact 330 -Line of Force, Kapp 312 -Line of Magnet, Neutral 361 -Line or Telegraph Insulator 306 -Lines, Halleyan 308 -Lines, Isoclinic 308 -Lines, Isodynamic 308 -Lines, Isogonal 308 -Lines, Isogonic 308 -Lines of Force 330 -Lines of Force, Cutting of 175 -Lines of Force, Electro-magnetic 219 -Lines of Force, Electrostatic 234 -Lines of Force, Magnetic 348 -Lines of Induction 330 -Lines of Slope 330 -Lines or Points of Least Sparking 490 -Lines, Trunk 550 -Links, Fuse 330 -Liquids, Electro-dynamic Rotation of 474 -Liquids, Electro-magnetic Rotation of 475 -Liquor, Spent 491 -Listening Cam 330 -Lithanode 331 -Load 331 -Load Curve 172 -Load of Armature 46 -Local Action 331 -Local Battery 331 -Local Circuit 331 -Local Currents 163, 331 -Localization 331 -Locus 331 -Lodestone 332 -Logarithm 332 -Logarithms, Hyperbolic 389 -Logarithms, Napierian 389 -Local Battery 66 -Long Coil Magnet 361 -Long Range Electro-magnet 220 -Long Shunt and Series Winding 579 -Long Shunt Winding 579 -Loop 332 -Loop Break 332 -Loop, Circuit 125 -Loop, Drip 192 -Lost Amperes 30 -Lost Volts 571 -Low Vacuum 557 -Luces 332 -Luminous Jar 332 -Luminous Pane 401 -Luminous Tube 550 -Lux 332 - -M 332 -Machine, Cylinder Electric 333 -Machine, Electric, Wimshurst 577 -Machine, Frictional Electric 333 -Machine, Holtz Influence 334 -Machine, Hydro-electric 293 -Machine, Influence 334 -Machine, Nairne's Electrical 389 -Machine, Plate Electrical 417 -Machine, Rheostatic 472 -Machine, Toeppler-Holtz 334 -Machine, Wimshurst 335 -Mack 335 -Magic Circle 119 -Magne-crystallic Action 335 -Magnet 335 -Magnet, Anomalous 335 -Magnet, Artificial 335 -Magnet, Axial 336 -Magnet, Bar 336 -Magnet, Bell Shaped 336 -Magnet Coils, Sheath for 481 -Magnet, Compensating 336 -Magnet, Compound 336 -Magnet, Controlling 185, 336 -Magnet, Damping 336 -Magnet, Deflection of 337 -Magnet, Directing 185 -Magnet, Electro- 215, 337 -Magnet, Equator of 337 -Magnet, Field 337 -Magnet, Haarlem 337 -Magnet, Heating 286 -Magnet, Horseshoe 337 -Magnet, Ironclad 356 -Magnet, Joule's Electro- 337 -Magnet-keeper 361 -Magnet, Lamination of 361 -Magnet, Long Coil 361 -Magnet, Natural 361 -Magnet, Neutral Line of 361 -Magnet, Normal 361 -Magnet Operation 365 -Magnet, Permanent 365 -Magnet Pole 365 -Magnet, Portative Power of 366 -Magnet, Projecting Power of a 435 -Magnet, Relay 457 -Magnet, Simple 366 -Magnet, Solenoidal 366 -Magnet, Sucking 366 -Magnet, Unipolar 366 -Magnet Coil 336 -Magnet Core 336 -Magnet Poles, Secondary 366 -Magnet Pole, Unit 366 -Magnetic Adherence 338 -Magnetic and Electro-magnetic Equipotential Surface 244 -Magnetic Attraction 338 -Magnetic Attraction and Repulsion, Coulomb's Law of 338 -Magnetic Axis 338 -Magnetic Azimuth 338 -Magnetic Battery 338 -Magnetic Bridge 338 -Magnetic Circuit 340 -Magnetic Circuit, Curve of Saturation of 174 -Magnetic Concentration of Ores 340 -Magnetic Concentrator 340 -Magnetic Continuity 340 -Magnetic Conductance and Conductivity 340 -Magnetic Control 341 -Magnetic Couple 341 -Magnetic Creeping 341 -Magnetic Curves 341 -Magnetic Cut Out 175 -Magnetic Declination 342 -Magnetic Density 342 -Magnetic Dip 342, 346 -Magnetic Discontinuity 342 -Magnetic Double Circuit 340 -Magnetic Eye, Electro- 248 -Magnetic Elements 342 -Magnetic Elongation 344 -Magnetic Equator 344 -Magnetic False Poles 350 -Magnetic, Ferro- 252 -Magnetic Field, Intensity of a 306 -Magnetic Field of Force 344 -Magnetic Field, Uniform 345 -Magnetic Figures 345 -Magnetic Filament 345 -Magnetic Fluid, North 357 -Magnetic Fluids 345 -Magnetic Flux 345 -Magnetic Force 346 -Magnetic Friction 295, 346 -Magnetic Friction Gear 276 -Magnetic Fluid, South 356 -Magnetic Foci 259 -Magnetic Gear 346 -Magnetic Hysteresis 294 -Magnetic Inclination 346 -Magnetic Induction 302 -Magnetic Induction, Apparent Coefficient of 346 -Magnetic Induction, Coefficient of 346-349 -Magnetic Induction, Dynamic 347 -Magnetic Induction, Static 347 -Magnetic Induction, Tube of 347 -Magnetic Inductive Capacity 349 -Magnetic Inertia 347 -Magnetic Influence 346 -Magnetic Insulation 347 -Magnetic Intensity 348 -Magnetic Lag 348 -Magnetic Latitude 348 -Magnetic Leakage 348 -'Magnetic Limit 348 -Magnetic Lines of Force 348 -Magnetic Mass 349 -Magnetic Matter 349 -Magnetic Memory 349 -Magnetic Meridian 349 -Magnetic Moment 349 -Magnetic Needle 349 -Magnetic Needle, Declination of the 178 -Magnetic Needle, Dip of 185 -Magnetic Needle, Oscillation of a 397 -Magnetic Output 399 -Magnetic Parallels 349 -Magnetic Permeability 349 -Magnetic Perturbations 350 -Magnetic Poles 350 -Magnetic Potential 350, 431 -Magnetic Proof Piece 350 -Magnetic Proof Plane 350 -Magnetic Quantity 350 -Magnetic Reluctance 351, 458 -Magnetic Reluctivity 351 -Magnetic Remanence 358 -Magnetic Repulsion 338 -Magnetic Resistance 458 -Magnetic Retentivity 351 -Magnetic Rotatory Polarization 351 -Magnetic Saturation 251 -Magnetic Screen 351 -Magnetic Self-induction 352 -Magnetic Separator 352 -Magnetic Shell 352 -Magnetic Shell, Strength of 352 -Magnetic Shield 353 -Magnetic Shunt 353 -Magnetic Storms 353 -Magnetic Strain 354 -Magnetic Stress 354 -Magnetic Susceptibility 254, 359 -Magnetic Tick 354 -Magnetic Top 542 -Magnetic Twist 354 -Magnetic Vane Ammeter 27 -Magnetic Variations 354 -Magnetism, Ampere's Theory of 354 -Magnetism, Blue 355 -Magnetism, Components of Earth's 356 -Magnetism, Creeping of 356 -Magnetism, Decay of 356 -Magnetism, Discharge of 356 -Magnetism, Electro 220 -Magnetism, Ewing's Theory of 356 -Magnetism, Free 356 -Magnetism, Hughes' Theory of 357 -Magnetism, Lamellar Distribution of 357 -Magnetism of Gases 357 -Magnetism, Red 357 -Magnetism, Residual 358 -Magnetism, Solenoidal Distribution of 358 -Magnetism, Sub-permanent 358 -Magnetism, Terrestrial 358 -Magnetism, Weber's Theory of 358 -Magnetization by the Earth 359 -Magnetization by Double Touch 358 -Magnetization by Separate Touch 359 -Magnetization by Single Touch 359 -Magnetization, Coefficient of Induced 359 -Magnetization Curve 172 -Magnetization, Cycle of 360 -Magnetization, Elias' Method of 360 -Magnetization, Hoffer's Method of 360 -Magnetization, Intensity of 360 -Magnetization, Isthmus Method of 360 -Magnetization, Jacobi's Method 360 -Magnetization, Limit of 361 -Magnetization, Maximum 361 -Magnetization, Specific 361 -Magnetization, Surface 356 -Magnetizing Coil 127 -Magneto 361 -Magneto Bell 80 -Magneto Call Bell 361 -Magneto-electric 361 -Magneto-electric Brake 362 -Magneto-electric Generator 362 -Magneto-electric Generator, or Dynamo, Flashing in a 257 -Magneto-electric Key 315 -Magneto-electric Telegraph 512 -Magnetograph 363 -Magneto-inductor 363 -Magnetometer 363 -Magnetometer, Differential 365 -Magnetometry 364 -Magneto-motive Force 365 -Magnetophone 367 -Magnetoscope 365 -Magnifying Spring Ammeter 28 -Magnus' Law 367 -Main Battery 66 -Main Battery Circuit 125 -Main Circuit 125 -Main or Standard Feeder 251 -Mains, Electric 367 -Make 367 -Make and Break Current 164, 367 -Make and Break Key 316 -Make-induced Current 163 -Malapterurus 367 -Map, Declination 309 -Map, Inclination 297 -Map, Isoclinic 308 -Map, Isodynamic 308 -Map, Isogonic 309 -Marié Davy's Battery 67 -Marine Galvanometer 269 -Mariner's Compass 142 -Marked End or Pole 368 -Marriage Joint 310 -Mass, Electric 368 -Mass, Magnetic 349 -Master Clock 127 -Mathematical Element 237 -Matteueci's Experiment 369 -Matter, Electric 368 -Matter, Fourth State of 261 -Matter, Magnetic 349 -Matter, Radiant 368 -Matter, Ultra Gaseous 551 -Matthiessen's Meter-gram Standard Resistance,. 466 -Matthiessen's Unit of Resistance 466 -Matting, Electric Floor 369 -Maximum Magnetization 361 -Maxwell's Theory of Light 369 -Mayer's Floating Magnet 370 -Maynooth's Battery 67 -Measurement, Absolute 8 -Measurements 370 -Mechanical Equivalent of Heat 286 -Mechanical Energy 241 -Mechanical Equivalent, Electro- 244 -Medical Battery 67 -Medium, Polarization of the 424 -Meg or Mega 370 -Meidinger's Battery 68 -Memoria Technica, Ampére's 30 -Memory, Magnetic 349 -Mercury 371 -Mercury Bichromate, Battery 63 -Mercury Circuit Breaker 121 -Mercury Cups 371 -Mercury, Sulphate of, Battery 67 -Mercurial Air Pump 16 -Meridian, Astronomical 372 -Meridian, Geographic 372 -Meridian, Magnetic. 349 -Merit, Figure of 256 -Merit, Formula of 256 -Metal, Gilding 277 -Metallic Arc 39 -Metallic Circuit 125 -Metallochromes 392 -Metallurgy, Electro- 222 -Metals, Law of Intermediate 323 -Meter. Alternating Current 373 -Meter, Ampere and Volt, Galvanometer . 274 -Meter, Balance Ampere 391 -Meter Bridge 373 -Meter Bridge, Slide 486 -Meter Candle 374 -Meter, Chemical Electric 375 -Meter, Current 375 -Meter, Electro-magnetic 375 -Meter, Energy 375 -Meter Gram Standard Resistance, Matthiesen's 466 -Meter-millimeter 375 -Meter-millimeter Unit of Resistance 466 -Meter, Neutral Wire Ampere. 391 -Meter, Quantity 445 -Meters. Ampere 39 -Meter, Thermal-Electric 375 -Meter, Time Electric 375 -Meter, Watt 375 -Method, Broadside 89 -Method, Deflection 178 -Method, End on 238 -Method, Idiostatic 295 -Method, Multiple Wire 388 -Method, Null 393 -Method of Magnetization, Elias' 360 -Method of Magnetization, Isthmus 360 -Method of Magnetization, Jacobi's 360 -Methven Standard or Screen 376 -Mho, 376 -Mica 376 -Mica, Moulded 376 -Micro 376 -Micrometer 376 -Micrometer, Arc 39, 376 -Micrometer, Spark 470 -Micron 376 -Microphone 376 -Microphone Relay 377, 457 -Microscope. Photo-electric 410 -Microtasimeter 377 -Mil 379 -Mil, Circular 379 -Mil-foot 379 -Mil-foot Unit of Resistance 467 -Milli 379 -Milligram 379 -Millimeter 379 -Milli-oerstedt 380 -Mil, Square 379 -Minute, Ampere- 30 -Mirror Galvanometer. 271 -Mixed Gases 275 -mm. 380 -Molar 380 -Molar Energy 241 -Molecular Affinity 380 -Molecular Attraction 380 -Molecular Bombardment 380 -Molecular Chain 380 -Molecular Energy 241 -Molecular Heat 286 -Molecular Rigidity 380, 473 -Molecular Shadow 480 -Molecule 380 -Moment 381 -Moment, Magnetic 349 -Moment of Couple 544 -Moment, Turning 544 -Monophote Lamp 321 -Mordey Effect 381 -Morse Receiver 381 -Morse Recorder 451 -Morse Telegraph 512 -Mortar, Electric 382 -Motion, Currents of 167 -Motograph, Electro- 229 -Motor. Compound or Compound Wound,. 382 -Motor, Differential 382 -Motor, Dynamo 200 -Motor, Electric 382 -Motor, Electro- 229 -Motor, Electro-motive Force 384 -Motor-generator 384 -Motor, Multiphase 384 -Motor, Overtype 399 -Motor, Prime 385 -Motor, Pulsating 386 -Motor, Pyromagnetic 442 -Motor, Reciprocating 385 -Motor, Series 386 -Motor, Shunt 386 -Moulded Mica 376 -Moulding 58 -Movable Secondary 477 -Mud, Battery 68 -Multiphase Currents 166 -Multiphase Motor 384 -Multiple 386 -Multiple Arc 387 -Multiple Arc Box 387 -Multiple Connected Battery 68 -Multiple-series 387, 480 -Multiple Switch 501 -Multiple Switch Board 387 -Multiple Transformer 548 -Multiple Winding 579 -Multiple Wire Method 388 -Multiplex Harmonic Telegraph 510 -Multiplex Telegraph 514 -Multiplex Telegraphy 388 -Multiplier, Schweigger's 476 -Multiplying Power 347, 349 -Multiplying Power of a Shunt 388 -Multipolar Armature 46 -Multipolar Dynamo 200 -Multipolar Electric Bath 57 -Multipolar Winding 579 -Muscular Pile 388 -Mutual Electro-magnetic Induction 302 -Mutual Electrostatic Induction 303 -Mutual Induction, Coefficient of 301 -Mutual Induction Protector 481 -Myria 388 - -Nairne's Electrical Machine 389 -Napierian Logarithms 389 -Nascent State 389 -Natural Currents 166, 389 -Natural Magnet 361 -Needle 389 -Needle Annunciator 35 -Needle, Astatic 50 -Needle, Dipping 185 -Needle, Magnetic 349 -Needle, Orientation of a Magnetic 397 -Needle of Oscillation 389 -Needle Telegraph, Single 519 -Needle, Telegraphic 389 -Negative Charge 389 -Negative Current 164 -Negative Electricity 389 -Negative, Electro- 229 -Negative Element 390 -Negative Feeder 251 -Negative Lead of Brushes 324 -Negative Plate 417 -Negative Pole 425 -Negative Potential 432 -Negative Side of Circuit 125 -Nerve and Muscle Current 164 -Nerve Currents 390 -Net Efficiency 205 -Net, Faraday's 250 -Network 390 -Neutral Armature 46 -Neutral Feeder 251 -Neutral Line of Commutator 390 -Neutral Line of Magnet 361 -Neutral Point 421 -Neutral Point of Commutator 390 -Neutral Point, Thermo-electric 390 -Neutral Relay Armature 46, 390 -Neutral Temperature 390 -Neutral Wire 390 -Neutral Wire Ampere Meter 391 -N. H. P. 391 -Niaudet's Battery 61 -Nickel 391 -Nickel Bath 391 -Night Bell 392 -Nitric Acid Battery 68 -Nobili's Rings 392 -Nodal Point 422 -Nodular Deposit 392 -Nominal Candle Power 101 -Non-conductor 392 -Non-essential Resistance 465-467 -Non-inductive Resistance 467 -Non-polar Dynamo 200 -Non-polarizable Electrodes 210 -Non-Polarized Armature 46 -Normal Magnet 361 -North Magnetic Fluid 357 -North Pole 392 -North Seeking Pole 393 -Null Method 393 -Null Point 422 - -Occlusion 393 -Oerstedt 394 -Oerstedt's Discovery 394 -Oerstedt, Milli- 380 -Ohm 394 -Ohmage 394 -Ohm, B. A. 394 -Ohm, Board of Trade 394 -Ohm, Congress 395 -Ohmic Resistance 394, 467 -Ohm, Legal 395 -Ohmmeter 395 -Ohm, Rayleigh 396 -Ohm's Law 396 -Ohm, True 396 -Oil Insulation 396 -Oil Transformer 548 -Old Armature, Siemens' 49 -Olefiant Gas 397 -Omnibus Bar 94 -Omnibus Rod 94 -Omnibus Wire 94 -One Coil Electro-magnet 219 -Open 397 -Open Circuit 125 -Open Circuit Battery 68 -Open Circuit Induction 303 -Open Circuit Oscillation 397 -Open Coil Armature 46 -Open Coil Dynamo 200 -Opening Shock 482 -Operation, Magnet 365 -Opposed Current 164 -Optics, Electro- 229 -Orders of Currents 167 -Ordinate 397 -Ordinates, Axis of 54, 397 -Ores, Electric Reduction of 453 -Ores, Magnetic Concentration of 340 -Organ, Electric 397 -Orientation of a Magnetic Needle 397 -Origin of Co-ordinates 397 -Oscillation, Centre of 112 -Oscillation, Electric 398 -Oscillation, Needle of 389 -Oscillation, Open Circuit 397 -Oscillatory 23 -Oscillatory Discharge 188 -Oscillatory Displacement 398 -Oscillatory Electro-motive Force 398 -Oscillatory Impedance 297 -Oscillatory Induction 398 -Osmose, Electric 398 -Outlet 399 -Output 399 -Output, Magnetic 399 -Output, Unit of 399 -Over-compounding 399 -Over, Flashing 258 -Overflow Alarm 18 -Over-house Telegraph 515 -Overload 399 -Overtype Dynamo or Motor 399 -Oxide of Copper Battery 68 -Ozone 399 - -Pacinotti's Inductor 400 -Pacinotti's Ring 400 -Pacinotti Teeth 400 -Page Effect 401 -Page's Revolving Armature 47 -Paillard Alloys 400 -Palladium 401 -Pane, Fulminating 262 -Pane, Luminous 401 -Pantelegraphy 402, 510 -Paper Filaments 402 -Parabola 402 -Parabolic Reflector 402 -Paraffine 402 -Paraffine Wax 402 -Paragrêles 403 -Parallax 403 -Parallel 403 -Parallel Circuits 123-126 -Parallelogram of Forces 260 -Parallels, Magnetic 349 -Paramagnetic 403 -Paramagnetism 404 -Parasitical Currents 163 -Parchmentizing 404 -Partial Current 164 -Partial Earth 203, 404 -Partial Vacuum 557 -Passive State 404 -Path, Alternative 24 -P. D. 404 -Peltier's Cross 405 -Peltier Effect 404 -Pen, Electric 405 -Pendant Cord 405 -Pendulum Circuit Breaker 121 -Pendulum, Electric 405 -Pendulum or Swinging Annunciator 35 -Pentane Standard, Harcourt's 406 -Pentode Working 581 -Percussion, Centre of 112 -Perforated Armature 45 -Perforated Core Discs 154 -Perforator 407 -Period 407 -Period, Vibration 560 -Periodic 23 -Periodic Current, Power of 433 -Periodicity 262, 408 -Peripolar Zone 582 -Permanency 408 -Permanent Magnet 365 -Permanent Magnet Ammeter 28 -Permanent State 408 -Permeability 346-349 -Permeability-temperature Curve, 174 -Permeameter 408 -Permeance 408 -Peroxide of Lead Battery 69 -Perturbations, Magnetic 350 -Pflüger's Law 409 -Phantom Wires 409 -Phase 409 -Phase, Retardation of 471 -Phenomenon, Porret's 427 -Pherope 409, 527 -Philosopher's Egg 409 -Phonautograph, 409 -Phone 409 -Phonic Wheel 409 -Phonograph 410 -Phonophone or Rate Governor, Langdon Davies' 450 -Phonozenograph 410 -Phosphorescence 410 -Phosphorous, Electrical Reduction of 410 -Photo-electric Microscope 410 -Photo-electricity 410 -Photo-electro-motive Force 410 -Photometer 411 -Photometer, Actinic 411 -Photometer, Bar 411 -Photometer, Bunsen's 412 -Photometer, Calorimetric 412 -Photometer, Dispersion 412 -Photometer, Shadow 414 -Photometer, Translucent Disc 412 -Photophore 415 -Photo-voltaic Effect 415 -Physical Energy 241 -Physiology, Electro- 231 -Piano, Electric 415 -Pickle 415 -Picture, Electric 415 -Piece, Bed 78 -Piece, Magnetic Proof 350 -Piece, Pole 423 -Pierced Core-discs, 152 -Pile 415 -Pile, Differential Thermo-electric 533 -Pile, Muscular 388 -Pile or Battery, Thermo-electric 530 -Pilot Brush 91 -Pilot Lamp 323 -Pilot Transformer 415 -Pilot Wires 415 -Pistol, Electric 416 -Pith 416 -Pith Ball Electroscope 234 -Pith-balls 416 -Pivoted Armature 47 -Pivot Suspension 416 -Plane, Magnetic Proof 350 -Plant 417 -Plant Electricity 417 -Plant, Isolated 309 -Planté's Secondary Battery, 72 -Plate, Arrester 417 -Plate Condenser 417 -Plate, Earth 203 -Plate Electrical Machine 417 -Plate, Franklin's 262 -Plate, Generating 277 -Plate, Ground 417 -Plate, Negative 417 -Plate, Positive 277, 417 -Plating Balance 417 -Plating Bath 418 -Plating, Electro- 418 -Platinized Carbon Battery 69 -Platinoid 418 -Platinum 419 -Platinum Alloy 419 -Platinum Black 419 -Platinum Silver Alloy 419 -Platinum Sponge 419 -Play, End 238 -Plow 420 -Plücker Tubes 420 -Plug 420 -Plug Cut Out 175 -Plug, Double 191 -Plug, Grid 420 -Plug, Infinity 305, 420 -Plug Key 316 -Plug Switch 420 -Plumbago 421 -Plunge Battery 69 -Plunge 421 -Plunger and Coil 131 -Plunger and Coil, Differential 132 -Plunger, Coil and 131 -Plunger Electro-magnet 220 -Pneumatic Battery 69 -Pneumatic Signals, Electro- 231 -P.O. 421 -Pockets, Armature 47 -Poggendorf's Solution 421 -Point, Contact 147 -Point, Indifferent 421 -Point, Neutral 421 -Point. Nodal 422 -Point, Null 422 -Point of Commutator, Neutral 390 -Point Poles 422 -Points, Consequent 422 -Points, Corresponding 422 -Points, Iso-electric 422 -Points of Derivation 180, 423 -Point, Thermo-electric Neutral 390 -Polar Angle 423 -Polar Extension 423 -Polarity, Diamagnetic 181, 423 -Polarity, Resultant 470 -Polarization 423 -Polarization, Back Electro-motive force of 156 -Polarization Capacity 424 -Polarization, Dielectric 183 -Polarization, Galvanic 265 -Polarization, Magnetic Rotary 351 -Polarization of the Medium 424 -Polarized Armature 47 -Polarized Electro-magnet 220 -Polarized Relay 458 -Polarized Relay, Tongue of 542 -Polarizing Current 164 -Polar Region 424 -Polar Span 424 -Polar Span, Angle of 32, 423 -Polar Tips 423 -Polar Zone 582 -Pole, Analogous 31, 425 -Pole, Antilogous 425 -Pole, Armature 47 -Pole, Austral 54 -Pole, Boreal 85 -Pole Brackets, Telegraph 515 -Pole Changer 425 -Pole Changing Switch, 501 -Pole Dynamo, Interior 199 -Pole, Magnet 366 -Pole, Negative 425 -Pole, North 392 -Pole, North-seeking 393 -Pole or End, Marked 368 -Pole Piece 423 -Pole Pieces 425 -Pole, Positive 425 -Pole, Salient 426 -Pole, Terminal 529 -Pole Tips 290, 426 -Pole, Traveling 426 -Pole, Unit Magnet 366 -Poles 425 -Poles, Compensating 426 -Poles, Consequent 146 -Poles, Idle 296 -Poles, Magnetic 350 -Poles, Magnetic, False 350 -Poles of Intensity 426 -Poles of Verticity 426, 560 -Poles, Point 422 -Poles, Secondary 478 -Poles, Secondary Magnet 366 -Polyphase Currents 167 -Polyphote Lamp 323 -Popgun, Electric 282 -Porous Cell 427 -Porous Cup 159, 426 -Porret's Phenomenon 427 -Portative Power of Magnet 366 -Portelectric Railroad 427 -Portrait, Electric 415 -Position, Energy of 241 -Position Finder 427 -Position, Sighted 484 -Positive Current 164 -Positive Direction 428 -Positive Electricity 428 -Positive Element 277 -Positive Feeder 251 -Positive Plate 277, 417 -Positive Pole 425 -Positive Potential 432 -Positive Side of Circuit 125 -Post Office 428 -Posts, Binding, or Screws 81 -Potential 428 -Potential, Absolute 428 -Potential, Constant 429 -Potential Difference, Contact 147 -Potential Difference, Electric 429 -Potential Difference, Electro-motive 429 -Potential, Electric Absolute 429 -Potential, Fall of 430 -Potential Galvanometer 269 -Potential in Armature, Curve of Distribution of 172 -Potential, Magnetic 350, 431 -Potential, Negative 432 -Potential or Static Energy 241 -Potential, Positive 432 -Potential Regulation, Constant 455 -Potential, Unit of Electric 432 -Potential, Zero 432, 582 -Potentiometer 432 -Poundal 433 -Pound-foot 259 -Power 438 -Power, Candle 100 -Power, Directive 187 -Power, Electric 433 -Power, Horse 290 -Power, Illuminating 296 -Power, Multiplying 349 -Power of Magnet, Portative 366 -Power of Periodic Current 433 -Powers of Ten 527 -Power, Stray 495 -Power, Thermo-electric 533 -Press Button 94 -Pressel 434 -Pressure 434 -Pressure, Electric 434 -Pressure, Electrification by 434 -Primary 434 -Primary Ampere-turns 31, 551 -Primary Battery 69, 434 -Prime 434 -Prime Conductor 146, 434 -Prime Conductor, Coatings of a 129 -Prime Motor 385 -Principle, Gauss' 276 -Printing Telegraph 515 -Probe, Electric 435 -Projecting Power of a Magnet 435 -Prony Brake 435 -Proof Piece, Magnetic 350 -Proof-plane 436 -Proof Plane, Magnetic 350 -Proof-sphere 436 -Proportional Galvanometer 269 -Proportionate Arms 436 -Prostration, Electric 437 -Protector, Body 84 -Protector, Comb 437 -Protector, Electric 437 -Pull 437 -Pulsatory Current 164 -Pulsatory Field 256 -Pulsating Motor 386 -Pulvermacher's Electro-medical Battery 69 -Pump, Geissler 437 -Pump, Sprengel 439 -Pump, Swinburne 440 -Pumping 439 -Puncture-electro 232 -Puncture-galvano 232 -Push Button 93. 98, 440 -Push, Desk 180 -Push, Floor 258 -Pyro-electricity 441 -Pyromagnetic Generator 442 -Pyromagnetic Motor 441 -Pyromagnetism 443 -Pyrometer, Siemens' Electric 443 - -Q 443 -Quad 288, 443 -Quadrant 288, 443 -Quadrantal Deviation 180 -Quadrant, Legal 444 -Quadrant, Standard 444 -Quadrature 444 -Quadruplex Telegraph 515 -Qualitative 444 -Quality of Sound 444 -Quantitative 444 -Quantity 444 -Quantity Armature 47 -Quantity, Electric 444 -Quantity, Electro-magnetic 445 -Quantity, Electro-magnetic, Practical Unit of 445 -Quantity, Electrostatic 445 -Quantity Galvanometer 269 -Quantity, Magnetic 350 -Quantity Meter 445 -Quartz 445 -Quicking 446 - -R 446 -Racing of Motors 446 -Radial Armature 47 -Radian 446 -Radiant Energy 446 -Radiant Matter 368 -Radiation 446 -Radicals 446 -Radiometer 447 -Radiometer, Electric 447 -Radio-micrometer 447 -Radiophony 447 -Railroad, Portelectric 427 -Range Finder 447 -Rate Governor 449 -Rate Governor or Phonophone, Langdon Davies' 450 -Rated Candle Power 101 -Ratio Arms 437 -Ratio, Core 154 -Ratio, Shunt 483 -Ratio, Velocity 560 -Ray, Electric 450 -Rayleigh Ohm 396 -Reaction Coil 132 -Reaction of a Dynamo Field and Armature 450 -Reaction of Degeneration 179 -Reactions, Anodic 36 -Reactions, Armature 47 -Reaction Telephone 527 -Reaction Wheel 259 -Reading Galvanometer, Direct 269 -Reading, Sound 489 -Reading Telescope 450 -Real Efficiency of Secondary Battery 205 -Real Hall Effect 284 -Réaumur Scale 450 -Recalescence 451 -Receiver 451 -Receiver, Harmonic 284, 451 -Receiver, Morse 381 -Receptive, Electro- 232 -Recharge 115 -Reciprocal 451 -Reciprocating Motor 385 -Recoil Circuit 125 -Recorder, Chemical 117 -Recorder, Morse 451 -Recorder, Siphon 452 -Record, Telephone 451 -Rectification of Alcohol, Electric 18 -Rectified Current 164 -Rectilinear Current 165 -Red Varnish 559 -Red Magnetism 357 -Redressed Current 165 -Reduced Resistance 467 -Reducteur for Ammeter 453 -Reducteur for Voltmeter 453 -Reduction of Ores, Electric 453 -Reduction of Phosphorous, Electrical 410 -Reflecting Galvanometer 270 -Reflector, Parabolic 402 -Refraction, Electric Double 454 -Refraction, Electrostatic 235 -Refreshing Action 454 -Region, Extra-polar 454 -Region, Intrapolar 307 -Region, Polar 424 -Register, Electric 454 -Register, Telegraphic 454 -Regulation, Constant Current 454 -Regulation, Constant Potential 455 -Regulation of Alternating Current Dynamo 195 -Regulation of Dynamos 455 -Reguline 456 -Relative 456 -Relative Calibration 98 -Relay 456 -Relay Bell 80 -Relay Bells 457 -Relay, Box Sounding 457 -Relay Connection 457 -Relay, Differential 457 -Relay Magnet 457 -Relay, Microphone 377, 457 -Relay, Neutral, Armature 390 -Relay, Polarized 457 -Reluctance 458 -Reluctance, Magnetic 351, 458 -Reluctance, Unit of 438 -Reluctivity 459 -Reluctivity, Magnetic 351 -Remanence 459 -Remanence, Magnetic 358 -Removal of Hair by Electrolysis 283 -Renovate 115 -Repeater 459 -Repeater, Telegraph 518 -Replenisher, Sir Wm. Thomson's 459 -Repulsion, Magnetic 338 -Repulsion and Attraction, Electrostatic 234 -Repulsion and Attraction, Electro-magnetic 217 -Reservoir, Common 460 -Residual Atmosphere 460 -Residual Capacity 103 -Residual Charge 116 -Residual Magnetism 358 -Residue, Electric 116, 460 -Resin 460 -Resinous Electricity 461 -Resistance 461 -Resistance, Apparent 297, 462 -Resistance, Assymmetrical 462 -Resistance Box 462 -Resistance, B. A. Unit of 462 -Resistance Box, Sliding 463 -Resistance, Breguet Unit of 463 -Resistance Bridge 577 -Resistance Coil 137 -Resistance Coil, Standard 464 -Resistance, Carbon 463 -Resistance, Combined 464 -Resistance, Compensating 144 -Resistance, Critical 464 -Resistance, Dielectric 183, 464 -Resistance, Digney Unit of 464 -Resistance, Electrolytic 464 -Resistance, English Absolute or Foot-second Unit of 465 -Resistance, Equivalent 465 -Resistance, Essential 465 -Resistance, External 465 -Resistance Frame 465 -Resistance, German Mile Unit of 466 -Resistance, Hittorf's 466 -Resistance, Inductive 466 -Resistance, Insulation 466 -Resistance, Internal 466 -Resistance, Jacobi's Unit of 466 -Resistance, Joint 464 -Resistance, Magnetic 351, 458 -Resistance, Matthiessen's Meter-gram Standard of 466 -Resistance, Matthiessen's Unit of 466 -Resistance, Meter-millimeter Unit of 466 -Resistance, Mil-foot Unit of 467 -Resistance, Non-essential 465, 467 -Resistance, Non-inductive 467 -Resistance of Human Body 467 -Resistance, Ohmic 394, 467 -Resistance, Reduced 467 -Resistance, Siemens' Unit of 467 -Resistance, Specific 467 -Resistance. Specific Conduction 467 -Resistance, Spurious 467 -Resistance, Steadying 468 -Resistance, Swiss Unit of 468 -Resistance, Thomson's Unit of 468 -Resistance to Sparking 490 -Resistance, True 467 -Resistance, Unit 468 -Resistance, Unit of, B. A. 78 -Resistance, Varley's 559 -Resistance, Varley's Unit of 468 -Resistance, Virtual 297 -Resistance, Weber's Absolute Unit 468 -Resolution of Forces 261 -Resonator, Electric 468-470 -Rest, Currents of 167 -Resultant 470 -Resultant Polarity 470 -Retardation 470 -Retardation of Phase 471 -Retentivity 471 -Retentivity, Magnetic 351 -Retort Carbon 471 -Return 471 -Return Circuit 125 -Return, Earth 203 -Return Stroke 55 -Reversal, Thermo-Electric 533 -Reverse Current Working 581 -Reverse-induced Current 163 -Reverser, Current 165 -Reversibility 471 -Reversible Bridge 472 -Reversing Key 316 -Reversing Switch 501 -Revivify 115 -Revolving Armature, Page's 47 -Rheochord 472 -Rheometer 472 -Rheomotor 472 -Rheophore 472 -Rheoscope 472 -Rheoscopic Frog 262 -Rheostat 472 -Rheostat Arm 472 -Rheostatic Machine 472 -Rheostat, Wheatstone's 472 -Rheotome 473 -Rheotrope 473 -Rhigolene 473 -Rhumbs 473 -Rhumkorff Coil 138, 473 -Ribbon Coil 138 -Ribbon Core 154 -Right-handed Screw Law 324 -Rigidity, Molecular 380, 473 -Ring, Ampere 30 -Ring Armature 48 -Ring. Collecting 139 -Ring Contact 473 -Ring Core 155 -Ring, Dynamo 200 -Ring, Faraday's 473 -Ring, Foundation 261 -Ring, Guard 282 -Ring, Pacinotti's 400 -Rings, Electric 392 -Rings, Nobili's 392 -Ring, Split, Commutator 141 -Roaring 474 -Rocker 474 -Rocker Arms 50, 474 -Rod, Bus 94 -Rod, Discharging 189 -Rod, Omnibus 94 -Roget's Spiral 474 -Rolling Armature 49 -Rosin 460 -Rotary Polarization, Magnetic 351 -Rotating Brush 91 -Rotating Field 256 -Rotation of Liquids, Electro-dynamic 474 -Rotation of Liquids, Electro-magnetic 475 -Rotatory Currents 167 -Rubber 102, 475 -Rubber, India 102 - -Saddle Bracket 475 -Safety Catch 175 -Safety Cut Out 175 -Safety Device 475 -Safety Fuse 175, 475 -Safety Fuse, Plug, or Strip 475 -Sal Ammoniac Battery 69 -Salient Pole 426 -Salt 475 -Salt, Dronier's 192 -Salt or Sea-salt Battery 69 -Sand Battery 90 -Saturated 476 -Saturation, Magnetic 351 -Saw, Electric 476 -Scale, Fahrenheit 248 -Scale, Réaumur 450 -Scale, Tangent 502 -Schweigger's Multiplier 476 -Scratch Brushes 476 -Screen, Electric 476 -Screen, Magnetic 351 -Screen, Methven 376 -Screws or Posts, Binding 81 -Sealed, Hermetically 289 -Sea Salt or Salt Battery 69 -Secohm 288 -Second, Ampere- 30 -Secondary Actions 477 -Secondary Ampere-turns 31, 551 -Secondary Battery 70 -Secondary Battery, Efficiency of, Quantity 205 -Secondary Battery, Planté's 72 -Secondary Clock 127 -Secondary Current 166 -Secondary Generator 277, 477 -Secondary Magnet Poles 366 -Secondary, Movable 477 -Secondary Plates, Colors of 478 -Secondary Poles 478 -Secretion Current 166 -Section Trolley 549 -Sectioned Coils 138 -Seebeck Effect 478 -Segments 56 -Segments, Commutator 56 -Selenium 478 -Selenium Cell 478 -Selenium Eye 478 -Self-exciting Dynamo 201 -Self-induction 303 -Self-induction, Magnetic 352 -Self-induction, Unit of 304 -Self-repulsion 478 -Self-winding Electric Clock 128 -Semi-circular Deviation 181 -Semi-conductors 478 -Semi-incandescent Lamp 323 -Sender, Zinc 582 -Sensibility 479 -Sensitiveness, Angle of Maximum 479 -Separate Circuit Dynamo 201 -Separate Touch 359, 479 -Separate Touch, Magnetization by 359 -Separately Excited Dynamo 201, 479 -Separation of Electricities 479 -Separator 479 -Separator, Magnetic 352 -Series 479 -Series and Long Shunt Winding 579 -Series and Separate Coil Winding 579 -Series and Short Shunt Winding 580 -Series, Contact 147 -Series Dynamo 201 -Series, Electro-chemical 209 -Series, Electro motive 228 -Series, Electrostatic 235 -Series Motor 386 -Series, Multiple- 387 -Series-multiple 480 -Series, Thermo-electric 534 -Series Transformer 548 -Series Winding 579 -Service Conductors 480 -Serving 480 -Shackle 480 -Shadow, Electric 480 -Shadow, Molecular 480 -Shadow Photometer 414 -Sheath for Magnet Coils 481 -Sheath for Transformers 481 -Sheath, Induction 303 -Sheet Current 166 -Shell, Magnetic 352 -Shell, Strength of Magnetic 352 -Shellac 481 -Shellac Varnish 481 -Shield, Anti-magnetic 37 -Shield, Magnetic 351, 353 -Shielded 481 -S. H. M. 482 -Shock, Back, or Stroke of Lightning 55 -Shock, Break 482 -Shock, Electric 482 -Shock, Opening 482 -Shock, Static 482 -Short Circuit 482 -Short Circuit Working 482 -Short Fall Air Pumps 16 -Short Shunt Winding 579 -Shovel Electrodes 483 -Shower Bath, Electric 57 -Shunt 483 -Shunt Box 483 -Shunt Circuit 123, 126 -Shunt Dynamo 202 -Shunt, Electro-magnetic 483 -Shunt, Galvanometer 271, 483 -Shunt, Magnetic 353 -Shunt Motor 386 -Shunt. Multiplying Power of a 388 -Shunt Ratio 483 -Shunt Winding 580 -Shuttle Armature 49 -Shuttle Current 483 -Shuttle Winding 483, 580 -Side Flash 484 -Siemens and Halske's Battery 72 -Siemens' Differential Voltameter 564 -Siemens' Electro-dynamometer 212 -Siemens' Old Armature 49 -Siemens' Unit of Resistance 467 -Sighted Position 484 -Signaling, Velocity of 560 -Signals, Electro-pneumatic 231 -Signal, Telegraph 519 -Silent Discharge 187, 189, 206 -Silver 484 -Silver Bath 484 -Silver, German 277 -Silver Stripping Bath 484 -Silver Voltameter 565 -Simple Arc 39 -Simple Circuit 126 -Simple Harmonic Motion 486 -Simple Immersion 185 -Simple Magnet 366 -Simple Substitution 485 -Sims-Edison Torpedo 543 -Sine Curve 174, 485 -Sine Galvanometer 271 -Sine Law 486 -Sines, Curve of 173, 485 -Single Coil Dynamo 202 -Single Curb Working 581 -Single Fluid Theory 486 -Single Fluid Voltaic Cell 486 -Single Needle Telegraph 519 -Single Touch, Magnetization by 359 -Sinistrotorsal 486 -Sinuous Current 166 -Sinusoidal Curve 174, 485 -Siphon Recorder 452 -Sir William Thomson's Battery 72 -Skin Effect 486 -Skrivanow Battery 72 -Sled 486 -Sleeve, Joint 310 -Slide, Balance 374 -Slide Bridge 374 -Slide Meter Bridge 486 -Sliding Condenser 144 -Sliding-contact Key 316 -Sliding Resistance Box 463 -Slope, Lines of 330 -Smee's Battery 73 -S. N. Code 486 -Snap Switch 501 -Soaking-in-and-out 486 -Socket, Lamp 323 -Socket, Wall 572 -Soldering, Electric 487 -Solenoid 487 -Solenoid Ammeter 28 -Solenoidal Distribution of Magnetism 358 -Solenoidal Magnet 366 -Solid Earth 203 -Solutions, Battery, Chromic Acid 73 -Solution, Chutaux's 119 -Solution, Delaurier's 179 -Solution, Hittorf's 289 -Solution, Kookogey's 318 -Solution, Poggendorf's 421 -Solution, Striking 496 -Solution, Tissandier's 542 -Solution, Trouvé's 549 -Sonometer, Hughes' 488 -Sonorescence 488 -Sound, Characteristics of 114 -Sounder 488 -Sounders, Tin 542 -Sound, Quality of 444 -Sound Reading 489 -South Magnetic Fluid 356 -Space, Clearance 489 -Space, Crookes' Dark 489 -Space, Dark, Faraday's 249, 489 -Space, Faraday's Dark 249, 489 -Space, Inter-air 489 -Space, Interferric 489 -Span, Polar 424 -Span, Polar, Angle of the 32 -Spark Arrester 489 -Spark Coil 489 -Spark Discharge 189 -Spark, Duration of Electric 490 -Spark Gap 490 -Spark, Length of 490 -Spark Micrometer 470 -Spark Tube 491 -Sparking 490 -Sparking Distance 190 -Sparking, Lines or Points of Least 490 -Sparking, Resistance to 490 -Specific Conduction Resistance 467 -Specific Conductivity 145 -Specific Heat 286 -Specific Heat of Electricity 491 -Specific Inductive Capacity 103 -Specific Magnetization 361 -Specific Resistance 467 -Speech, Articulate 50 -Speed, Critical 157 -Spent Acid 491 -Spent Liquor 491 -Spherical Armature 49 -Spherical Candle Power 101 -Spherical Illuminating Power 296 -Sphygmophone 491 -Sphygmophone, Electric 491 -Spiders 491 -Spiral 492 -Spiral Battery 73 -Spiral, Roget's 474 -Spiral Winding 492 -Spirit Compass 143 -Splayed Joint 311 -Splice Box 492 -Split Battery 73 -Split Ring Commutator 141 -Spluttering 492 -Sponge, Platinum 419 -Spot, Grease 92 -Sprengel Pump 439 -Spring Ammeter 28 -Spring and Fibre Suspension 252 -Spring-contact 148 -Spring Control 492 -Spring Jack Cut-out 493 -Spurious Hall Effect 284 -Spurious Resistance 467 -Spurious Voltage 493 -Square Mil 379 -Square Wire 493 -Squares, Law of Inverse 323 -St. Elmo's Fire 494 -Staggering 493 -Standard Candle 101 -Standard Candle, German 99 -Standard, Harcourt's Pentane 406 -Standard, Methven 376 -Standard of Illuminating Power, Viole's 561 -Standard or Main Feeder 251 -Standard Quadrant 444 -Standard Resistance Coil 464 -Standard Voltaic Cell 109 -Standard Voltaic Cell, Daniell's 109 -Standard Voltaic Cell, Latimer Clark's. 110 -State, Electrotonic 493 -State, Nascent 389 -State of Matter, Fourth 261 -State, Passive 404 -State, Permanent 408 -Static Breeze 493 -Static Condenser, Armature of 46 -Static Electricity 493 -Static Hysteresis 295 -Static Induction, Magnetic 347 -Static Shock 482 -Station, Central 493 -Station, Distant 493 -Station, Home 493 -Station, Transforming 494 -Steadying Resistance 468 -Steel 494 -Steeling 494 -Steel Yard Ammeter 28 -Step-by-step Telegraph 506 -Step-by-step Telegraphy 494 -Step-down 494 -Step, Foot- 259 -Sticking 494 -Stool, Insulating 305 -Stopped Coil Electro-magnets 221 -Stopping Off 495 -Storage Battery 70 -Storage Battery Changing Switch 501 -Storage Battery, Planté's 72 -Storage Capacity 105, 495 -Storage of Electricity 495 -Storms, Electric 495 -Storms. Magnetic 353 -Strain 495 -Strain, Dielectric 183 -Strain, Magnetic 354 -Stranded Conductor Armature 49 -Stranded Core 155 -Stray Field 256, 495 -Stray Power 495 -Streamlets. Current 495 -Strength, Dielectric 183 -Strength of Magnetic Shell 352 -Stress 495 -Stress, Dielectric 496 -Stress, Electro-magnetic 219, 496 -Stress, Electrostatic 236, 496 -Stress, Energy of 241 -Stress, Magnetic 354 -Striae, Electric 496 -Striking Distance 496 -Striking Solution 496 -Stripping 496 -Stripping Bath 57 -Stripping Bath, Gold 279 -Stripping Bath, Silver 484 -Stroke, Back 55 -Stroke or Shock of Lightning, Back 55 -Stroke, Return 55 -Sub-branch 496 -Sub-main 496 -Sub-permanent Magnetism 358 -Substitution, Simple 485 -Subway, Electric 496 -Successive Temperatures, Law of 324 -Sucking Coil 182 -Sucking Magnet 366 -Sulphate of Lead Battery 66 -Sulphate of Mercury Battery 67 -Sulphating 497 -Sulphur Dioxide 497 -Sulphuric Acid 497 -Sulphuric Acid Voltameter 564 -Sulphurous Acid Gas 497 -Sunstroke, Electric 497 -Superficial Density, Electric 180 -Supersaturated, 497 -Supply, Isolated 309 -Surface 497 -Surface Density 498 -Surface, Equipotential 498 -Surface Leakage 498 -Surface Magnetization 356 -Surgical Electro-magnet 222 -Surging Discharge 188 -Surveyors' Compass 143 -Susceptibility, Magnetic 354, 359 -Suspension 498 -Suspension, Bifilar 498 -Suspension, Fibre 252 -Suspension, Knife Edge 317 -Suspension, Pivot 416 -Suspension, Spring and Fibre 252 -Suspension, Torsion 545 -Suspension Wire of Cable 97 -Swaging. Electric 499 -Swelling Current 167 -S. W. G. 499 -Swinburne Pump 440 -Swinging Earth 203 -Swinging or Pendulum Annunciator 35 -Swiss Unit of Resistance 468 -Switch 499 -Switch, Automatic 500 -Switch Board 500 -Switch Board, Multiple 387 -Switch Board, Trunking 550 -Switch, Break-down 88 -Switch, Changing 500 -Switch, Changing Over 500 -Switch, Circuit Changing 500 -Switch, Double Break 500 -Switch, Double Pole 500 -Switch Feeder 500 -Switch, Knife 501 -Switch, Knife Break 501 -Switch, Knife Edge 501 -Switch, Multiple 501 -Switch, Plug 420 -Switch, Pole Changing 501 -Switch, Reversing 501 -Switch, Snap 501 -Switch, Storage Battery Changing 501 -Switch, Three Way 501 -Switches, Distributing 190 -Symmer's Theory 191 -Sympathetic Vibration 501, 561 -System, Block 83 -System of Co-ordinates 150 -System, Tower 545 - -T 501 -Tailing Current 501 -Tailings 501 -Talk, Cross 158 -Tamidine 502 -Tangent Galvanometer 272 -Tangent Law 502 -Tangent Positions of, Gauss 276 -Tangent Scale 502 -Tangentially Laminated Core 155 -Tank, Cable 97 -Tape, Insulating 305 -Tapper Key, Double 314 -Teazer 504 -Technica, Memoria, Ampére's 30 -Tee, Lead 504 -Teeth, Pacinotti 400 -Tel-autograph 504 -Tele-barometer, Electric 504 -Telegraph, A. B. C. 504 -Telegraph, Autographic 510 -Telegraph, Automatic 504 -Telegraph, Dial 505 -Telegraph, Double Needle 506 -Telegraph, Duplex 506 -Telegraph, Duplex, Bridge 506 -Telegraph, Duplex, Differential 507 -Telegraph Embosser 237 -Telegraph, Facsimile 510 -Telegraph, Harmonic Multiplex 510 -Telegraph. Hughes' 511 -Telegraph Insulator 306 -Telegraph Key 316 -Telegraph, Magneto-electric 512 -Telegraph, Morse 512 -Telegraph, Multiplex 514 -Telegraph, Single Needle 519 -Telegraph, Overhouse 515 -Telegraph Pole Brackets 515 -Telegraph, Printing 515 -Telegraph, Quadruplex 515 -Telegraph Repeater 518 -Telegraph Signal 519 -Telegraph, Step-by-step 506 -Telegraph, Wheatstone's, A. B. C. 521 -Telegraph. Writing 521 -Telegraphic Alphabet 19 -Telegraphic Code 130, 511 -Telegraphic Needle 389 -Telegraphic Register 454 -Telegraphy, Multiplex 388 -Telegraphy, Step-by-step 494 -Telemanometer, Electric 521 -Telemeter, Electric 521 -Telepherage 522 -Telephone 522 -Telephone, Bi- 524 -Telephone, Capillary 525 -Telephone, Carbon 525 -Telephone, Chemical 526 -Telephone, Electrostatic 526 -Telephone Exchange 246 -Telephone Induction Coil 137, 526 -Telephone, Reaction 527 -Telephone Record 451 -Telephone, Thermo-electric 527 -Telephone Tinnitus 542 -Telephotography 521 -Telephote 527 -Telescope, Reading 450 -Teleseme 527 -Tele-thermometer 527 -Terminal 529 -Terminal Pole 529 -Terminal Voltage 562 -Temperature, Absolute 8 -Temperature, Neutral 390 -Temperatures, Laws of Successive 324 -Tempering, Electric 527 -Temporary Magnetism or Magnetization 357 -Ten, Powers of 527 -Tension 529 -Tension, Disruptive 189 -Tension, Electric 529 -Terrestrial Magnetism 358 -Tetanus, Acoustic 529 -Tetrode Working 581 -Theatrophone 529 -Theory, Contact 148 -Theory, Double Fluid 191 -Theory, Franklin's 262 -Theory of Dimensions 184 -Theory of Light, Electro-magnetic 219 -Theory of Light, Maxwell's 369 -Theory of Magnetism, Ampére's 354 -Theory of Magnetism, Ewing's 356 -Theory of Magnetism, Hughes' 357 -Theory of Magnetism, Weber's 358 -Theory, Symmer's 191 -Therapeutic Electrode 210 -Therapeutics, Electro- 236 -Therm 529 -Thermaesthesiometer 530 -Thermal Electric Meter 375 -Thermal Equivalent, Electro- 245 -Thermal Energy 242 -Thermic Balance 85 -Thermo Call 530 -Thermo-chemical Battery 530 -Thermo-chemical Equivalent 245 -Thermo-electric Battery or Pile 530 -Thermo-electric Call 531 -Thermo-electric Couple 532 -Thermo-electric Current 167 -Thermo-electric Diagram 532 -Thermo-electric Element 237 -Thermo-electric Inversion 533 -Thermo-electric Junction 533 -Thermo-electric Neutral Point 390 -Thermo-electric Pile, Differential 533 -Thermo-electric Power 533 -Thermo-electric Reversal 533 -Thermo-electric Series 534 -Thermo-electric Telephone 527 -Thermo-electric Thermometer 535 -Thermo-electricity 533 -Thermo-electricity, Laws of, Becquerel's 78 -Thermo-electricity, Volta's Law of 568 -Thermo-electrometer 536 -Thermolysis 535 -Thermo-multiplier 536 -Thermometer 535 -Thermometer, Electric 535 -Thermometer, Kinnersley's 536 -Thermometer, Tele- 527 -Thermometer, Thermo-electric 535 -Thermophone 537 -Thermostat, Electric 537 -Third Brush 91 -Thomson Effect 538 -Thomson's Replenisher, Sir William 459 -Thomson's Battery, Sir William 72 -Thomson's Unit of Resistance 468 -Three Filament Incandescent Lamp 322 -Three Way Switch 501 -Three Wire System 539 -Throw 237, 540 -Throw-back Indicator 540 -Thrust Bearings 540 -Thunder 540 -Ticker 540 -Tick, Magnetic 354 -Timbre 444 -Time Constant 541 -Time Cut-outs 541 -Time Electric Meter 375 -Time-fall 541 -Time-reaction 541 -Time-rise 541 -Tin 541 -Tin Sounders 542 -Tinnitus, Telephone 542 -Tips, Polar 423 -Tips, Pole 290, 426 -Tissandier's Solution 542 -Toeppler-Holtz Machine 334 -Tongs, Cable Hanger 97 -Tongs, Discharging 189 -Tongue of Polarized Relay 542 -Tongue of Polarized Relay, Bias of 542 -Toothed Core-discs 154 -Top, Magnetic 542 -Torpedo, Electric 543 -Torpedo, Sims-Edison 543 -Torque 543 -Torque, Curve of 174 -Torricellian Vacuum 557 -Torsion Balance, Coulomb's 544 -Torsion Galvanometer 273, 544 -Torsion Head 544 -Torsion Suspension 545 -Total Earth 203 -Touch 545 -Touch, Separate 479 -Tourmaline 545 -Tower, Electric 545 -Tower System 545 -Trailing Horns 259 -Transformer 545 -Transformer, Commuting 547 -Transformer, Continuous Alternating 547 -Transformer, Continuous Current 384, 547 -Transformer, Core 547 -Transformer, Faraday's 250 -Transformer, Hedgehog 548 -Transformer, Multiple 548 -Transformer, Oil 548 -Transformer, Pilot 415 -Transformer, Series 548 -Transformer. Sheath for 481 -Transforming Station 494 -Transformer, Welding 548, 575 -Translator 519 -Translucent Disc Photometer 412 -Transmitter 548 -Transmitter, Carbon 549 -Transmission of Energy, Electric 240 -Transposing 549 -Transverse Electro-motive Force 549 -Trap, Bug 92 -Traveling Pole 426 -Trembling Bell 78 -Trolley 549 -Trolley, Double 549 -Trolley Section 549 -Trough Battery 73 -Trouvé's Blotting Paper Battery 73 -Trouvé's Solution 549 -True Contact Force 549 -True Ohm 396 -True Resistance 467 -Trimmer, Brush 549 -Trumpet, Electric 550 -Trunk Lines 550 -Trunking Switch Board 550 -Tube, Electric 550 -Tube, Guard 282 -Tube, Luminous 550 -Tube of Magnetic Induction 347 -Tube, Spark 491 -Tube, Stratification 495 -Tubes, Geissler 276 -Tubes of Force 261 -Tubes, Plücker 420 -Tubular Braid 550 -Tubular Core 155 -Tubular Magnet 356 -Tuning Fork Circuit Breaker 121 -Tuning Fork Dynamo 202 -Tuning Fork, Interrupter for 307 -Turning Moment 544 -Turns 550 -Turns, Ampere- 31 -Turns, Dead, of a Dynamo 551 -Turns, Primary Ampere- 551 -Turns, Secondary Ampere- 551 -Twist Joint, American 309 -Twist, Magnetic 354 -Tyer's Battery 74 -Typewriter, Electric 551 -Type Printer, Hughes' 511 - -Ultra-gaseous Matter 551 -Unbuilding 552 -Underground Conductor 552 -Underground Electric Subway 552 -Undulatory 23 -Undulatory Current 167 -Unidirectional 553 -Uniform Field 256 -Uniform Field of Force 553 -Uniform Magnetic Field 345 -Unipolar 553 -Unipolar Armature 50, 553 -Unipolar Current Induction 553 -Unipolar Dynamo 202-553 -Unipolar Electric Bath 57 -Unipolar Induction 304 -Unipolar Magnet 366 -Unit 553 -Unit, Absolute 554 -Unit Angle 554 -Unit. B. A. 554 -Unit, B. A., of Resistance 462 -Unit Current 167 -Unit Electro-motive Force 228 -Unit, Fundamental 554 -Unit Jar 554 -Unit Magnet Pole 366 -Unit of Capacity 105 -Unit of Conductivity 145 -Unit of Electric Potential 432 -Unit of Energy, Electro-magnetic 220 -Unit of Force 261 -Unit of Illumination 296 -Unit of Output 399 -Unit of Reluctance 458 -Unit of Resistance, B. A. 78 -Unit of Resistance, Breguet 463 -Unit of Resistance, Digney 464 -U nit of Resistance, English Absolute or Foot-second 465 -Unit of Resistance, German Mile 466 -Unit of Resistance, Jacobi's 466 -Unit of Resistance, Meter-millimeter. 466 -Unit of Resistance, Mil-foot 467 -Unit of Resistance, Siemens' 467 -Unit of Resistance, Swiss 468 -Unit of Resistance, Thomson's 468 -Unit of Resistance, Varley's 468 -Unit of Self-induction 304 -Unit of Supply 554 -Unit of Work 581 -Unit Resistance 468 -Units, Circular 126, 555 -Units, Derived 555 -Units, Heat 288 -Units, Practical 555 -Universal Battery System 556 -Universal Discharger 189 -Unmarked End 556 -Upright Galvanometer 274 -Upward's Battery 75 - -V 556 -V. A. 557 -Vacuum 557 -Vacuum, Absolute 557 -Vacuum, High 557 -Vacuum Lightning Arrester 329 -Vacuum, Low 557 -Vacuum, Partial 557 -Vacuum, Torricellian 557 -Valency 557 -Valve, Electrically Controlled 558 -Vapor Globe 558 -Variable Conductivity 145 -Variable Period 558 -Variable State 558 -Variation of the Compass 32, 558 -Variations, Magnetic 354 -Variometer 559 -Varley's Battery 76 -Varley's Condenser 559 -Varley's Resistance 559 -Varley's Unit of Resistance 468 -Varnish 559 -Varnish, Electric 559 -Varnish, Insulating 306 -Varnish, Red 559 -Varnish, Shellac 481 -Vat 559 -Velocity 559 -Velocity, Angular 32, 559 -Velocity of Signaling 560 -Velocity Ratio 560 -Ventilation of Armature 560 -Vertical Galvanometer 274 -Vertical Induction 304 -Verticity, Poles of 426, 560 -Vibrating Bell 78 -Vibration Period 560 -Vibration, Sympathetic 501, 561 -Vibrator, Electro-magnetic 561 -Villari's Critical Value 561 -Viole 562 -Viole's Standard of Illuminating Power 561 -Virtual Resistance 297 -Viscous Hysteresis 295, 356 -Vis Viva 562 -Vitreous Electricity 562 -Vitriol, Blue 562 -Vitriol, Green 562 -Vitriol, White 562 -Volatilization of Carbon 108 -Volt 562 -Volt-ampere 573 -Volt and Ampere Meter Galvanometer 274 -Volt, B. A. 568 -Volt, Congress 568 -Volt, Coulomb 568, 573 -Volt Indicator 568 -Volt. Legal 568 -Voltage 562 -Voltage, Spurious 493 -Voltage, Terminal 562 -Voltaic 563 -Voltaic Alternatives 563 -Voltaic Arc 39 -Voltaic Cell, Daniell's Standard 109 -Voltaic Cell, Double Fluid 191 -Voltaic Cell, Capacity of Polarization of a 103 -Voltaic Cell, Single Fluid 486 -Voltaic Cell, Standard 109 -Voltaic Cell, Standard, Latimer Clark's 110 -Voltaic Circuit 126 -Voltaic Effect 563 -Voltaic Electricity 563 -Voltaic Element 237 -Voltaic or Galvanic Battery 76 -Voltaic or Galvanic Circle 119 -Voltaic or Galvanic Couple 156 -Voltameter 563 -Voltameter, Copper 563 -Voltameter, Differential, Siemens' 564 -Voltameter, Faraday's 250 -Voltameter, Gas 564 -Voltameter, Silver 565 -Voltameter, Sulphuric Acid 564 -Voltameter, Volume 564 -Voltameter, Weight 566 -Voltametric Law 567 -Volta's Battery 76 -Volta's Fundamental Experiments 567 -Volta's Law of Galvanic Action 568 -Volta's Law of Thermo-electricity 568 -Voltmeter 568 -Voltmeter, Battery 569 -Voltmeter, Cardew 569 -Voltmeter, Electrostatic 571 -Voltmeter, Reducteur for 453 -Volts, Lost 571 -Volume Voltameter 564 -Vulcanite 571 - -W 572 -Wall Bracket 572 -Wall Socket 572 -Ward 572 -Waste Field 256 -Water 572 -Water Battery 77 -Water Equivalent 572 -Water Level Alarm 18 -Waterproof Lamp Globe 572 -Wattless Current 168 -Watt 572 -Watt-hour 573 -Watt Meter 375 -Watt-minute 573 -Watt-second 573 -Watts, Apparent 573 -Wave Winding 580 -Waves, Amplitude of 31 -Waves. Electro-magnetic 573 -Wax, Paraffine 402 -Weber 574 -Weber s Absolute Unit Resistance 468 -Weber-meter 574 -Weber's Theory of Magnetism 358 -Wedge Cut-out 175 -Wedge. Double 191 -Weight, Atomic 53 -Weight, Breaking 89 -Weight Electrometer 223 -Weight Voltameter 566 -Welding, Electric 574 -Welding Transformer 548, 575 -Wheatstone's A. B. C. Telegraph 521 -Wheatstone's Balance 577 -Wheatstone's Bridge 575 -Wheatstone's Bridge, Commercial 86 -Wheatstone's Rheostat 472 -Wheel, Phonic 409 -Wheel, Reaction 259 -Whirl, Electric 577 -White Vitriol 562 -Wilde Candle 101 -Wimshurst Electric Machine 335, 577 -Wimshurst Machine 335, 577 -Wind, Electric 578 -Windage 578 -Windings, Ampere 31 -Winding, Bifilar 81 -Winding, Compound 578 -Winding, Disc 579 -Winding, Lap 579 -Winding, Long Shunt 579 -Winding, Long Shunt and Series 579 -Winding, Multiple 579 -Winding, Multipolar 579 -Winding, Series 579 -Winding, Series and Separate Coil 579 -Winding, Series and Short Shunt 580 -Winding, Short Shunt 579 -Winding, Shunt 483, 580 -Winding Shuttle 580 -Winding, Wave 580 -Winding Working, Differential 183 -Wire, Block 83 -Wire, Bus 94 -Wire, Dead 177 -Wire Finder 580 -Wire Gauze Brush 92 -Wire, Idle 296 -Wire, Neutral 390 -Wire, Omnibus 94 -Wire, Square 493 -Wire System, Three 539 -Wires, Crossing 158 -Wires, Leading-in 324 -Wires, Phantom 409 -Wires, Pilot 415 -Wollaston Battery 78 -Work 580 -Work, Electric, Unit of 580 -Work, Unit of 581 -Working, Contraplex 580 -Working, Diode 580 -Working, Diplex 580 -Working, Double Curb 581 -Working, Hexode 581 -Working, Pentode 581 -Working, Reverse Current 581 -Working, Single Curb 581 -Working Tetrode 581 -Writing Telegraph 521 - -X, Axis of 54 - -Y, Axis of 54, 397 -Yoke 581 - -Zamboni's Dry Pile 581 -Zero 581 -Zero, Absolute 581 -Zero Potential 432, 582 -Zero, Thermometric 582 -Zinc 582 -Zinc Sender 582 -Zincode 582 -Zone, Peripolar 582 -Zone, Polar 582 - - - - - -End of the Project Gutenberg EBook of The Standard Electrical Dictionary, by -T. 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