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diff --git a/22766.txt b/22766.txt new file mode 100644 index 0000000..ecacb8a --- /dev/null +++ b/22766.txt @@ -0,0 +1,6661 @@ +The Project Gutenberg EBook of Electricity for Boys, by J. S. Zerbe + +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: Electricity for Boys + +Author: J. S. Zerbe + +Release Date: September 25, 2007 [EBook #22766] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK ELECTRICITY FOR BOYS *** + + + + +Produced by Joe Longo and the Online Distributed +Proofreading Team at http://www.pgdp.net + + + +WARNING: This book of one hundred years ago describes +experiments which are too dangerous to attempt by either +adults or children. It is published for historical +interest only. + + + + + +THE "HOW-TO-DO-IT" BOOKS + +ELECTRICITY FOR BOYS + +[Illustration: Fig. 1. WORK BENCH] + + + + +THE "HOW-TO-DO-IT" BOOKS + +ELECTRICITY FOR BOYS + +A working guide, in the successive +steps of electricity, described in +simple terms + +WITH MANY ORIGINAL ILLUSTRATIONS + +By J. S. ZERBE, M.E. + +AUTHOR OF +CARPENTRY FOR BOYS +PRACTICAL MECHANICS FOR BOYS + +[Illustration: Printer's Mark] + +THE NEW YORK BOOK COMPANY +NEW YORK + + + + +COPYRIGHT, 1914, BY +THE NEW YORK BOOK COMPANY + + + + +CONTENTS + + +INTRODUCTORY Page 1 + +I. ELECTRICITY CONSIDERED. BRIEF HISTORICAL +EVENTS Page 5 + + The Study of Electricity. First Historical Accounts. Bottling + Electricity. Discovery of Galvanic Electricity. Electro-motive Force. + Measuring Instruments. Rapidity of Modern Progress. How to Acquire the + Vast Knowledge. The Means Employed. + +II. WHAT TOOLS AND APPARATUS ARE NEEDED Page 11 + + Preparing the Workshop. Uses of Our Workshop. What to Build. What to + Learn. Uses of the Electrical Devices. Tools. Magnet-winding Reel. + +III. MAGNETS, COILS, ARMATURES, ETC. Page 18 + + The Two Kinds of Magnets. Permanent Magnets. Electro-Magnets. + Magnetism. Materials for Magnets. Non-magnetic Material. Action of a + _Second_ Magnet. What North and South Pole Mean. Repulsion and + Attraction. Positives and Negatives. Magnetic Lines of Force. The + Earth as a Magnet. Why the Compass Points North and South. Peculiarity + of a Magnet. Action of the Electro-Magnet. Exterior Magnetic Influence + Around a Wires Carrying a Current. Parallel Wires. + +IV. FRICTIONAL, VOLTAIC OR GALVANIC AND ELECTRO-MAGNETIC +ELECTRICITY Page 29 + + Three Electrical Sources. Frictional Electricity. Leyden Jar. Voltaic + or Galvanic Electricity. Voltaic Pile; How Made. Plus and Minus + Signs. The Common Primary Cell. Battery Resistance. Electrolyte and + Current. Electro-magnetic Electricity. Magnetic Radiation. Different + Kinds of Dynamos. Direct Current Dynamos. Simple Magnet Construction. + How to Wind. The Dynamo Fields. The Armature. Armature Windings. + Mounting the Armature. The Commutator. Commutator Brushes. Dynamo + Windings. The Field. Series-wound Field. Shunt-wound. Compound-wound. + +V. HOW TO DETECT AND MEASURE ELECTRICITY Page 49 + + Measuring Instruments. The Detector. Direction of Current. Simple + Current Detector. How to Place the Detector. Different Ways to Measure + a Current. The Sulphuric Acid Voltameter. The Copper Voltameter. The + Galvanoscope Electro-magnetic Method. The Calorimeter. The Light + Method. The Preferred Method. How to Make a Sulphuric Acid Voltameter. + How to Make a Copper Voltameter. Objections to the Calorimeter. + +VI. VOLTS, AMPERES, OHMS AND WATTS Page 60 + +Understanding Terms. Intensity and Quantity. Voltage. +Amperage Meaning of Watts and Kilowatt. A +Standard of Measurement. The Ampere Standard. The +Voltage Standard. The Ohm. Calculating the Voltage. + +VII. PUSH BUTTONS, SWITCHES, ANNUNCIATORS, BELLS AND +LIKE APPARATUS Page 65 + + Simple Switches. A Two-Pole Switch. Double-Pole Switch. Sliding + Switch. Reversing Switch. Push Buttons. Electric Bells. How Made. How + Operated. Annunciators. Burglar Alarm. Wire Circuiting. Circuiting + System with Two Bells and Push Buttons. The Push Buttons, Annunciators + and Bells. Wiring Up a House. + +VIII. ACCUMULATORS, STORAGE OR SECONDARY BATTERIES Page 82 + + Storing Up Electricity. The Accumulator. Accumulator Plates. The Grid. + The Negative Pole. Connecting Up the Plates. Charging the Cells. The + Initial Charge. The Charging Current. + +IX. THE TELEGRAPH Page 90 + + Mechanism in Telegraph Circuit. The Sending Key. The Sounder. + Connecting Up the Key and Sounder. Two Stations in Circuit. The Double + Click. Illustrating the Dot and the Dash. The Morse Telegraph Code. + Example in Use. + +X. HIGH-TENSION APPARATUS, CONDENSERS, ETC. Page 98 + + Induction. Low and High Tension. Elastic Property of Electricity. The + Condenser. Connecting up a Condenser. The Interrupter. Uses of + High-tension Coils. + +XI. WIRELESS TELEGRAPHY Page 104 + + Telegraphing Without Wires. Surging Character of High-tension + Currents. The Coherer. How Made. The Decoherer. The Sending Apparatus. + The Receiving Apparatus. How the Circuits are Formed. + +XII. THE TELEPHONE Page 110 + + Vibrations. The Acoustic Telephone. Sound Waves. Hearing Electricity. + The Diaphragm in a Magnetic Field. A Simple Telephone Circuit. How to + Make a Telephone. Telephone Connections. Complete Installation. The + Microphone. Light Contact Points. How to Make a Microphone. + Microphone, the Father of the Transmitter. Automatic Cut-outs for + Telephones. Complete Circuiting with Transmitters. + +XIII. ELECTROLYSIS, WATER PURIFICATION, ELECTROPLATING Page 123 + + Decomposing Liquids. Making Hydrogen and Oxygen. Purifying Water. + Rust. Oxygen as a Purifier. Composition of Water. Common Air Not a + Good Purifier. Pure Oxygen a Water Purifier. The Use of Hydrogen in + Purification. Aluminum Electrodes. Electric Hand Purifier. + Purification and Separation of Metals. Electroplating. Plating Iron + with Copper. Direction of Current. + +XIV. ELECTRIC HEATING. THERMO-ELECTRICITY Page 135 + + Generating Heat in a Wire. Resistance of Substances. Signs of + Connectors. Comparison of Metals. A Simple Electric Heater. How to + Arrange for Quantity of Current Used. An Electric Iron. + Thermo-Electricity Converting Heat Directly into Electricity Metals. + Electric, Positive, Negative. Thermo-electric Coupler. + +XV. ALTERNATING CURRENTS, CHOKING COIL, TRANSFORMER Page 145 + + Direct Current. Alternating Current. The Magnetic Field. Action of a + Magnetized Wire. The Movement of a Current in a Charged Wire. Current + Reversing Itself. Self-Induction. Brushes in a Direct Current Dynamo: + Alternating, Positive and Negative Poles. How an Alternating Current + Dynamo is Made. The Windings. The Armature Wires. Choking Coils. The + Transformer. How the Voltage is Determined. Voltage and Amperage in + Transformers. + +XVI. ELECTRIC LIGHTING Page 161 + + Early conditions. Fuels. Reversibility of Dynamo. Electric arc. + Mechanism to maintain the arc. Resistance coil. Parallel carbons for + making arc. Series current. Incandescent system. Multiple circuit. + Subdivision of electric light. The filament. The glass bulb. Metallic + filaments. Vapor lamps. Directions for improvements. Heat in electric + lighting. Curious superstitions concerning electricity. Magnetism. + Amber. Discovery of the properties of a magnet. Electricity in + mountain regions. Early beliefs as to magnetism and electricity. The + lightning rod. Protests against using it. Pliny's explanation of + electricity. + +XVII. POWER, AND VARIOUS OTHER ELECTRICAL MANIFESTATIONS Page 175 + + Early beliefs concerning the dynamo. Experiments with magnets. + Physical action of dynamo and motor. Electrical influence in windings. + Comparing motor and dynamo. How the current acts in a dynamo. Its + force in a motor. Loss in power transmission. The four ways in which + power is dissipated. Disadvantages of electric power. Its advantages. + Transmission of energy. High voltages. The transformer. Step-down + transformers. Electric furnaces. Welding by electricity. Merging the + particles of the joined ends. + +XVIII. X-RAY, RADIUM AND THE LIKE Page 184 + + The camera and the eye. Actinic rays. Hertzian waves. High-tension + apparatus. Vacuum tubes. Character of the ultra-violet rays. How + distinguished. The infra-red rays. Their uses. X-rays not capable of + reflection. Not subject to refraction. Transmission through opaque + substances. Reducing rates of vibration. Radium. Radio-activity. + Radio-active materials. Pitchblende. A new form of energy. Electrical + source. Healing power. Problems for scientists. + + + + +LIST OF ILLUSTRATIONS + + FIG. + + 1. Work bench Frontispiece + + PAGE + 2. Top of magnet-winding reel 14 + 3. Side of magnet-winding reel 14 + 4. Journal block 15 + 5. Plain magnet bar 19 + 6. Severed magnet 20 + 7. Reversed magnets 21 + 8. Horseshoe magnet 22 + 9. Earth's magnetic lines 23 + 10. Two permanent magnets 24 + 11. Magnets in earth's magnetic field 24 + 12. Armatures for magnets 25 + 13. Magnetized field 26 + 14. Magnetized bar 26 + 15. Direction of current 27 + 16. Direction of induction current 28 + 17. Frictional-electricity machine 30 + 18. Leyden jar 32 + 19. Galvanic electricity. Crown of cups 33 + 20. Voltaic electricity 34 + 21. Primary battery 36 + 22. Dynamo field and pole piece 39 + 23. Base and fields assembled 41 + 24. Details of the armature, core 42 + 25. Details of the armature, body 42 + 26. Armature Journals 43 + 27. Commutator 43 + 28. End view of armature, mounted 44 + 29. Top view of armature on base 45 + 30. Field winding 47 + 31. Series-wound 47 + 32. Shunt-wound 48 + 33. Compound-wound 48 + 34. Compass magnet, swing to the right 50 + 35. Magnetic compass 50 + 36. Magnet, swing to the left 50 + 37. Indicating direction of current 51 + 38. The bridge of the detector 52 + 39. Details of detector 53 + 40. Cross-section of detector 54 + 41. Acid voltameter 56 + 42. Copper voltameter 56 + 43. Two-pole switch 66 + 44. Double-pole switch 66 + 45. Sliding switch 67 + 46. Rheostat form of switch 68 + 47. Reversing switch 69 + 48. Push button 70 + 49. Electric bell 71 + 50. Armature of electric bell 72 + 51. Vertical section of annunciator 72 + 52. Front view of annunciator 72 + 53. Horizontal section of annunciator 72 + 54. Front plate of annunciator 72 + 55. Alarm switch on window 76 + 56. Burglar alarm on window 76 + 57. Burglar alarm contact 77 + 58. Neutral position of contact 78 + 59. Circuiting for electric bell 79 + 60. Annunciators in circuit 80 + 61. Wiring system for a house 80 + 62. Accumulator grids 83 + 63. Assemblage of accumulator grids 85 + 64. Connecting up storage battery in series 87 + 65. Parallel series 88 + 66. Charging circuit 88 + 67. Telegraph sending key 91 + 68. Telegraph sounder 92 + 69. A telegraph circuit 94 + 70. Induction coil and circuit 99 + 71. Illustrating elasticity 100 + 72. Condenser 101 + 73. High-tension circuit 102 + 74. Current interrupter 103 + 75. Wireless-telegraphy coherer 105 + 76. Wireless sending-apparatus 107 + 77. Wireless receiving-apparatus 108 + 78. Acoustic telephone 111 + 79. Illustrating vibrations 111 + 80. The magnetic field 112 + 81. Section of telephone receiver 114 + 82. The magnet and receiver head 115 + 83. Simple telephone connection 116 + 84. Telephone stations in circuit 117 + 85. Illustrating light contact points 118 + 86. The microphone 119 + 87. The transmitter 119 + 88. Complete telephone circuit 121 + 89. Device for making hydrogen and oxygen 124 + 90. Electric-water purifier 127 + 91. Portable electric purifier 129 + 92. Section of positive plate 130 + 93. Section of negative plate 130 + 94. Positive and negative in position 130 + 95. Form of the insulator 130 + 96. Simple electric heater 137 + 97. Side view of resistance device 139 + 98. Top view of resistance device 139 + 99. Plan view of electric iron 140 +100. Section of electric iron 141 +101. Thermo-electric couple 143 +102. Cutting a magnetic field 146 +103. Alternations, first position 148 +104. Alternations, second position 148 +105. Alternations, third position 148 +106. Alternations, fourth position 148 +107. Increasing alternations, first view 149 +108. Increasing alternations, second view 149 +109. Connection of alternating dynamo armature 150 +110. Direct current dynamo 151 +111. Circuit wires in direct current dynamo 152 +112. Alternating polarity lines 154 +113. Alternating current dynamo 155 +114. Choking coil 157 +115. A transformer 158 +116. Parallel carbons 164 +117. Arc-lighting circuit 165 +118. Interrupted conductor 166 +119. Incandescent circuit 167 +120. Magnetic action in dynamo, 1st 177 +121. Magnetic action in dynamo, 2d 177 +122. Magnetic action in dynamo, 3d 178 +123. Magnetic action in dynamo, 4th 178 +124. Magnetic action in motor, 1st 179 +125. Magnetic action in motor, 2d 179 +126. Magnetic action in motor, 3d 180 +127. Magnetic action in motor, 4th 180 + + + + +INTRODUCTORY + + +Electricity, like every science, presents two phases to the student, one +belonging to a theoretical knowledge, and the other which pertains to +the practical application of that knowledge. The boy is directly +interested in the practical use which he can make of this wonderful +phenomenon in nature. + +It is, in reality, the most successful avenue by which he may obtain the +theory, for he learns the abstract more readily from concrete examples. + +It is an art in which shop practice is a greater educator than can be +possible with books. Boys are not, generally, inclined to speculate or +theorize on phenomena apart from the work itself; but once put them into +contact with the mechanism itself, let them become a living part of it, +and they will commence to reason and think for themselves. + +It would be a dry, dull and uninteresting thing to tell a boy that +electricity can be generated by riveting together two pieces of +dissimilar metals, and applying heat to the juncture. But put into his +hands the metals, and set him to perform the actual work of riveting the +metals together, then wiring up the ends of the metals, heating them, +and, with a galvanometer, watching for results, it will at once make him +see something in the experiment which never occurred when the abstract +theory was propounded. + +He will inquire first what metals should be used to get the best +results, and finally, he will speculate as to the reasons for the +phenomena. When he learns that all metals are positive-negative or +negative-positive to each other, he has grasped a new idea in the realm +of knowledge, which he unconsciously traces back still further, only to +learn that he has entered a field which relates to the constitution of +matter itself. As he follows the subject through its various channels he +will learn that there is a common source of all things; a manifestation +common to all matter, and that all substances in nature are linked +together in a most wonderful way. + +An impulse must be given to a boy's training. The time is past for the +rule-and-rote method. The rule can be learned better by a manual +application than by committing a sentence to memory. + +In the preparation of this book, therefore, I have made practice and +work the predominating factors. It has been my aim to suggest the best +form in which to do the things in a practical way, and from that work, +as the boy carries it out, to deduce certain laws and develop the +principles which underlie them. Wherever it is deemed possible to do so, +it is planned to have the boy make these discoveries for himself, so as +to encourage him to become a thinker and a reasoner instead of a mere +machine. + +A boy does not develop into a philosopher or a scientist through being +told he must learn the principles of this teaching, or the fundamentals +of that school of reasoning. He will unconsciously imbibe the spirit and +the willingness if we but place before him the tools by which he may +build even the simple machinery that displays the various electrical +manifestations. + + + + +CHAPTER I + +THE STUDY OF ELECTRICITY. HISTORICAL + + +There is no study so profound as electricity. It is a marvel to the +scientist as well as to the novice. It is simple in its manifestations, +but most complex in its organization and in its ramifications. It has +been shown that light, heat, magnetism and electricity are the same, but +that they differ merely in their modes of motion. + +FIRST HISTORICAL ACCOUNT.--The first historical account of electricity +dates back to 600 years B. C. Thales of Miletus was the first to +describe the properties of amber, which, when rubbed, attracted and +repelled light bodies. The ancients also described what was probably +tourmaline, a mineral which has the same qualities. The torpedo, a fish +which has the power of emitting electric impulses, was known in very +early times. + +From that period down to about the year 1600 no accounts of any +historical value have been given. Dr. Gilbert, of England, made a number +of researches at that time, principally with amber and other materials, +and Boyle, in 1650, made numerous experiments with frictional +electricity. + +Sir Isaac Newton also took up the subject at about the same period. In +1705 Hawksbee made numerous experiments; also Gray, in 1720, and a +Welshman, Dufay, at about the same time. The Germans, from 1740 to 1780, +made many experiments. In 1740, at Leyden, was discovered the jar which +bears that name. Before that time, all experiments began and ended with +frictional electricity. + +The first attempt to "bottle" electricity was attempted by +Muschenbr[oe]ck, at Leyden, who conceived the idea that electricity in +materials might be retained by surrounding them with bodies which did +not conduct the current. He electrified some water in a jar, and +communication having been established between the water and the prime +conductor, his assistant, who was holding the bottle, on trying to +disengage the communicating wire, received a sudden shock. + +In 1747 Sir William Watson fired gunpowder by an electric spark, and, +later on, a party from the Royal Society, in conjunction with Watson, +conducted a series of experiments to determine the velocity of the +electric fluid, as it was then termed. + +Benjamin Franklin, in 1750, showed that lightning was electricity, and +later on made his interesting experiments with the kite and the key. + +DISCOVERING GALVANIC ELECTRICITY.--The great discovery of Galvani, in +1790, led to the recognition of a new element in electricity, called +galvanic or voltaic (named after the experimenter, Volta), and now known +to be identical with frictional electricity. In 1805 Poisson was the +first to analyze electricity; and when [OE]rsted of Copenhagen, in 1820, +discovered the magnetic action of electricity, it offered a great +stimulus to the science, and paved the way for investigation in a new +direction. Ampere was the first to develop the idea that a motor or a +dynamo could be made operative by means of the electro-magnetic current; +and Faraday, about 1830, discovered electro-magnetic rotation. + +ELECTRO-MAGNETIC FORCE.--From this time on the knowledge of electricity +grew with amazing rapidity. Ohm's definition of electro-motive force, +current strength and resistance eventuated into Ohm's law. Thomson +greatly simplified the galvanometer, and Wheatstone invented the +rheostat, a means of measuring resistance, about 1850. Then primary +batteries were brought forward by Daniels, Grove, Bunsen and Thomson, +and electrolysis by Faraday. Then came the instruments of precision--the +electrometer, the resistance bridge, the ammeter, the voltmeter--all of +the utmost value in the science. + +MEASURING INSTRUMENTS.--The perfection of measuring instruments did more +to advance electricity than almost any other field of endeavor; so that +after 1875 the inventors took up the subject, and by their energy +developed and put into practical operation a most wonderful array of +mechanism, which has become valuable in the service of man in almost +every field of human activity. + +RAPIDITY OF MODERN PROGRESS.--This brief history is given merely to show +what wonders have been accomplished in a few years. The art is really +less than fifty years old, and yet so rapidly has it gone forward that +it is not at all surprising to hear the remark, that the end of the +wonders has been reached. Less than twenty-five years ago a high +official of the United States Patent Office stated that it was probable +the end of electrical research had been reached. The most wonderful +developments have been made since that time; and now, as in the past, +one discovery is but the prelude to another still more remarkable. We +are beginning to learn that we are only on the threshold of that +storehouse in which nature has locked her secrets, and that there is no +limit to human ingenuity. + +HOW TO ACQUIRE THE VAST KNOWLEDGE.--As the boy, with his limited vision, +surveys this vast accumulation of tools, instruments and machinery, and +sees what has been and is now being accomplished, it is not to be +wondered at that he should enter the field with timidity. In his mind +the great question is, how to acquire the knowledge. There is so much to +learn. How can it be accomplished? + +The answer to this is, that the student of to-day has the advantage of +the knowledge of all who have gone before; and now the pertinent thing +is to acquire that knowledge. + +THE MEANS EMPLOYED.--This brings us definitely down to an examination of +the means that we shall employ to instil this knowledge, so that it may +become a permanent asset to the student's store of information. + +The most significant thing in the history of electrical development is +the knowledge that of all the great scientists not one of them ever +added any knowledge to the science on purely speculative reasoning. All +of them were experimenters. They practically applied and developed their +theories in the laboratory or the workshop. The natural inference is, +therefore, that the boy who starts out to acquire a knowledge of +electricity, must not only theorize, but that he shall, primarily, +conduct the experiments, and thereby acquire the information in a +practical way, one example of which will make a more lasting impression +than pages of dry text. + +Throughout these pages, therefore, I shall, as briefly as possible, +point out the theories involved, as a foundation for the work, and then +illustrate the structural types or samples; and the work is so arranged +that what is done to-day is merely a prelude or stepping-stone to the +next phase of the art. In reality, we shall travel, to a considerable +extent, the course which the great investigators followed when they were +groping for the facts and discovering the great manifestations in +nature. + + + + +CHAPTER II + +WHAT TOOLS AND APPARATUS ARE NEEDED + + +PREPARING THE WORKSHOP.--Before commencing actual experiments we should +prepare the workshop and tools. Since we are going into this work as +pioneers, we shall have to be dependent upon our own efforts for the +production of the electrical apparatus, so as to be able, with our +home-made factory, to provide the power, the heat and the electricity. +Then, finding we are successful in these enterprises, we may look +forward for "more worlds to conquer." + +By this time our neighbors will become interested in and solicit work +from us. + +USES OF OUR WORKSHOPS.--They may want us to test batteries, and it then +becomes necessary to construct mechanism to detect and measure +electricity; to install new and improved apparatus; and to put in and +connect up electric bells in their houses, as well as burglar alarms. To +meet the requirements, we put in a telegraph line, having learned, as +well as we are able, how they are made and operated. But we find the +telegraph too slow and altogether unsuited for our purposes, as well as +for the uses of the neighborhood, so we conclude to put in a telephone +system. + +WHAT TO BUILD.--It is necessary, therefore, to commence right at the +bottom to build a telephone, a transmitter, a receiver and a +switch-board for our system. From the telephone we soon see the +desirability of getting into touch with the great outside world, and +wireless telegraphy absorbs our time and energies. + +But as we learn more and more of the wonderful things electricity will +do, we are brought into contact with problems which directly interest +the home. Sanitation attracts our attention. Why cannot electricity act +as an agent to purify our drinking water, to sterilize sewage and to +arrest offensive odors? We must, therefore, learn something about the +subject of electrolysis. + +WHAT TO LEARN.--The decomposition of water is not the only thing that we +shall describe pertaining to this subject. We go a step further, and +find that we can decompose metals as well as liquids, and that we can +make a pure metal out of an impure one, as well as make the foulest +water pure. But we shall also, in the course of our experiments, find +that a cheap metal can be coated with a costly one by means of +electricity--that we can electroplate by electrolysis. + +USES OF THE ELECTRICAL DEVICES.--While all this is progressing and our +factory is turning out an amazing variety of useful articles, we are led +to inquire into the uses to which we may devote our surplus electricity. +The current may be diverted for boiling water; for welding metals; for +heating sad-irons, as well as for other purposes which are daily +required. + +TOOLS.--To do these things tools are necessary, and for the present they +should not be expensive. A small, rigidly built bench is the first +requirement. This may be made, as shown in Fig. 1, of three 2-inch +planks, each 10 inches wide and 6 feet long, mounted on legs 36 inches +in height. In the front part are three drawers for your material, or the +small odds and ends, as well as for such little tools as you may +accumulate. Then you will need a small vise, say, with a 2-inch jaw, and +you will also require a hand reel for winding magnets. This will be +fully described hereafter. + +You can also, probably, get a small, cheap anvil, which will be of the +greatest service in your work. It should be mounted close up to the work +bench. Two small hammers, one with an A-shaped peon, and the other with +a round peon, should be selected, and also a plane and a small wood saw +with fine teeth. A bit stock, or a ratchet drill, if you can afford it, +with a variety of small drills; two wood chisels, say of 3/8-inch and +3/4-inch widths; small cold chisels; hack saw, 10-inch blade; small +iron square; pair of dividers; tin shears; wire cutters; 2 pairs of +pliers, one flat and the other round-nosed; 2 awls, centering punch, +wire cutters, and, finally, soldering tools. + +[Illustration: _Fig. 2. Top View_ MAGNET-WINDING REEL] + +[Illustration: _Fig. 3. Side View_ MAGNET-WINDING REEL] + +If a gas stove is not available, a brazing torch is an essential tool. +Numerous small torches are being made, which are cheap and easily +operated. A small soldering iron, with pointed end, should be provided; +also metal shears and a small square; an awl and several sizes of +gimlets; a screwdriver; pair of pliers and wire cutters. + +From the foregoing it will be seen that the cost of tools is not a very +expensive item. + +This entire outfit, not including the anvil and vise, may be purchased +new for about $20.00, so we have not been extravagant. + +MAGNET-WINDING REEL.--Some little preparation must be made, so we may be +enabled to handle our work by the construction of mechanical aids. + +[Illustration: _Fig. 4. Journal Block._] + +First of these is the magnet-winding reel, a plan view of which is shown +in Fig. 2. This, for our present work, will be made wholly of wood. + +Select a plank 1-1/2 inches thick and 8 inches wide, and from this cut +off two pieces (A), each 7 inches long, and then trim off the corners +(B, B), as shown in Fig. 4. To serve as the mandrel (C, Fig. 2), select +a piece of broomstick 9 inches long. Bore a hole (D) in each block (A) a +half inch below the upper margin of the block, this hole being of such +diameter that the broomstick mandrel will fit and easily turn therein. + +Place a crank (E), 5 inches long, on the outer end of the mandrel, as in +Fig. 3. Then mount one block on the end of the bench and the other block +3 inches away. Affix them to the bench by nails or screws, preferably +the latter. + +On the inner end of the mandrel put a block (F) of hard wood. This is +done by boring a hole 1 inch deep in the center of the block, into which +the mandrel is driven. On the outer face of the block is a square hole +large enough to receive the head of a 3/8-inch bolt, and into the +depression thus formed a screw (G) is driven through the block and into +the end of the mandrel, so as to hold the block (F) and mandrel firmly +together. When these parts are properly put together, the inner side of +the block will rest and turn against the inner journal block (A). + +The tailpiece is made of a 2" x 4" scantling (H), 10 inches long, one +end of it being nailed to a transverse block (I) 2" x 2" x 4". The inner +face of this block has a depression in which is placed a V-shaped cup +(J), to receive the end of the magnet core (K) or bolt, which is to be +used for this purpose. The tailpiece (H) has a longitudinal slot (L) 5 +inches long adapted to receive a 1/2-inch bolt (M), which passes down +through the bench, and is, therefore, adjustable, so it may be moved to +and from the journal bearing (A), thereby providing a place for the +bolts to be put in. These bolts are the magnet cores (K), 6 inches long, +but they may be even longer, if you bore several holes (N) through the +bench so you may set over the tailpiece. + +With a single tool made substantially like this, over a thousand of the +finest magnets have been wound. Its value will be appreciated after you +have had the experience of winding a few magnets. + +ORDER IN THE WORKSHOP.--Select a place for each tool on the rear upright +of the bench, and make it a rule to put each tool back into its place +after using. This, if persisted in, will soon become a habit, and will +save you hours of time. Hunting for tools is the unprofitable part of +any work. + + + + +CHAPTER III + +MAGNETS, COILS, ARMATURES, ETC. + + +THE TWO KINDS OF MAGNET.--Generally speaking, magnets are of two kinds, +namely, permanent and electro-magnetic. + +PERMANENT MAGNETS.--A permanent magnet is a piece of steel in which an +electric force is exerted at all times. An electro-magnet is a piece of +iron which is magnetized by a winding of wire, and the magnet is +energized only while a current of electricity is passing through the +wire. + +ELECTRO-MAGNET.--The electro-magnet, therefore, is the more useful, +because the pull of the magnet can be controlled by the current which +actuates it. + +The electro-magnet is the most essential of all contrivances in the +operation and use of electricity. It is the piece of mechanism which +does the physical work of almost every electrical apparatus or machine. +It is the device which has the power to convert the unseen electric +current into motion which may be observed by the human eye. Without it +electricity would be a useless agent to man. + +While the electro-magnet is, therefore, the form of device which is +almost wholly used, it is necessary, first, to understand the principles +of the permanent magnet. + +MAGNETISM.--The curious force exerted by a magnet is called magnetism, +but its origin has never been explained. We know its manifestations +only, and laws have been formulated to explain its various phases; how +to make it more or less intense; how to make its pull more effective; +the shape and form of the magnet and the material most useful in its +construction. + +[Illustration: _Fig 5._ PLAIN MAGNET BAR] + +MATERIALS FOR MAGNETS.--Iron and steel are the best materials for +magnets. Some metals are non-magnetic, this applying to iron if combined +with manganese. Others, like sulphur, zinc, bismuth, antimony, gold, +silver and copper, not only are non-magnetic, but they are actually +repelled by magnetism. They are called the diamagnetics. + +NON-MAGNETIC MATERIALS.--Any non-magnetic body in the path of a magnetic +force does not screen or diminish its action, whereas a magnetic +substance will. + +In Fig. 5 we show the simplest form of magnet, merely a bar of steel (A) +with the magnetic lines of force passing from end to end. It will be +understood that these lines extend out on all sides, and not only along +two sides, as shown in the drawing. The object is to explain clearly how +the lines run. + +[Illustration: _Fig. 6._ SEVERED MAGNET] + +ACTION OF A SEVERED MAGNET.--Now, let us suppose that we sever this bar +in the middle, as in Fig. 6, or at any other point between the ends. In +this case each part becomes a perfect magnet, and a new north pole (N) +and a new south pole (S) are made, so that the movement of the magnetic +lines of force are still in the same direction in each--that is, the +current flows from the north pole to the south pole. + +WHAT NORTH AND SOUTH POLES MEAN.--If these two parts are placed close +together they will attract each other. But if, on the other hand, one of +the pieces is reversed, as in Fig. 7, they will repel each other. From +this comes the statement that likes repel and unlikes attract each +other. + +REPULSION AND ATTRACTION.--This physical act of repulsion and attraction +is made use of in motors, as we shall see hereinafter. + +It will be well to bear in mind that in treating of electricity the +north pole is always associated with the plus sign (+) and the south +pole with the minus sign (-). Or the N sign is positive and the S sign +negative electricity. + +[Illustration: _Fig. 7._ REVERSED MAGNETS] + +POSITIVES AND NEGATIVES.--There is really no difference between positive +and negative electricity, so called, but the foregoing method merely +serves as a means of identifying or classifying the opposite ends of a +magnet or of a wire. + +MAGNETIC LINES OF FORCE.--It will be noticed that the magnetic lines of +force pass through the bar and then go from end to end through the +atmosphere. Air is a poor conductor of electricity, so that if we can +find a shorter way to conduct the current from the north pole to the +south pole, the efficiency of the magnet is increased. + +This is accomplished by means of the well-known horseshoe magnet, where +the two ends (N, S) are brought close together, as in Fig. 8. + +THE EARTH AS A MAGNET.--The earth is a huge magnet and the magnetic +lines run from the north pole to the south pole around all sides of the +globe. + +[Illustration: _Fig. 8._ HORSESHOE MAGNET] + +The north magnetic pole does not coincide with the true north pole or +the pivotal point of the earth's rotation, but it is sufficiently near +for all practical purposes. Fig. 9 shows the magnetic lines running from +the north to the south pole. + +WHY THE COMPASS POINTS NORTH AND SOUTH.--Now, let us try to ascertain +why the compass points north and south. + +Let us assume that we have a large magnet (A, Fig. 10), and suspend a +small magnet (B) above it, so that it is within the magnetic field of +the large magnet. This may be done by means of a short pin (C), which is +located in the middle of the magnet (B), the upper end of this pin +having thereon a loop to which a thread (D) is attached. The pin also +carries thereon a pointer (E), which is directed toward the north pole +of the bar (B). + +[Illustration: _Fig. 9._ EARTH'S MAGNETIC LINES] + +You will now take note of the interior magnetic lines (X), and the +exterior magnetic lines (Z) of the large magnet (A), and compare the +direction of their flow with the similar lines in the small magnet (B). + +The small magnet has both its exterior and its interior lines within the +exterior lines (Z) of the large magnet (A), so that as the small magnet +(B) is capable of swinging around, the N pole of the bar (B) will point +toward the S pole of the larger bar (A). The small bar, therefore, is +influenced by the exterior magnetic field (Z). + +[Illustration: _Fig. 10._ TWO PERMANENT MAGNETS] + +[Illustration: _Fig. 11._ MAGNETS IN THE EARTH'S MAGNETIC FIELD] + +Let us now take the outline represented by the earth's surface (Fig. +11), and suspend a magnet (A) at any point, like the needle of a +compass, and it will be seen that the needle will arrange itself north +and south, within the magnetic field which flows from the north to the +south pole. + +PECULIARITY OF A MAGNET.--One characteristic of a magnet is that, while +apparently the magnetic field flows out at one end of the magnet, and +moves inwardly at the other end, the power of attraction is just the +same at both ends. + +In Fig. 12 are shown a bar (A) and a horseshoe magnet (B). The bar (A) +has metal blocks (C) at each end, and each of these blocks is attracted +to and held in contact with the ends by magnetic influence, just the +same as the bar (D) is attracted by and held against the two ends of the +horseshoe magnet. These blocks (C) or the bar (D) are called armatures. +Through them is represented the visible motion produced by the magnetic +field. + +[Illustration: _Fig. 12._ ARMATURES FOR MAGNETS] + +ACTION OF THE ELECTRO-MAGNET.--The electro-magnet exerts its force in +the same manner as a permanent magnet, so far as attraction and +repulsion are concerned, and it has a north and a south pole, as in the +case with the permanent magnet. An electro-magnet is simply a bar of +iron with a coil or coils of wire around it; when a current of +electricity flows through the wire, the bar is magnetized. The moment +the current is cut off, the bar is demagnetized. The question that now +arises is, why an electric current flowing through a wire, under those +conditions, magnetizes the bar, or _core_, as it is called. + +[Illustration: _Fig. 13._ MAGNETIZED FIELD] + +[Illustration: _Fig. 14._ MAGNETIZED BAR] + +In Fig. 13 is shown a piece of wire (A). Let us assume that a current of +electricity is flowing through this wire in the direction of the darts. +What actually takes place is that the electricity extends out beyond the +surface of the wire in the form of the closed rings (B). If, now, this +wire (A) is wound around an iron core (C, Fig. 14), you will observe +that this electric field, as it is called, entirely surrounds the core, +or rather, that the core is within the magnetic field or influence of +the current flowing through the wire, and the core (C) thereby becomes +magnetized, but it is magnetized only when the current passes through +the wire coil (A). + +[Illustration: _Fig. 15._ DIRECTION OF CURRENT] + +From the foregoing, it will be understood that a wire carrying a current +of electricity not only is affected within its body, but that it also +has a sphere of influence exteriorly to the body of the wire, at all +points; and advantage is taken of this phenomenon in constructing +motors, dynamos, electrical measuring devices and almost every kind of +electrical mechanism in existence. + +EXTERIOR MAGNETIC INFLUENCE AROUND A WIRE CARRYING A CURRENT.--Bear in +mind that the wire coil (A, Fig. 14) does not come into contact with the +core (C). It is insulated from the core, either by air or by rubber or +other insulating substance, and a current passing from A to C under +those conditions is a current of _induction_. On the other hand, the +current flowing through the wire (A) from end to end is called a +_conduction_ current. Remember these terms. + +In this connection there is also another thing which you will do well to +bear in mind. In Fig. 15 you will notice a core (C) and an insulated +wire coil (B) wound around it. The current, through the wire (B), as +shown by the darts (D), moves in one direction, and the induced current +in the core (C) travels in the opposite direction, as shown by the darts +(D). + +[Illustration: _Fig. 16._ DIRECTION OF INDUCTION CURRENT] + +PARALLEL WIRES.--In like manner, if two wires (A, B, Fig. 16) are +parallel with each other, and a current of electricity passes along the +wire (A) in one direction, the induced current in the wire (B) will move +in the opposite direction. + +These fundamental principles should be thoroughly understood and +mastered. + + + + +CHAPTER IV + +FRICTIONAL, VOLTAIC OR GALVANIC, AND ELECTRO-MAGNETIC ELECTRICITY + + +THREE ELECTRICAL SOURCES.--It has been found that there are three kinds +of electricity, or, to be more accurate, there are three ways to +generate it. These will now be described. + +When man first began experimenting, he produced a current by frictional +means, and collected the electricity in a bottle or jar. Electricity, so +stored, could be drawn from the jar, by attaching thereto suitable +connection. This could be effected only in one way, and that was by +discharging the entire accumulation instantaneously. At that time they +knew of no means whereby the current could be made to flow from the jar +as from a battery or cell. + +FRICTIONAL ELECTRICITY.--With a view of explaining the principles +involved, we show in Fig. 17 a machine for producing electricity by +friction. + + +[Illustration: _Fig. 17._ FRICTION-ELECTRICITY MACHINE] + +This is made up as follows: A represents the base, having thereon a flat +member (B), on which is mounted a pair of parallel posts or standards +(C, C), which are connected at the top by a cross piece (D). Between +these two posts is a glass disc (E), mounted upon a shaft (F), which +passes through the posts, this shaft having at one end a crank (G). Two +leather collecting surfaces (H, H), which are in contact with the glass +disc (E), are held in position by arms (I, J), the arm (I) being +supported by the cross piece (D), and the arm (J) held by the base piece +(B). A rod (K), U-shaped in form, passes over the structure here thus +described, its ends being secured to the base (B). The arms (I, J) are +both electrically connected with this rod, or conductor (K), joined to a +main conductor (L), which has a terminating knob (M). On each side and +close to the terminal end of each leather collector (H) is a fork-shaped +collector (N). These two collectors are also connected electrically with +the conductor (K). When the disc is turned electricity is generated by +the leather flaps and accumulated by the collectors (N), after which it +is ready to be discharged at the knob (M). + +In order to collect the electricity thus generated a vessel called a +Leyden jar is used. + +LEYDEN JAR.--This is shown in Fig. 18. The jar (A) is of glass coated +exteriorly at its lower end with tinfoil (B), which extends up a little +more than halfway from the bottom. This jar has a wooden cover or top +(C), provided centrally with a hole (D). The jar is designed to receive +within it a tripod and standard (E) of lead. Within this lead standard +is fitted a metal rod (F), which projects upwardly through the hole (D), +its upper end having thereon a terminal knob (G). A sliding cork (H) on +the rod (F) serves as a means to close the jar when not in use. When in +use this cork is raised so the rod may not come into contact, +electrically, with the cover (C). + +The jar is half filled with sulphuric acid (I), after which, in order +to charge the jar, the knob (G) is brought into contact with the knob +(M) of the friction generator (Fig. 17). + +VOLTAIC OR GALVANIC ELECTRICITY.--The second method of generating +electricity is by chemical means, so called, because a liquid is used as +one of the agents. + +[Illustration: _Fig. 18._ LEYDEN JAR] + +Galvani, in 1790, made the experiments which led to the generation of +electricity by means of liquids and metals. The first battery was called +the "crown of cups," shown in Fig. 19, and consisting of a row of glass +cups (A), containing salt water. These cups were electrically connected +by means of bent metal strips (B), each strip having at one end a copper +plate (C), and at the other end a zinc plate (D). The first plate in the +cup at one end is connected with the last plate in the cup at the other +end by a conductor (E) to make a complete circuit. + +[Illustration: _Fig. 19._ GALVANIC ELECTRICITY. CROWN OF CUPS] + +THE CELL AND BATTERY.--From the foregoing it will be seen that within +each cup the current flows from the zinc to the copper plates, and +exteriorly from the copper to the zinc plates through the conductors (B +and E). + +A few years afterwards Volta devised what is known as the voltaic pile +(Fig. 20). + +VOLTAIC PILE--HOW MADE.--This is made of alternate discs of copper and +zinc with a piece of cardboard of corresponding size between each zinc +and copper plate. The cardboard discs are moistened with acidulated +water. The bottom disc of copper has a strip which connects with a cup +of acid, and one wire terminal (A) runs therefrom. The upper disc, which +is of zinc, is also connected, by a strip, with a cup of acid from which +extends the other terminal wire (B). + +[Illustration: _Fig. 20._ VOLTAIC ELECTRICITY] + +_Plus and Minus Signs._--It will be noted that the positive or copper +disc has the plus sign (+) while the zinc disc has the minus (-) sign. +These signs denote the positive and the negative sides of the current. + +The liquid in the cells, or in the moistened paper, is called the +_electrolyte_ and the plates or discs are called _electrodes_. To define +them more clearly, the positive plate is the _anode_, and the negative +plate the _cathode_. + +The current, upon entering the zinc plate, decomposes the water in the +electrolyte, thereby forming oxygen. The hydrogen in the water, which +has also been formed by the decomposition, is carried to the copper +plate, so that the plate finally is so coated with hydrogen that it is +difficult for the current to pass through. This condition is called +"polarization," and to prevent it has been the aim of all inventors. To +it also we may attribute the great variety of primary batteries, each +having some distinctive claim of merit. + +THE COMMON PRIMARY CELL.--The most common form of primary cell contains +sulphuric acid, or a sulphuric acid solution, as the electrolyte, with +zinc for the _anode_, and carbon, instead of copper, for the _cathode_. + +The ends of the zinc and copper plates are called _terminals_, and while +the zinc is the anode or positive element, its _terminal_ is designated +as the positive pole. In like manner, the carbon is the negative +element or cathode, and its terminal is designated as negative pole. + +Fig. 21 will show the relative arrangement of the parts. It is customary +to term that end or element from which the current flows as positive. A +cell is regarded as a whole, and as the current passes out of the cell +from the copper element, the copper terminal becomes positive. + +[Illustration: _Fig. 21._ PRIMARY BATTERY] + +BATTERY RESISTANCE, ELECTROLYTE AND CURRENT.--The following should be +carefully memorized: + +A cell has reference to a single vessel. When two or more cells are +coupled together they form a _battery_. + +_Resistance_ is opposition to the movement of the current. If it is +offered by the electrolyte, it is designated "Internal Resistance." If, +on the other hand, the opposition takes place, for instance, through the +wire, it is then called "External Resistance." + +The electrolyte must be either acid, or alkaline, or saline, and the +electrodes must be of dissimilar metals, so the electrolyte will attack +one of them. + +The current is measured in amperes, and the force with which it is +caused to flow is measured in volts. In practice the word "current" is +used to designate ampere flow; and electromotive force, or E. M. F., is +used instead of voltage. + +ELECTRO-MAGNETIC ELECTRICITY.--The third method of generating +electricity is by electro-magnets. The value and use of induction will +now be seen, and you will be enabled to utilize the lesson concerning +magnetic action referred to in the previous chapter. + +MAGNETIC RADIATION.--You will remember that every piece of metal which +is within the path of an electric current has a space all about its +surface from end to end which is electrified. This electrified field +extends out a certain distance from the metal, and is supposed to +maintain a movement around it. If, now, another piece of metal is +brought within range of this electric or magnetic zone and moved across +it, so as to cut through this field, a current will be generated +thereby, or rather added to the current already exerted, so that if we +start with a feeble current, it can be increased by rapidly "cutting the +lines of force," as it is called. + +DIFFERENT KINDS OF DYNAMO.--While there are many kinds of dynamo, they +all, without exception, are constructed in accordance with this +principle. There are also many varieties of current. For instance, a +dynamo may be made to produce a high voltage and a low amperage; another +with high amperage and low voltage; another which gives a direct current +for lighting, heating, power, and electroplating; still another which +generates an alternating current for high tension power, or +transmission, arc-lighting, etc., all of which will be explained +hereafter. + +In this place, however, a full description of a direct-current dynamo +will explain the principle involved in all dynamos--that to generate a +current of electricity makes it necessary for us to move a field of +force, like an armature, rapidly and continuously through another field +of force, like a magnetic field. + +DIRECT-CURRENT DYNAMO.--We shall now make the simplest form of dynamo, +using for this purpose a pair of permanent magnets. + +[Illustration: _Fig. 22._ DYNAMO FIELD AND POLE PIECE] + +SIMPLE MAGNET CONSTRUCTION.--A simple way to make a pair of magnets for +this purpose is shown in Fig. 22. A piece of round 3/4-inch steel core +(A), 5-1/2 inches long, is threaded at both ends to receive at one end a +nut (B), which is screwed on a sufficient distance so that the end of +the core (A) projects a half inch beyond the nut. The other end of the +steel core has a pole piece of iron (C) 2" x 2" x 4", with a hole +midway between the ends, threaded entirely through, and provided along +one side with a concave channel, within which the armature is to turn. +Now, before the pole piece (C) is put on, we will slip on a disc (E), +made of hard rubber, then a thin rubber tube (F), and finally a rubber +disc (G), so as to provide a positive insulation for the wire coil which +is wound on the bobbin thus made. + +HOW TO WIND.--In practice, and as you go further along in this work, you +will learn the value, first, of winding one layer of insulated wire on +the spool, coating it with shellac, and then putting on the next layer, +and so on; when completely wound, the two wire terminals may be brought +out at one end; but for our present purpose, and to render the +explanation clearer, the wire terminals are at the opposite ends of the +spool (H, H'). + +THE DYNAMO FIELDS.--Two of these spools are so made and they are called +the _fields_ of the dynamo. + +We will next prepare an iron bar (I), 5 inches long and 1/2 inch thick +and 1-1/2 inches wide, then bore two holes through it so the distance +measures 3 inches from center to center. These holes are to be threaded +for the 3/4-inch cores (A). This bar holds together the upper ends of +the cores, as shown in Fig. 23. + +[Illustration: _Fig. 23._ BASE AND FIELDS ASSEMBLED] + +We then prepare a base (J) of any hard wood, 2 inches thick, 8 inches +long and 8 inches wide, and bore two 3/4-inch holes 3 inches apart on a +middle line, to receive a pair of 3/4-inch cap screws (K), which pass +upwardly through the holes in the base and screw into the pole pieces +(C). A wooden bar (L), 1-1/2" x 1-1/2", 8 inches long, is placed under +each pole piece, which is also provided with holes for the cap screws +(K). The lower side of the base (J) should be countersunk, as at M, so +the head of the nut will not project. The fields of the dynamo are now +secured in position to the base. + +[Illustration: _Fig. 24._ DETAILS OF THE ARMATURE, CORE + +_Fig. 25._ DETAILS OF THE ARMATURE, BODY] + +THE ARMATURE.--A bar of iron (Fig. 24), 1" x 1" and 2-1/4 inches long, +is next provided. Through this bar (1) are then bored two 5/16-inch +holes 1-3/4 inches apart, and on the opposite sides of this bar are two +half-rounded plates of iron (3) (Fig. 25). + +ARMATURE WINDING.--Each plate is 1/2 inch thick, 1-3/4 inches wide and 4 +inches long, each plate having holes (4) to coincide with the holes (2) +of the bar (1), so that when the two plates are applied to opposite +sides of the bar, and riveted together, a cylindrical member is formed, +with two channels running longitudinally, and transversely at the ends; +and in these channels the insulated wires are wound from end to end +around the central block (1). + +MOUNTING THE ARMATURE.--It is now necessary to provide a means for +revolving this armature. To this end a brass disc (5, Fig. 26) is made, +2 inches in diameter, 1/8 inch thick. Centrally, at one side, is a +projecting stem (6) of round brass, which projects out 2 inches, and the +outer end is turned down, as at 7, to form a small bearing surface. + +[Illustration: _Fig. 26._ JOURNALS _Fig. 27._ COMMUTATOR, +ARMATURE MOUNTINGS] + +The other end of the armature has a similar disc (8), with a central +stem (9), 1-1/2 inches long, turned down to 1/4-inch diameter up to +within 1/4 inch of the disc (7), so as to form a shoulder. + +THE COMMUTATOR.--In Fig. 27 is shown, at 10, a wooden cylinder, 1 inch +long and 1-1/4 inches in diameter, with a hole (11) bored through +axially, so that it will fit tightly on the stem (6) of the disc (5). On +this wooden cylinder is driven a brass or copper tube (12), which has +holes (13) opposite each other. Screws are used to hold the tube to the +wooden cylinder, and after they are properly secured together, the tube +(12) is cut by a saw, as at 14, so as to form two independent tubular +surfaces. + +[Illustration: _Fig. 28._ END VIEW ARMATURE, MOUNTED] + +These tubular sections are called the commutator plates. + +[Illustration: _Fig. 29._ TOP VIEW OF ARMATURE ON BASE] + +In order to mount this armature, two bearings are provided, each +comprising a bar of brass (15, Fig. 28), each 1/4 inch thick, 1/2 inch +wide and 4-1/2 inches long. Two holes, 3 inches apart, are formed +through this bar, to receive round-headed wood screws (16), these screws +being 3 inches long, so they will pass through the wooden pieces (I) +and enter the base (J). Midway between the ends, each bar (15) has an +iron bearing block (17), 3/4" x 1/2" and 1-1/2 inches high, the 1/4-inch +hole for the journal (7) being midway between its ends. + +COMMUTATOR BRUSHES.--Fig. 28 shows the base, armature and commutator +assembled in position, and to these parts have been added the commutator +brushes. The brush holder (18) is a horizontal bar made of hard rubber +loosely mounted upon the journal pin (7), which is 2-1/2 inches long. At +each end is a right-angled metal arm (19) secured to the bar (18) by +screws (20). To these arms the brushes (21) are attached, so that their +spring ends engage with the commutator (12). An adjusting screw (22) in +the bearing post (17), with the head thereof bearing against the +brush-holder (18), serves as a means for revolubly adjusting the brushes +with relation to the commutator. + +DYNAMO WINDINGS.--There are several ways to wind the dynamos. These +can be shown better by the following diagrams (Figs. 30, 31, 32, 33): + +THE FIELD.--If the field (A, Fig. 30) is not a permanent magnet, it must +be excited by a cell or battery, and the wires (B, B') are connected up +with a battery, while the wires (C, C') may be connected up to run a +motor. This would, therefore, be what is called a "separately excited" +dynamo. In this case the battery excites the field and the armature +(D), cutting the lines of force at the pole pieces (E), so that the +armature gathers the current for the wires (C, C'). + +[Illustration: _Fig. 30._ FIELD WINDING] + +[Illustration: _Fig. 31._ SERIES-WOUND] + +SERIES-WOUND FIELD.--Fig. 31 shows a "series-wound" dynamo. The wires of +the fields (A) are connected up in series with the brushes of the +armature (D), and the wires (G, G') are led out and connected up with a +lamp, motor or other mechanism. In this case, as well as in Figs. 32 and +33, both the field and the armature are made of soft gray iron. With +this winding and means of connecting the wires, the field is constantly +excited by the current passing through the wires. + +SHUNT-WOUND FIELD.--Fig. 32 represents what is known as a "shunt-wound" +dynamo. Here the field wires (H, H) connect with the opposite brushes +of the armature, and the wires (I, I') are also connected with the +brushes, these two wires being provided to perform the work required. +This is a more useful form of winding for electroplating purposes. + +[Illustration: _Fig. 32._ SHUNT-WOUND _Fig. 32._ COMPOUND-WOUND] + +COMPOUND-WOUND FIELD.--Fig. 33 is a diagram of a "compound-wound" +dynamo. The regular field winding (J) has its opposite ends connected +directly with the armature brushes. There is also a winding, of a +comparatively few turns, of a thicker wire, one terminal (K) of which is +connected with one of the brushes and the other terminal (K') forms one +side of the lighting circuit. A wire (L) connects with the other +armature brush to form a complete lighting circuit. + + + + +CHAPTER V + +HOW TO DETECT AND MEASURE ELECTRICITY + + +MEASURING INSTRUMENTS.--The production of an electric current would not +be of much value unless we had some way by which we might detect and +measure it. The pound weight, the foot rule and the quart measure are +very simple devices, but without them very little business could be +done. There must be a standard of measurement in electricity as well as +in dealing with iron or vegetables or fabrics. + +As electricity cannot be seen by the human eye, some mechanism must be +made which will reveal its movements. + +THE DETECTOR.--It has been shown in the preceding chapter that a current +of electricity passing through a wire will cause a current to pass +through a parallel wire, if the two wires are placed close together, but +not actually in contact with each other. An instrument which reveals +this condition is called a _galvanometer_. It not only detects the +presence of a current, but it shows the direction of its flow. We shall +now see how this is done. + +For example, the wire (A, Fig. 35) is connected up in an electric +circuit with a permanent magnet (B) suspended by a fine wire (C), so +that the magnet (B) may freely revolve. + +[Illustration: _Fig. 34._ _Fig. 35._ _Fig. 36._ + TO THE RIGHT, COMPASS MAGNET, TO THE LEFT] + +For convenience, the magnetic field is shown flowing in the direction of +the darts, in which the dart (D) represents the current within the +magnet (B) flowing toward the north pole, and the darts (E) showing the +exterior current flowing toward the south pole. Now, if the wire (A) is +brought up close to the magnet (B), and a current passed through A, the +magnet (B) will be affected. Fig. 35 shows the normal condition of the +magnetized bar (B) parallel with the wire (A) when a current is not +passing through the latter. + +DIRECTION OF CURRENT.--If the current should go through the wire (A) +from right to left, as shown in Fig. 34, the magnet (B) would swing in +the direction taken by the hands of a clock and assume the position +shown in Fig. 34. If, on the other hand, the current in the wire (A) +should be reversed or flow from left to right, the magnet (B) would +swing counter-clock-wise, and assume the position shown in Fig. 36. The +little pointer (G) would, in either case, point in the direction of the +flow of the current through the wire (A). + +[Illustration: _Fig. 37._ INDICATING DIRECTION OF CURRENT] + +SIMPLE CURRENT DETECTOR.--A simple current detector may be made as +follows: + +Prepare a base 3' x 4' in size and 1 inch thick. At each corner of one +end fix a binding post, as at A, A', Fig. 37. Then select 20 feet of No. +28 cotton-insulated wire, and make a coil (B) 2 inches in diameter, +leaving the ends free, so they may be affixed to the binding posts (A, +A'). Now glue or nail six blocks (C) to the base, each block being 1" x +1" x 2", and lay the coil on these blocks. Then drive an L-shaped nail +(D) down into each block, on the inside of the coil, as shown, so as to +hold the latter in place. + +[Illustration: _Fig. 38._ THE BRIDGE] + +Now make a bridge (E, Fig. 38) of a strip of brass 1/2 inch wide, 1/16 +inch thick and long enough to span the coil, and bend the ends down, as +at F, so as to form legs. A screw hole (G) is formed in each foot, so it +may be screwed to the base. + +Midway between the ends this bridge has a transverse slot (H) in one +edge, to receive therein the pivot pin of the swinging magnet. In order +to hold the pivot pin in place, cut out an H-shaped piece of sheet brass +(I), which, when laid on the bridge, has its ends bent around the +latter, as shown at J, and the crossbar of the H-shaped piece then will +prevent the pivot pin from coming out of the slot (H). + +[Illustration: _Fig. 39._ DETAILS OF DETECTOR] + +The magnet is made of a bar of steel (K, Fig. 39) 1-1/2 inches long, 3/8 +inch wide and 1/16 inch thick, a piece of a clock spring being very +serviceable for this purpose. The pivot pin is made of an ordinary pin +(L), and as it is difficult to solder the steel magnet (K) to the pin, +solder only a small disc (M) to the pin (L). Then bore a hole (N) +through the middle of the magnet (K), larger in diameter than the pin +(L), and, after putting the pin in the hole, pour sealing wax into the +hole, and thereby secure the two parts together. Near the upper end of +the pin (L) solder the end of a pointer (O), this pointer being at right +angles to the armature (K). It is better to have a metal socket for the +lower end of the pin. When these parts are put together, as shown in +Fig. 37, a removable glass top, or cover, should be provided. + +This is shown in Fig. 40, in which a square, wooden frame (P) is used, +and a glass (Q) fitted into the frame, the glass being so arranged that +when the cover is in position it will be in close proximity to the upper +projecting end of the pivot pin (L), and thus prevent the magnet from +becoming misplaced. + +[Illustration: _Fig. 40._ CROSS SECTION OF DETECTOR] + +HOW TO PLACE THE DETECTOR.--If the detector is placed north and south, +as shown by the two markings, N and S (Fig. 37), the magnet bar will +point north and south, being affected by the earth's magnetism; but when +a current of electricity flows through the coil (B), the magnet will be +deflected to the right or to the left, so that the pointer (O) will then +show the direction in which the current is flowing through the wire (R) +which you are testing. + +The next step of importance is to _measure_ the current, that is, to +determine its strength or intensity, as well as the flow or quantity. + +DIFFERENT WAYS OF MEASURING A CURRENT.--There are several ways to +measure the properties of a current, which may be defined as follows: + +1. THE SULPHURIC ACID VOLTAMETER.--By means of an electrolytic action, +whereby the current decomposes an acidulated solution--that is, water +which has in it a small amount of sulphuric acid--and then measuring the +gas generated by the current. + +2. THE COPPER VOLTAMETER.--By electro-chemical means, in which the +current passes through plates immersed in a solution of copper sulphate. + +3. THE GALVANOSCOPE.--By having a coil of insulated wire, with a magnet +suspended so as to turn freely within the coil, forming what is called a +galvanoscope. + +4. ELECTRO-MAGNETIC METHOD.--By using a pair of magnets and sending a +current through the coils, and then measuring the pull on the armature. + +5. THE POWER OR SPEED METHOD.--By using an electric fan, and noting the +revolutions produced by the current. + +6. THE CALORIMETER.--By using a coil of bare wire, immersed in paraffine +oil, and then measuring the temperature by means of a thermometer. + +[Illustration: _Fig. 41._ ACID VOLTAMETER] + +[Illustration: _Fig. 42._ COPPER VOLTAMETER] + +7. THE LIGHT METHOD.--Lastly, by means of an electric light, which +shows, by its brightness, a greater or less current. + +THE PREFERRED METHODS.--It has been found that the first and second +methods are the only ones which will accurately register current +strength, and these methods have this advantage--that the chemical +effect produced is not dependent upon the size or shape of the apparatus +or the plates used. + +HOW TO MAKE A SULPHURIC ACID VOLTAMETER.--In Fig. 41 is shown a simple +form of sulphuric acid voltameter, to illustrate the first method. A is +a jar, tightly closed by a cover (B). Within is a pair of platinum +plates (C, C), each having a wire (D) through the cover. The cover has a +vertical glass tube (E) through it, which extends down to the bottom of +the jar, the electrolyte therein being a weak solution of sulphuric +acid. When a current passes through the wires (D), the solution is +partially decomposed--that is, converted into gas, which passes up into +the vacant space (F) above the liquid, and, as it cannot escape, it +presses the liquid downwardly, and causes the latter to flow upwardly +into the tube (E). It is then an easy matter, after the current is on +for a certain time, to determine its strength by the height of the +liquid in the tube. + +HOW TO MAKE A COPPER VOLTAMETER.--The second, or copper voltameter, is +shown in Fig. 42. The glass jar (A) contains a solution of copper +sulphate, known in commerce as blue vitriol. A pair of copper plates +(B, B') are placed in this solution, each being provided with a +connecting wire (C). When a current passes through the wires (C), one +copper plate (B) is eaten away and deposited on the other plate (B'). It +is then an easy matter to take out the plates and find out how much in +weight B' has gained, or how much B has lost. + +In this way, in comparing the strength of, say, two separate currents, +one should have each current pass through the voltameter the same length +of time as the other, so as to obtain comparative results. + +It is not necessary, in the first and second methods, to consider the +shapes, the sizes of the plates or the distances between them. In the +first method the gas produced, within a given time, will be the same, +and in the second method the amount deposited or eaten away will be the +same under all conditions. + +DISADVANTAGES OF THE GALVANOSCOPE.--With the third method (using the +galvanoscope) it is necessary, in order to get a positively correct +reading instrument, to follow an absolutely accurate plan in +constructing each part, in every detail, and great care must be +exercised, particularly in winding. It is necessary also to be very +careful in selecting the sizes of wire used and in the number of turns +made in the coils. + +This is equally true of the fourth method, using the electro-magnet, +because the magnetic pull is dependent upon the size of wire from which +the coils are made and the number of turns of wire. + +OBJECTIONS TO THE CALORIMETER.--The calorimeter, or sixth method, has +the same objection. The galvanoscope and electro-magnet do not respond +equally to all currents, and this is also true, even to a greater +extent, with the calorimeter. + + + + +CHAPTER VI + +VOLTS, AMPERES, OHMS AND WATTS + + +UNDERSTANDING TERMS.--We must now try to ascertain the meaning of some +of the terms so frequently used in connection with electricity. If you +intended to sell or measure produce or goods of any kind, it would be +essential to know how many pints or quarts are contained in a gallon, or +in a bushel, or how many inches there are in a yard, and you also ought +to know just what the quantity term _bushel_ or the measurement _yard_ +means. + +INTENSITY AND QUANTITY.--Electricity, while it has no weight, is capable +of being measured by means of its intensity, or by its quantity. Light +may be measured or tested by its brilliancy. If one light is of less +intensity than another and both of them receive their impulses from the +same source, there must be something which interferes with that light +which shows the least brilliancy. Electricity can also be interfered +with, and this interference is called _resistance_. + +VOLTAGE.--Water may be made to flow with greater or less force, or +velocity, through a pipe, the degree of same depending upon the height +of the water which supplies the pipe. So with electricity. It may pass +over a wire with greater or less force under one condition than another. +This force is called voltage. If we have a large pipe, a much greater +quantity of water will flow through it than will pass through a small +pipe, providing the pressure in each case is alike. This quantity in +electricity is called _amperage_. + +In the case of water, a column 1" x 1", 28 inches in height, weighs 1 +pound; so that if a pipe 1 inch square draws water from the bottom it +flows with a pressure of 1 pound. If the pipe has a measurement of 2 +square inches, double the quantity of water will flow therefrom, at the +same pressure. + +AMPERAGE.--If, on the other hand, we have a pipe 1 inch square, and +there is a depth of 56 inches of water in the reservoir, we shall get as +much water from the reservoir as though we had a pipe of 2 square inches +drawing water from a reservoir which is 28 inches deep. + +MEANING OF WATTS.--It is obvious, therefore, that if we multiply the +height of the water in inches with the area of the pipe, we shall obtain +a factor which will show how much water is flowing. + +Here are two examples: + +1. 28 inches = height of the water in the reservoir. + +2 square inches = size of the pipe. +Multiply 28 x 2 = 56. + +2. 56 = height of the water in the reservoir. +1 square inch = size of the pipe. +Multiply 56 x 1 = 56. + +Thus the two problems are equal. + +A KILOWATT.--Now, in electricity, remembering that the height of the +water corresponds with _voltage_ in electricity, and the size of the +pipe with _amperage_, if we multiply volts by amperes, or amperes by +volts, we get a result which is indicated by the term _watts_. One +thousand of these watts make a kilowatt, and the latter is the standard +of measurement by which a dynamo or motor is judged or rated. + +Thus, if we have 5 amperes and 110 volts, the result of multiplying them +would be 550 watts, or 5 volts and 110 amperes would produce 550 watts. + +A STANDARD OF MEASUREMENT.--But with all this we must have some +standard. A bushel measure is of a certain size, and a foot has a +definite length, so in electricity there is a recognized force and +quantity which are determined as follows: + +THE AMPERE STANDARD.--It is necessary, first, to determine what an +ampere is. For this purpose a standard solution of nitrate of silver is +used, and a current of electricity is passed through this solution. In +doing so the current deposits silver at the rate of 0.001118 grains per +second for each ampere. + +THE VOLTAGE STANDARD.--In order to determine the voltage we must know +something of _resistance_. Different metals do not transmit a current +with equal ease. The size of a conductor, also, is an important factor +in the passage of a current. A large conductor will transmit a current +much better than a small conductor. We must therefore have a standard +for the _ohm_, which is the measure of resistance. + +THE OHM.--It is calculated in this way: There are several standards, but +the one most generally employed is the _International Ohm_. To determine +it, by this system, a column of pure mercury, 106.3 millimeters long and +weighing 14.4521 grams, is used. This would make a square tube about 94 +inches long, and a little over 1/25 of an inch in diameter. The +resistance to a current flow in such a column would be equal to 1 ohm. + +CALCULATING THE VOLTAGE.--In order to arrive at the voltage we must use +a conductor, which, with a resistance of 1 ohm, will produce 1 ampere. +It must be remembered that the volt is the practical unit of +electro-motive force. + +While it would be difficult for the boy to conduct these experiments in +the absence of suitable apparatus, still, it is well to understand +thoroughly how and why these standards are made and used. + + + + +CHAPTER VII + +PUSH BUTTONS, SWITCHES, ANNUNCIATORS, BELLS AND +LIKE APPARATUS + + +SIMPLE SWITCHES.--We have now gone over the simpler or elementary +outlines of electrical phenomena, and we may commence to do some of the +practical work in the art. We need certain apparatus to make +connections, which will be constructed first. + +A TWO-POLE SWITCH.--A simple two-pole switch for a single line is made +as follows: + +A base block (A, Fig. 43) 3 inches long, 2 inches wide and 3/4 inch +thick, has on it, at one end, a binding screw (B), which holds a pair of +fingers (C) of brass or copper, these fingers being bent upwardly and so +arranged as to serve as fingers to hold a switch bar (D) between them. +This bar is also of copper or brass and is pivoted to the fingers. Near +the other end of the base is a similar binding screw (E) and fingers (F) +to receive the blade of the switch bar. The bar has a handle (G) of +wood. The wires are attached to the respective binding screws (B, E). + +DOUBLE-POLE SWITCH.--A double-pole switch or a switch for a double line +is shown in Fig. 44. This is made similar in all respects to the one +shown in Fig. 43, excepting that there are two switch blades (A, A) +connected by a cross bar (B) of insulating material, and this bar +carries the handle (C). + +[Illustration: _Fig. 43._ TWO-POLE SWITCH] + +[Illustration: _Fig. 44._ DOUBLE-POLE SWITCH] + +Other types of switch will be found very useful. In Fig. 45 is a simple +sliding switch in which the base block has, at one end, a pair of copper +plates (A, B), each held at one end to the base by a binding screw (C), +and having a bearing or contact surface (D) at its other end. At the +other end of the base is a copper plate (E) held by a binding screw (F), +to the inner end of which plate is hinged a swinging switch blade (G), +the free end of which is adapted to engage with the plates (A, B). + +[Illustration: _Fig. 45._ SLIDING SWITCH] + +SLIDING SWITCH.--This sliding switch form may have the contact plates +(A, B and C, Fig. 46) circularly arranged and any number may be located +on the base, so they may be engaged by a single switching lever (H). It +is the form usually adopted for rheostats. + +REVERSING SWITCH.--A reversing switch is shown in Fig. 47. The base has +two plates (A, B) at one end, to which the parallel switch bars (C, D) +are hinged. The other end of the base has three contact plates (E, F, G) +to engage the swinging switch bars, these latter being at such distance +apart that they will engage with the middle and one of the outer plates. +The inlet wires, positive and negative, are attached to the plates (A, +B, respectively), and one of the outlet wires (H) is attached to the +middle contact plate (F), while the other wire is connected up with both +of the outside plates. When the switch bars (C, D) are thrown to the +left so as to be in contact with E, F, the outside plate (E) and the +middle plate (F) will be positive and negative, respectively; but when +the switch is thrown to the right, as shown in the figure, plate F +becomes positive and plate E negative, as shown. + +[Illustration: _Fig. 46._ RHEOSTAT FORM OF SWITCH] + +PUSH BUTTONS.--A push button is but a modified structure of a switch, +and they are serviceable because they are operating, or the circuit is +formed only while the finger is on the button. + +[Illustration: _Fig. 47._ REVERSING SWITCH] + +In its simplest form (Fig. 48) the push button has merely a circular +base (A) of insulating material, and near one margin, on the flat side, +is a rectangular plate (B), intended to serve as a contact plate as well +as a means for attaching one of the wires thereto. In line with this +plate is a spring finger (C), bent upwardly so that it is normally out +of contact with the plate (B), its end being held by a binding screw +(D). To effect contact, the spring end of the finger (C) is pressed +against the bar (B), as at E. This is enclosed in a suitable casing, +such as will readily suggest itself to the novice. + +ELECTRIC BELL.--One of the first things the boy wants to make, and one +which is also an interesting piece of work, is an electric bell. + +To make this he will be brought, experimentally, in touch with several +important features in electrical work. He must make a battery for the +production of current, a pair of electro-magnets to be acted upon by the +current, a switch to control it, and, finally, he must learn how to +connect it up so that it may be operated not only from one, but from two +or more push buttons. + +[Illustration: _Fig. 48._ PUSH BUTTON] + +HOW MADE.--In Fig. 49 is shown an electric bell, as usually constructed, +so modified as to show the structure at a glance, with its connections. +A is the base, B, B' the binding posts for the wires, C, C the +electro-magnets, C' the bracket for holding the magnets, D the armature, +E the thin spring which connects the armature with the post F, G the +clapper arm, H the bell, I the adjusting screw on the post J, K the wire +lead from the binding post B to the first magnet, L the wire which +connects the two magnets, M the wire which runs from the second magnet +to the post J, and N a wire leading from the armature post to the +binding post B'. + +[Illustration: _Fig. 49._ ELECTRIC BELL] + +The principle of the electric bell is this: In looking at Fig. 49, you +will note that the armature bar D is held against the end of the +adjusting screw by the small spring E. When a current is turned on, it +passes through the connections and conduits as follows: Wire K to the +magnets, wire M to the binding post J, and set screw I, then through the +armature to the post F, and from post F to the binding post B'. + +[Illustration: _Fig. 50._ ARMATURE OF ELECTRIC BELL] + +ELECTRIC BELL--HOW OPERATED.--The moment a current passes through the +magnets (C, C), the core is magnetized, and the result is that the +armature (D) is attracted to the magnets, as shown by the dotted lines +(O), when the clapper strikes the bell. But when the armature moves over +to the magnet, the connection is broken between the screw (I) and +armature (D), so that the cores of the magnets are demagnetized and lose +their pull, and the spring (E) succeeds in drawing back the armature. +This operation of vibrating the armature is repeated with great +rapidity, alternately breaking and re-establishing the circuit, by the +action of the current. + +In making the bell, you must observe one thing, the binding posts (B, +B') must be insulated from each other, and the post J, or the post F, +should also be insulated from the base. For convenience we show the post +F insulated, so as to necessitate the use of wire (N) from post (F) to +binding post (B'). + +The foregoing assumes that you have used a cast metal base, as most +bells are now made; but if you use a wooden base, the binding posts (B, +B') and the posts (F, J) are insulated from each other, and the +construction is much simplified. + +It is better, in practice, to have a small spring (P, Fig. 50) between +the armature (D) and the end of the adjusting screw (I), so as to give a +return impetus to the clapper. The object of the adjusting screw is to +push and hold the armature close up to the ends of the magnets, if it +seems necessary. + +If two bells are placed on the base with the clapper mounted between +them, both bells will be struck by the swinging motion of the armature. + +An easily removable cap or cover is usually placed over the coils and +armature, to keep out dust. + +A very simple annunciator may be attached to the bell, as shown in the +following figures: + +[Illustration: _Figs. 51-54._ ANNUNCIATOR] + +ANNUNCIATORS.--Make a box of wood, with a base (A) 4" x 5" and 1/2 inch +thick. On this you can permanently mount the two side pieces (B) and two +top and bottom pieces (C), respectively, so they project outwardly +4-1/2 inches from the base. On the open front place a wood or metal +plate (D), provided with a square opening (D), as in Fig. 54, near its +lower end. This plate is held to the box by screws (E). + +Within is a magnet (F), screwed into the base (A), as shown in Fig. 51; +and pivoted to the bottom of the box is a vertical armature (G), which +extends upwardly and contacts with the core of the magnet. The upper end +of the armature has a shoulder (H), which is in such position that it +serves as a rest for a V-shaped stirrup (I), which is hinged at J to the +base (C). This stirrup carries the number plate (K), and when it is +raised to its highest point it is held on the shoulder (H), unless the +electro-magnet draws the armature out of range of the stirrup. A spring +(L) bearing against the inner side of the armature keeps its upper end +normally away from the magnet core. When the magnet draws the armature +inwardly, the number plate drops and exposes the numeral through the +opening in the front of the box. In order to return the number plate to +its original position, as shown in Fig. 51, a vertical trigger (M) +passes up through the bottom, its upper end being within range of one of +the limbs of the stirrup. + +This is easily made by the ingenious boy, and will be quite an +acquisition to his stock of instruments. In practice, the annunciator +may be located in any convenient place and wires run to that point. + +[Illustration: _Fig. 55._ ALARM SWITCH ON WINDOW] + +[Illustration: _Fig. 56._ BURGLAR ALARM ATTACHMENT TO WINDOW] + +BURGLAR ALARM.--In order to make a burglar alarm connection with a bell, +push buttons or switches may be put in circuit to connect with the +windows and doors, and by means of the annunciators you may locate the +door or window which has been opened. The simplest form of switch for a +window is shown in the following figures: + +The base piece (A), which may be of hard rubber or fiber, is 1/4 inch +thick and 1" x 1-1/2" in size. + +[Illustration: _Fig. 57._ BURGLAR ALARM CONTACT] + +At one end is a brass plate (B), with a hole for a wood screw (C), this +screw being designed to pass through the plate and also into the +window-frame, so as to serve as a means of attaching one of the wires +thereto. The inner end of the plate has a hole for a round-headed screw +(C') that also goes through the base and into the window-frame. It also +passes through the lower end of the heart-shaped metal switch-piece +(D). + +The upper end of the base has a brass plate (E), also secured to the +base and window by a screw (F) at its upper end. The heart-shaped switch +is of such length and width at its upper end that when it is swung to +the right with one of the lobes projecting past the edge of the +window-frame, the other lobe will be out of contact with the plate (E). + +[Illustration: _Fig. 58._ NEUTRAL POSITION OF CONTACT] + +The window sash (G) has a removable pin (H), which, when the sash moves +upwardly, is in the path of the lobe of the heart-shaped switch, as +shown in Fig. 56, and in this manner the pin (H) moves the upper end of +the switch (D) inwardly, so that the other lobe contacts with the plate +(E), and establishes an electric circuit, as shown in Fig. 57. During +the daytime the pin (H) may be removed, and in order to protect the +switch the heart-shaped piece (D) is swung inwardly, as shown in Fig. +58, so that neither of the lobes is in contact with the plate (E). + +WIRE CIRCUITING.--For the purpose of understanding fully the circuiting, +diagrams will be shown of the simple electric bell with two push +buttons; next in order, the circuiting with an annunciator and then the +circuiting necessary for a series of windows and doors, with annunciator +attachments. + +[Illustration: _Fig. 59._ CIRCUITING FOR ELECTRIC BELL] + +CIRCUITING SYSTEM WITH A BELL AND TWO PUSH BUTTONS.--Fig. 59 shows a +simple circuiting system which has two push buttons, although any number +may be used, so that the bell will ring when the circuit is closed by +either button. + +THE PUSH BUTTONS AND THE ANNUNCIATOR BELLS.--Fig. 60 shows three push +buttons and an annunciator for each button. These three circuits are +indicated by A, B and C, so that when either button makes contact, a +complete circuit is formed through the corresponding annunciator. + +[Illustration: _Fig. 60._ _Annunciators_] + +[Illustration: _Fig. 61._ WIRING SYSTEM FOR A HOUSE] + +WIRING UP A HOUSE.--The system of wiring up a house so that all doors +and windows will be connected to form a burglar alarm outfit, is shown +in Fig. 61. It will be understood that, in practice, the bell is mounted +on or at the annunciator, and that, for convenience, the annunciator +box has also a receptacle for the battery. The circuiting is shown +diagramatically, as it is called, so as fully to explain how the lines +are run. Two windows and a door are connected up with an annunciator +having three drops, or numbers 1, 2, 3. The circuit runs from one pole +of the battery to the bell and then to one post of the annunciator. From +the other post a wire runs to one terminal of the switch at the door or +window. The other switch terminal has a wire running to the other pole +of the battery. + +A, B, C represent the circuit wires from the terminals of the window and +door switches, to the annunciators. + +It is entirely immaterial which side of the battery is connected up with +the bell. + +From the foregoing it will readily be understood how to connect up any +ordinary apparatus, remembering that in all cases the magnet must be +brought into the electric circuit. + + + + +CHAPTER VIII + +ACCUMULATORS. STORAGE OR SECONDARY BATTERIES + + +STORING UP ELECTRICITY.--In the foregoing chapters we have seen that, +originally, electricity was confined in a bottle, called the Leyden jar, +from which it was wholly discharged at a single impulse, as soon as it +was connected up by external means. Later the primary battery and the +dynamo were invented to generate a constant current, and after these +came the second form of storing electricity, called the storage or +secondary battery, and later still recognized as accumulators. + +THE ACCUMULATOR.--The term _accumulator_ is, strictly speaking, the more +nearly correct, as electricity is, in reality, "_stored_" in an +accumulator. But when an accumulator is charged by a current of +electricity, a chemical change is gradually produced in the active +element of which the accumulator is made. This change or decomposition +continues so long as the charging current is on. When the accumulator is +disconnected from the charging battery or dynamo, and its terminals are +connected up with a lighting system, or with a motor, for instance, a +reverse process is set up, or the particles re-form themselves into +their original compositions, which causes a current to flow in a +direction opposite to that of the charging current. + +It is immaterial to the purposes of this chapter, as to the charging +source, whether it be by batteries or dynamos; the same principles will +apply in either case. + +[Illustration: _Fig. 62._ ACCUMULATOR GRIDS] + +ACCUMULATOR PLATES.--The elements used for accumulator plates are red +lead for the positive plates, and precipitated lead, or the well-known +litharge, for the negative plates. Experience has shown that the best +way to hold this material is by means of lead grids. + +Fig. 62 shows the typical form of one of these grids. It is made of +lead, cast or molded in one piece, usually square, as at A, with a wing +or projection (B), at one margin, extending upwardly and provided with a +hole (C). The grid is about a quarter of an inch thick. + +THE GRID.--The open space, called the grid, proper, comprises cross +bars, integral with the plate, made in a variety of shapes. Fig. 62 +shows three forms of constructing these bars or ribs, the object being +to provide a form which will hold in the lead paste, which is pressed in +so as to make a solid-looking plate when completed. + +THE POSITIVE PLATE.--The positive plate is made in the following manner: +Make a stiff paste of red lead and sulphuric acid; using a solution, +say, of one part of acid to two parts of water. The grid is laid on a +flat surface and the paste forced into the perforations with a stiff +knife or spatula. Turn over the grid so as to get the paste in evenly on +both sides. + +The grid is then stood on its edge, from 18 to 20 hours, to dry, and +afterwards immersed in a concentrated solution of chloride of lime, so +as to convert it into lead peroxide. When the action is complete it is +thoroughly rinsed in cold water, and is ready to use. + +THE NEGATIVE PLATE.--The negative plate is filled, in like manner, with +precipitated lead. This lead is made by putting a strip of zinc into a +standard solution of acetate of lead, and crystals will then form on the +zinc. These will be very thin, and will adhere together, firmly, forming +a porous mass. This, when saturated and kept under water for a short +time, may be put into the openings of the negative plate. + +[Illustration: _Fig. 63._ ASSEMBLAGE OF ACCUMULATOR PLATES] + +CONNECTING UP THE PLATES.--The next step is to put these plates in +position to form a battery. In Fig. 63 is shown a collection of plates +connected together. + +For simplicity in illustrating, the cell is made up of glass, porcelain, +or hard rubber, with five plates (A), A, A representing the negative and +B, B the positive plates. A base of grooved strips (C, C) is placed in +the batteries of the cell to receive the lower ends of the plates. The +positive plates are held apart by means of a short section of tubing +(D), which is clamped and held within the plates by a bolt (E), this +bolt also being designed to hold the terminal strip (F). + +In like manner, the negative plates are held apart by the two tubular +sections (G), each of which is of the same length as the section D of +the positives. The bolt (H) holds the negatives together as well as the +terminal (I). The terminals should be lead strips, and it would be well, +owing to the acid fumes which are formed, to coat all brass work, +screws, etc., with paraffine wax. + +The electrolyte or acid used in the cell, for working purposes, is a +pure sulphuric acid, which should be diluted with about four times its +weight in water. Remember, you should always add the strong acid to the +water, and never pour the water into the acid, as the latter method +causes a dangerous ebullition, and does not produce a good mixture. + +Put enough of this solution into the cell to cover the tops of the +plates, and the cell is ready. + +[Illustration: _Fig. 64._ CONNECTING UP STORAGE BATTERY IN SERIES] + +CHARGING THE CELLS.--The charge of the current must never be less than +2.5 volts. Each cell has an output, in voltage, of about 2 volts, hence +if we have, say, 10 cells, we must have at least 25 volts charging +capacity. We may arrange these in one line, or in series, as it is +called, so far as the connections are concerned, and charge them with a +dynamo, or other electrical source, which shows a pressure of 25 volts, +as illustrated in Fig. 64, or, instead of this, we may put them into two +parallel sets of 5 cells each, as shown in Fig. 65, and use 12.5 volts +to charge with. In this case it will take double the time because we are +charging with only one-half the voltage used in the first case. + +The positive pole of the dynamo should be connected with the positive +pole of the accumulator cell, and negative with negative. When this has +been done run up the machine until it slightly exceeds the voltage of +the cells. Thus, if we have 50 cells in parallel, like in Fig. 64, at +least 125 volts will be required, and the excess necessary should bring +up the voltage in the dynamo to 135 or 140 volts. + +[Illustration: _Fig. 65._ PARALLEL SERIES] + +[Illustration: _Fig. 66._ CHARGING CIRCUIT] + +THE INITIAL CHARGE.--It is usual initially to charge the battery from +periods ranging from 36 to 40 hours, and to let it stand for 12 or 15 +hours, after which to re-charge, until the positive plates have turned +to a chocolate color, and the negative plates to a slate or gray color, +and both plates give off large bubbles of gas. + +In charging, the temperature of the electrolyte should not exceed 100 deg. +Fahrenheit. + +When using the accumulators they should never be fully discharged. + +THE CHARGING CIRCUIT.--The diagram (Fig. 66) shows how a charging +circuit is formed. The lamps are connected up in parallel, as +illustrated. Each 16-candle-power 105-volt lamp will carry 1/2 ampere, +so that, supposing we have a dynamo which gives 110 volts, and we want +to charge a 4-volt accumulator, there will be 5-volt surplus to go to +the accumulator. If, for instance, you want the cell to have a charge of +2 amperes, four of these lamps should be connected up in parallel. If 3 +amperes are required, use 6 lamps, and so on. + + + + +CHAPTER IX + +THE TELEGRAPH + + +The telegraph is a very simple instrument. The key is nothing more or +less than a switch which turns the current on and off alternately. + +The signals sent over the wires are simply the audible sounds made by +the armature, as it moves to and from the magnets. + +MECHANISM IN TELEGRAPH CIRCUITS.--A telegraph circuit requires three +pieces of mechanism at each station, namely, a key used by the sender, a +sounder for the receiver, and a battery. + +THE SENDING KEY.--The base of the sending instrument is six inches long, +four inches wide, and three-quarters of an inch thick, made of wood, or +any suitable non-conducting material. The key (A) is a piece of brass +three-eighths by one-half inch in thickness and six inches long. Midway +between its ends is a cross hole, to receive the pivot pin (B), which +also passes through a pair of metal brackets (C, D), the bracket C +having a screw to hold one of the line wires, and the other bracket +having a metal switch (E) hinged thereto. This switch bar, like the +brackets, is made of brass, one-half inch wide by one-sixteenth of an +inch thick. + +Below the forward end of the key (A) is a cross bar of brass (F), +screwed to the base by a screw at one end, to receive the other line +wire. Directly below the key (A) is a screw (G), so that the key will +strike it when moved downwardly. The other end of the bar (F) contacts +with the forward end of the switch bar (E) when the latter is moved +inwardly. + +[Illustration: _Fig. 67._ TELEGRAPH SENDING KEY] + +The forward end of the key (A) has a knob (H) for the fingers, and the +rear end has an elastic (I) attached thereto which is secured to the end +of the base, so that, normally, the rear end is held against the base +and away from the screw head (G). The head (J) of a screw projects from +the base at its rear end. Key A contacts with it. + +When the key A contacts with the screw heads G, J, a click is produced, +one when the key is pressed down and the other when the key is released. + +You will notice that the two plates C, F are connected up in circuit +with the battery, so that, as the switch E is thrown, so as to be out of +contact, the circuit is open, and may be closed either by the key A or +the switch E. The use of the switch will be illustrated in connection +with the sounder. + +[Illustration: _Fig. 68._ TELEGRAPH SOUNDER] + +When the key A is depressed, the circuit of course goes through plate C, +key A and plate F to the station signalled. + +THE SOUNDER.--The sounder is the instrument which carries the +electro-magnet. + +In Fig. 68 this is shown in perspective. The base is six inches long and +four inches wide, being made, preferably, of wood. Near the forward end +is mounted a pair of electro-magnets (A, A), with their terminal wires +connected up with plates B, B', to which the line wires are attached. + +Midway between the magnets and the rear end of the base is a pair of +upwardly projecting brackets (C). Between these are pivoted a bar (D), +the forward end of which rests between the magnets and carries, thereon, +a cross bar (E) which is directly above the magnets, and serves as the +armature. + +The rear end of the base has a screw (F) directly beneath the bar D of +such height that when the rear end of the bar D is in contact therewith +the armature E will be out of contact with the magnet cores (A, A). A +spiral spring (G) secured to the rear ends of the arm and to the base, +respectively, serves to keep the rear end of the key normally in contact +with the screw F. + +CONNECTING UP THE KEY AND SOUNDER.--Having made these two instruments, +we must next connect them up in the circuit, or circuits, formed for +them, as there must be a battery, a key, and a sounder at each end of +the line. + +In Fig. 69 you will note two groups of those instruments. Now observe +how the wires connect them together. There are two line wires, one (A) +which connects up the two batteries, the wire being attached so that +one end connects with the positive terminal of the battery, and the +other end with the negative terminal. + +[Illustration: _Fig. 69._ A TELEGRAPH CIRCUIT] + +The other line wire (B), between the two stations, has its opposite ends +connected with the terminals of the electro-magnet C of the sounders. +The other terminals of each electro-magnet are connected up with one +terminal of each key by a wire (D), and to complete the circuit at each +station, the other terminal of the key has a wire (E) to its own +battery. + +TWO STATIONS IN CIRCUIT.--The illustration shows station 2 telegraphing +to station 1. This is indicated by the fact that the switch F' of that +instrument is open, and the switch F of station 1 closed. When, +therefore, the key of station 2 is depressed, a complete circuit is +formed which transmits the current through wire E' and battery, through +line A, then through the battery of station 1, through wire E to the +key, and from the key, through wire D, to the sounder, and finally from +the sounder over line wire B back to the sounder of station 2, +completing the circuit at the key through wire D'. + +When the operator at station 2 closes the switch F', and the operator at +station 1 opens the switch F, the reverse operation takes place. In both +cases, however, the sounder is in at both ends of the line, and only the +circuit through the key is cut out by the switch F, or F'. + +THE DOUBLE CLICK.--The importance of the double click of the sounder +will be understood when it is realized that the receiving operator must +have some means of determining if the sounder has transmitted a dot or a +dash. Whether he depresses the key for a dot or a dash, there must be +one click when the key is pressed down on the screw head G (Fig. 62), +and also another click, of a different kind, when the key is raised up +so that its rear end strikes the screw head J. This action of the key is +instantly duplicated by the bar D (Fig. 68) of the sounder, so that the +sounder as well as the receiver knows the time between the first and the +second click, and by that means he learns that a dot or a dash is made. + +ILLUSTRATING THE DOT AND THE DASH.--To illustrate: Let us suppose, for +convenience, that the downward movement of the lever in the key, and the +bar in the sounder, make a sharp click, and the return of the lever and +bar make a dull click. In this case the ear, after a little practice, +can learn readily how to distinguish the number of downward impulses +that have been given to the key. + +_The Morse Telegraph Code_ + +A . - N - . & . ... +B - ... O .. 1 . - - . +C .. . P ..... 2 .. - .. +D - . . Q .. - . 3 ... - . +E . R . .. 4 .... - +F . - . S ... 5 - - - +G - - . T - 6 ...... +H .... U .. - 7 - - .. +I .. V ... - 8 - .... +J - . - . W . - - 9 - .. - +K - . - X . - .. 0 ---- ------ +L -- Y .. .. +M - - Z ... . + +EXAMPLE IN USE.--Let us take an example in the word "electrical." + +E L E C T R I C A L +. -- . .. . - . .. .. .. . . - -- + +The operator first makes a dot, which means a sharp and a dull click +close together; there is then a brief interval, then a lapse, after +which there is a sharp click, followed, after a comparatively longer +interval, with the dull click. Now a dash by itself may be an L, a T, or +the figure 0, dependent upon its length. The short dash is T, and the +longest dash the figure 0. The operator will soon learn whether it is +either of these or the letter L, which is intermediate in length. + +In time the sender as well as receiver will give a uniform length to the +dash impulse, so that it may be readily distinguished. In the same way, +we find that R, which is indicated by a dot, is followed, after a short +interval, by two dots. This might readily be mistaken for the single dot +for E and the two dots for I, were it not that the time element in R is +not as long between the first and second dots, as it ordinarily is +between the single dot of E when followed by the two dots of I. + + + + +CHAPTER X + +HIGH TENSION APPARATUS, CONDENSERS, ETC. + + +INDUCTION.--One of the most remarkable things in electricity is the +action of induction--that property of an electric current which enables +it to pass from one conductor to another conductor through the air. +Another singular and interesting thing is that the current so +transmitted across spaces changes its direction of flow, and, +furthermore, the tension of such a current may be changed by +transmitting it from one conductor to another. + +LOW AND HIGH TENSION.--In order to effect this latter change--that is, +to convert it from a low tension to a high tension--coils are used, one +coil being wound upon the other; one of these coils is called the +primary and the other the secondary. The primary coil receives the +current from the battery, or source of electrical power, and the +secondary coil receives charges, and transmits the current. + +For an illustration of this examine Fig. 70, in which you will note a +coil of heavy wire (A), around which is wound a coil of fine wire (B). +If, for instance, the primary coil has a low voltage, the secondary +coil will have a high voltage, or tension. Advantage is taken of this +phase to use a few cells, as a primary battery, and then, by a set of +_Induction Coils_, as they are called, to build up a high-tension +electro-motive force, so that the spark will jump across a gap, as shown +at C, for the purpose of igniting the charges of gas in a gasoline +motor; or the current may be used for medical batteries, and for other +purposes. + +[Illustration: _Fig. 70._ INDUCTION COIL AND CIRCUIT] + +The current passes, by induction, from the primary to the secondary +coil. It passes from a large conductor to a small conductor, the small +conductor having a much greater resistance than the large one. + +ELASTIC PROPERTY OF ELECTRICITY.--While electricity has no resiliency, +like a spring, for instance, still it acts in the manner of a cushion +under certain conditions. It may be likened to an oscillating spring +acted upon by a bar. + +Referring to Fig. 71, we will assume that the bar A in falling down upon +the spring B compresses the latter, so that at the time of greatest +compression the bar goes down as far as the dotted line C. It is obvious +that the spring B will throw the bar upwardly. Now, electricity appears +to have a kind of elasticity, which characteristic is taken advantage of +in order to increase the efficiency of the induction in the coil. + +[Illustration: _Fig. 71._ ILLUSTRATING ELASTICITY] + +THE CONDENSER.--To make a condenser, prepare two pine boards like A, +say, eight by ten inches and a half inch thick, and shellac thoroughly +on all sides. Then prepare sheets of tinfoil (B), six by eight inches in +size, and also sheets of paraffined paper (C), seven by nine inches in +dimensions. Also cut out from the waste pieces of tinfoil strips (D), +one inch by two inches. To build up the condenser, lay down a sheet of +paraffined paper (C), then a sheet of tinfoil (B), and before putting +on the next sheet of paraffined paper lay down one of the small strips +(D) of tinfoil, as shown in the illustration, so that its end projects +over one end of the board A; then on the second sheet of paraffine paper +lay another sheet of tinfoil, and on this, at the opposite end, place +one of the small strips (D), and so on, using from 50 to 100 of the +tinfoil sheets. When the last paraffine sheet is laid on, the other +board is placed on top, and the whole bound together, either by wrapping +cords around the same or by clamping them together with bolts. + +[Illustration: _Fig. 72._ CONDENSER] + +You may now make a hole through the projecting ends of the strips, and +you will have two sets of tinfoil sheets, alternately connected together +at opposite ends of the condenser. + +Care should be exercised to leave the paraffine sheets perfect or +without holes. You can make these sheets yourself by soaking them in +melted paraffine wax. + +CONNECTING UP A CONDENSER.--When completed, one end of the condenser is +connected up with one terminal of the secondary coil, and the other end +of the condenser with the other secondary terminal. + +[Illustration: _Fig. 73._ HIGH-TENSION CIRCUIT] + +In Fig. 73 a high-tension circuit is shown. Two coils, side by side, are +always used to show an induction coil, and a condenser is generally +shown, as illustrated, by means of a pair of forks, one resting within +the other. + +THE INTERRUPTER.--One other piece of mechanism is necessary, and that is +an _Interrupter_, for the purpose of getting the effect of the +pulsations given out by the secondary coil. + +A simple current interrupter is made as follows: Prepare a wooden base +(A), one inch thick, six inches wide, and twelve inches long. Upon this +mount a toothed wheel (B), six inches in diameter, of thin sheet metal, +or a brass gear wheel will answer the purpose. The standard (C), which +supports the wheel, may be of metal bent up to form two posts, between +which the crankshaft (D) is journaled. The base of the posts has an +extension plate (E), with a binding post for a wire. At the front end of +the base is an L-shaped strip (F), with a binding post for a wire +connection, and the upwardly projecting part of the strip contacts with +the toothed wheel. When the wheel B is rotated the spring finger (F) +snaps from one tooth to the next, so that, momentarily, the current is +broken, and the frequency is dependent upon the speed imparted to the +wheel. + +[Illustration: _Fig. 74._ CURRENT INTERRUPTER] + +USES OF HIGH-TENSION COILS.--This high-tension coil is made use of, and +is the essential apparatus in wireless telegraphy, as we shall see in +the chapter treating upon that subject. + + + + +CHAPTER XI + +WIRELESS TELEGRAPHY + + +TELEGRAPHING WITHOUT WIRES.--Wireless telegraphy is an outgrowth of the +ordinary telegraph system. When Maxwell, and, later on, Hertz, +discovered that electricity, magnetism, and light were transmitted +through the ether, and that they differed only in their wave lengths, +they laid the foundations for wireless telegraphy. Ether is a substance +which is millions and millions of times lighter than air, and it +pervades all space. It is so unstable that it is constantly in motion, +and this phase led some one to suggest that if a proper electrical +apparatus could be made, the ether would thereby be disturbed +sufficiently so that its impulses would extend out a distance +proportioned to the intensity of the electrical agitation thereby +created. + +SURGING CHARACTER OF HIGH-TENSION CURRENTS.--When a current of +electricity is sent through a wire, hundreds of miles in length, the +current surges back and forth on the wire many thousands of times a +second. Light comes to us from the sun, over 90,000,000 of miles, +through the ether. It is as reasonable to suppose, or infer, that the +ether can, therefore, convey an electrical impulse as readily as does a +wire. + +It is on this principle that impulses are sent for thousands of miles, +and no doubt they extend even farther, if the proper mechanism could be +devised to detect movement of the waves so propagated. + +THE COHERER.--The instrument for detecting these impulses, or +disturbances, in the ether is generally called a _coherer_, although +detector is the term which is most satisfactory. The name coherer comes +from the first practical instrument made for this purpose. + +[Illustration: _Fig. 75._ WIRELESS TELEGRAPHY COHERER] + +HOW MADE.--The coherer is simply a tube, say, of glass, within which is +placed iron filings. When the oscillations surge through the secondary +coil the pressure or potentiality of the current finally causes it to +leap across the small space separating the filings and, as it were, it +welds together their edges so that a current freely passes. The +bringing together of the particles, under these conditions, is called +cohering. + +Fig. 75 shows the simplest form of coherer. The posts (A) are firmly +affixed to the base (B), each post having an adjusting screw (C) in its +upper end, and these screw downwardly against and serve to bind a pair +of horizontal rods (D), the inner ends of which closely approach each +other. These may be adjusted so as to be as near together or as far +apart as desired. E is a glass tube in which the ends of the rods (D) +rest, and between the separated ends of the rods (D) the iron filings +(F) are placed. + +THE DECOHERERS.--For the purpose of causing the metal filings to fall +apart, or decohere, the tube is tapped lightly, and this is done by a +little object like the clapper of an electric bell. + +In practice, the coils and the parts directly connected with it are put +together on one base. + +THE SENDING APPARATUS.--Fig. 76 shows a section of a coil with its +connection in the sending station. The spark gap rods (A) may be swung +so as to bring them closer together or farther apart, but they must not +at any time contact with each other. + +The induction coil has one terminal of the primary coil connected up by +a wire (B) with one post of a telegraph key, and the other post of the +key has a wire connection (C), with one side of a storage battery. The +other side of the battery has a wire (D) running to the other terminal +of the primary. + +[Illustration: _Fig. 76._ WIRELESS SENDING APPARATUS] + +The secondary coil has one of its terminals connected with a binding +post (E). This binding post has an adjustable rod with a knob (F) on its +end, and the other binding post (G), which is connected up with the +other terminal of the secondary coil, carries a similar adjusting rod +with a knob (H). + +From the post (E) is a wire (I), which extends upwardly, and is called +the aerial wire, or wire for the antennae, and this wire also connects +with one side of the condenser by a conductor (J). The ground wire (K) +connects with the other binding post (G), and a branch wire (L) also +connects the ground wire (K) with one end of the condenser. + +[Illustration: _Fig. 77._ WIRELESS RECEIVING APPARATUS] + +THE RECEIVING APPARATUS.--The receiving station, on the other hand, has +neither condenser, induction coil, nor key. When the apparatus is in +operation, the coherer switch is closed, and the instant a current +passes through the coherer and operates the telegraph sounder, the +galvanometer indicates the current. + +Of course, when the coherer switch is closed, the battery operates the +decoherer. + +HOW THE CIRCUITS ARE FORMED.--By referring again to Fig. 76, it will be +seen that when the key is depressed, a circuit is formed from the +battery through wire B to the primary coil, and back again to the +battery through wire D. The secondary coil is thereby energized, and, +when the full potential is reached, the current leaps across the gap +formed between the two knobs (F, H), thereby setting up a disturbance in +the ether which is transmitted through space in all directions. + +It is this impulse, or disturbance, which is received by the coherer at +the receiving station, and which is indicated by the telegraph sounder. + + + + +CHAPTER XII + +THE TELEPHONE + + +VIBRATIONS.--Every manifestation in nature is by way of vibration. The +beating of the heart, the action of the legs in walking, the winking of +the eyelid; the impulses from the sun, which we call light; sound, taste +and color appeal to our senses by vibratory means, and, as we have +hereinbefore stated, the manifestations of electricity and magnetism are +merely vibrations of different wave lengths. + +THE ACOUSTIC TELEPHONE.--That sound is merely a product of vibrations +may be proven in many ways. One of the earliest forms of telephones was +simply a "sound" telephone, called the _Acoustic Telephone_. The +principle of this may be illustrated as follows: + +Take two cups (A, B), as in Fig. 78, punch a small hole through the +bottom of each, and run a string or wire (C) from the hole of one cup to +that of the other, and secure it at both ends so it may be drawn taut. +Now, by talking into the cup (A) the bottom of it will vibrate to and +fro, as shown by the dotted lines and thereby cause the bottom of the +other cup (B) to vibrate in like manner, and in so vibrating it will +receive not only the same amplitude, but also the same character of +vibrations as the cup (A) gave forth. + +[Illustration: _Fig. 78._ ACOUSTIC TELEPHONE] + +[Illustration: _Fig. 79._ ILLUSTRATING VIBRATIONS] + +SOUND WAVES.--Sound waves are long and short; the long waves giving +sounds which are low in the musical scale, and the short waves high +musical tones. You may easily determine this by the following +experiment: + +Stretch a wire, as at B (Fig. 79), fairly tight, and then vibrate it. +The amplitude of the vibration will be as indicated by dotted line A. +Now, stretch it very tight, as at C, so that the amplitude of vibration +will be as shown at E. By putting your ear close to the string you will +find that while A has a low pitch, C is very much higher. This is the +principle on which stringed instruments are built. You will note that +the wave length, which represents the distance between the dotted lines +A is much greater than E. + +HEARING ELECTRICITY.--In electricity, mechanism has been made to enable +man to note the action of the current. By means of the armature, +vibrating in front of a magnet, we can see its manifestations. It is now +but a step to devise some means whereby we may hear it. In this, as in +everything else electrically, the magnet comes into play. + +[Illustration: _Fig. 80._ THE MAGNETIC FIELD] + +In the chapter on magnetism, it was stated that the magnetic field +extended out beyond the magnet, so that if we were able to see the +magnetism, the end of a magnet would appear to us something like a +moving field, represented by the dotted lines in Fig. 80. + +The magnetic field is shown in Fig. 80 at only one end, but its +manifestations are alike at both ends. It will be seen that the magnetic +field extends out to a considerable distance and has quite a radius of +influence. + +THE DIAPHRAGM IN A MAGNETIC FIELD.--If, now, we put a diaphragm (A) in +this magnetic field, close up to the end of the magnet, but not so close +as to touch it, and then push it in and out, or talk into it so that the +sound waves strike it, the movement or the vibration of the diaphragm +(A) will disturb the magnetic field emanating from the magnet, and this +disturbance of the magnetic field at one end of the magnet also affects +the magnetic field at the other end in the same way, so that the +disturbance there will be of the same amplitude. It will also display +the same characteristics as did the magnetic field when the diaphragm +(A) disturbed it. + +A SIMPLE TELEPHONE CIRCUIT.--From this simple fact grew the telephone. +If two magnets are connected up in the same circuit, so that the +magnetic fields of the two magnets have the same source of electric +power, the disturbance of one diaphragm will affect the other similarly, +just the same as the two magnetic fields of the single magnet are +disturbed in unison. + +HOW TO MAKE A TELEPHONE.--For experimental and testing purposes two of +these telephones should be made at the same time. The case or holder +(A) may be made either of hard wood or hard rubber, so that it is of +insulating material. The core (B) is of soft iron, 3/8 inch in diameter +and 5 inches long, bored and threaded at one end to receive a screw (C) +which passes through the end of the case (A). + +The enlarged end of the case should be, exteriorly, 2-1/4 inches in +diameter, and the body of the case 1 inch in diameter. + +[Illustration: _Fig. 81._ SECTION OF TELEPHONE RECEIVER] + +Interiorly, the large end of the case is provided with a circular recess +1-3/4 inches in diameter and adapted to receive therein a spool which +is, diametrically, a little smaller than the recess. The spool fits +fairly tight upon the end of the core, and when in position rests +against an annular shoulder in the recess. A hollow space (F) is thus +provided behind the spool (D), so the two wires from the magnet may +have room where they emerge from the spool. + +The spool is a little shorter than the distance between the shoulder (E) +and the end of the casing, at G, and the core projects only a short +distance beyond the end of the spool, so that when the diaphragm (H) is +put upon the end of the case, and held there by screws (I) it will not +touch the end of the core. A wooden or rubber mouthpiece (J) is then +turned up to fit over the end of the case. + +[Illustration: _Fig. 82._ THE MAGNET AND RECEIVER HEAD] + +The spool (D) is made of hard rubber, and is wound with No. 24 +silk-covered wire, the windings to be well insulated from each other. +The two ends of the wire are brought out, and threaded through holes (K) +drilled longitudinally through the walls of the case, and affixed to the +end by means of screws (L), so that the two wires may be brought +together and connected with a duplex wire (M). + +As the screw (C), which holds the core in place, has its head hidden +within a recess, which can be closed up by wax, the two terminals of the +wires are well separated so that short-circuiting cannot take place. + +TELEPHONE CONNECTIONS.--The simplest form of telephone connection is +shown in Fig. 83. This has merely the two telephones (A and B), with a +single battery (C) to supply electricity for both. One line wire (D) +connects the two telephones directly, while the other line (E) has the +battery in its circuit. + +[Illustration: _Fig. 83._ SIMPLE TELEPHONE CONNECTION] + +COMPLETE INSTALLATION.--To install a more complete system requires, at +each end, a switch, a battery and an electro-magneto bell. You may use, +for this purpose, a bell, made as shown in the chapter on bells. + +Fig. 84 shows such a circuit. We now dispense with one of the line +wires, because it has been found that the ground between the two +stations serves as a conductor, so that only one line wire (A) is +necessary to connect directly with the telephones of the two stations. +The telephones (B, B', respectively) have wires (C, C') running to the +pivots of double-throw switches (D, D'), one terminal of the switches +having wires (E, E'), which go to electric bells (F, F'), and from the +bells are other wires (G, G'), which go to the ground. The ground wires +also have wires (H, H'), which go to the other terminals of the switch +(D, D'). The double-throw switch (D, D'), in the two stations, is thrown +over so the current, if any should pass through, will go through the +bell to the ground, through the wires (E, G or E', G'). + +[Illustration: _Fig. 84._ TELEPHONE STATIONS IN CIRCUIT] + +Now, supposing the switch (D'), in station 2, should be thrown over so +it contacts with the wire (H'). It is obvious that the current will then +flow from the battery (I') through wires (H', C') and line (A) to +station 1; then through wire C, switch D, wire E to the bell F, to the +ground through wire G. From wire G the current returns through the +ground to station 2, where it flows up wire G' to the battery, thereby +completing the circuit. + +[Illustration: _Fig. 85._ ILLUSTRATING LIGHT CONTACT POINTS] + +The operator at station 2, having given the signal, again throws his +switch (D') back to the position shown in Fig. 84, and the operator at +station 1 throws on his switch (D), so as to ring the bell in station 2, +thereby answering the signal, which means that both switches are again +to be thrown over so they contact with the battery wires (H and H'), +respectively. When both are thus thrown over, the bells (G, G') are cut +out of the circuit, and the batteries are both thrown in, so that the +telephones are now ready for talking purposes. + +MICROPHONE.--Originally this form of telephone system was generally +employed, but it was found that for long distances a more sensitive +instrument was necessary. + +LIGHT CONTACT POINTS.--In 1877 Professor Hughes discovered, +accidentally, that a light contact point in an electric circuit +augmented the sound in a telephone circuit. If, for instance, a light +pin, or a nail (A, Fig. 85) should be used to connect the severed ends +of a wire (B), the sounds in the telephone not only would be louder, but +they would be more distinct, and the first instrument made practically, +to demonstrate this, is shown in Fig. 86. + +[Illustration: _Fig. 86._ MICROPHONE] + +[Illustration: _Fig. 87._ TRANSMITTER] + +HOW TO MAKE A MICROPHONE.--This instrument has simply a base (A) of +wood, and near one end is a perpendicular sounding-board (B) of wood, to +one side of which is attached, by wax or otherwise, a pair of carbon +blocks (C, D). The lower carbon block (C) has a cup-shaped depression in +its upper side, and the upper block has a similar depression in its +lower side. A carbon pencil (E) is lightly held within these cups, so +that the lightest contact of the upper end of the pencil with the +carbon block, makes the instrument so sensitive that a fly, walking upon +the sounding-board, may be distinctly heard through the telephone which +is in the circuit. + +MICROPHONE THE FATHER OF THE TRANSMITTER.--This instrument has been +greatly modified, and is now used as a transmitter, the latter thereby +taking the place of the pin (A), shown in Fig. 85. + +AUTOMATIC CUT-OUTS FOR TELEPHONES.--In the operation of the telephone, +the great drawback originally was in inducing users of the lines to +replace or adjust their instruments carefully. When switches were used, +they would forget to throw them back, and all sorts of trouble resulted. + +It was found necessary to provide an automatic means for throwing in and +cutting out an instrument, this being done by hanging the telephone on +the hook, so that the act merely of leaving the telephone made it +necessary, in replacing the instrument, to cut out the apparatus. + +Before describing the circuiting required for these improvements, we +show, in Fig. 87, a section of a transmitter. + +A cup-shaped case (A) is provided, made of some insulating material, +which has a diaphragm (B) secured at its open side. This diaphragm +carries the carbon pencil (C) on one side and from the blocks which +support the carbon pencil the wires run to binding posts on the case. +Of course the carbon supporting posts must be insulated from each other, +so the current will go through the carbon pencil (C). + +COMPLETE CIRCUITING WITH TRANSMITTER.--In showing the circuiting (Fig. +88) it will not be possible to illustrate the boxes, or casings, which +receive the various instruments. For instance, the hook which carries +the telephone or the receiver, is hinged within the transmitter box. The +circuiting is all that it is intended to show. + +[Illustration: _Fig. 88._ COMPLETE TELEPHONIC CIRCUIT] + +The batteries of the two stations are connected up by a wire (A), unless +a ground circuit is used. The other side of each battery has a wire +connection (B, B') with one terminal of the transmitter, and the other +terminal of the transmitter has a wire (C, C') which goes to the +receiver. From the other terminal of the receiver is a wire (D, D') +which leads to the upper stop contact (E, E') of the telephone hook. A +wire (F, F') from the lower stop contact (G, G') of the hook goes to one +terminal of the bell, and from the other terminal of the bell is a wire +(H, H') which makes connection with the line wire (A). In order to make +a complete circuit between the two stations, a line wire (I) is run from +the pivot of the hook in station 1 to the pivot of the hook in station +2. + +In the diagram, it is assumed that the receivers are on the hooks, and +that both hooks are, therefore, in circuit with the lower contacts (G, +G'), so that the transmitter and receiver are both out of circuit with +the batteries, and the bell in circuit; but the moment the receiver, for +instance, in station 1 is taken off the hook, the latter springs up so +that it contacts with the stop (E), thus establishing a circuit through +the line wire (I) to the hook of station 2, and from the hook through +line (F') to the bell. From the bell, the line (A) carries the current +back to the battery of station (A), thence through the wire (B) to the +transmitter wire (C) to receiver and wire (D) to the post (E), thereby +completing the circuit. + +When, at station 2, the receiver is taken off the hook, and the latter +contacts with the post (E'), the transmitter and receiver of both +stations are in circuit with each other, but both bells are cut out. + + + + +CHAPTER XIII + +ELECTROLYSIS, WATER PURIFICATION, ELECTROPLATING + + +DECOMPOSING LIQUIDS.--During the earlier experiments in the field of +electricity, after the battery or cell was discovered, it was noted that +when a current was formed in the cell, the electrolyte was charged and +gases evolved from it. A similar action takes place when a current of +electricity passes through a liquid, with the result that the liquid is +decomposed--that is, the liquid is broken up into its original +compounds. Thus, water is composed of two parts, by bulk, of hydrogen +and of oxygen, so that if two electrodes are placed in water, and a +current is sent through the electrodes in either direction, all the +water will finally disappear in the form of hydrogen and oxygen gases. + +MAKING HYDROGEN AND OXYGEN.--During this electrical action, the hydrogen +is set free at the negative pole and the oxygen at the positive pole. A +simple apparatus, which any boy can make, to generate pure oxygen and +pure hydrogen, is shown in Fig. 89. + +It is constructed of a glass or earthen jar (A), preferably square, to +which is fitted a wooden top (B), this top being provided with a +packing ring (C), so as to make it air-tight. Within is a vertical +partition (D), the edges of which, below the cap, fit tightly against +the inner walls of the jar. This partition extends down into the jar a +sufficient distance so it will terminate below the water level. A pipe +is fitted through the top on each side of the partition, and each pipe +has a valve. An electrode, of any convenient metal, is secured at its +upper end to the top of the cap, on each side of the partition. These +electrodes extend down to the bottom of the jar, and an electric wire +connects with each of them at the top. + +[Illustration: _Fig. 89._ DEVICE FOR MAKING HYDROGEN AND OXYGEN] + +If a current of electricity is passed through the wires and the +electrodes, in the direction shown by the darts, hydrogen will form at +the negative pole, and oxygen at the positive pole. These gases will +escape upwardly, so that they will be trapped in their respective +compartments, and may be drawn off by means of the pipes. + +PURIFYING WATER.--Advantage is taken of this electrolytic action, to +purify water. Oxygen is the most wonderful chemical in nature. It is +called the acid-maker of the universe. The name is derived from two +words, _oxy_ and _gen_; one denoting oxydation, and the other that it +generates. In other words, it is the _generator of oxides_. It is the +element which, when united with any other element, produces an acid, an +alkali or a neutral compound. + +RUST.--For instance, iron is largely composed of ferric acid. When +oxygen, in a free or gaseous state, comes into contact with iron, it +produces ferrous oxide, which is recognized as rust. + +OXYGEN AS A PURIFIER.--But oxygen is also a purifier. All low forms of +animal life, like bacteria or germs in water, succumb to free oxygen. By +_free oxygen_ is meant oxygen in the form of gas. + +COMPOSITION OF WATER.--Now, water, in which harmful germs live, is +one-third oxygen. Nevertheless, the germs thrive in water, because the +oxygen is in a compound state, and, therefore, not an active agent. But +if oxygen, in the form of gas, can be forced through water, it will +attack the germs, and destroy them. + +COMMON AIR NOT A GOOD PURIFIER.--Water may be purified, to a certain +extent, by forcing common air through it, and the foulest water, if run +over rocks, will be purified, in a measure, because air is intermingled +with it. But common air is composed of four-fifths nitrogen, and only +one-fifth oxygen, and, as nitrogen is the staple article of food for +bacteria, the purifying method by air is not effectual. + +PURE OXYGEN.--When, however, oxygen is generated from water, by means of +electrolysis, it is pure; hence is more active and is not tainted by a +life-giving substance for germs, such as nitrogen. + +The mechanism usually employed for purifying water is shown in Fig. 90. + +A WATER PURIFIER.--The case (A, Fig. 90) may be made of metal or of an +insulating material. If made of metal it must be insulated within with +slate, glass, marble or hard rubber, as shown at B. The case is provided +with exterior flanges (C, D), with upper and lower ends, and it is +mounted upon a base plate (E) and affixed thereto by bolts. The upper +end has a conically-formed cap (F) bolted to the flanges (C), and this +has an outlet to which a pipe (G) is attached. The water inlet pipe (H) +passes through the lower end of the case (A). The electrodes (I, J) are +secured, vertically, within the case, separated from each other +equidistant, each alternate electrode being connected up with one wire +(K), and the alternate electrodes with a wire (L). + +[Illustration: _Fig. 90._ ELECTRIC WATER PURIFIER] + +When the water passes upwardly, the decomposed or gaseous oxygen +percolates through the water and thus attacks the germs and destroys +them. + +THE USE OF HYDROGEN IN PURIFICATION.--On the other hand, the hydrogen +also plays an important part in purifying the water. This depends upon +the material of which the electrodes are made. Aluminum is by far the +best material, as it is one of nature's most active purifiers. All clay +contains aluminum, in what is known as the sulphate form, and water +passing through the clay of the earth thereby becomes purified, because +of this element. + +ALUMINUM ELECTRODES.--When this material is used as the electrodes in +water, hydrate of aluminum is formed, or a compound of hydrogen and +oxygen with aluminum. The product of decomposition is a flocculent +matter which moves upwardly through the water, giving it a milky +appearance. This substance is like gelatine, so that it entangles or +enmeshes the germ life and prevents it from passing through a filter. + +If no filter is used, this flocculent matter, as soon as it has given +off the gases, will settle to the bottom and carry with it all +decomposed matter, such as germs and other organic matter attacked by +the oxygen, which has become entangled in the aluminum hydrate. + +ELECTRIC HAND PURIFIER.--An interesting and serviceable little purifier +may be made by any boy with the simplest tools, by cutting out three +pieces of sheet aluminum. Hard rolled is best for the purpose. It is +better to have one of the sheets (A), the middle one, thicker than the +two outer plates (B). + +[Illustration: _Fig. 91._ PORTABLE ELECTRIC PURIFIER] + +Let each sheet be 1-1/2 inches wide and 5-1/2 inches thick. One-half +inch from the upper ends of the two outside plates (B, B) bore bolt +holes (C), each of these holes being a quarter of an inch from the edge +of the plate. The inside plate (A) has two large holes (D) corresponding +with the small holes (C) in the outside plates. At the upper end of this +plate form a wing (E), 1/2 inch wide and 1/2 inch long, provided with a +small hole for a bolt. Next cut out two hard-rubber blocks (F), each +1-1/2 inches long, 1 inch wide and 3/8 inch thick, and then bore a hole +(G) through each, corresponding with the small holes (C) in the plates +(B). The machine is now ready to be assembled. If the inner plate is 1/8 +inch thick and the outer plates each 1/16 inch thick, use two small +eighth-inch bolts 1-1/4 inches long, and clamp together the three +plates with these bolts. One of the bolts may be used to attach thereto +one of the electric wires (H), and the other wire (I) is attached by a +bolt to the wing (E). + +[Illustration: _Figs. 92-95._ DETAILS OF PORTABLE PURIFIER] + +Such a device will answer for a 110-volt circuit, in ordinary water. Now +fill a glass nearly full of water, and stand the purifier in the glass. +Within a few minutes the action of electrolysis will be apparent by the +formation of numerous bubbles on the plates, followed by the +decomposition of the organic matter in the water. At first the +flocculent decomposed matter will rise to the surface of the water, but +before many minutes it will settle to the bottom of the glass and leave +clear water above. + +PURIFICATION AND SEPARATION OF METALS.--This electrolytic action is +utilized in metallurgy for the purpose of producing pure metals, but it +is more largely used to separate copper from its base. In order to +utilize a current for this purpose, a high ampere flow and low voltage +are required. The sheets of copper, containing all of its impurities, +are placed within a tank, parallel with a thin copper sheet. The impure +sheet is connected with the positive pole of an electroplating dynamo, +and the thin sheet of copper is connected with the negative pole. The +electrolyte in the tank is a solution of sulphate of copper. The action +of the current will cause the pure copper in the impure sheet to +disintegrate and it is then carried over and deposited upon the thin +sheet, this action continuing until the impure sheet is entirely eaten +away. All the impurities which were in the sheet fall to the bottom of +the tank. + +Other metals are treated in the same way, and this treatment has a very +wide range of usefulness. + +ELECTROPLATING.--The next feature to be considered in electrolysis is a +most interesting and useful one, because a cheap or inferior metal may +be coated by a more expensive metal. Silver and nickel plating are +brought about by this action of a current passing through metals, which +are immersed in an electrolyte. + +PLATING IRON WITH COPPER.--We have room in this chapter for only one +concrete example of this work, which, with suitable modifications, is an +example of the art as practiced commercially. Iron, to a considerable +extent, is now being coated with copper to preserve it from rust. To +carry out this work, however, an electroplating dynamo, of large +amperage, is required, the amperage, of course, depending upon the +surface to be treated at one time. The pressure should not exceed 5 +volts. + +The iron surface to be treated should first be thoroughly cleansed, and +then immediately put into a tank containing a cyanide of copper +solution. Two forms of copper solution are used, namely, the cyanide, +which is a salt solution of copper, and the sulphate, which is an acid +solution of copper. Cyanide is first used because it does not attack the +iron, as would be the case if the sulphate solution should first come +into contact with the iron. + +A sheet of copper, termed the anode, is then placed within the tank, +parallel with the surface to be plated, known as the cathode, and so +mounted that it may be adjusted to or from the iron surface, or cathode. +A direct current of electricity is then caused to flow through the +copper plate and into the iron plate or surface, and the plating +proceeded with until the iron surface has a thin film of copper +deposited thereon. This is a slow process with the cyanide solution, so +it is discontinued as soon as possible, after the iron surface has been +completely covered with copper. This copper surface is thoroughly +cleaned off to remove therefrom the saline or alkaline solution, and it +is then immersed within a bath, containing a solution of sulphate of +copper. The current is then thrown on and allowed so to remain until it +has deposited the proper thickness of copper. + +DIRECTION OF CURRENT.--If a copper and an iron plate are put into a +copper solution and connected up in circuit with each other, a primary +battery is thereby formed, which will generate electricity. In this +case, the iron will be positive and the copper negative, so that the +current within such a cell would flow from the iron (in this instance, +the anode) to the negative, or cathode. + +The action of electroplating reverses this process and causes the +current to flow from the copper to the iron (in this instance, the +cathode). + + + + +CHAPTER XIV + +ELECTRIC HEATING, THERMO ELECTRICITY + + +GENERATING HEAT IN A WIRE.--When a current of electricity passes through +a conductor, like a wire, more or less heat is developed in the +conductor. This heat may be so small that it cannot be measured, but it +is, nevertheless, present in a greater or less degree. Conductors offer +a resistance to the passage of a current, just the same as water finds a +resistance in pipes through which it passes. This resistance is measured +in ohms, as explained in a preceding chapter, and it is this resistance +which is utilized for electric heating. + +RESISTANCE OF SUBSTANCES.--Silver offers less resistance to the passage +of a current than any other metal, the next in order is copper, while +iron is, comparatively, a poor conductor. + +The following is a partial list of metals, showing their relative +conductivity: + +Silver 1. +Copper 1.04 to 1.09 +Gold 1.38 to 1.41 +Aluminum 1.64 +Zinc 3.79 +Nickel 4.69 +Iron 6.56 +Tin 8.9 +Lead 13.2 +German Silver 12.2 to 15 + +From this table it will be seen that, for instance, iron offers six and +a half times the resistance of silver, and that German silver has +fifteen times the resistance of silver. + +This table is made up of strands of the different metals of the same +diameters and lengths, so as to obtain their relative values. + +SIZES OF CONDUCTORS.--Another thing, however, must be understood. If two +conductors of the same metal, having different diameters, receive the +same current of electricity, the small conductor will offer a greater +resistance than the large conductor, hence will generate more heat. This +can be offset by increasing the diameter of the conductor. The metal +used is, therefore, of importance, on account of the cost involved. + +COMPARISON OF METALS.--A conductor of aluminum, say, 10 feet long and of +the same weight as copper, has a diameter two and a quarter times +greater than copper; but as the resistance of aluminum is 50 per cent. +more than that of silver, it will be seen that, weight for weight, +copper is the cheaper, particularly as aluminum costs fully three times +as much as copper. + +[Illustration: _Fig. 96._ SIMPLE ELECTRIC HEATER] + +The table shows that German silver has the highest resistance. Of +course, there are other metals, like antimony, platinum and the like, +which have still higher resistance. German silver, however, is most +commonly used, although there are various alloys of metal made which +have high resistance and are cheaper. + +The principle of all electric heaters is the same, namely, the +resistance of a conductor to the passage of a current, and an +illustration of a water heater will show the elementary principles in +all of these devices. + +A SIMPLE ELECTRIC HEATER.--In Fig. 96 the illustration shows a cup or +holder (A) for the wire, made of hard rubber. This may be of such +diameter as to fit upon and form the cover for a glass (B). The rubber +should be 1/2 inch thick. Two holes are bored through the rubber cup, +and through them are screwed two round-headed screws (C, D), each screw +being 1-1/2 inches long, so they will project an inch below the cap. +Each screw should have a small hole in its lower end to receive a pin +(E) which will prevent the resistance wire from slipping off. + +The resistance wire (F) is coiled for a suitable length, dependent upon +the current used, one end being fastened by wrapping it around the screw +(C). The other end of the wire is then brought upwardly through the +interior of the coil and secured in like manner to the other screw (D). + +Caution must be used to prevent the different coils or turns from +touching each other. When completed, the coil may be immersed in water, +the current turned on, and left so until the water is sufficiently +heated. + +[Illustration: _Figs. 97-98._ RESISTANCE DEVICE] + +HOW TO ARRANGE FOR QUANTITY OF CURRENT USED.--It is difficult to +determine just the proper length the coil should be, or the sizes of the +wire, unless you know what kind of current you have. You may, however, +rig up your own apparatus for the purpose of making it fit your heater, +by preparing a base of wood (A) 8 inches long, 3 inches wide and 1 inch +thick. On this mount four electric lamp sockets (B). Then connect the +inlet wire (C) by means of short pieces of wire (D) with all the sockets +on one side. The outlet wire (E) should then be connected up with the +other sides of the sockets by the short wires (F). If, now, we have one +16-candlepower lamp in one of the sockets, there is a half ampere going +through the wires (C, F). If there are two lamps on the board you will +have 1 ampere, and so on. By this means you may readily determine how +much current you are using and it will also afford you a means of +finding out whether you have too much or too little wire in your coil to +do the work. + +[Illustration: _Fig. 99._ PLAN VIEW OF ELECTRIC IRON] + +AN ELECTRIC IRON.--An electric iron is made in the same way. The upper +side of a flatiron has a circular or oval depression (A) cast therein, +and a spool of slate (B) is made so it will fit into the depression and +the high resistance wire (C) is wound around this spool, and insulating +material, such as asbestos, must be used to pack around it. Centrally, +the slate spool has an upwardly projecting circular extension (D) which +passes through the cap or cover (E) of the iron. The wires of the +resistance coil are then brought through this circular extension and +are connected up with the source of electrical supply. Wires are now +sold for this purpose, which are adapted to withstand an intense heat. + +[Illustration: _Fig. 100._ SECTION OF ELECTRIC IRON] + +The foregoing example of the use of the current, through resistance +wires, has a very wide application, and any boy, with these examples +before him, can readily make these devices. + +THERMO ELECTRICITY.--It has long been the dream of scientists to convert +heat directly into electricity. The present practice is to use a boiler +to generate steam, an engine to provide the motion, and a dynamo to +convert that motion into electricity. The result is that there is loss +in the process of converting the fuel heat into steam; loss to change +the steam into motion, and loss to make electricity out of the motion +of the engine. By using water-power there is less actual loss; but +water-power is not available everywhere. + +CONVERTING HEAT DIRECTLY INTO ELECTRICITY.--Heat may be converted +directly into electricity without using a boiler, an engine or a dynamo, +but it has not been successful from a commercial standpoint. It is +interesting, however, to know and understand the subject, and for that +reason it is explained herein. + +METALS; ELECTRIC POSITIVE-NEGATIVE.--To understand the principle, it may +be stated that all metals are electrically positive-negative to each +other. You will remember that it has hereinbefore been stated that if, +for instance, iron and copper are put into an acid solution, a current +will be created or generated thereby. So with zinc and copper, the usual +primary battery elements. In all such cases an electrolyte is used. + +Thermo-electricity dispenses with the electrolyte, and nothing is used +but the metallic elements and heat. The word thermo means heat. If, now, +we can select two strips of different metals, and place them as far +apart as possible--that is, in their positive-negative relations with +each other, and unite the end of one with one end of other by means of a +rivet, and then heat the riveted ends, a current will be generated in +the strips. If, for instance, we use an iron in conjunction with a +copper strip, the current will flow from the copper to the iron, because +copper is positive to iron, and iron negative to copper. It is from this +that the term positive-negative is taken. + +The two metals most available, which are thus farthest apart in the +scale of positive-negative relation, are bismuth and antimony. + +[Illustration: _Fig. 101._ THERMO-ELECTRIC COUPLE] + +In Fig. 101 is shown a thermo-electric couple (A, B) riveted together, +with thin outer ends connected by means of a wire (C) to form a circuit. +A galvanometer (D) or other current-testing means is placed in this +circuit. A lamp is placed below the joined ends. + +THERMO-ELECTRIC COUPLES.--Any number of these couples may be put +together and joined at each end to a common wire and a fairly large flow +of current obtained thereby. + +One thing must be observed: A current will be generated only so long as +there exists a difference in temperature between the inner and the outer +ends of the bars (A, B). This may be accomplished by water, or any other +cooling means which may suggest itself. + + + + +CHAPTER XV + +ALTERNATING CURRENTS, CHOKING COILS, TRANSFORMERS, CONVERTERS AND +RECTIFIERS + + +DIRECT CURRENT.--When a current of electricity is generated by a cell, +it is assumed to move along the wire in one direction, in a steady, +continuous flow, and is called a _direct_ current. This direct current +is a natural one if generated by a cell. + +ALTERNATING CURRENT.--On the other hand, the natural current generated +by a dynamo is alternating in its character--that is, it is not a +direct, steady flow in one direction, but, instead, it flows for an +instant in one direction, then in the other direction, and so on. + +A direct-current dynamo such as we have shown in Chapter IV, is much +easier to explain, hence it is illustrated to show the third method used +in generating an electric current. + +It is a difficult matter to explain the principle and operation of +alternating current machines, without becoming, in a measure, too +technical for the purposes of this book, but it is important to know the +fundamentals involved, so that the operation and uses of certain +apparatus, like the choking coil, transformers, rectifiers and +converters, may be explained. + +THE MAGNETIC FIELD.--It has been stated that when a wire passes through +the magnetic field of a magnet, so as to cut the lines of force flowing +out from the end of a magnet, the wire will receive a charge of +electricity. + +[Illustration: _Fig. 102._ CUTTING A MAGNETIC FIELD] + +To explain this, study Fig. 102, in which is a bar magnet (A). If we +take a metal wire (B) and bend it in the form of a loop, as shown, and +mount the ends on journal-bearing blocks, the wire may be rotated so +that the loop will pass through the magnetic field. When this takes +place, the wire receives a charge of electricity, which moves, say, in +the direction of the darts, and will make a complete circuit if the ends +of the looped wire are joined, as shown by the conductor (D). + +ACTION OF THE MAGNETIZED WIRE.--You will remember, also that we have +pointed out how, when a current passes over a wire, it has a magnetic +field extending out around it at all points, so that while it is passing +through the magnetic field of the magnet (A), it becomes, in a measure, +a magnet of its own and tries to set up in business for itself as a +generator of electricity. But when the loop leaves the magnetic field, +the magnetic or electrical impulse in the wire also leaves it. + +THE MOVEMENT OF A CURRENT IN A CHARGED WIRE.--Your attention is +directed, also, to another statement, heretofore made, namely, that when +a current from a charged wire passes by induction to a wire across +space, so as to charge it with an electric current, it moves along the +charged wire in a direction opposite to that of the current in the +charging wire. + +Now, the darts show the direction in which the current moves while it is +approaching and passing through the magnetic field. But the moment the +loop is about to pass out of the magnetic field, the current in the loop +surges back in the opposite direction, and when the loop has made a +revolution and is again entering the magnetic field, it must again +change the direction of flow in the current, and thus produce +alternations in the flow thereof. + +Let us illustrate this by showing the four positions of the revolving +loop. In Fig. 103 the loop (B) is in the middle of the magnetic field, +moving upwardly in the direction of the curved dart (A), and while in +that position the voltage, or the electrical impulse, is the most +intense. The current used flows in the direction of the darts (C) or to +the left. + +In Fig. 104, the loop (A) has gone beyond the influence of the magnetic +field, and now the current in the loop tries to return, or reverse +itself, as shown by the dart (D). It is a reaction that causes the +current to die out, so that when the loop has reached the point farthest +from the magnet, as shown in Fig. 105, there is no current in the loop, +or, if there is any, it moves faintly in the direction of the dart (E). + +[Illustration: _Figs. 103-106._ ILLUSTRATING ALTERNATIONS] + +CURRENT REVERSING ITSELF.--When the loop reaches its lowest point (Fig. +106) it again comes within the magnetic field and the current commences +to flow back to its original direction, as shown by darts (C). + +SELF-INDUCTION.--This tendency of a current to reverse itself, under the +conditions cited, is called self-induction, or inductance, and it would +be well to keep this in mind in pursuing the study of alternating +currents. + +You will see from the foregoing, that the alternations, or the change of +direction of the current, depends upon the speed of rotation of the loop +past the end of the magnet. + +[Illustration: _Figs. 107-108._ FORM FOR INCREASING ALTERNATIONS] + +Instead, therefore, of using a single loop, we may make four loops (Fig. +107), which at the same speed as we had in the case of the single loop, +will give four alternations, instead of one, and still further, to +increase the periods of alternation, we may use the four loops and two +magnets, as in Fig. 108. By having a sufficient number of loops and of +magnets, there may be 40, 50, 60, 80, 100 or 120 such alternating +periods in each second. Time, therefore, is an element in the operation +of alternating currents. + +Let us now illustrate the manner of connecting up and building the +dynamo, so as to derive the current from it. In Fig. 109, the loop (A) +shows, for convenience, a pair of bearings (B). A contact finger (C) +rests on each, and to these the circuit wire (D) is attached. Do not +confuse these contact fingers with the commutator brushes, shown in the +direct-current motor, as they are there merely for the purpose of making +contact between the revolving loop (A) and stationary wire (D). + +[Illustration: _Fig. 109._ CONNECTION OF ALTERNATING DYNAMO ARMATURE] + +BRUSHES IN A DIRECT-CURRENT DYNAMO.--The object of the brushes in the +direct-current dynamo, in connection with a commutator, is to convert +this _inductance_ of the wire, or this effort to reverse itself into a +current which will go in one direction all the time, and not in both +directions alternately. + +To explain this more fully attention is directed to Figs. 110 and 111. +Let A represent the armature, with a pair of grooves (B) for the wires. +The commutator is made of a split tube, the parts so divided being +insulated from each other, and in Fig. 110, the upper one, we shall call +and designate the positive (+) and the lower one the negative (-). The +armature wire (C) has one end attached to the positive commutator +terminal and the other end of this wire is attached to the negative +terminal. + +[Illustration: _Fig. 110._ DIRECT CURRENT DYNAMO] + +One brush (D) contacts with the positive terminal of the commutator and +the other brush (E) with the negative terminal. Let us assume that the +current impulse imparted to the wire (C) is in the direction of the dart +(F, Fig. 110). The current will then flow through the positive (+) +terminal of the commutator to the brush (D), and from the brush (D) +through the wire (G) to the brush (E), which contacts with the negative +(-) terminal of the commutator. This will continue to be the case, while +the wire (C) is passing the magnetic field, and while the brush (D) is +in contact with the positive (+) terminal. But when the armature makes a +half turn, or when it reaches that point where the brush (D) contacts +with the negative (-) terminal, and the brush (E) contacts with the +positive (+) terminal, a change in the direction of the current through +the wire (G) takes place, unless something has happened to change it +before it has reached the brushes (D, E). + +[Illustration: _Fig. 111._ CIRCUIT WIRES IN DIRECT CURRENT DYNAMO] + +Now, this change is just exactly what has happened in the wire (C), as +we have explained. The current attempts to reverse itself and start out +on business of its own, so to speak, with the result that when the +brushes (D and E) contact with the negative and positive terminals, +respectively, the surging current in the wire (C) is going in the +direction of the dart (H)--that is, while, in Fig. 110, the current +flows from the wire (C) into the positive terminal, and out of the +negative terminal into the wire (C), the conditions are exactly reversed +in Fig. 111. Here the current in wire C flows _into_ the negative (-) +terminal, and _from_ the positive (+) terminal into the wire C, so that +in either case the current will flow out of the brush D and into the +brush E, through the external circuit (G). + +It will be seen, therefore, that in the direct-current motor, advantage +is taken of the surging, or back-and-forth movement, of the current to +pass it along in one direction, whereas in the alternating current no +such change in direction is attempted. + +ALTERNATING POSITIVE AND NEGATIVE POLES.--The alternating current, +owing to this surging movement, makes the poles alternately positive and +negative. To express this more clearly, supposing we take a line (A, +Fig. 112), which is called the zero line, or line of no electricity. The +current may be represented by the zigzag line (B). The lines (B) above +zero (A) may be designated as positive, and those below the line as +negative. The polarity reverses at the line A, goes up to D, which is +the maximum intensity or voltage above zero, and, when the current falls +and crosses the line A, it goes in the opposite direction to E, which is +its maximum voltage in the other direction. In point of time, if it +takes one second for the current to go from C to F, on the down line, +then it takes only a half second to go from C to G, so that the line A +represents the time, and the line H the intensity, a complete cycle +being formed from C, D, F, then through F, E, C, and so on. + +[Illustration: _Fig. 112._ ALTERNATING POLARITY LINES] + +HOW AN ALTERNATING DYNAMO IS MADE.--It is now necessary to apply these +principles in the construction of an alternating-current machine. Fig. +113 is a diagram representing the various elements, and the circuiting. + +[Illustration: _Fig. 113._ ALTERNATING CURRENT DYNAMO] + +Let A represent the ring or frame containing the inwardly projecting +field magnet cores (B). C is the shaft on which the armature revolves, +and this carries the wheel (D), which has as many radially disposed +magnet cores (E) as there are of the field magnet cores (B). + +The shaft (C) also carries two pulleys with rings thereon. One of these +rings (F) is for one end of the armature winding, and the other ring +(G) for the other end of the armature wire. + +THE WINDINGS.--The winding is as follows: One wire, as at H, is first +coiled around one magnet core, the turnings being to the right. The +outlet terminal of this wire is then carried to the next magnet core and +wound around that, in the opposite direction, and so on, so that the +terminal of the wire is brought out, as at I, all of these wires being +connected to binding posts (J, J'), to which, also, the working circuits +are attached. + +THE ARMATURE WIRES.--The armature wires, in like manner, run from the +ring (G) to one armature core, being wound from right to left, then to +the next core, which is wound to the right, afterward to the next core, +which is wound to the left, and so on, the final end of the wire being +connected up with the other ring (F). The north (N) and the south (S) +poles are indicated in the diagram. + +CHOKING COIL.--The self-induction in a current of this kind is utilized +in transmitting electricity to great distances. Wires offer resistance, +or they impede the flow of a current, as hereinbefore stated, so that it +is not economical to transmit a direct current over long distances. This +can be done more efficiently by means of the alternating current, which +is subject to far less loss than is the case with the direct current. +It affords a means whereby the flow of a current may be checked or +reduced without depending upon the resistance offered by the wire over +which it is transmitted. This is done by means of what is called a +choking coil. It is merely a coil of wire, wound upon an iron core, and +the current to be choked passes through the coil. To illustrate this, +let us take an arc lamp designed to use a 50-volt current. If a current +is supplied to it carrying 100 volts, it is obvious that there are 50 +volts more than are needed. We must take care of this excess of 50 volts +without losing it, as would happen were we to locate a resistance of +some kind in the circuit. This result we accomplish by the introduction +of the choking coil, which has the effect of absorbing the excessive 50 +volts, the action being due to its quality of self-induction, referred +to in the foregoing. + +[Illustration: _Fig. 114._ CHOKING COIL] + +In Fig. 114, A is the choking coil and B an arc lamp, connected up, in +series, with the choking coil. + +THE TRANSFORMER.--It is more economical to transmit 10,000 volts a long +distance than 1,000 volts, because the lower the pressure, or the +voltage, the larger must be the conductor to avoid loss. It is for this +reason that 500 volts, or more, are used on electric railways. For +electric light purposes, where the current goes into dwellings, even +this is too high, so a transformer is used to take a high-voltage +current from the main line and transform it into a low voltage. This is +done by means of two distinct coils of wire, wound upon an iron core. + +[Illustration: _Fig. 115._ A TRANSFORMER] + +In Fig. 115 the core is O-shaped, so that a primary winding (A), from +the electrical source, can be wound upon one limb, and the secondary +winding (B) wound around the other limb. The wires, to supply the +lamps, run from the secondary coil. There is no electrical connection +between the two coils, but the action from the primary to the secondary +coil is solely by induction. When a current passes through the primary +coil, the surging movement, heretofore explained, is transmitted to the +iron core, and the iron core, in turn, transmits this electrical energy +to the secondary coil. + +HOW THE VOLTAGE IS DETERMINED.--The voltage produced by the secondary +coil will depend upon several things, namely, the strength of the +magnetism transmitted to it; the rapidity, or periodicity of the +current, and the number of turns of wire around the coil. The voltage is +dependent upon the length of the winding. But the voltage may also be +increased, as well as decreased. If the primary has, we will say, 100 +turns of wire, and has 200 volts, and the secondary has 50 turns of +wire, the secondary will give forth only one-half as much as the +primary, or 100 volts. + +If, on the other hand, 400 volts would be required, the secondary should +have 200 turns in the winding. + +VOLTAGE AND AMPERAGE IN TRANSFORMERS.--It must not be understood that, +by increasing the voltage in this way, we are getting that much more +electricity. If the primary coil, with 100 turns, produces a current of +200 volts and 50 amperes, which would be 200 x 50 = 10,000 watts, and +the secondary coil has 50 turns, we shall have 100 volts and 100 +amperes: 100 (V.) x 100 (A.) = 10,000 watts. Or, if, on the other hand, +our secondary winding is composed of 200 turns, we shall have 400 volts +and 25 amperes, 400 (volts) x 25 (amperes) also gives 10,000 watts. + +Necessarily, there will be some loss, but the foregoing is offered as +the theoretical basis of calculation. + + + + +CHAPTER XVI + +ELECTRIC LIGHTING + + +The most important step in the electric field, after the dynamo had been +brought to a fairly workable condition, was its utilization to make +light. It was long known prior to the discovery of practical electric +dynamos, that the electric current would produce an intense heat. + +Ordinary fuels under certain favorable conditions will produce a +temperature of 4,500 degrees of heat; but by means of the electric arc, +as high as six, eight and ten thousand degrees are available. + +The fact that when a conductor, in an electric current, is severed, a +spark will follow the drawing part of the broken ends, led many +scientists to believe, even before the dynamo was in a practical shape, +that electricity, sooner or later, would be employed as the great +lighting agent. + +When the dynamo finally reached a stage in development where its +operation could be depended on, and was made reversible, the first +active steps were taken to not only produce, but to maintain an arc +between two electrodes. + +It would be difficult and tedious to follow out the first experiments +in detail, and it might, also, be useless, as information, in view of +the present knowledge of the science. A few steps in the course of the +development are, however, necessary to a complete understanding of the +subject. + +Reference has been made in a previous chapter to what is called the +_Electric Arc_, produced by slightly separated conductors, across which +the electric current jumps, producing the brilliantly lighted area. + +This light is produced by the combustion of the carbon of which the +electrodes are composed. Thus, the illumination is the result of +directly burning a fuel. The current, in passing from one electrode to +the other, through the gap, produces such an intense heat that the fuel +through which the current passes is consumed. + +Carbon in a comparatively pure state is difficult to ignite, owing to +its great resistance to heat. At about 7,000 degrees it will fuse, and +pass into a vapor which causes the intense illumination. + +The earliest form of electric lighting was by means of the arc, in which +the light is maintained so long as the electrodes were kept a certain +distance apart. + +To do this requires delicate mechanism, for the reason that when contact +is made, and the current flows through the two electrodes, which are +connected up directly with the coils of a magnet, the cores, or +armatures, will be magnetized. The result is that the electrode, +connected with the armature of the magnet, is drawn away from the other +electrode, and the arc is formed, between the separated ends. + +As the current also passes through a resistance coil, the moment the +ends of the electrodes are separated too great a distance, the +resistance prevents a flow of the normal amount of current, and the +armature is compelled to reduce its pull. The effect is to cause the two +electrodes to again approach each other, and in doing so the arc becomes +brighter. + +It will be seen, therefore, that there is a constant fight between the +resistance coil and the magnet, the combined action of the two being +such, that, if properly arranged, and with powers in correct relation to +each other, the light may be maintained without undue flickering. Such +devices are now universally used, and they afford a steady and reliable +means of illumination. + +Many improvements are made in this direction, as well as in the +ingredients of the electrodes. A very novel device for assuring a +perfect separation at all times between the electrodes, is by means of a +pair of parallel carbons, held apart by a non-conductor such as clay, or +some mixture of earth, a form of which is shown in Fig. 116. + +The drawing shows two electrodes, separated by a non-conducting +material, which is of such a character that it will break down and +crumble away, as the ends of the electrodes burn away. + +[Illustration: _Fig. 116. Parallel Carbons._] + +This device is admirable where the alternating current is used, because +the current moves back and forth, and the two electrodes are thus burned +away at the same rate of speed. + +In the direct or continuous current the movement is in one direction +only, and as a result the positive electrode is eaten away twice as fast +as the negative. + +This is the arc form of lamp universally used for lighting large spaces +or areas, such as streets, railway stations, and the like. It is +important also as the means for utilizing searchlight illumination, and +frequently for locomotive headlights. + +Arc lights are produced by what is called the _series current_. This +means that the lamps are all connected in a single line. This is +illustrated by reference to Fig. 117, in which A represents the wire +from the dynamo, and B, C the two electrodes, showing the current +passing through from one lamp to the next. + +[Illustration: _Fig. 117. Arc-Lighting Circuit._] + +A high voltage is necessary in order to cause the current to leap across +the gap made by the separation of the electrodes. + +THE INCANDESCENT SYSTEM.--This method is entirely different from the arc +system. It has been stated that certain metals conduct electricity with +greater facility than others, and some have higher resistance than +others. If a certain amount of electricity is forced through some +metals, they will become heated. This is true, also, if metals, which, +ordinarily, will conduct a current freely, are made up into such small +conductors that it is difficult for the current to pass. + +[Illustration: _Fig 118. Interrupted Conductor._] + +In the arc method high voltage is essential; in the incandescent plan, +current is the important consideration. In the arc, the light is +produced by virtue of the break in the line of the conductor; in the +incandescent, the system is closed at all times. + +Supposing we have a wire A, a quarter of an inch in diameter, carrying a +current of, say, 500 amperes, and at any point in the circuit the wire +is made very small, as shown at B, in Fig. 118, it is obvious that the +small wire would not be large enough to carry the current. + +The result would be that the small connection B would heat up, and, +finally, be fused. While the large part of the wire would carry 500 +amperes, the small wire could not possibly carry more than, say, 10 +amperes. Now these little wires are the filaments in an electric bulb, +and originally the attempt was made to have them so connected up that +they could be illuminated by a single wire, as with the arc system above +explained, one following the other as shown in Fig. 117. + +[Illustration: _Fig. 119. Incandescent Circuit._] + +It was discovered, however, that the addition of each successive lamp, +so wired, would not give light in proportion to the addition, but at +only about one-fourth the illumination, and such a course would, +therefore, make electric lighting enormously expensive. + +This knowledge resulted in an entirely new system of wiring up the lamps +in a circuit. This is explained in Fig. 119. In this figure A represents +the dynamo, B, B the brushes, C, D the two line wires, E the lamps, and +F the short-circuiting wires between the two main conductors C, D. + +It will be observed that the wires C, D are larger than the cross wires +F. The object is to show that the main wires might carry a very heavy +amperage, while the small cross wires F require only a few amperes. + +This is called the _multiple_ circuit, and it is obvious that the entire +amperage produced by the dynamo will not be required to pass through +each lamp, but, on the other hand, each lamp takes only enough necessary +to render the filament incandescent. + +This invention at once solved the problem of the incandescent system and +was called the subdivision of the electric light. By this means the cost +was materially reduced, and the wiring up and installation of lights +materially simplified. + +But the divisibility of the light did not, by any means, solve the great +problem that has occupied the attention of electricians and +experimenters ever since. The great question was and is to preserve the +little filament which is heated to incandescence, and from which we get +the light. + +The effort of the current to pass through the small filament meets with +such a great resistance that the substance is heated up. If it is made +of metal there is a point at which it will fuse, and thus the lamp is +destroyed. + +It was found that carbon, properly treated, would heat to a brilliant +white heat without fusing, or melting, so that this material was +employed. But now followed another difficulty. As this intense heat +consumed the particles of carbon, owing to the presence of oxygen, means +were sought to exclude the air. + +This was finally accomplished by making a bulb of glass, from which the +air was exhausted, and as such a globe had no air to support combustion, +the filaments were finally made so that they would last a long time +before being finally disintegrated. + +The quest now is, and has been, to find some material of a purely +metallic character, which will have a very high fusing point, and which +will, therefore, dispense with the cost of the exhausted bulb. Some +metals, as for instance, osmium, tantalum, thorium, and others, have +been used, and others, also, with great success, so that the march of +improvements is now going forward with rapid strides. + +VAPOR LAMPS.--One of the directions in which considerable energy has +been directed in the past, was to produce light from vapors. The Cooper +Hewitt mercury vapor lamp is a tube filled with the vapor of mercury, +and a current is sent through the vapor which produces a greenish +light, and owing to that peculiar color, has not met with much success. + +It is merely cited to show that there are other directions than the use +of metallic conductors and filaments which will produce light, and the +day is no doubt close at hand when we may expect some important +developments in the production of light by means of the Hertzian waves. + +DIRECTIONS FOR IMPROVEMENTS.--Electricity, however, is not a cheap +method of illumination. The enormous heat developed is largely wasted. +The quest of the inventor is to find a means whereby light can be +produced without the generation of the immense heat necessary. + +Man has not yet found a means whereby he can make a heat without +increasing the temperature, as nature does it in the glow worm, or in +the firefly. A certain electric energy will produce both light and heat, +but it is found that much more of this energy is used in the heat than +in the light. + +What wonderful possibilities are in store for the inventor who can make +a heatless light! It is a direction for the exercise of ingenuity that +will well repay any efforts. + +_Curious Superstitions Concerning Electricity_ + +Electricity, as exhibited in light, has been the great marvel of all +times. The word electricity itself comes from the thunderbolt of the +ancient God Zeus, which is known to be synonymous with the thunderbolt +and the lightning. + +Magnetism, which we know to be only another form of electricity, was not +regarded the same as electricity by the ancients. Iron which had the +property to attract, was first found near the town of Magnesia, in +Lydia, and for that reason was called magnetism. + +Later on, a glimmer of the truth seemed to dawn on the early scientists, +when they saw the resemblance between the actions of the amber and the +loadstone, as both attracted particles. And here another curious thing +resulted. Amber will attract particles other than metals. The magnet did +not; and from this imperfect observation and understanding, grew a +belief that electricity, or magnetism would attract all substances, even +human flesh, and many devices were made from magnets, and used as cures +for the gout, and to affect the brain, or to remove pain. + +Even as early as 2,500 years before the birth of Christ the Chinese knew +of the properties of the magnet, and also discovered that a bar of the +permanent magnet would arrange itself north and south, like the +mariners' compass. There is no evidence, however, that it was used as a +mariner's compass until centuries afterwards. + +But the matter connected with light, as an electrical development, which +interests us, is its manifestations to the ancients in the form of +lightning. The electricity of the earth concentrates itself on the tops +of mountains, or in sharp peaks, and accounts for the magnificent +electrical displays always found in mountainous regions. + +Some years ago, a noted scientist, Dr. Siemens, while standing on the +top of the great pyramid of Cheops, in Egypt, during a storm, noted that +an electrical discharge flowed from his hand when extended toward the +heavens. The current manifested itself in such a manner that the hissing +noise was plainly perceptible. + +The literature of all ages and of all countries shows that this +manifestation of electrical discharges was noted, and became the subject +of discussions among learned men. + +All these displays were regarded as the bolts of an angry God, and +historians give many accounts of instances where, in His anger, He sent +down the lightning to destroy. + +Among the Romans Jupiter thus hurled forth his wrath; and among many +ancient people, even down to the time of Charlemagne, any space struck +by lightning was considered sacred, and made consecrated ground. + +From this grew the belief that it was sacrilegious to attempt to imitate +the lightning of the sky--that Deity would visit dire punishment on any +man who attempted to produce an electric light. Virgil relates accounts +where certain princes attempted to imitate the lightning, and were +struck by thunderbolts as punishments. + +Less than a century ago Benjamin Franklin devised the lightning rod, in +order to prevent lightning from striking objects. The literature of that +day abounds with instances of protests made, on the part of those who +were as superstitions as the people in ancient times, who urged that it +was impious to attempt to ward off Heaven's lightnings. It was argued +that the lightning was one way in which the Creator manifested His +displeasure, and exercised His power to strike the wicked. + +When such writers as Pliny will gravely set forth an explanation of the +causes of lightning, as follows in the paragraph below, we can +understand why it inculcated superstitious fears in the people of +ancient times. He says: + +"Most men are ignorant of that secret, which, by close observation of +the heavens, deep scholars and principal men of learning have found +out, namely, that they are the fires of the uppermost planets, which, +falling to the earth, are called lightning; but those especially which +are seated in the middle, that is about Jupiter, perhaps because +participating in the excessive cold and moisture from the upper circle +of Saturn, and the immoderate heat of Mars, that is next beneath, by +this means he discharges his superfluity, and therefore it is commonly +said, 'That Jupiter shooteth and darteth lightning.' Therefore, like as +out of a burning piece of wood a coal flieth forth with a crack, even so +from a star is spit out, as it were, and voided forth this celestial +fire, carrying with it presages of future things; so that the heavens +showeth divine operations, even in these parcels and portions which are +rejected and cast away as superfluous." + + + + +CHAPTER XVII + +POWER, AND VARIOUS OTHER ELECTRICAL MANIFESTATIONS + + +It would be difficult to mention any direction in human activity where +electricity does not serve as an agent in some form or manner. Man has +learned that the Creator gave this great power into the hands of man to +use, and not to curse. + +When the dynamo was first developed it did not appear possible that it +could generate electricity, and then use that electricity in order to +turn the dynamo in the opposite direction. It all seems so very natural +to us now, that such a thing should practically follow; but man had to +learn this. + +Let us try to make the statement plain by a few simple illustrations. By +carefully going over the chapter on the making of the dynamo, it will be +evident that the basis of the generation of the current depends on the +changing of the direction of the flow of an electric current. + +Look at the simple horse-shoe magnet. If two of them are gradually moved +toward each other, so that the north pole of one approaches the north +pole of the other, there is a sensible attempt for them to push away +from each other. If, however, one of them is turned, so that the north +pole of one is opposite the south pole of the other, they will draw +together. + +In this we have the foundation physical action of the dynamo and the +motor. When power is applied to an armature, and it moves through a +magnetic field, the action is just the same as in the case of the hand +drawing the north and the south pole of the two approaching magnets from +each other. + +The influence of the electrical disturbance produced by that act +permeated the entire winding of the field and armature, and extended out +on the whole line with which the dynamo was connected. In this way a +current was established and transmitted, and with proper wires was sent +in the form of circuits and distributed so as to do work. + +But an electric current, without suitable mechanism, is of no value. It +must have mechanism to use it, as well as to make it. In the case of +light, we have explained how the arc and the incandescent lamps utilize +it for that purpose. + +But now, attempting to get something from it in the way of power, means +another piece of mechanism. This is done by the motor, and this motor is +simply a converter, or a device for reversing the action of the +electricity. + +Attention is called to Figs. 120 and 121. Let us assume that the field +magnets A, A are the positives, and the magnets B, B the negatives. The +revolving armature has also four magnet coils, two of them, C, C, being +positive, and the other two, D, D, negative, each of these magnet coils +being so connected up that they will reverse the polarities of the +magnets. + +[Illustration: _Figs. 120-121._ ACTION OF MAGNETS IN A DYNAMO] + +Now in the particular position of the revolving armature, in Fig. 120, +the magnets of the armature have just passed the respective poles of the +field magnets, and the belt E is compelled to turn the armature past the +pole pieces by force in the direction of the arrow F. After the armature +magnets have gone to the positions in Fig. 121, the positives A try to +draw back the negatives D of the armature, and at the same time the +negatives B repel the negatives D, because they are of the same +polarities. + +This repulsion of the negatives A, B continues until the armature poles +C, D have slightly passed them, when the polarities of the magnets C, D +are changed; so that it will be seen, by reference to Fig. 122, that D +is now retreating from B, and C is going away from A--that is, being +forced away contrary to their natural attractive influences, and in Fig. +123, when the complete cycle is nearly finished, the positives are again +approaching each other and the negatives moving together. + +[Illustration: _Figs. 122-123._ CYCLE ACTION IN DYNAMO] + +In this manner, at every point, the sets of magnets are compelled to +move against their magnetic pull. This explains the dynamo. + +Now take up the cycle of the motor, and note in Fig. 124 that the +negative magnets D of the armature are closely approaching the positive +and negative magnets, on one side; and the positive magnets C are +nearing the positive and negatives on the other side. The positives A, +therefore, attract the negatives D, and the negative B exert a pull on +the positives C at the same time. The result is that the armature is +caused to revolve, as shown by the dart G, in a direction opposite to +the dart in Fig. 120. + +[Illustration: _Figs. 124-125._ ACTION OF MAGNETS IN MOTOR] + +When the pole pieces of the magnets C, D are about to pass magnets A, B, +as shown in Fig. 125, it is necessary to change the polarities of the +armature magnets C, D; so that by reference to Fig. 126, it will be seen +that they are now indicated as C-, and D+, respectively, and have moved +to a point midway between the poles A, B (as in Fig. 125), where the +pull on one side, and the push on the other are again the same, and the +last Figure 127 shows the cycle nearly completed. + +The shaft of the motor armature is now the element which turns the +mechanism which is to be operated. To convert electrical impulses into +power, as thus shown, results in great loss. The first step is to take +the steam boiler, which is the first stage in that source which is the +most common and universal, and by means of fuel, converting water into +steam. The second is to use the pressure of this steam to drive an +engine; the third is to drive the dynamo which generates the electrical +impulse; and the fourth is the conversion from the dynamo into a motor +shaft. Loss is met with at each step, and the great problem is to +eliminate this waste. + +[Illustration: _Figs. 126-127._ POSITIONS OF MAGNETS IN MOTOR] + +The great advantage of electrical power is not in utilizing it for +consumption at close ranges, but where it is desired to transmit it for +long distances. Such illustrations may be found in electric railways, +and where water power can be obtained as the primal source of energy, +the cost is not excessive. It is found, however, that even with the most +improved forms of mechanism, in electrical construction, the internal +combustion engines are far more economical. + + +_Transmission of Energy_ + +One of the great problems has been the transmission of the current to +great distances. By using a high voltage it may be sent hundreds of +miles, but to use a current of that character in the cars, or shops, or +homes, would be exceedingly dangerous. + +To meet this requirement transformers have been devised, which will take +a current of very high voltage, and deliver a current of low tension, +and capable of being used anywhere with the ordinary motors. + +THE TRANSFORMER.--This is an electrical device made up of a core or +cores of thin sheet metal, around which is wound sets of insulated +wires, one set being designed to receive the high voltage, and the other +set to put out the low voltage, as described in a former chapter. + +These may be made where the original output is a very high voltage, so +that they will be stepped down, first from one voltage to a lower, and +then from that to the next lower stage. This is called the "Step down" +transformer, and is now used over the entire world, where large voltages +are generated. + +ELECTRIC FURNACES.--The most important development of electricity in the +direction of heat is its use in furnaces. As before stated, an intense +heat is capable of being generated by the electric current, so that it +becomes the great agent to use for the treatment of refractory material. + +In furnaces of this kind the electric arc is the mechanical form used to +produce the great heat, the only difference being in the size of the +apparatus. The electric furnace is simply an immense form of arc light, +capable of taking a high voltage, and such an arc is enclosed within a +suitable oven of refractory material, which still further conserves the +heat. + +WELDING BY ELECTRICITY.--The next step is to use the high heat thus +capable of being produced, to fuse metals so that they may be welded +together. It is a difficult matter to unite two large pieces of metal by +the forging method, because the highest heat is required, owing to their +bulk, and in addition immense hammers, weighing tons, must be employed. + +Electric welding offers a simple and easy method of accomplishing the +result, and in the doing of which it avoids the oxidizing action of the +forging heat. Instead of heating the pieces to be welded in a forge, as +is now done, the ends to be united are simply brought into contact, and +the current is sent through the ends until they are in a soft condition, +after which the parts are pressed together and united by the simple +merging of the plastic condition in which they are reduced by the high +electric heat. + +This form of welding makes the most perfect joint, and requires no +hammering, as the mass of the metal flows from one part or end to the +other; the unity is a perfect one, and the advantage is that the metals +can be kept in a semi-fluid state for a considerable time, thus assuring +a perfect admixture of the two parts. + +With the ordinary form of welding it is necessary to drive the heated +parts together without any delay, and at the least cooling must be +reheated, or the joint will not be perfect. + +The smallest kinds of electric heating apparatus are now being made, so +that small articles, sheet metal, small rods, and like parts can be +united with the greatest facility. + + + + +CHAPTER XVIII + +X-RAY, RADIUM, AND THE LIKE + + +The camera sees things invisible to the human eye. Its most effective +work is done with beams which are beyond human perception. The +photographer uses the _Actinic_ rays. Ordinary light is composed of the +seven primary colors, of which the lowest in the scale is the red, and +the highest to violet. + +Those below the red are called the Infra-red, and they are the Hertzian +waves, or those used in wireless telegraphy. Those above the violet are +called Ultra-violet, and these are employed for X-ray work. The former +are produced by the high tension electric apparatus, which we have +described in the chapter relating to wireless telegraphy; and the +latter, called also the Roentgen rays, are generated by the Crookes' +Tube. + +This is a tube from which all the atmosphere has been extracted so that +it is a practical vacuum. Within this are placed electrodes so as to +divert the action of the electrical discharge in a particular direction, +and this light, when discharged, is of such a peculiar character that +its discovery made a sensation in the scientific world. + +The reason for this great wonder was not in the fact that it projected a +light, but because of its character. Ordinary light, as we see it with +the eye, is capable of being reflected, as when we look into a mirror at +an angle. The X-ray will not reflect, but instead, pass directly through +the glass. + +Then, ordinary light is capable of refraction. This is shown by a ray of +light bending as it passes through a glass of water, which is noticed +when the light is at an angle to the surface. + +The X-ray will pass through the water without being changed from a +straight line. The foregoing being the case, it was but a simple step to +conclude that if it were possible to find a means whereby the human eye +could see within the ultra-violet beam, it would be possible to see +through opaque substances. + +From the discovery so important and far reaching it was not long until +it was found that if the ultra-violet rays, thus propagated, were +transmitted through certain substances, their rates of vibration would +be brought down to the speeds which send forth the visible rays, and now +the eye is able to see, in a measure at least, what the actinic rays +show. + +This discovery was but the forerunner of a still more important +development, namely, the discovery of _radium_. The actual finding of +the metal was preceded by the knowledge that certain minerals, and +water, as well, possessed the property of radio-activity. + +Radio-activity is a word used to express that quality in metals or other +material by means of which obscure rays are emitted, that have the +capacity of discharging electrified bodies, and the power to ionize +gases, as well as to actually affect photograph plates. + +Certain metals had this property to a remarkable degree, particularly +uranium, thorium, polonium, actinium, and others, and in 1898 the +Curies, husband and wife, French chemists, isolated an element, very +ductile in its character, which was a white metal, and had a most +brilliant luster. + +Pitchblende, the base metal from which this was extracted, was +discovered to be highly radio-active, and on making tests of the product +taken from it, they were surprised to find that it emitted a form of +energy that far exceeded in calculations any computations made on the +basis of radio-activity in the metals hitherto examined. + +But this was not the most remarkable part of the developments. The +energy, whatever it was, had the power to change many other substances +if brought into close proximity. It darkens the color of diamonds, +quartz, mica, and glass. It changes some of the latter in color, some +kinds being turned to brown and others into violet or purple tinges. + +Radium has the capacity to redden the skin, and affect the flesh of +persons, even at some considerable distance, and it is a most powerful +germicide, destroying bacteria, and has been found also to produce some +remarkable cures in diseases of a cancerous nature. + +The remarkable similarity of the rays propagated by this substance, with +the X-rays, lead many to believe that they are electrical in their +character, and the whole scientific world is now striving to use this +substance, as well as the more familiar light waves of the Roentgen +tube, in the healing of diseases. + +It is not at all remarkable that this use of it should first be +considered, as it has been the history of the electrical developments, +from the earliest times, that each successive stage should find +advocates who would urge its virtues to heal the sick. + +It was so when the dynamo was invented, when the high tension current +was produced; and electrical therapeutics became a leading theme when +transmission by induction became recognized as a scientific fact. + +It is not many years since the X-rays were discovered, and the first +announcement was concerning its wonderful healing powers. + +This was particularly true in the case of radium, but for some reason, +after the first tests, all experimenters were thwarted in their +theories, because the science, like all others, required infinite +patience and experience. It was discovered, in the case of the X-ray, +that it must be used in a modified form, and accordingly, various +modifications of the waves were introduced, called the _m_ and the _n_ +rays, as well as many others, each having some peculiar qualification. + +In time, no doubt, the investigators will find the right quality for +each disease, and learn how to apply it. Thus, electricity, that most +alluring thing which, in itself, cannot be seen, and is of such a +character that it cannot even be defined in terms which will suit the +exact scientific mind, is daily bringing new wonders for our +investigation and use. + +It is, indeed, a study which is so broad that it has no limitations, and +a field which never will be exhausted. + +THE END + + + + +GLOSSARY OF WORDS +USED IN TEXT OF THIS VOLUME + + +Acid. Accumulator material is sulphuric acid, diluted + with water. + +Active That part of the material in accumulator plates + Material. which is acted upon by the electric current. + +Accumulator. A cell, generally known as a storage battery, which + while it initially receives a charge of electricity, + is nevertheless, of such a character, owing to the + active material of which it is made, that it + accumulates, or, as it were, generates electricity. + +Aerial Wire, The wire which, in wireless telegraphy, is carried + or Conductor. up into the air to connect the antennae with the + receiving and sending apparatus. + +Alarm, Burglar. A circulating system in a building, connected up with + a bell or other signaling means. + +Alloy. A mixture of two or more metals; as copper and zinc + to make brass; nickel and zinc to form German silver. + +Alternating Current. A current which goes back and forth in opposite + directions, unlike a direct current which flows + continuously in one direction over a wire. + +Alternation. The term applied to a change in the direction of an + alternating current, the frequency of the alternations + ranging up to 20,000 or more vibrations per second. + +Amber. A resin, yellow in color, which when rubbed with a + cloth, becomes excited and gives forth negative + electricity. + +Ammeter. An instrument for measuring the quantity or flow of + electricity. + +Ampere. The unit of current; the term in which strength of + the current is measured. An ampere is an + electromotive force of one volt through a resistance + of one ohm. + +Annunciator. A device which indicates or signals a call given from + some distant point. + +Anode. The positive terminal in a conducting circuit, like + the terminal of the carbon plate in a battery. It is + a plate in an electroplating bath from which the + current goes over to the cathode or negative plate or + terminal. + +Arc. A term employed to designate the gap, or the current + which flows across between the conductors, like the + space between the two carbons of an arc lamp, which + gives the light. + +Armature. A body of iron, or other suitable metal, which is in + the magnetic field of a magnet. + +Armature Bar. The piece which holds the armature. Also one of a + series of bars which form the conductors in armature + windings. + +Armature Coil. The winding around an armature, or around the core + of an armature. + +Armature Core. The part in a dynamo or motor which revolves, + and on which the wire coils are wound. + +Astatic (Galvanometer). That which has no magnetic action to direct + or divert anything exterior to it. + +Atom. The ultimate particle of an elementary substance. + +Attraction. That property of matter which causes particles to + adhere, or cohere, to each other. It is known under + a variety of terms, such as gravitation, chemical + affinity, electro-magnetism and dynamic attraction. + +Automatic Cut-out. A device which acts through the operation of the + mechanism with which it is connected. It is usually + applied to a device which cuts out a current when it + overcharges or overloads the wire. + +Bath. In electroplating, the vessel or tank which holds + the electroplating solution. + +Battery. A combination of two or more cells. + +Battery, Dry. A primary battery in which the electrolyte is made + in a solid form. + +Battery, Galvanic. A battery which is better known by the name of the + Voltaic Pile, made up of zinc and copper plates + which alternate, and with a layer of acidulated paper + between each pair of plates. + +Battery, Storage. A battery which accumulates + electricity generated by a primary battery or a + generator. + +Brush. A term applied to the conducting medium that + bears against the cylindrical surface of a commutator. + +Buzzer. An electric call produced by a rapidly moving + armature of an electro-magnet. + +Cable. A number of wires or conductors assembled in one + strand. + +Candle-power. The amount of light given by the legal-standard + candle. This standard is a sperm candle, which burns + two grains a minute. + +Capacity. The carrying power of a wire or circuit, without + heating. When heated there is an overload, or the + _capacity_ of the wire is overtaxed. + +Capacity, Storage. The quantity of electricity in a secondary battery + when fully charged, usually reckoned in ampere hours. + +Carbon. A material, like coke, ground or crushed, and formed + into sticks or plates by molding or compression. It + requires a high heat to melt or burn, and is used as + electrodes for arc lamps and for battery elements. It + has poor conductivity, and for arc lamps is coated + with copper to increase its conductivity. + +Cell, Electrolytic. A vessel containing an electrolyte for + electroplating purposes. + +Charge. The quantity of electricity on the surface of a body + or conductor. + +Chemical Change. When a current passes through electrodes in a + solution, a change takes place which is chemical + in its character. Adding sulphuric acid to water + produces heat. If electrodes of opposite polarity are + placed in such an acid solution, a chemical change is + produced, which is transformed into electricity. + +Choking Coil. An instrument in a circuit which by a form of + resistance regulates the flow of the current, or + returns part of it to the source of its generation. + +Counter-electromotive Force. Cells which are inserted in opposition to + a battery to reduce high voltage. + +Circuit, Astatic. A circuit in an instrument so wound that the earth's + magnetism will not affect it. + +Circuit Breaker. Any instrument in a circuit which cuts out or + interrupts the flow of a current. + +Circuit, External. A current flows through a wire or conductor, + and also along the air outside of the conductor, + the latter being the _external circuit._ + +Circuit Indicator. An instrument, like a galvanometer, that shows + the direction in which a current is flowing through + a conductor. + +Circuit, Return. Usually the ground return, or the negative wire from + a battery. + +Circuit, Short. Any connection between the mains or parallel lines + of a circuit which does not go through the + apparatus for which the circuit is intended. + +Coherer. A tube, or other structure, containing normally + high resistance particles which form a path or bridge + between the opposite terminals of a circuit. + +Coil. A wire, usually insulated, wound around a spool. + +Coil, Induction. One of a pair of coils designed to change the + voltage of a current of electricity, from a higher + to a lower, or from a lower to a higher + electro-motive force. + +Coil, Resistance. A coil so wound that it will offer a resistance + to a steady current, or reduce the flow of electricity. + +Commutator. A cylinder on the end of the armature of a dynamo + or motor and provided with a pair of contact plates + for each particular coil in the armature, in order + to change the direction of the current. + +Compass. An apparatus which indicates the direction or flow + of the earth's magnetism. + +Condenser. A device for storing up electro-static charges. + +Conductance. That quality of a conductor to carry a current of + electricity, dependent on its shape for the best + results. + +Conduction. The transmission of a current through a rod, wire + or conductor. + +Conductivity. That quality which has reference to the capacity + to conduct a current. + +Conductor. Any body, such as a bar, rod, wire, or machine, + which will carry a current. + +Connector. A binding post, clamp, screw, or other means to + hold the end of a wire, or electric conductor. + +Contact. To unite any parts in an electric circuit. + +Controller. The handle of a switchboard, or other contact + making and breaking means in a circuit. + +Converter. An induction coil in an alternating circuit for + changing potential difference, such as high + alternating voltage into low direct current voltage. + +Convolution. To wind like a clock spring. + +Core. The inner portion of an electro-magnet. The inside + part of an armature wound with wire. + +Core, Laminated. When the core is built up of a number of separate + pieces of the same material, but not insulated from + each other. + +Coulomb. The unit of electrical quantity. It is the quantity + passed by a current of one ampere intensity in one + second of time. + +Couple, Electric. Two or more electrodes in a liquid to produce an + electric force. + +Current, Alternating. A natural current produced by the action of + electro-magnets. It is a succession of short impulses + in opposite directions. + +Current, Constant. A current which is uniformly maintained in a steady + stream. + +Current, Induced. A current produced by electro-dynamic induction. + +Current Meter. An apparatus for indicating the strength of a current. + An ammeter. + +Current, Oscillating. A current which periodically alternates. + +Current, Periodic. A periodically varying current strength. + +Current, Undulating. A current which has a constant direction, + but has a continuously varying strength. + +Decomposition. The separation of a liquid, such as an electrolyte, + into its prime elements, either electrically or + otherwise. + +Deflection. The change of movement of a magnetic needle out of + its regular direction of movement. + +Demagnetization. When a current passes through a coil wound on an + iron core, the core becomes magnetized. When the + current ceases the core is no longer a magnet. It + is then said to be _demagnetized_. It also has + reference to the process for making a watch + non-magnetic so that it will not be affected when + in a magnetic field. + +Density. The quantity of an electric charge in a + conductor or substance. + +Depolarization. The removal of magnetism from a permanent magnet, + or a horse-shoe magnet, for instance. It is generally + accomplished by applying heat. + +Deposition, The act of carrying metal from one pole of a cell to + Electrolysis. another pole, as in electroplating. + +Detector. Mechanism for indicating the presence of a current + in a circuit. + +Diaphragm. A plate in a telephone, which, in the receiver, is + in the magnetic field of a magnet, and in a + transmitter carries the light contact points. + +Dielectric. A non-conductor for an electric current, but through + which electro-static induction will take place. + For example: glass and rubber are dielectrics. + +Discharge. The current flowing from an accumulator. + +Disintegration. The breaking up of the plate or active material. + +Disruptive. A static discharge passing through a dielectric. + +Duplex Wire. A pair of wires usually twisted together and + insulated from each other to form the conducting + circuit of a system. + +Dynamic Electricity. The term applied to a current flowing through + a wire. + +Dynamo. An apparatus, consisting of core and field magnets, + which, when the core is turned, will develop a + current of electricity. + +Earth Returns. Instead of using two wires to carry a circuit, + the earth is used for what is called the _return_ + circuit. + +Efficiency. The total electrical energy produced, in which that + wasted, as well as that used, is calculated. + +Elasticity. That property of any matter which, after a stress, + will cause the substance to return to its original + form or condition. Electricity has elasticity, + which is utilized in condensers, as an instance. + +Electricity, Lightning, and, in short, any current or electrical + Atmospheric. impulse, like wireless telegraphic waves, is called + _atmospheric_. + +Electricity, Electricity with a low potentiality and large current + Voltaic. density. + +Electrification. The process of imparting a charge of electricity + to any body. + +Electro-chemistry. The study of which treats of electric and chemical + forces, such as electric plating, electric fusing, + electrolysis, and the like. + +Electrode. The terminals of a battery, or of any circuit; as, + for instance, an arc light. + +Electrolyte. Any material which is capable of being decomposed + by an electric current. + +Electro-magnetism. Magnetism which is created by an electric current. + +Electrometer. An instrument for measuring static electricity, + differing from a galvanometer, which measures a + current in a wire that acts on the magnetic needle + of the galvanometer. + +Electro-motive Voltage, which is the measure or unit of e. m. f. + Force. (E. M. F.) + +Electroscope. A device for indicating not only the + presence of electricity, but whether it is positive + or negative. + +Electro-static Surfaces separated by a dielectric for opposite + Accumulator. charging of the surface. + +Element. In electricity a form of matter, as, for instance, + gold, or silver, that has no other matter or + compound. Original elements cannot be separated, + because they are not made up of two or more elements, + like brass, for instance. + +Excessive Charge. A storage battery charged at too high a rate. + +Excessive Discharge. A storage battery discharged at too high a rate. + +Excessive Overcharge. Charging for too long a time. + +Exciter. A generator, either a dynamo or a battery, for + exciting the field of a dynamo. + +Exhaustive Discharge. An excessive over-discharge of an accumulator. + +F. The sign used to indicate the heat term Fahrenheit. + +Fall of Voltage. The difference between the initial and the final + voltage in a current. + +Field. The space or region near a magnet or charged wire. + Also the electro-magnets in a dynamo or motor. + +Flow. The volume of a current going through a conductor. + +Force, Electro-magnetic. The pull developed by an electro-magnet. + +Frictional A current produced by rubbing dissimilar + Electricity. substances together. + + +Full Load. The greatest load a battery, accumulator or dynamo + will sustain. + +Galvanic. Pertaining to the electro-chemical relations of + metals toward each other. + +Galvanizing. The art of coating one metal with another, such, + for instance, as immersing iron in molten zinc. + +Galvanometry. An instrument having a permanently magnetized needle, + which is influenced by a coil or a wire in close + proximity to it. + +Galvanoscope. An instrument, like a galvanometer, which determines + whether or not a current is present in a tested wire. + +Generator. A term used to generally indicate any device which + originates a current. + +German Silver. An alloy of copper, nickel and zinc. + +Graphite. One form of carbon. It is made artificially by the + electric current. + +Grid. The metallic frame of a plate used to hold the active + material of an accumulator. + +Gravity. The attraction of mass for mass. Weight. The + accelerating tendency of material to move toward the + earth. + +Gutta Percha. Caoutchouc, which has been treated with sulphur, + to harden it. It is produced from the sap of + tropical trees, and is a good insulator. + +Harmonic Receiver. A vibrating reed acted on by an electro-magnet, + when tuned to its pitch. + +High E. M. F. A term to indicate currents which have a high + voltage, and usually low amperage. + +Igniter. Mechanism composed of a battery, induction coil and + a vibrator, for making a jump spark, to ignite gas, + powder, etc. + +I. H. P. Abbreviation, which means Indicated Horse Power. + +Impulse. A sudden motion of one body acting against another. + An electro-magnetic wave magnetizing soft iron, + and this iron attracting another piece of iron, as an + example. + +Incandescence, A conductor heated up by a current so it will + Electric. glow. + +Induced Current. A current of electricity which sets up lines of + force at right angles to the body of the wire + through which the current is transmitted. + +Induction, Magnetic. A body within a magnetic field which is excited + by the magnetism. + +Installation. Everything belonging to an equipment of a building, + or a circuiting system to do a certain thing. + +Insulation. A material or substance which resists the passage + of a current placed around a conductor. + +Intensity. The strength of a magnetic field, or of a current + flowing over a wire. + +Internal Resistance. The current strength of electricity of a wire + to resist the passage. + +Interrupter. A device in a wire or circuit for checking a + current. It also refers to the vibrator of an + induction coil. + +Joint. The place where two or more conductors are united. + +Joint Resistance. The combined resistance offered by two or more + substances or conductors. + +Jump Spark. A spark, disruptive in its character, between two + conducting points. + +Initial Charge. The charge required to start a battery. + +Kathode, or Cathode. The negative plate or side of a battery. The + plate on which the electro deposit is made. + +Key. The arm of a telegraph sounder. A bar with a finger + piece, which is hinged and so arranged that it will + make and break contacts in an electric circuit. + +Keyboard. A switch-board; a board on which is mounted a number + of switches. + +Kilowatt. A unit, representing 1,000 watts. An electric current + measure, usually expressed thus: K.W. + +Kilowatt Hour. The computation of work equal to the exertion of one + kilowatt in one hour. + +Knife Switch. A bar of a blade-like form, adapted to move down + between two fingers, and thus establish metallic + connections. + +Laminated. Made up of thin plates of the same material, laid + together, but not insulated from each other. + +Lamp Arc. A voltaic arc lamp, using carbon electrodes, with + mechanism for feeding the electrodes regularly. + +Lamp, Incandescent. A lamp with a filament heated up to a glow by the + action of an electric current. The filament is within + a vacuum in a glass globe. + +Leak. Loss of electrical energy through a fault in wiring, + or in using bare wires. + +Load. The ampere current delivered by a dynamo under certain + conditions. + +Low Frequency. A current in which the vibrations are of + few alternations per second. + +Magnet. A metallic substance which has power to attract + iron and steel. + +Magnet Bar. A straight piece of metal. + +Magnet Coil. A coil of wire, insulated, surrounding a core of + iron, to receive a current of electricity. + +Magnet Core. A bar of iron adapted to receive a winding of wire. + + +Magnet, Field. A magnet in a dynamo. A motor to produce electric + energy. + +Magnet, Permanent. A short steel form, to hold magnetism for a long + time. + +Magnetic Adherence. The adherence of particles to the + poles of a magnet. + +Magnetic That quality of a metal which draws metals. Also + Attraction and the pulling action of unlike poles for each + Repulsion. other, and pushing away of like poles when brought + together. + +Magnetic Force. The action exercised by a magnet of attracting + or repelling. + +Magnetic Pole. The earth has North and South magnetic poles. + The south pole of a magnetic needle is attracted + so it points to the north magnetic pole; and the north + pole of the needle is attracted to point to the south + magnetic pole. + +Magneto-generator. A permanent magnet and a revolving armature for + generating a current. + +Maximum Voltage. The final voltage after charging. + +Molecule. Invisible particles made up of two or more atoms + of different matter. An atom is a particle of one + substance only. + +Morse Sounder. An electric instrument designed to make a clicking + sound, when the armature is drawn down by a + magnet. + +Motor-dynamo. A motor and a dynamo having their armatures + connected together, whereby the motor is driven + by the dynamo, so as to change the current into a + different voltage and amperage. + +Motor-transformer. A motor which delivers the current like a generator. + +Needle. A bar magnet horizontally poised on a vertical + pivot point, like the needle of a mariner's compass. + +Negative Amber, when rubbed, produces negative electricity. + Electricity. A battery has positive as well as negative + electricity. + +Negative Element. That plate in the solution of a battery + cell which is not disintegrated. + +Normal. The usual, or ordinary. The average. In a + current the regular force required to do the work. + +North Pole, The term applied to the force located near + Electric. the north pole of the globe, to which a permanent + magnet will point if allowed to swing freely. + +O. Abbreviation for Ohm. + +Ohm. The unit of resistance. Equal to the resistance of + a column of mercury one square millimeter in cross + section, and 106.24 centimeters in length. + +Ohm's Law. It is expressed as follows: + 1. The current strength is equal to the electro-motive + force divided by its resistance. + 2. The electro-motive force is equal to the current + strength multiplied by the resistance. + 3. The resistance is equal to the electro-motive force + divided by the current strength. + +Overload. In a motor an excess of mechanical work which causes + the armature to turn too slowly and produces heat. + +Phase. One complete oscillation. The special form of a + wave at any instant, or at any interval of time. + +Plate, Condenser. In a static machine it is usually a plate of glass + and revoluble. + +Plate, Negative. The plate in a battery, such as carbon, copper or + platinum, which is not attacked by the solution. + +Plating, Electro-. The method of coating one metal with another by + electrolysis. + +Polarity. The peculiarity, in a body, of arranging itself + with reference to magnetic influence. + +Parallel. When a number of cells are coupled so that their + similar poles are grouped together. That is to say, + as the carbon plates, for instance, are connected + with one terminal, and all the zinc plates with the + other terminal. + +Polarization. When the cell is deprived of its electro-motive + force, or any part of it, polarization is the result. + It is usually caused by coating of the plates. + +Porosity. Having small interstices or holes. + +Positive Current. One which deflects a needle to the left. + +Positive Any current flowing from the active element, + Electricity. such as zinc, in a battery. The negative + electricity flows from the carbon to the zinc. + +Potential, + Electric. The power which performs work in a circuit. + +Potential Energy. That form of force, which, when liberated, does or + performs work. + +Power Unit. The volt-amperes or watt. + +Primary. The induction coil in induction machines, or in + a transformer. + +Push Button. A thumb piece which serves as a switch to + close a circuit while being pressed inwardly. + +Quantity. Such arrangement of electrical connections + which give off the largest amount of current. + +Receiver. An instrument in telephony and telegraphy which + receives or takes in the sound or impulses. + +Relay. The device which opens or closes a circuit so as to + admit a new current which is sent to a more distant + point. + +Repulsion, That tendency in bodies to repel each other when + Electric. similarly charged. + +Resilience. The springing back to its former condition or + position. Electricity has resilience. + +Resistance. The quality in all conductors to oppose the passage + of a current. + +Resistance Coil. A coil made up of wire which prevents the passage + of a current to a greater or less degree. + +Resistance, The counter force in an electrolyte which seeks + Electrolytic. to prevent a decomposing current to pass through it. + +Resistance: Internal, The opposing force to the movement of a current + External. which is in the cell or generator. This is called the + _internal_. That opposite action outside of the cell + or generator is the _external_. + +Resonator, An open-circuited conductor for electrically + Electric. resounding or giving back a vibration, usually + exhibited by means of a spark. + +Rheostat. A device which has an adjustable resistance, so + arranged that while adjusting the same the circuit + will not be open. + +Safety Fuse. A piece of fusible metal of such resistance that + it breaks down at a certain current strength. + +Saturated. When a liquid has taken up a soluble material + to the fullest extent it is then completely saturated. + +Secondary. One of the two coils in a transformer, or induction + coil. + +Secondary Plates. The brown or deep red plates in a storage battery + when charged. + +Self-excited. Producing electricity by its own current. + +Series. Arranged in regular order. From one to the other + directly. If lamps, for instance, should be arranged + in circuit on a single wire, they would be in series. + +Series, Multiple. When lamps are grouped in sets in parallel, + and these sets are then connected up in series. + +Series Windings. A generator or motor wound in such a manner that + one of the commutator brush connections is joined + to the field magnet winding, and the other end of + the magnet winding joined to the outer circuit. + +Shunt. Going around. + +Shunt Winding. A dynamo in which the field winding is parallel with + the winding of the armature. + +Snap Switch. A switch so arranged that it will quickly make a + break. + +Sounder. The apparatus at one end of a line actuated by a key + at the other end of the line. + +Spark Coil. A coil, to make a spark from a low electro-motive + force. + +Spark, Electric. The flash caused by drawing apart the ends of a + conductor. + +Specific Gravity. The weight or density of a body. + +Static Electricity. Generated by friction. Also lightning. + Any current generated by a high electro-motive force. + +Strength of Current. The quantity of electricity in a circuit. + +Synchronize. Operating together; acting in unison. + +Terminal. The end of any electric circuit or of a body + or machine which has a current passing through it. + +Thermostat, Electric. An electric thermometer. Usually made + with a metal coil which expands through the action + of the electricity passing through it, and, in + expanding, it makes a contact and closes a circuit. + +Transformer. The induction coil with a high initial E. M. F. + changes into a low electro-motive force. + +Unit. A standard of light, heat, electricity, or of + other phenomena. + +Vacuum. A space from which all matter has been exhausted. + +Vibrator. Mechanism for making and breaking circuits in + induction coils or other apparatus. + +Volt. The unit of electro-motive force. + +Voltage. Electro-motive force which is expressed in volts. + +Voltaic. A term applied to electric currents and devices. + +Volt-meter. An apparatus for showing the difference of + potential, or E. M. F. in the term of volts. + +Watt. The unit of electrical activity. The product of + amperes multiplied by volts. + +Watt Hour. One watt maintained through one hour of time. + +Waves, Electric Waves in the ether caused by electro-magnetic + Magnetic. disturbances. + +X-rays. The radiation of invisible rays of light, which + penetrate or pass through opaque substances. + +Yoke, or Bar. A soft iron body across the ends of a + horseshoe magnet, to enable the magnet to retain its + magnetism an indefinite time. + +Zinc Battery. A battery which uses zinc for one of its elements. + + + + +INDEX + +A + +Accumulated, 31. + +Accumulation, 29. + +Accumulator cell, 87. + +Accumulators, 82, 88, 89. + +Accumulators, plates, 83. + +Acid, 34, 37, 125. + +Acid maker, 125. + +Acid, sulphuric, 31, 84. + +Acidulated, 55. + +Acidulated water, 34. + +Acoustics, 110. + +Actinic rays, 184, 185. + +Actinium, 186. + +Active element, 82. + +Adjustable rod, 107. + +Adjusting screw, 70, 71, 72, 73, 106. + +Aerial wire, 108. + +Agents, 13, 32. + +Alarms, burglar, 11, 76, 80. + +Alkali, 125. + +Alkaline, 37. + +Alternate, 127. + +Alternating, 38, 149, 150, 153, 154, 155, 156. + +Alternating current, 145. + +Alternating periods, 149. + +Alternations, 147. + +Aluminum, 128, 129, 135, 137. + +Aluminum hydrate, 129. + +Amber, 5, 171. + +Ammeter, 7, 88. + +Amperage, 38, 61, 62, 132, 159, 160, 168. + +Ampere, 7, 37, 60, 63, 139, 140, 167. + +Amplitude, 111. + +Annunciator, 65, 74, 76, 79, 80, 81. + +Annunciator bells, 11. + +Anode, 35, 133, 134. + +Antennae, 108. + +Antimony 137, 143. + +Anvil, 13, 14. + +Apparatus, 11, 57, 106, 139, 145. + +Arc, 163, 182. + +Arc lighting, 38, 165. + +Arc system, 166. + +Armature, 18, 25, 38, 40, 42, 43, 45, 46, 47, 48, 53, 55, 70, 72, 73, + 74, 90, 93, 112, 151, 152, 155, 163, 176, 177, 178, 179, 180. + +Armature brush, 48. + +Armature post, 71. + +Armature, vertical, 75. + +Armature winding, 42, 43, 156. + +Asbestos, 140. + +Astatic galvanometer, 108. + +Atmosphere, 184. + +Attract, 30. + +Attracted, 72. + +Attraction, 21, 25. + +Attractive, 178. + +Automatic, 120. + +Auxiliary, 44. + +Awls, 14. + + +B + +Bacteria, 126, 187. + +Bar, cross, 66. + +Bar, horizontal, 46. + +Bar, parallel switch, 67. + +Bar, switch, 65, 68. + +Base block, 66. + +Batteries, 11, 93, 122. + +Battery, 29, 30, 32, 35, 36, 46, 47, 80, 81, 82, 83, 85, 86, 88, 92, 94, + 95, 107, 108, 116, 117, 118, 121, 134, 142. + +Battery charging, 82. + +Bearings, 45, 46. + +Bells, 65, 73, 76, 122. + +Bells, electric, 70. + +Bench, 13, 15, 17. + +Binding post, 52, 70, 71, 72, 103, 107, 108, 121. + +Binding screw, 65, 66. + +Bismuth, 18, 143. + +Bit, 13. + +Blue vitriol, 57. + +Brass plate, 77, 78. + +Brazing, 17, 65. + +Bridge, 52. + +Brush holder, 46. + +Brushes, 48, 150, 151, 153, 167. + +Burglar, 11. + +Burglar alarm, 76, 80. + +Buttons, contact, 80. + +Buttons, push, 65, 68, 69, 70, 76, 79. + + +C + +Calorimeter, 56. + +Cancerous, 187. + +Candle power, 89, 139. + +Cap, removable, 73. + +Cap screws, 42. + +Carbon, 35, 119, 121, 162, 163, 169. + +Carbon block, 120. + +Carbon pencil, 119. + +Cathode, 35, 36, 133, 134. + +Cell, 29, 33. + +Cell, accumulator, 87. + +Cell, charging, 87. + +Channel, 43. + +Channel, concave, 40. + +Charged, 120. + +Charged battery, 82. + +Charging circuit, 82, 89. + +Charging source, 83. + +Charged wire, 147. + +Chemical, 57. + +Chisels, 13. + +Chloride of lime, 84. + +Choked, 157. + +Choking coils, 145, 146, 156, 158. + +Circuit, 33, 69, 73, 76, 78, 80, 81, 90, 92, 93, 109, 113, 116, 121, + 122, 131, 134, 143, 156. + +Circuit, primary, 99. + +Circuit, secondary, 99. + +Circuiting, 81, 155. + +Circuiting system, 79. + +Clapper arm, 70. + +Closed rings, 26. + +Coherer, 105, 108, 109. + +Cohering, 106. + +Coils, 18, 26, 52, 55, 74, 160. + +Coils, choking, 145, 146, 156, 158. + +Coils, induction, 99, 102. + +Coils, primary, 109. + +Coils, secondary, 102, 109. + +Coincide, 42. + +Cold, 14. + +Collecting surfaces, 30. + +Collector, 31. + +Column, 61. + +Combustion, 169. + +Commutator, 44, 46, 151, 152. + +Commutator brushes, 46. + +Commutator plates, 45. + +Compass, 22, 24, 172. + +Composition, 83, 124. + +Compound wound, 47. + +Concave channel, 40. + +Condenser, 98, 100, 101, 102, 108. + +Conduct, 6, 108. + +Conduction, 135, 136, 138, 166, 170. + +Conduction current, 27. + +Conductor, 21, 31, 33, 63, 98, 116, 161, 162. + +Conduit, 72. + +Conically formed, 126. + +Conjunction, 143. + +Connecting wire, 58. + +Connection, 72, 76. + +Construction, magnet, 39. + +Consumption, 180. + +Contact, 122, 123, 152, 162. + +Contact finger, 150. + +Contact plate, 67, 68, 79. + +Contact screws, 93. + +Contact surface, 66. + +Continuous, 145. + +Converter, 176. + +Converting, 142, 145, 146. + +Copper, 18, 34, 36, 65, 66, 132, 133, 134, 135, 136, 137, 142, 143. + +Copper cyanide, 133. + +Copper plate, 33, 35, 58, 67. + +Copper sulphate, 57. + +Copper voltameter, 55, 57. + +Core, 27, 28, 36, 39, 40, 115. + +Core, magnet, 75, 93. + +Counter, clock-wise, 51. + +Coupled, 36. + +Crank, 30. + +Crookes' tube, 184. + +Cross bar, 52, 66. + +Crown of cups, 32. + +Crystal, 85. + +Current, 6, 7, 13, 18, 26, 27, 28, 35, 36, 37, 38, 47, 50, 51, 52, 55, + 56, 57, 58, 59, 62, 63, 70, 72, 73, 90, 95, 98, 105, 108, 116, 133, 134, + 135, 136, 138, 139, 140, 141, 142, 143, 147, 148, 149, 150, 152, 153, + 157, 160, 161, 163, 165, 166, 170. + +Current, alternating, 150. + +Current changing, 82. + +Current conduction, 27. + +Current, continuous, 164. + +Current, direct, 145, 150. + +Current direction, 50. + +Current, exterior, 50, 150. + +Current, reversing, 148. + +Current strength, 7, 57. + +Current testing, 143. + +Cut-out, 120. + +Cutter, 14. + +Cutting, lines of force, 38. + +Cylinder, 44. + +Cylindrical, 43. + + +D + +Dash, 95, 97. + +Decoherer, 106, 108. + +Decomposed, 57, 128. + +Decomposes, 55. + +Decomposing, 123. + +Decomposition, 12, 35, 82. + +Deflected, 54. + +Degree, 135, 162. + +Demagnetized, 24, 72. + +Deposited, 58, 133. + +Depression, 15, 140. + +Detecting current, 49. + +Detector, 49, 52, 54, 105. + +Devices, measuring, 27. + +Diagrams, 46, 48, 79, 89. + +Diagrammatically, 81. + +Diamagnetic, 19. + +Diametrically, 114. + +Diaphragm, 112, 113, 116, 120, 122. + +Diamonds, 186. + +Diluted, 86. + +Direct current, 38, 140. + +Direction of current, 50. + +Direction of flow, 98. + +Discharge, 172. + +Disintegrate, 132. + +Disk, 43. + +Dissimilar, 37. + +Disturbance, 176. + +Dividers, 14. + +Divisibility, 168. + +Dot, 96, 97. + +Dot and dash, 96. + +Double click, 95. + +Double line, 65. + +Double-pole switch, 65. + +Double-throw switch, 117. + +Drawing, 20. + +Drill, ratchet, 13. + +Drops, 81. + +Ductile, 186. + +Duplex wire, 115. + +Dynamo, 7, 27, 38, 42, 46, 48, 62, 82, 83, 87, 89, 132, 141, 142, 145, + 150, 155, 161, 165, 167, 175, 176, 180, 187. + +Dynamo fields, 40, 41. + + +E + +Earth, 22. + +Elasticity, 100, 142. + +Electric, 6, 31, 49, 50, 76, 78, 81, 131, 142, 158, 162, 173, 176. + +Electric arc, 63, 163. + +Electric bell, 19, 69, 70, 71, 72, 106, 117. + +Electric bulbs, 167. + +Electric circuit, 118. + +Electric fan, 55. + +Electric field, 76. + +Electric hand purifier, 129. + +Electric heating, 135, 137, 161. + +Electric iron, 130, 141. + +Electric lamp socket, 139. + +Electric light, 56, 66. + +Electric lighting, 161. + +Electric power, 113. + +Electric welding, 183. + +Electrical, 8, 11, 65, 96, 98, 104, 141, 159, 180, 184, 187. + +Electrical impulses, 105, 147, 148. + +Electrical manifestations, 175. + +Electrically, 32, 70. + +Electricity, 5, 6, 7, 8, 9, 12, 13, 18, 21, 26, 27, 28, 29, 38, 49, 54, + 60, 61, 62, 82, 97, 98, 100, 104, 110, 112, 116, 123, 124, 133, 134, + 136, 138, 145, 146, 147, 154, 156, 160, 166, 170, 171, 172, 175, 182, + 187. + +Electricity measuring, 49. + +Electricity, thermo-, 142. + +Electrified, 37, 186. + +Electro-chemical, 55. + +Electrode, 35, 124, 127, 128, 161, 162, 163, 164, 165, 184. + +Electrolysis, 7, 123, 126, 132. + +Electrolyte, 33, 35, 36, 57, 86, 88, 123, 132, 142. + +Electrolytic, 55, 123, 125. + +Electro-magnet, 59, 78. + +Electro-magnetic, 7, 24, 25, 29, 37, 55, 92, 93, 94. + +Electro-magnetic force, 7. + +Electro-magnetic rotation, 7. + +Electro-magnetic switch, 116. + +Electro-meter, 7. + +Electro-motive force, 37, 63, 99. + +Electroplate, 12, 38, 48, 123, 132, 134. + +Electro-positive-negative, 142, 143. + +Elements, 36, 83. + +Engine energy, 170, 180. + +Equidistant, 127. + +Ether, 104. + +Example, 61. + +Excited, 47. + +Extension plate, 103. + +Exterior, 3. + +Exterior magnetic, 27. + +External, 37. + +External circuit, 153. + +External current, 50. + +External resistance, 37. + + +F + +Factor, 61. + +Ferrous oxide, 125. + +Field, 46, 47. + +Field, dynamo, 40, 41. + +Field magnet cores, 155. + +Field, magnetic, 38. + +Field of force, 33. + +Field wire, 48. + +Filament, 168, 169, 170. + +Filter, 128. + +Flat iron, 140. + +Flocculent, 128. + +Force, 50. + +Formulated, 19. + +Friction, 32. + +Frictional, 6, 7, 29. + +Fuse, 169. + + +G + +Galvani, 7. + +Galvanic, 7, 23, 30. + +Galvanometer, 7, 49, 108, 143. + +Galvanoscope, 55, 58, 59. + +Gaseous, 128. + +Gasoline, 99. + +Gas stove, 17. + +Gelatine, 128. + +Generate, 29, 38, 134, 136, 145. + +Generated, 55. + +Generating, 32, 134. + +Generation, 170. + +Generator, 32, 125, 147. + +German silver, 136, 137. + +Germicide, 187. + +Gimlets, 17. + +Glass, 30, 86, 126, 186. + +Gold, 135. + +Grid, 84. + +Ground circuit, 121. + +Gunpowder, 6. + + +H + +Hack-saw, 14. + +Hammer, 13. + +Heart-shaped switch, 77. + +Heater, 136. + +Heating, 13, 38. + +Hertzian rays, 170. + +Hertzian wave, 184. + +High tension, 38, 102, 184. + +High tension apparatus, 98. + +High tension coils, 103. + +High voltage, 158. + +Horizontal bar, 46. + +Horseshoe magnet, 22, 24, 175. + +Hydrate of aluminum, 129. + +Hydrogen, 35, 123, 125, 128. + + +I + +Igniting, 99. + +Illumination, 162, 163, 165, 167, 170. + +Immersed, 133. + +Impulses, 60, 62, 96, 104, 109, 152, 179. + +Incandescent, 166, 168. + +Induced, 28. + +Inductance, 149, 150. + +Induction, 27, 37, 98, 147. + +Induction coils, 99, 102, 106. + +Influences, 178. + +Initial charge, 88. + +Insulated, 27, 28, 40, 43, 52, 55, 73, 115, 151, 180. + +Insulating, 66, 69, 120, 140, 164. + +Insulating material, 114. + +Insulation, 40, 116. + +Instruments, 49, 94, 112, 118, 120. + +Instruments, measuring, 8. + +Intensity, 55, 60, 104, 154. + +Interior, magnetic, 23. + +Internal resistance, 37. + +Interruption, 102, 103. + +Installation, 168. + +Ionize, 186. + +Iron, 19, 132, 133, 136, 142, 171. + +Isolated, 186. + + +J + +Jar, 29, 31, 32. + +Journal, 46. + +Journal block, 16, 146. + +Jump spark, 99. + + +K + +Key, 90, 91, 95. + +Key, sending, 90. + +Knob, 32. + +Knob, terminal, 31. + + +L + +Laboratory, 9. + +Lead, 31, 136. + +Lead, precipitated, 83, 85. + +Lead, red, 83, 84. + +Lever switching, 67. + +Light, 104. + +Light method, 56. + +Lighting, 9, 38. + +Lighting circuit, 48. + +Lighting system, 82. + +Lightning, 6, 171, 172, 173. + +Lightning rod, 173. + +Lime, chloride of, 84. + +Line of force, 146. + +Line wire, 122. + +Line, magnetic, 22, 23. + +Liquid, 32. + +Litharge, 83. + +Loadstone, 17. + +Locomotives, 165. + +Low tension, 38, 98, 102, 179. + + +M + +Magnet bar, 20. + +Magnet core, 16, 75, 93. + +Magnet, electro, 59, 78. + +Magnet, horseshoe, 22, 25, 175. + +Magnet lines, 22, 23. + +Magnet, permanent, 25, 38, 46, 50, 172. + +Magnet, reversed, 20. + +Magnet, steel, 53. + +Magnet, swinging, 53. + +Magnetic, 7, 19, 20, 21, 22, 25, 113, 178. + +Magnetic construction, 39. + +Magnetic exterior, 27. + +Magnetic field, 22, 24, 27, 38, 50, 112, 146, 148, 155. + +Magnetic interior, 23. + +Magnetic pull, 59. + +Magnetic radiator, 37. + +Magnetism, 19, 54, 104, 110, 159, 171. + +Magnetized, 18, 25, 27, 50. + +Magnetized wire, 146. + +Magnets, 13, 14, 18, 19, 20, 21, 22, 23, 24, 25, 39, 51, 53, 54, 70, 71, + 73, 75, 81, 90, 93, 112, 113, 115, 147, 150, 163, 176, 177, 178. + +Main conductor, 31. + +Mandrel, 15, 16. + +Manganese, 19. + +Manifestations, 19. + +Mariner, 172. + +Material, non-conducting, 90. + +Maximum, 154. + +Measure, 55, 56, 60, 62. + +Measurement, 62. + +Measuring devices, 27. + +Measuring instruments, 8. + +Mechanism, 47, 180. + +Medical batteries, 99. + +Mercury, 63, 169. + +Metal base, 73. + +Mica, 186. + +Microphone, 118, 119, 120. + +Millimeter, 63. + +Minus, 34. + +Minus sign, 21. + +Morse code, 76. + +Motor, 7, 21, 27, 46, 47, 62, 82, 99, 150, 176, 180. + +Mouthpiece, 115. + +Mouthpiece rays, 188. + +Moving field, 117. + +Multiple, 168. + +Musical scale, 111. + + +N + +Negative, 21, 35, 36, 68, 83, 86, 87, 94, 125, 151, 152, 154, 165, 177, + 178, 179. + +Neutral, 125. + +Neutral plate, 84. + +Nickel, 136. + +Nickel plating, 132. + +Nitrate of silver, 62. + +Nitrogen, 126. + +Non-conducting material, 90. + +Non-conductor, 164. + +Non-magnetic, 19. + +North pole, 20, 21, 22, 23, 25, 50, 54, 156. + +Number plate, 75. + +N-ray, 188. + + +O + +Ohms, 60, 63. + +Ohms, international, 63. + +Ohms law, 7. + +Operator, 95, 118. + +Oscillating, 99, 105. + +Osmium, 169. + +Oxides, 125. + +Oxidizing, 183. + +Oxygen, 35, 123, 125, 126, 128, 129, 169. + + +P + +Packing ring, 124. + +Paraffine, 56, 100, 101, 102. + +Paraffine wax, 86. + +Parallel, 87, 88, 89. + +Parallel switch bar, 67. + +Parallel wires, 28, 49. + +Partition, 124. + +Peon, 13. + +Percolate, 128. + +Periodicity, 159. + +Periods of alternations, 149. + +Permanent, 18, 19, 50. + +Permanent magnet, 25, 38, 46, 50, 172. + +Phase, 19. + +Phenomenon, 27, 65. + +Photograph, 186. + +Physical, 21. + +Pile, voltaic, 33. + +Pipe, 61. + +Pitchblende, 186. + +Pivot pin, 53. + +Pivotal, 22. + +Plane, 13. + +Plate, 57, 93. + +Plate, contact, 67, 68, 79. + +Plate, copper, 33, 35, 58, 67. + +Plate, negative, 84. + +Plate, number, 75. + +Plate, positive, 84, 88. + +Plate, zinc, 33. + +Platinum, 13, 57, 137. + +Pliers, 14. + +Plus sign, 21, 24. + +Pointer, 53. + +Polarity, 154, 177, 178, 179. + +Polarization, 35. + +Pole, north, 20, 21, 22, 23, 25, 50, 54, 156. + +Pole piece, 40, 42. + +Pole, south, 20, 21, 22, 25, 50, 54, 156. + +Poles, 177, 179. + +Polonium, 186. + +Porcelain, 86. + +Porous, 85. + +Positive, 4, 21, 25, 36, 40, 68, 83, 86, 87, 94, 123, 125, 151, 152, + 153, 155, 165. + +Post, binding, 52, 71. + +Potentiality, 105, 109. + +Power, 38, 186. + +Power, candle, 89, 139. + +Precipitate of lead, 83, 85. + +Precision, 7. + +Pressure, 87. + +Primary, 35, 62, 98, 134, 142, 159, 184. + +Primary battery, 7, 99. + +Primary circuit, 99. + +Primary coil, 106, 109. + +Prime conductor, 6. + +Projected, 185. + +Propagated, 105, 185. + +Properties, 55. + +Purification, 123, 128. + +Purifier, 126, 131. + +Push button, 65, 68, 69, 70, 76, 79. + + +Q + +Quantity, 55, 60, 61, 138. + +Quartz, 186. + + +R + +Radio-activity, 186. + +Radium, 184, 185, 187, 188. + +Ratchet drill, 13. + +Reaction, 148. + +Receiver, 12, 90, 97, 121, 122. + +Receiving station, 109. + +Rectangular, 69. + +Rectifiers, 146. + +Red lead, 83, 84. + +Reel, 13. + +Reflected, 185. + +Refraction, 185. + +Refractory, 182. + +Register, 57. + +Removable, 54. + +Removable cap, 73. + +Repel, 20. + +Repulsion, 21, 128. + +Reservoir, 61, 62. + +Resiliency, 99. + +Resistance, 7, 36, 37, 60, 63, 99, 135, 136, 137, 138, 140, 141, 156, + 157, 163, 166, 168. + +Resistance bridge, 7. + +Resistance, external, 37. + +Resistance, internal, 37. + +Rheostat, 7. + +Reversed, 20, 50, 153. + +Reversible, 163. + +Reversing, 176. + +Reversing switch, 67. + +Revolubly, 46. + +Revolve, 179. + +Revolving, 177. + +Roentgen rays, 184. + +Roentgen tube, 187. + +Rotation, 149. + +Rubber, 40, 46, 77, 115, 126, 130, 138. + + +S + +Sad-irons, 13. + +Saline, 133. + +Sanitation, 12. + +Saturated, 85. + +Screw, 15. + +Screw, binding, 65, 66. + +Screw-driver, 14. + +Screw, set, 72. + +Sealing wax, 53. + +Secondary, 62, 98, 105, 158, 159, 160. + +Secondary circuit, 99. + +Secondary coil, 107, 108. + +Self-induction, 149, 156. + +Sender, 90, 97. + +Sending apparatus, 106. + +Sending key, 90. + +Separately excited, 46. + +Series-wound, 47. + +Severed magnet, 20. + +Sewage, 12. + +Shaft, 30. + +Shears, 14, 17. + +Shellac, 40. + +Shunt-wound, 47. + +Signal, 118. + +Silver, 19, 63, 125. + +Silver nitrate, 62. + +Socket, 54, 139. + +Soldering, 14. + +Soldering iron, 17. + +Solution, 55, 57, 62, 63, 84, 86, 133, 134, 142. + +Sounder, 90, 92, 95, 96. + +Sounding board, 119. + +Source, charging, 83. + +South pole, 20, 21, 22, 25, 50, 54, 156. + +Spark gap, 102, 106. + +Spark jump, 99. + +Spring finger, 69. + +Square, 14, 17. + +Standard, 62, 63. + +Station, 94, 95, 117, 122. + +Steel, 18, 19. + +Steel magnet, 53. + +Sterilized, 12. + +Stirrup, 75. + +Stock bit, 13. + +Stock contact, 121. + +Storage, 82. + +Storage battery, 107. + +Storing, 82. + +Substances, 135. + +Sulphate, 55, 128, 133. + +Sulphur, 19. + +Sulphuric acid, 31, 84. + +Sulphuric acid voltameter, 55, 57. + +Superstition, 171, 173. + +Surging, 153, 154. + +Swinging magnet, 53. + +Swinging switch blade, 67. + +Switch blades, 66. + +Switches, 65, 66, 70, 77, 78, 90, 117. + +Switches, bar, 65, 68, 90, 91. + +Switches, bar, parallel, 67. + +Switches, heart-shaped, 78. + +Switches, piece, 77. + +Switches, reversing, 67. + +Switches, sliding, 67, 80. + +Switches, terminal, 8. + +Switches, two-pole, 65. + +System, circuiting, 79. + + +T + +Tail-piece, 16. + +Tantalum, 169. + +Telegraph, 11, 90, 96. + +Telegraph key, 106. + +Telegraph sounder, 108, 109. + +Telegraphing, 94. + +Telephone, 12, 110, 113, 117, 118, 119, 120. + +Telephone circuit, 118. + +Telephone connections, 116. + +Telephone hook, 122. + +Temperature, 56, 88, 134, 161, 170. + +Tension, high, 38, 102, 184. + +Tension, low, 38, 98, 102, 179. + +Terminal, 31, 34, 35, 40, 48, 82, 86, 93, 95, 107, 116, 121, 122, 151, + 152, 153, 154, 156. + +Terminal knob, 31. + +Terminal, secondary, 102. + +Terminal switch, 81. + +Theoretical, 160. + +Therapeutics, 187. + +Thermo-electric couples, 146. + +Thermo-electricity, 135. + +Thermometer, 56. + +Thorium, 169, 186. + +Thunderbolt, 171, 173. + +Tin, 136. + +Tinfoil, 31, 101. + +Tools, 11, 13, 17. + +Torch, brazing, 17. + +Transformer, 145, 146, 158, 159, 180, 182. + +Transformer, step-down, 182. + +Transmission, 38, 187. + +Transmit, 63, 95, 157. + +Transmitter, 12, 120, 121, 122, 123. + +Transverse, 16, 52. + +Transversely, 43. + +Trigger, 75. + +Tripod, 31. + +Tubular, 44, 45. + +Two-pole switch, 65. + + +U + +Ultra-violet, 185. + +Uranium, 186. + + +V + +Vacuum, 184. + +Vapor lamps, 169. + +Velocity, 60, 73. + +Vertical armature, 75. + +Vibration, 110, 111, 113. + +Vibratory, 110. + +Vise, 13. + +Voltage, 37, 38, 60, 61, 62, 63, 87, 88, 99, 147, 154, 165, 180, 182. + +Voltage, high, 158. + +Voltaic, 29, 32. + +Voltaic pile, 33. + +Voltameter, 7, 58, 88. + +Voltameter, sulphuric, acid, 55, 57. + +Volts, 60, 62, 87, 89, 132, 158, 159. + + +W + +Water, 123, 138, 144. + +Water power, 142. + +Watts, 60, 61, 160. + +Wave lengths, 104, 110. + +Weight, 49. + +Welding, 13, 182. + +Winding, 18, 40, 47, 58, 159, 196. + +Winding reel, 14. + +Window connection, 76. + +Window frame, 78. + +Wire, 6, 18, 21, 26, 28, 156. + +Wire, circuiting, 79. + +Wire coil, 40. + +Wire lead, 70. + +Wire, parallel, 28, 49. + +Wireless, 12. + +Wireless telegraphy, 103, 104, 184. + +Wiring, 80. + +Wiring, window, 77. + +Workshop, 11, 17. + +Wound, compound, 48. + +Wound-series, 47. + +Wound-shunt, 47. + + +X + +X-ray, 184, 185, 187, 188. + + +Z + +Zinc, 17, 34, 35, 85, 135. + +Zinc plates, 33. + + + + +THE "HOW-TO-DO-IT" BOOKS + + +CARPENTRY FOR BOYS + +A book which treats, in a most practical and fascinating manner all +subjects pertaining to the "King of Trades"; showing the care and use of +tools; drawing; designing, and the laying out of work; the principles +involved in the building of various kinds of structures, and the +rudiments of architecture. It contains over two hundred and fifty +illustrations made especially for this work, and includes also a +complete glossary of the technical terms used in the art. The most +comprehensive volume on this subject ever published for boys. + + +ELECTRICITY FOR BOYS + +The author has adopted the unique plan of setting forth the fundamental +principles in each phase of the science, and practically applying the +work in the successive stages. It shows how the knowledge has been +developed, and the reasons for the various phenomena, without using +technical words so as to bring it within the compass of every boy. It +has a complete glossary of terms, and is illustrated with two hundred +original drawings. + + +PRACTICAL MECHANICS FOR BOYS + +This book takes the beginner through a comprehensive series of practical +shop work, in which the uses of tools, and the structure and handling of +shop machinery are set forth; how they are utilized to perform the work, +and the manner in which all dimensional work is carried out. Every +subject is illustrated, and model building explained. It contains a +glossary which comprises a new system of cross references, a feature +that will prove a welcome departure in explaining subjects. Fully +illustrated. + + +_Price 60 cents per volume_ + +THE NEW YORK BOOK COMPANY +147 FOURTH AVENUE NEW YORK + + + + + +-----------------------------------------------------------------+ + | Transcriber's Note. | + | | + | Every effort has been made to replicate this text as faithfully | + | as possible, including obsolete and variant spellings and other | + | inconsistencies. | + | | + | Minor punctuation and printing errors have been corrected. | + | | + | The first page of the original book is an advertisement. 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