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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-15 01:54:00 -0700 |
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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-15 01:54:00 -0700 |
| commit | 504a310bb8cddd4a5d52b1a2e54db97c4a20d2cc (patch) | |
| tree | 0ac751735494e6356d091eac1cafa735e754ca83 /22766-h | |
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diff --git a/22766-h/22766-h.htm b/22766-h/22766-h.htm new file mode 100644 index 0000000..5f8b406 --- /dev/null +++ b/22766-h/22766-h.htm @@ -0,0 +1,8907 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <link rel="schema.DC" href="http://dublincore.org/documents/1998/09/dces/" /> + <meta name="author" content="J. S. Zerbe, M.E." /> + <meta name="DC.Creator" content="J. S. Zerbe, M.E." /> + <meta name="DC.Title" content="Electricity For Boys" /> + <meta name="DC.Date" content="2007" /> + <meta name="DC.Language" content="en" /> + <title> + The Project Gutenberg eBook of Electricity for Boys, by J. S. Zerbe, M.E. + </title> + <style type="text/css"> +/*<![CDATA[ XML blockout */ +<!-- + + @media print { + .pagenum {position: absolute; left: 92%; font-size: x-small; background-color: inherit; + text-align: right; color: gray; display: none; visibility: hidden; } + } + @media screen { + .pagenum {position: absolute; left: 92%; font-size: x-small; background-color: inherit; white-space: nowrap; + text-align: right; color: gray; display: inline; visibility: visible;text-indent:0;} + .pagenum a {text-decoration:none; color:#444;} + .pagenum a:hover {color:#F00;} + } + + body p { text-align: justify; font-size: medium; + max-width: 46em; margin-left: auto; margin-right: auto;} + + p {margin-top: .75em; text-align: justify; margin-bottom: .75em} + p.chapter {margin-top: 0em; margin-bottom: 0em; line-height: 100%;} + p.pn {margin-top: 0em; margin-bottom: 0em; line-height: 100%;} + p.right {text-align: right; margin-top: 0.0em; margin-bottom: 0.0em;} + p.titleblock {margin-top: 0em; margin-bottom: 0em; text-indent: 0em; text-align: center; line-height: 125%;} + + hr {width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + body {margin-left: 10%; margin-right: 10%;} + + .center {text-align: center;} + .smcap {font-variant: small-caps;} + .u {text-decoration: underline;} + + img {border: none;} + .figcenter {margin: auto; text-align: center;} + .figcenter a:hover {border-bottom: none; } + .caption {font-size: 90%;font-weight: bold;} + .italcaption {font-size: 90%; font-style: italic; font-weight: bold} + + h1,h2,h3,h4 { + text-align: center; clear: both; page-break-after: avoid ! important;} + .index.h4 {margin-top: 0em; margin-bottom: 0em;} + + hr {width: 33%; + margin-top: 2em; margin-bottom: 2em; + margin-left: auto; margin-right: auto; + clear: both;} + hr.chapter {width: 55%; margin-top: 1.5em; margin-bottom: 0em; page-break-before: always;} + hr.minor {width: 30%; margin-top: 0.5em; margin-bottom: 0.5em;} + + a {text-decoration: none;} + a:hover {border-bottom: thin dotted silver; } + + .tr {margin-left: 10%; + margin-right: 10%; + margin-top: 5%; + margin-bottom: 5%; + padding: 1em; + background-color: #f6f2f2; + color: black; + border: dotted black 1px;} /* transcriber's notes */ + + /* index styles */ + div.index {font-size: 87.5%} + ul.IX {list-style-type: none; + font-size:inherit} + .IX li {margin-top: .075em} + + .totoc {position: absolute; left: 92%; font-size: x-small; text-align: right; color: gray;} /* Table of contents anchor */ + + /* table styles */ + table {margin-left: auto; margin-right: auto;empty-cells: show;margin-bottom: 2em} + td a[href]:hover {border-bottom:none; } + td.chap {text-align: left; padding-left: 10px; font-variant: small-caps;} + td.chap a[href]:hover {border-bottom: thin dotted silver; } + td.imgr {text-align: left; padding-left: 10px; font-variant: normal;} + td.pr {text-align: right; padding-left: 6px; font-size: 90%;} + td.pr a[href]:hover {border-bottom: thin dotted silver; } + td.abstract p {letter-spacing: 0.02em; text-align: justify; line-height: 1.35em; + margin-left: 14%; margin-right: 0%; margin-top: .25em; margin-bottom: 0.75em;} + td.tdnwc {text-align: center; white-space: nowrap;} /* center align, no wrap */ + + // --> + /* XML end ]]>*/ + </style> + </head> +<body> + + +<pre> + +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: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK ELECTRICITY FOR BOYS *** + + + + +Produced by Joe Longo and the Online Distributed +Proofreading Team at http://www.pgdp.net + + + + + + +</pre> + + + + +<h2>WARNING: This book of one hundred years ago describes<br /> +experiments which are too dangerous to attempt by either<br /> +adults or children. It is published for historical<br /> +interest only.<br /><br /><br /></h2> + + + + + +<h1 class="smcap">The "How-to-do-it" Books</h1> + +<hr class="minor" /> + +<h1>ELECTRICITY FOR BOYS</h1> + +<div class="figcenter" style="width: 617px;margin-bottom:2em"> +<a id="fig1" name="fig1"></a> +<img src="images/illus-fig1.png" width="617" height="316" alt="Fig. 1. WORK BENCH" title="Fig. 1. WORK BENCH" /> +<span class="caption"><i>Fig. 1.</i> WORK BENCH</span> +</div> + +<div class="center"> +<table width="450" style="page-break-before: always;" cellpadding="2" cellspacing="0" border="1"> + <col style="width:80%;" /> + <tr> + <td align="center"> +<br /><br /> +<p class="titleblock" style="margin-top: 2px; font-weight: 600; + margin-bottom: .5em; font-variant: small-caps; word-spacing: 0.4em; font-size: 145%;">THE "HOW-TO-DO-IT" BOOKS</p> +<p class="titleblock" style="font-size: 180%; margin-top: 2px; font-weight: 600; margin-bottom: 1em;"> +ELECTRICITY FOR BOYS</p> + +<table width="70%" cellpadding="2" cellspacing="0" border="0"> +<tr> +<td align="left"> +<p>A working guide, in the successive +steps of electricity, described in +simple terms +</p> +<p class="titleblock" +style="word-spacing: 0.4em; letter-spacing: 0.08em; margin-top: 1em; margin-bottom: 2em; font-size: 90%;"> +WITH MANY ORIGINAL ILLUSTRATIONS</p> +</td> +</tr> +</table> + +<p class="titleblock" style="margin-top: 0em; font-size: 120%;">By J. S. ZERBE, M.E.</p> + +<p class="titleblock" style="margin-top: 2em; margin-bottom: 0em; font-size: 80%;">AUTHOR OF</p> +<p class="titleblock" style="margin-top: .25em; margin-bottom: 3em; font-size: 80%;"> +CARPENTRY FOR BOYS<span style="margin-left:4em">PRACTICAL MECHANICS FOR BOYS</span> +</p> + + +<div class="figcenter" style="width: 119px;"> +<img src="images/nybc.png" width="119" height="116" +alt="Printer's Mark: NYBC/Windmill" title="Printer's Mark: NYBC/Windmill" /> +</div> + +<p class="titleblock" style="margin-top: 3em; font-size: 90%; margin-bottom: 0em;">THE NEW YORK BOOK COMPANY</p> +<p class="titleblock" style="font-variant: small-caps; margin-top: 0px; font-size: 90%; margin-bottom: 2em;">New York</p> + </td> + </tr> +</table> +</div> + +<p class="center" style="margin-top: 2em;" > +<span class="smcap" style="font-size: 80%;">Copyright, 1914, by</span> +<br /><span style="font-size: 80%;">THE NEW YORK BOOK COMPANY</span> +</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="pi" id="pi">p. i</a></span></p> +<h3><a name="toc" id="toc"></a>CONTENTS</h3> + +<table border="0" width="76%" cellpadding="1" cellspacing="0" summary="Contents"> + <col style="width:5%;" /><col style="width:80%;" /><col style="width:15%;" /> +<tbody valign="top"> + <tr> + <td align="right"> </td> + <td class="chap">Introductory</td> + <td class="pr"><a href="#INTRODUCTORY">Page 1</a></td> + </tr> + <tr> + <td class="chap" colspan="2"> </td> + <td class="pr"> </td> + </tr> +<tr> + <td align="right">I.</td> + <td class="chap">Electricity Considered. Brief Historical Events</td> + <td class="pr"><a href="#CHAPTER_I">Page 5</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">II.</td> + <td class="chap">What Tools and Apparatus are Needed</td> + <td class="pr"><a href="#CHAPTER_II">Page 11</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>Preparing the Workshop. Uses of Our Workshop. What +to Build. What to Learn. Uses of the Electrical Devices. +Tools. Magnet-winding Reel.</p></td> +</tr> +<tr> + <td align="right">III.</td> <td class="chap">Magnets, Coils, Armatures, Etc.</td> <td class="pr"><a href="#CHAPTER_III">Page 18</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>The Two Kinds of Magnets. Permanent Magnets. Electro-Magnets. +Magnetism. Materials for Magnets. Non-magnetic +Material. Action of a <i>Second</i> 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.</p></td> +</tr> +<tr> + <td align="right">IV.</td> <td class="chap">Frictional, Voltaic or Galvanic and Electro-magnetic Electricity</td> <td class="pr"><a href="#CHAPTER_IV">Page 29</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>Three Electrical Sources. Frictional Electricity. Leyden +<span class='pagenum'><a name="pii" id="pii">p. ii</a></span>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.</p></td> +</tr> +<tr> + <td align="right">V.</td> <td class="chap">How to Detect and Measure Electricity</td> <td class="pr"><a href="#CHAPTER_V">Page 49</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">VI.</td> <td class="chap">Volts, Amperes, Ohms and Watts</td> <td class="pr"><a href="#CHAPTER_VI">Page 60</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">VII.</td> <td class="chap">Push Buttons, Switches, Annunciators, Bells and Like Apparatus</td> <td class="pr"><a href="#CHAPTER_VII">Page 65</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>Simple Switches. A Two-Pole Switch. Double-Pole +Switch. Sliding Switch. Reversing Switch. Push Buttons. +<span class='pagenum'><a name="piii" id="piii">p. iii</a></span>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.</p></td> +</tr> +<tr> + <td align="right">VIII.</td> <td class="chap">Accumulators, Storage or Secondary Batteries</td> <td class="pr"><a href="#CHAPTER_VIII">Page 82</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">IX.</td> <td class="chap">The Telegraph</td> <td class="pr"><a href="#CHAPTER_IX">Page 90</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">X.</td> <td class="chap">High-tension Apparatus, Condensers, Etc.</td> <td class="pr"><a href="#CHAPTER_X">Page 98</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>Induction. Low and High Tension. Elastic Property of +Electricity. The Condenser. Connecting up a Condenser. +The Interrupter. Uses of High-tension Coils.</p></td> +</tr> +<tr> + <td align="right">XI.</td> <td class="chap">Wireless Telegraphy</td> <td class="pr"><a href="#CHAPTER_XI">Page 104</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">XII.</td> <td class="chap">The Telephone</td> <td class="pr"><a href="#CHAPTER_XII">Page 110</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>Vibrations. The Acoustic Telephone. Sound Waves. +<span class='pagenum'><a name="piv" id="piv">p. iv</a></span>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.</p></td> +</tr> +<tr> + <td align="right">XIII.</td> <td class="chap">Electrolysis, Water Purification, Electroplating</td> <td class="pr"><a href="#CHAPTER_XIII">Page 123</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">XIV.</td> <td class="chap">Electric Heating. Thermo-Electricity</td> <td class="pr"><a href="#CHAPTER_XIV">Page 135</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">XV.</td> <td class="chap">Alternating Currents, Choking Coil, Transformer</td> <td class="pr"><a href="#CHAPTER_XV">Page 145</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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: +<span class='pagenum'><a name="pv" id="pv">p. v</a></span>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.</p></td> +</tr> +<tr> + <td align="right">XVI.</td> <td class="chap">Electric Lighting</td> <td class="pr"><a href="#CHAPTER_XVI">Page 161</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">XVII.</td> <td class="chap">Power, and Various Other Electrical Manifestations</td> <td class="pr"><a href="#CHAPTER_XVII">Page 175</a></td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td align="right">XVIII.</td> <td class="chap">X-Ray, Radium and the Like</td> <td class="pr"><a href="#CHAPTER_XVIII">Page 184</a> +<span class='pagenum'><a name="pvi" id="pvi">p. vi</a></span> +</td> +</tr> +<tr> + <td class="abstract" colspan="3"><p>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.</p></td> +</tr> +<tr> + <td class="chap" colspan="2">Glossary of Words Used in the Text</td> <td class="pr"><a href="#GLOSSARY_OF_WORDS">Page 189</a> +</td> +</tr> +<tr> + <td class="chap" colspan="2">Index</td> <td class="pr"><a href="#INDEX">Page 207</a> +</td> +</tr> + </tbody> +</table> + +<p class="chapter"><span class='pagenum'><a name="pvii" id="pvii">p. vii</a></span></p> + + +<hr class="chapter" /> +<h3><a name="toi" id="toi"></a>LIST OF ILLUSTRATIONS</h3> + +<table border="0" width="76%" cellpadding="1" cellspacing="1" summary="Illustrations"> + <col style="width:10%;" /><col style="width:75%;" /><col style="width:15%;" /> +<tbody valign="top"> +<tr><td align="right">1.</td> +<td align="left"> Work bench</td> + <td class="pr"><a href="#fig1">Frontispiece</a></td> +</tr> + <tr> + <td align="right"> </td> + <td class="imgr"> </td> + <td class="pr" style="font-size: small;">PAGE</td> + </tr> +<tr><td align="right">2.</td> +<td align="left">Top of magnet-winding reel</td> + <td class="pr"><a href="#fig2">14</a></td> +</tr> +<tr><td align="right">3.</td> +<td align="left">Side of magnet-winding reel</td> + <td class="pr"><a href="#fig3">14</a></td> +</tr> +<tr><td align="right">4.</td> +<td align="left">Journal block</td> + <td class="pr"><a href="#fig4">15</a></td> +</tr> +<tr><td align="right">5.</td> +<td align="left">Plain magnet bar</td> + <td class="pr"><a href="#fig5">19</a></td> +</tr> +<tr><td align="right">6.</td> +<td align="left">Severed magnet</td> + <td class="pr"><a href="#fig6">20</a></td> +</tr> +<tr><td align="right">7.</td> +<td align="left">Reversed magnets</td> + <td class="pr"><a href="#fig7">21</a></td> +</tr> +<tr><td align="right">8.</td> +<td align="left">Horseshoe magnet</td> + <td class="pr"><a href="#fig8">22</a></td> +</tr> +<tr><td align="right">9.</td> +<td align="left">Earth's magnetic lines</td> + <td class="pr"><a href="#fig9">23</a></td> +</tr> +<tr><td align="right">10.</td> +<td align="left">Two permanent magnets</td> + <td class="pr"><a href="#fig10">24</a></td> +</tr> +<tr><td align="right">11.</td> +<td align="left">Magnets in earth's magnetic field</td> + <td class="pr"><a href="#fig11">24</a></td> +</tr> +<tr><td align="right">12.</td> +<td align="left">Armatures for magnets</td> + <td class="pr"><a href="#fig12">25</a></td> +</tr> +<tr><td align="right">13.</td> +<td align="left">Magnetized field</td> + <td class="pr"><a href="#fig13">26</a></td> +</tr> +<tr><td align="right">14.</td> +<td align="left">Magnetized bar</td> + <td class="pr"><a href="#fig14">26</a></td> +</tr> +<tr><td align="right">15.</td> +<td align="left">Direction of current</td> + <td class="pr"><a href="#fig15">27</a></td> +</tr> +<tr><td align="right">16.</td> +<td align="left">Direction of induction current</td> + <td class="pr"><a href="#fig16">28</a></td> +</tr> +<tr><td align="right">17.</td> +<td align="left">Frictional-electricity machine</td> + <td class="pr"><a href="#fig17">30</a></td> +</tr> +<tr><td align="right">18.</td> +<td align="left">Leyden jar</td> + <td class="pr"><a href="#fig18">32</a></td> +</tr> +<tr><td align="right">19.</td> +<td align="left">Galvanic electricity. Crown of cups</td> + <td class="pr"><a href="#fig19">33</a></td> +</tr> +<tr><td align="right">20.</td> +<td align="left">Voltaic electricity</td> + <td class="pr"><a href="#fig20">34</a></td> +</tr> +<tr><td align="right">21.</td> +<td align="left">Primary battery</td> + <td class="pr"><a href="#fig21">36</a></td> +</tr> +<tr><td align="right">22.</td> +<td align="left">Dynamo field and pole piece</td> + <td class="pr"><a href="#fig22">39</a></td> +</tr> +<tr><td align="right">23.</td> +<td align="left">Base and fields assembled</td> + <td class="pr"><a href="#fig23">41</a></td> +</tr> +<tr><td align="right">24.</td> +<td align="left">Details of the armature, core</td> + <td class="pr"><a href="#fig24">42</a></td> +</tr> +<tr><td align="right">25.</td> +<td align="left">Details of the armature, body</td> + <td class="pr"><a href="#fig25">42</a></td> +</tr> +<tr><td align="right">26.</td> +<td align="left">Armature Journals</td> + <td class="pr"><a href="#fig26">43</a> +<span class='pagenum'><a name="pviii" id="pviii">p. viii</a></span> +</td> +</tr> +<tr><td align="right">27.</td> +<td align="left">Commutator</td> + <td class="pr"><a href="#fig27">43</a></td> +</tr> +<tr><td align="right">28.</td> +<td align="left">End view of armature, mounted</td> + <td class="pr"><a href="#fig28">44</a></td> +</tr> +<tr><td align="right">29.</td> +<td align="left">Top view of armature on base</td> + <td class="pr"><a href="#fig29">45</a></td> +</tr> +<tr><td align="right">30.</td> +<td align="left">Field winding</td> + <td class="pr"><a href="#fig30-31">47</a></td> +</tr> +<tr><td align="right">31.</td> +<td align="left">Series-wound</td> + <td class="pr"><a href="#fig30-31">47</a></td> +</tr> +<tr><td align="right">32.</td> +<td align="left">Shunt-wound</td> + <td class="pr"><a href="#fig32-33">48</a></td> +</tr> +<tr><td align="right">33.</td> +<td align="left">Compound-wound</td> + <td class="pr"><a href="#fig32-33">48</a></td> +</tr> +<tr><td align="right">34.</td> +<td align="left">Compass magnet, swing to the right</td> + <td class="pr"><a href="#fig34-36">50</a></td> +</tr> +<tr><td align="right">35.</td> +<td align="left">Magnetic compass</td> + <td class="pr"><a href="#fig34-36">50</a></td> +</tr> +<tr><td align="right">36.</td> +<td align="left">Magnet, swing to the left</td> + <td class="pr"><a href="#fig34-36">50</a></td> +</tr> +<tr><td align="right">37.</td> +<td align="left">Indicating direction of current</td> + <td class="pr"><a href="#fig37">51</a></td> +</tr> +<tr><td align="right">38.</td> +<td align="left">The bridge of the detector</td> + <td class="pr"><a href="#fig38">52</a></td> +</tr> +<tr><td align="right">39.</td> +<td align="left">Details of detector</td> + <td class="pr"><a href="#fig39">53</a></td> +</tr> +<tr><td align="right">40.</td> +<td align="left">Cross-section of detector</td> + <td class="pr"><a href="#fig40">54</a></td> +</tr> +<tr><td align="right">41.</td> +<td align="left">Acid voltameter</td> + <td class="pr"><a href="#fig41">56</a></td> +</tr> +<tr><td align="right">42.</td> +<td align="left">Copper voltameter</td> + <td class="pr"><a href="#fig42">56</a></td> +</tr> +<tr><td align="right">43.</td> +<td align="left">Two-pole switch</td> + <td class="pr"><a href="#fig43">66</a></td> +</tr> +<tr><td align="right">44.</td> +<td align="left">Double-pole switch</td> + <td class="pr"><a href="#fig44">66</a></td> +</tr> +<tr><td align="right">45.</td> +<td align="left">Sliding switch</td> + <td class="pr"><a href="#fig45">67</a></td> +</tr> +<tr><td align="right">46.</td> +<td align="left">Rheostat form of switch</td> + <td class="pr"><a href="#fig46">68</a></td> +</tr> +<tr><td align="right">47.</td> +<td align="left">Reversing switch</td> + <td class="pr"><a href="#fig47">69</a></td> +</tr> +<tr><td align="right">48.</td> +<td align="left">Push button</td> + <td class="pr"><a href="#fig48">70</a></td> +</tr> +<tr><td align="right">49.</td> +<td align="left">Electric bell</td> + <td class="pr"><a href="#fig49">71</a></td> +</tr> +<tr><td align="right">50.</td> +<td align="left">Armature of electric bell</td> + <td class="pr"><a href="#fig50">72</a></td> +</tr> +<tr><td align="right">51.</td> +<td align="left">Vertical section of annunciator</td> + <td class="pr"><a href="#fig51-54">72</a></td> +</tr> +<tr><td align="right">52.</td> +<td align="left">Front view of annunciator</td> + <td class="pr"><a href="#fig51-54">72</a></td> +</tr> +<tr><td align="right">53.</td> +<td align="left">Horizontal section of annunciator</td> + <td class="pr"><a href="#fig51-54">72</a></td> +</tr> +<tr><td align="right">54.</td> +<td align="left">Front plate of annunciator</td> + <td class="pr"><a href="#fig51-54">72</a></td> +</tr> +<tr><td align="right">55.</td> +<td align="left">Alarm switch on window</td> + <td class="pr"><a href="#fig55">76</a></td> +</tr> +<tr><td align="right">56.</td> +<td align="left">Burglar alarm on window</td> + <td class="pr"><a href="#fig56">76</a></td> +</tr> +<tr><td align="right">57.</td> +<td align="left">Burglar alarm contact</td> + <td class="pr"><a href="#fig57">77</a></td> +</tr> +<tr><td align="right">58.</td> +<td align="left">Neutral position of contact</td> + <td class="pr"><a href="#fig58">78</a></td> +</tr> +<tr><td align="right">59.</td> +<td align="left">Circuiting for electric bell</td> + <td class="pr"><a href="#fig59">79</a> +<span class='pagenum'><a name="pix" id="pix">p. ix</a></span></td> +</tr> +<tr><td align="right">60.</td> +<td align="left">Annunciators in circuit</td> + <td class="pr"><a href="#fig60">80</a></td> +</tr> +<tr><td align="right">61.</td> +<td align="left">Wiring system for a house</td> + <td class="pr"><a href="#fig61">80</a></td> +</tr> +<tr><td align="right">62.</td> +<td align="left">Accumulator grids</td> + <td class="pr"><a href="#fig62">83</a></td> +</tr> +<tr><td align="right">63.</td> +<td align="left">Assemblage of accumulator grids</td> + <td class="pr"><a href="#fig63">85</a></td> +</tr> +<tr><td align="right">64.</td> +<td align="left">Connecting up storage battery in series</td> + <td class="pr"><a href="#fig64">87</a></td> +</tr> +<tr><td align="right">65.</td> +<td align="left">Parallel series</td> + <td class="pr"><a href="#fig65">88</a></td> +</tr> +<tr><td align="right">66.</td> +<td align="left">Charging circuit</td> + <td class="pr"><a href="#fig66">88</a></td> +</tr> +<tr><td align="right">67.</td> +<td align="left">Telegraph sending key</td> + <td class="pr"><a href="#fig67">91</a></td> +</tr> +<tr><td align="right">68.</td> +<td align="left">Telegraph sounder</td> + <td class="pr"><a href="#fig68">92</a></td> +</tr> +<tr><td align="right">69.</td> +<td align="left">A telegraph circuit</td> + <td class="pr"><a href="#fig69">94</a></td> +</tr> +<tr><td align="right">70.</td> +<td align="left">Induction coil and circuit</td> + <td class="pr"><a href="#fig70">99</a></td> +</tr> +<tr><td align="right">71.</td> +<td align="left">Illustrating elasticity</td> + <td class="pr"><a href="#fig71">100</a></td> +</tr> +<tr><td align="right">72.</td> +<td align="left">Condenser</td> + <td class="pr"><a href="#fig72">101</a></td> +</tr> +<tr><td align="right">73.</td> +<td align="left">High-tension circuit</td> + <td class="pr"><a href="#fig73">102</a></td> +</tr> +<tr><td align="right">74.</td> +<td align="left">Current interrupter</td> + <td class="pr"><a href="#fig74">103</a></td> +</tr> +<tr><td align="right">75.</td> +<td align="left">Wireless-telegraphy coherer</td> + <td class="pr"><a href="#fig75">105</a></td> +</tr> +<tr><td align="right">76.</td> +<td align="left">Wireless sending-apparatus</td> + <td class="pr"><a href="#fig76">107</a></td> +</tr> +<tr><td align="right">77.</td> +<td align="left">Wireless receiving-apparatus</td> + <td class="pr"><a href="#fig77">108</a></td> +</tr> +<tr><td align="right">78.</td> +<td align="left">Acoustic telephone</td> + <td class="pr"><a href="#fig78">111</a></td> +</tr> +<tr><td align="right">79.</td> +<td align="left">Illustrating vibrations</td> + <td class="pr"><a href="#fig79">111</a></td> +</tr> +<tr><td align="right">80.</td> +<td align="left">The magnetic field</td> + <td class="pr"><a href="#fig80">112</a></td> +</tr> +<tr><td align="right">81.</td> +<td align="left">Section of telephone receiver</td> + <td class="pr"><a href="#fig81">114</a></td> +</tr> +<tr><td align="right">82.</td> +<td align="left">The magnet and receiver head</td> + <td class="pr"><a href="#fig82">115</a></td> +</tr> +<tr><td align="right">83.</td> +<td align="left">Simple telephone connection</td> + <td class="pr"><a href="#fig83">116</a></td> +</tr> +<tr><td align="right">84.</td> +<td align="left">Telephone stations in circuit</td> + <td class="pr"><a href="#fig84">117</a></td> +</tr> +<tr><td align="right">85.</td> +<td align="left">Illustrating light contact points</td> + <td class="pr"><a href="#fig85">118</a></td> +</tr> +<tr><td align="right">86.</td> +<td align="left">The microphone</td> + <td class="pr"><a href="#fig86">119</a></td> +</tr> +<tr><td align="right">87.</td> +<td align="left">The transmitter</td> + <td class="pr"><a href="#fig87">119</a></td> +</tr> +<tr><td align="right">88.</td> +<td align="left">Complete telephone circuit</td> + <td class="pr"><a href="#fig88">121</a></td> +</tr> +<tr><td align="right">89.</td> +<td align="left">Device for making hydrogen and oxygen</td> + <td class="pr"><a href="#fig89">124</a></td> +</tr> +<tr><td align="right">90.</td> +<td align="left">Electric-water purifier</td> + <td class="pr"><a href="#fig90">127</a></td> +</tr> +<tr><td align="right">91.</td> +<td align="left">Portable electric purifier</td> + <td class="pr"><a href="#fig91">129</a><span class='pagenum'><a name="px" id="px">p. x</a></span> +</td> +</tr> +<tr><td align="right">92.</td> +<td align="left">Section of positive plate</td> + <td class="pr"><a href="#fig92-95">130</a></td> +</tr> +<tr><td align="right">93.</td> +<td align="left">Section of negative plate</td> + <td class="pr"><a href="#fig92-95">130</a></td> +</tr> +<tr><td align="right">94.</td> +<td align="left">Positive and negative in position</td> + <td class="pr"><a href="#fig92-95">130</a></td> +</tr> +<tr><td align="right">95.</td> +<td align="left">Form of the insulator</td> + <td class="pr"><a href="#fig92-95">130</a></td> +</tr> +<tr><td align="right">96.</td> +<td align="left">Simple electric heater</td> + <td class="pr"><a href="#fig96">137</a></td> +</tr> +<tr><td align="right">97.</td> +<td align="left">Side view of resistance device</td> + <td class="pr"><a href="#fig97">139</a></td> +</tr> +<tr><td align="right">98.</td> +<td align="left">Top view of resistance device</td> + <td class="pr"><a href="#fig98">139</a></td> +</tr> +<tr><td align="right">99.</td> +<td align="left">Plan view of electric iron</td> + <td class="pr"><a href="#fig99">140</a></td> +</tr> +<tr><td align="right">100.</td> +<td align="left">Section of electric iron</td> + <td class="pr"><a href="#fig100">141</a></td> +</tr> +<tr><td align="right">101.</td> +<td align="left">Thermo-electric couple</td> + <td class="pr"><a href="#fig101">143</a></td> +</tr> +<tr><td align="right">102.</td> +<td align="left">Cutting a magnetic field</td> + <td class="pr"><a href="#fig102">146</a></td> +</tr> +<tr><td align="right">103.</td> +<td align="left">Alternations, first position</td> + <td class="pr"><a href="#fig103-106">148</a></td> +</tr> +<tr><td align="right">104.</td> +<td align="left">Alternations, second position</td> + <td class="pr"><a href="#fig103-106">148</a></td> +</tr> +<tr><td align="right">105.</td> +<td align="left">Alternations, third position</td> + <td class="pr"><a href="#fig103-106">148</a></td> +</tr> +<tr><td align="right">106.</td> +<td align="left">Alternations, fourth position</td> + <td class="pr"><a href="#fig103-106">148</a></td> +</tr> +<tr><td align="right">107.</td> +<td align="left">Increasing alternations, first view</td> + <td class="pr"><a href="#fig107">149</a></td> +</tr> +<tr><td align="right">108.</td> +<td align="left">Increasing alternations, second view</td> + <td class="pr"><a href="#fig108">149</a></td> +</tr> +<tr><td align="right">109.</td> +<td align="left">Connection of alternating dynamo armature</td> + <td class="pr"><a href="#fig109">150</a></td> +</tr> +<tr><td align="right">110.</td> +<td align="left">Direct current dynamo</td> + <td class="pr"><a href="#fig110">151</a></td> +</tr> +<tr><td align="right">111.</td> +<td align="left">Circuit wires in direct current dynamo</td> + <td class="pr"><a href="#fig111">152</a></td> +</tr> +<tr><td align="right">112.</td> +<td align="left">Alternating polarity lines</td> + <td class="pr"><a href="#fig112">154</a></td> +</tr> +<tr><td align="right">113.</td> +<td align="left">Alternating current dynamo</td> + <td class="pr"><a href="#fig113">155</a></td> +</tr> +<tr><td align="right">114.</td> +<td align="left">Choking coil</td> + <td class="pr"><a href="#fig114">157</a></td> +</tr> +<tr><td align="right">115.</td> +<td align="left">A transformer</td> + <td class="pr"><a href="#fig115">158</a></td> +</tr> +<tr><td align="right">116.</td> +<td align="left">Parallel carbons</td> + <td class="pr"><a href="#fig116">164</a></td> +</tr> +<tr><td align="right">117.</td> +<td align="left">Arc-lighting circuit</td> + <td class="pr"><a href="#fig117">165</a></td> +</tr> +<tr><td align="right">118.</td> +<td align="left">Interrupted conductor</td> + <td class="pr"><a href="#fig118">166</a></td> +</tr> +<tr><td align="right">119.</td> +<td align="left">Incandescent circuit</td> + <td class="pr"><a href="#fig119">167</a></td> +</tr> +<tr><td align="right">120.</td> +<td align="left">Magnetic action in dynamo, 1st</td> + <td class="pr"><a href="#fig120">177</a></td> +</tr> +<tr><td align="right">121.</td> +<td align="left">Magnetic action in dynamo, 2d</td> + <td class="pr"><a href="#fig121">177</a></td> +</tr> +<tr><td align="right">122.</td> +<td align="left">Magnetic action in dynamo, 3d</td> + <td class="pr"><a href="#fig122">178</a></td> +</tr> +<tr><td align="right">123.</td> +<td align="left">Magnetic action in dynamo, 4th</td> + <td class="pr"><a href="#fig123">178</a><span class='pagenum'><a name="pxi" id="pxi">p. xi</a></span></td> +</tr> +<tr><td align="right">124.</td> +<td align="left">Magnetic action in motor, 1st</td> + <td class="pr"><a href="#fig124">179</a></td> +</tr> +<tr><td align="right">125.</td> +<td align="left">Magnetic action in motor, 2d</td> + <td class="pr"><a href="#fig125">179</a></td> +</tr> +<tr><td align="right">126.</td> +<td align="left">Magnetic action in motor, 3d</td> + <td class="pr"><a href="#fig126">180</a></td> +</tr> +<tr><td align="right">127.</td> +<td align="left">Magnetic action in motor, 4th</td> + <td class="pr"><a href="#fig127">180</a></td> +</tr> +</tbody> +</table> + +<p class="chapter"><span class='pagenum'><a name="p1" id="p1">p. 1</a></span></p> + +<hr class="chapter" /> +<h2><a name="INTRODUCTORY" id="INTRODUCTORY"></a>INTRODUCTORY</h2> + + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>It would be a dry, dull and uninteresting thing +to tell a boy that electricity can be generated by<span class='pagenum'><a name="p2" id="p2">p. 2</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>In the preparation of this book, therefore, I<span class='pagenum'><a name="p3" id="p3">p. 3</a></span> +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.</p> + +<p>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.</p> + +<p class="pn"><span class='pagenum'><a name="p4" id="p4"></a></span></p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p5" id="p5">p. 5</a></span></p> + +<h2><a name="CHAPTER_I" id="CHAPTER_I"></a>CHAPTER I</h2> + +<h3>THE STUDY OF ELECTRICITY. HISTORICAL</h3> + + +<p>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.</p> + +<p><span class="smcap">First Historical Account.</span>—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.</p> + +<p>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.</p> + +<p>Sir Isaac Newton also took up the subject at<span class='pagenum'><a name="p6" id="p6">p. 6</a></span> +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.</p> + +<p>The first attempt to "bottle" electricity was +attempted by Muschenbrœck, 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.</p> + +<p>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.</p> + +<p>Benjamin Franklin, in 1750, showed that lightning +was electricity, and later on made his interesting +experiments with the kite and the key.</p> + +<p><span class="smcap">Discovering Galvanic Electricity.</span>—The great +discovery of Galvani, in 1790, led to the recognition<span class='pagenum'><a name="p7" id="p7">p. 7</a></span> +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 Œrsted 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.</p> + +<p><span class="smcap">Electro-magnetic Force.</span>—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.</p> + +<p><span class="smcap">Measuring Instruments.</span>—The perfection of +measuring instruments did more to advance electricity<span class='pagenum'><a name="p8" id="p8">p. 8</a></span> +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.</p> + +<p><span class="smcap">Rapidity of Modern Progress.</span>—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.</p> + +<p><span class="smcap">How to Acquire the Vast Knowledge.</span>—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<span class='pagenum'><a name="p9" id="p9">p. 9</a></span> +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?</p> + +<p>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.</p> + +<p><span class="smcap">The Means Employed.</span>—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.</p> + +<p>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</p> +<p class="pn"><span class='pagenum'><a name="p10" id="p10">p. 10</a></span></p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p11" id="p11">p. 11</a></span></p> + +<h2><a name="CHAPTER_II" id="CHAPTER_II"></a>CHAPTER II<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>WHAT TOOLS AND APPARATUS ARE NEEDED</h3> + + +<p><span class="smcap">Preparing the Workshop.</span>—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."</p> + +<p>By this time our neighbors will become interested +in and solicit work from us.</p> + +<p><span class="smcap">Uses of Our Workshops.</span>—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,<span class='pagenum'><a name="p12" id="p12">p. 12</a></span> +so we conclude to put in a telephone +system.</p> + +<p><span class="smcap">What to Build.</span>—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.</p> + +<p>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.</p> + +<p><span class="smcap">What to Learn.</span>—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.</p> + +<p><span class="smcap">Uses of the Electrical Devices.</span>—While all<span class='pagenum'><a name="p13" id="p13">p. 13</a></span> +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.</p> + +<p><span class="smcap">Tools.</span>—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. <a href="#fig1">1</a>, 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.</p> + +<p>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 ⅜-inch and ¾-inch widths;<span class='pagenum'><a name="p14" id="p14">p. 14</a></span> +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.</p> + +<div class="figcenter" style="width: 370px;"> +<a id="fig2" name="fig2"></a><a href="#p14"> +<img src="images/illus-fig2.png" width="370" height="128" alt="Fig. 2. Top View" title="Fig. 2. Top View" /></a> +<span class="caption"><i>Fig. 2.</i></span> +</div> + +<div class="figcenter" style="width: 369px;"> +<a id="fig3" name="fig3"></a><a href="#p14"> +<img src="images/illus-fig3.png" width="369" height="134" alt="Fig. 3. Side View" title="Fig. 3. Side View" /></a> +<span class="caption"><i>Fig. 3.</i><br /><span class="smcap">Magnet-winding Reel</span></span> +</div> + +<p>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</p> +<p class="pn"><span class='pagenum'><a name="p15" id="p15">p. 15</a></span></p> + +<p>From the foregoing it will be seen that the cost +of tools is not a very expensive item.</p> + +<p>This entire outfit, not including the anvil and +vise, may be purchased new for about $20.00, so +we have not been extravagant.</p> + +<p><span class="smcap">Magnet-winding Reel.</span>—Some little preparation +must be made, so we may be enabled to handle +our work by the construction of mechanical aids.</p> + +<div class="figcenter" style="width: 353px;"> +<a id="fig4" name="fig4"></a><a href="#p15"> +<img src="images/illus-fig4.png" width="353" height="100" alt="Fig. 4. Journal Block." title="Fig. 4. Journal Block." /></a> +<span class="italcaption">Fig. 4. <span class="u">Journal</span> <span class="u">Block</span>.</span> +</div> + +<p>First of these is the magnet-winding reel, a +plan view of which is shown in Fig. <a href="#fig2">2</a>. This, for +our present work, will be made wholly of wood.</p> + +<p>Select a plank 1½ 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. <a href="#fig4">4</a>. To serve as the mandrel (C, +Fig. <a href="#fig2">2</a>), 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</p> +<p class="pn"><span class='pagenum'><a name="p16" id="p16">p. 16</a></span></p> + +<p>Place a crank (E), 5 inches long, on the outer +end of the mandrel, as in Fig. <a href="#fig3">3</a>. 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.</p> + +<p>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 ⅜-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).</p> + +<p>The tailpiece is made of a 2" × 4" scantling +(H), 10 inches long, one end of it being nailed +to a transverse block (I) 2" × 2" × 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 ½-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),<span class='pagenum'><a name="p17" id="p17">p. 17</a></span> +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.</p> + +<p>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.</p> + +<p><span class="smcap">Order in the Workshop.</span>—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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p18" id="p18">p. 18</a></span></p> + +<h2><a name="CHAPTER_III" id="CHAPTER_III"></a>CHAPTER III<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>MAGNETS, COILS, ARMATURES, ETC.</h3> + + +<p><span class="smcap">The Two Kinds of Magnet.</span>—Generally speaking, +magnets are of two kinds, namely, permanent +and electro-magnetic.</p> + +<p><span class="smcap">Permanent Magnets</span>.—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.</p> + +<p><span class="smcap">Electro-Magnet</span>.—The electro-magnet, therefore, +is the more useful, because the pull of the +magnet can be controlled by the current which +actuates it.</p> + +<p>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.</p> + +<p>While the electro-magnet is, therefore, the form<span class='pagenum'><a name="p19" id="p19">p. 19</a></span> +of device which is almost wholly used, it is necessary, +first, to understand the principles of the +permanent magnet.</p> + +<p><span class="smcap">Magnetism.</span>—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.</p> + +<div class="figcenter" style="width: 347px;"> +<a id="fig5" name="fig5"></a><a href="#p19"> +<img src="images/illus-fig5.png" width="347" height="93" alt="Fig 5. Plain Magnet Bar" title="Fig 5. Plain Magnet Bar" /></a> +<span class="caption"><i>Fig 5.</i> <span class="smcap">Plain Magnet Bar</span></span> +</div> + +<p><span class="smcap">Materials for Magnets.</span>—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.</p> + +<p><span class="smcap">Non-magnetic Materials.</span>—Any non-magnetic +body in the path of a magnetic force does not +screen or diminish its action, whereas a magnetic +substance will</p> +<p class="pn"><span class='pagenum'><a name="p20" id="p20">p. 20</a></span></p> + +<p>In Fig. <a href="#fig5">5</a> 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.</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig6" name="fig6"></a><a href="#p20"> +<img src="images/illus-fig6.png" width="349" height="63" alt="Fig. 6. Severed Magnet" title="Fig. 6. Severed Magnet" /></a> +<span class="caption"><i>Fig 6.</i> <span class="smcap">Severed Magnet</span></span> +</div> + +<p><span class="smcap">Action of a Severed Magnet.</span>—Now, let us suppose +that we sever this bar in the middle, as in Fig. <a href="#fig6">6</a>, +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.</p> + +<p><span class="smcap">What North and South Poles Mean.</span>—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. <a href="#fig7">7</a>, they will +repel each other. From this comes the statement +that likes repel and unlikes attract each other</p> +<p class="pn"><span class='pagenum'><a name="p21" id="p21">p. 21</a></span></p> + +<p><span class="smcap">Repulsion and Attraction.</span>—This physical act +of repulsion and attraction is made use of in +motors, as we shall see hereinafter.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 337px;"> +<a id="fig7" name="fig7"></a><a href="#p21"> +<img src="images/illus-fig7.png" width="337" height="85" alt="Fig. 7. Reversed Magnets" title="Fig. 7. Reversed Magnets" /></a> +<span class="caption"><i>Fig. 7.</i> <span class="smcap">Reversed Magnets</span></span> +</div> + +<p><span class="smcap">Positives and Negatives.</span>—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.</p> + +<p><span class="smcap">Magnetic Lines of Force.</span>—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.</p> + +<p>This is accomplished by means of the well-known<span class='pagenum'><a name="p22" id="p22">p. 22</a></span> +horseshoe magnet, where the two ends +(N, S) are brought close together, as in Fig. <a href="#fig8">8</a>.</p> + +<p><span class="smcap">The Earth as a Magnet.</span>—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.</p> + +<div class="figcenter" style="width: 340px;"> +<a id="fig8" name="fig8"></a><a href="#p22"> +<img src="images/illus-fig8.png" width="340" height="139" alt="Fig. 8. Horseshoe Magnet" title="Fig. 8. Horseshoe Magnet" /></a> +<span class="caption"><i>Fig. 8.</i> <span class="smcap">Horseshoe Magnet</span></span> +</div> + +<p>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. <a href="#fig9">9</a> shows the magnetic +lines running from the north to the south pole.</p> + +<p><span class="smcap">Why the Compass Points North and South.</span>—Now, +let us try to ascertain why the compass +points north and south.</p> + +<p>Let us assume that we have a large magnet (A, +Fig. <a href="#fig10">10</a>), 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<span class='pagenum'><a name="p23" id="p23">p. 23</a></span> +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).</p> + +<div class="figcenter" style="width: 354px;"> +<a id="fig9" name="fig9"></a><a href="#p23"> +<img src="images/illus-fig9.png" width="354" height="235" alt="Fig. 9. Earth's Magnetic Lines" title="Fig. 9. Earth's Magnetic Lines" /></a> +<span class="caption"><i>Fig. 9.</i> <span class="smcap">Earth's Magnetic Lines</span></span> +</div> + +<p>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).</p> + +<p>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<span class='pagenum'><a name="p24" id="p24">p. 24</a></span> +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).</p> + +<div class="figcenter" style="width: 363px;"> +<a id="fig10" name="fig10"></a><a href="#p24"> +<img src="images/illus-fig10.png" width="363" height="127" alt="Fig. 10. Two Permanent Magnets" title="Fig. 10. Two Permanent Magnets" /></a> +<span class="caption"><i>Fig. 10.</i> <span class="smcap">Two Permanent Magnets</span></span> +</div> + +<div class="figcenter" style="width: 363px;"> +<a id="fig11" name="fig11"></a><a href="#p24"> +<img src="images/illus-fig11.png" width="363" height="215" alt="Fig. 11. Magnets in the Earth's Magnetic Field" + title="Fig. 11. Magnets in the Earth's Magnetic Field" /></a> +<span class="caption"><i>Fig. 11.</i> <span class="smcap">Magnets in the Earth's Magnetic Field</span></span> +</div> + +<p>Let us now take the outline represented by the +earth's surface (Fig. <a href="#fig11">11</a>), 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</p> +<p class="pn"><span class='pagenum'><a name="p25" id="p25">p. 25</a></span></p> + +<p><span class="smcap">Peculiarity of a Magnet.</span>—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.</p> + +<p>In Fig. <a href="#fig12">12</a> 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.</p> + +<div class="figcenter" style="width: 361px;"> +<a id="fig12" name="fig12"></a><a href="#p25"> +<img src="images/illus-fig12.png" width="361" height="111" alt="Fig. 12. Armatures for Magnets" title="Fig. 12. Armatures for Magnets" /></a> +<span class="caption"><i>Fig. 12.</i> <span class="smcap">Armatures for Magnets</span></span> +</div> + +<p><span class="smcap">Action of the Electro-Magnet.</span>—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<span class='pagenum'><a name="p26" id="p26">p. 26</a></span> +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 <i>core</i>, as it is called.</p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig13" name="fig13"></a><a href="#p26"> +<img src="images/illus-fig13.png" width="350" height="80" alt="Fig. 13. Magnetized Field" title="Fig. 13. Magnetized Field" /></a> +<span class="caption"><i>Fig. 13.</i> <span class="smcap">Magnetized Field</span></span> +</div> + +<div class="figcenter" style="width: 350px;"> +<a id="fig14" name="fig14"></a><a href="#p26"> +<img src="images/illus-fig14.png" width="350" height="104" alt="Fig. 14. Magnetized Bar" title="Fig. 14. Magnetized Bar" /></a> +<span class="caption"><i>Fig. 14.</i> <span class="smcap">Magnetized Bar</span></span> +</div> + +<p>In Fig. <a href="#fig13">13</a> 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. +<a href="#fig14">14</a>), you will observe that this electric field, as<span class='pagenum'><a name="p27" id="p27">p. 27</a></span> +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).</p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig15" name="fig15"></a><a href="#p27"> +<img src="images/illus-fig15.png" width="350" height="73" alt="Fig. 15. Direction of Current" title="Fig. 15. Direction of Current" /></a> +<span class="caption"><i>Fig. 15.</i> <span class="smcap">Direction of Current</span></span> +</div> + +<p>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.</p> + +<p><span class="smcap">Exterior Magnetic Influence Around a Wire +Carrying a Current.</span>—Bear in mind that the wire +coil (A, Fig. <a href="#fig14">14</a>) 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 <i>induction</i>. On the other +hand, the current flowing through the wire (A)<span class='pagenum'><a name="p28" id="p28">p. 28</a></span> +from end to end is called a <i>conduction</i> current. +Remember these terms.</p> + +<p>In this connection there is also another thing +which you will do well to bear in mind. In Fig. +<a href="#fig15">15</a> 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).</p> + +<div class="figcenter" style="width: 352px;"> +<a id="fig16" name="fig16"></a><a href="#p28"> +<img src="images/illus-fig16.png" width="352" height="124" alt="Fig. 16. Direction of Induction Current" title="Fig. 16. Direction of Induction Current" /></a> +<span class="caption"><i>Fig. 16.</i> <span class="smcap">Direction of Induction Current</span></span> +</div> + +<p><span class="smcap">Parallel Wires.</span>—In like manner, if two wires +(A, B, Fig. <a href="#fig16">16</a>) 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.</p> + +<p>These fundamental principles should be thoroughly +understood and mastered.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p29" id="p29">p. 29</a></span></p> + +<h2><a name="CHAPTER_IV" id="CHAPTER_IV"></a>CHAPTER IV<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>FRICTIONAL, VOLTAIC OR GALVANIC, AND ELECTRO-MAGNETIC ELECTRICITY</h3> + + +<p><span class="smcap">Three Electrical Sources.</span>—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.</p> + +<p>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.</p> + +<p><span class="smcap">Frictional Electricity.</span>—With a view of explaining +the principles involved, we show in Fig. +<a href="#fig17">17</a> a machine for producing electricity by friction.</p> + + +<div class="figcenter" style="width: 355px;"> +<a id="fig17" name="fig17"></a><a href="#p29"> +<img src="images/illus-fig17.png" width="355" height="374" alt="Fig. 17. Friction-Electricity Machine" title="Fig. 17. Friction-Electricity Machine" /></a> +<span class="caption"><i>Fig. 17.</i> <span class="smcap">Friction-Electricity Machine</span></span> +</div> + +<p>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<span class='pagenum'><a name="p30" id="p30">p. 30</a></span> +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<span class='pagenum'><a name="p31" id="p31">p. 31</a></span> +(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).</p> + +<p>In order to collect the electricity thus generated +a vessel called a Leyden jar is used.</p> + +<p><span class="smcap">Leyden Jar.</span>—This is shown in Fig. <a href="#fig18">18</a>. 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).</p> + +<p>The jar is half filled with sulphuric acid (I),<span class='pagenum'><a name="p32" id="p32">p. 32</a></span> +after which, in order to charge the jar, the knob +(G) is brought into contact with the knob (M) of +the friction generator (Fig. <a href="#fig17">17</a>).</p> + +<p><span class="smcap">Voltaic or Galvanic Electricity.</span>—The second +method of generating electricity is by chemical +means, so called, because a liquid is used as one +of the agents.</p> + +<div class="figcenter" style="width: 308px;"> +<a id="fig18" name="fig18"></a><a href="#p32"> +<img src="images/illus-fig18.png" width="308" height="302" alt="Fig. 18. Leyden Jar" title="Fig. 18. Leyden Jar" /></a> +<span class="caption"><i>Fig. 18.</i> <span class="smcap">Leyden Jar</span></span> +</div> + +<p>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. <a href="#fig19">19</a>, and consisting<span class='pagenum'><a name="p33" id="p33">p. 33</a></span> +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.</p> + +<div class="figcenter" style="width: 361px;"> +<a id="fig19" name="fig19"></a><a href="#p33"> +<img src="images/illus-fig19.png" width="361" height="181" alt="Fig. 19. Galvanic Electricity. Crown of Cups" +title="Fig. 19. Galvanic Electricity. Crown of Cups" /></a> +<span class="caption"><i>Fig. 19.</i> <span class="smcap"> Galvanic Electricity. Crown of Cups</span></span> +</div> + +<p><span class="smcap">The Cell and Battery.</span>—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).</p> + +<p>A few years afterwards Volta devised what is +known as the voltaic pile (Fig. <a href="#fig20">20</a>).</p> + +<p><span class="smcap">Voltaic Pile—How Made.</span>—This is made of alternate +discs of copper and zinc with a piece of<span class='pagenum'><a name="p34" id="p34">p. 34</a></span> +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).</p> + +<div class="figcenter" style="width: 348px;"> +<a id="fig20" name="fig20"></a><a href="#p34"> +<img src="images/illus-fig20.png" width="348" height="300" alt="Fig. 20. Voltaic Electricity" title="Fig. 20. Voltaic Electricity" /></a> +<span class="caption"><i>Fig. 20.</i> <span class="smcap">Voltaic Electricity</span></span> +</div> + +<p><i>Plus and Minus Signs.</i>—It will be noted that +the positive or copper disc has the plus sign<span class='pagenum'><a name="p35" id="p35">p. 35</a></span> +(+) while the zinc disc has the minus (-) sign. +These signs denote the positive and the negative +sides of the current.</p> + +<p>The liquid in the cells, or in the moistened +paper, is called the <i>electrolyte</i> and the plates or +discs are called <i>electrodes</i>. To define them more +clearly, the positive plate is the <i>anode</i>, and the +negative plate the <i>cathode</i>.</p> + +<p>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.</p> + +<p><span class="smcap">The Common Primary Cell.</span>—The most common +form of primary cell contains sulphuric acid, +or a sulphuric acid solution, as the electrolyte, +with zinc for the <i>anode</i>, and carbon, instead of copper, +for the <i>cathode</i>.</p> + +<p>The ends of the zinc and copper plates are +called <i>terminals</i>, and while the zinc is the anode +or positive element, its <i>terminal</i> is designated as +the positive pole. In like manner, the carbon is<span class='pagenum'><a name="p36" id="p36">p. 36</a></span> +the negative element or cathode, and its terminal +is designated as negative pole.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 353px;"> +<a id="fig21" name="fig21"></a><a href="#p36"> +<img src="images/illus-fig21.png" width="353" height="233" alt="Fig. 21. Primary Battery" title="Fig. 21. Primary Battery" /></a> +<span class="caption"><i>Fig. 21.</i> <span class="smcap">Primary Battery</span></span> +</div> + +<p><span class="smcap">Battery Resistance, Electrolyte and Current.</span>—The +following should be carefully memorized:</p> + +<p>A cell has reference to a single vessel. When +two or more cells are coupled together they form +a <i>battery</i></p> +<p class="pn"><span class='pagenum'><a name="p37" id="p37">p. 37</a></span></p> + +<p><i>Resistance</i> 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."</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="smcap">Electro-magnetic Electricity.</span>—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.</p> + +<p><span class="smcap">Magnetic Radiation.</span>—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<span class='pagenum'><a name="p38" id="p38">p. 38</a></span> +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.</p> + +<p><span class="smcap">Different Kinds of Dynamo.</span>—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.</p> + +<p>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.</p> + +<p><span class="smcap">Direct-Current Dynamo.</span>—We shall now make +the simplest form of dynamo, using for this purpose +a pair of permanent magnets</p> +<p class="pn"><span class='pagenum'><a name="p39" id="p39">p. 39</a></span></p> + +<div class="figcenter" style="width: 352px;"> +<a id="fig22" name="fig22"></a><a href="#p39"> +<img src="images/illus-fig22.png" width="352" height="379" alt="Fig. 22. Dynamo Field and Pole Piece" title="Fig. 22. Dynamo Field and Pole Piece" /></a> +<span class="caption"><i>Fig. 22.</i> <span class="smcap">Dynamo Field and Pole Piece</span></span> +</div> + +<p><span class="smcap">Simple Magnet Construction.</span>—A simple way +to make a pair of magnets for this purpose is +shown in Fig. <a href="#fig22">22</a>. A piece of round ¾-inch steel +core (A), 5½ 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<span class='pagenum'><a name="p40" id="p40">p. 40</a></span> +iron (C) 2" × 2" × 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.</p> + +<p><span class="smcap">How to Wind.</span>—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').</p> + +<p><span class="smcap">The Dynamo Fields</span>.—Two of these spools are +so made and they are called the <i>fields</i> of the dynamo.</p> + +<p>We will next prepare an iron bar (I), 5 inches +long and ½ inch thick and 1½ 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 ¾-inch cores (A). This +bar holds together the upper ends of the cores, +as shown in Fig. <a href="#fig23">23</a></p> +<p class="pn"><span class='pagenum'><a name="p41" id="p41">p. 41</a></span></p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig23" name="fig23"></a><a href="#p41"> +<img src="images/illus-fig23.png" width="350" height="487" alt="Fig. 23. Base and Fields Assembled" title="Fig. 23. Base and Fields Assembled" /></a> +<span class="caption"><i>Fig. 23.</i> <span class="smcap"> Base and Fields Assembled</span></span> +</div> + +<p>We then prepare a base (J) of any hard wood, +2 inches thick, 8 inches long and 8 inches wide,<span class='pagenum'><a name="p42" id="p42">p. 42</a></span> +and bore two ¾-inch holes 3 inches apart on a middle +line, to receive a pair of ¾-inch cap screws (K), +which pass upwardly through the holes in the base +and screw into the pole pieces (C). A wooden bar +(L), 1½" × 1½", 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.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> + <td align="center"><a id="fig24" name="fig24"></a><a href="#p42"> +<img src="images/illus-fig24.png" width="211" height="131" alt="Fig. 24. Details of the Armature, core" +title="Fig. 24. Details of the Armature, core" /></a></td> + <td align="center"><a id="fig25" name="fig25"></a><a href="#p42"> +<img src="images/illus-fig25.png" width="142" height="132" alt="Fig. 25. Details of the Armature, body" +title="Fig. 25. Details of the Armature, body" /></a></td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 24-25.</i> <span class="smcap">Details of the Armature</span></span> + </td> + </tr> +</tbody> +</table> + +</div> + +<p><span class="smcap">The Armature.</span>—A bar of iron (Fig. <a href="#fig24">24</a>), 1" × 1" +and 2¼ inches long, is next provided. Through this +bar (1) are then bored two 5/16-inch holes 1¾ +inches apart, and on the opposite sides of this bar +are two half-rounded plates of iron (3) (Fig. <a href="#fig25">25</a>).</p> + +<p><span class="smcap">Armature Winding.</span>—Each plate is ½ inch thick, +1¾ 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<span class='pagenum'><a name="p43" id="p43">p. 43</a></span> +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).</p> + +<p><span class="smcap">Mounting the Armature.</span>—It is now necessary +to provide a means for revolving this armature. +To this end a brass disc (5, Fig. <a href="#fig26">26</a>) is made, 2 +inches in diameter, ⅛ 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.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> + <td align="center"> +<a id="fig26" name="fig26"></a><a href="#p43"> +<img src="images/illus-fig26.png" width="230" height="148" +alt="Fig. 26. Journals" title="Fig. 26. Journals" /></a> +</td> + <td align="center"> +<a id="fig27" name="fig27"></a><a href="#p43"> +<img src="images/illus-fig27.png" width="116" height="151" +alt="Fig. 27. Commutator" title="Fig. 27. Commutator" /></a> + </td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 26-27.</i> <span class="smcap">Armature Mountings</span></span> + </td> + </tr> +</tbody> +</table> + +</div> + + + +<p>The other end of the armature has a similar +disc (8), with a central stem (9), 1½ inches long, +turned down to ¼-inch diameter up to within ¼ +inch of the disc (7), so as to form a shoulder</p> +<p class="pn"><span class='pagenum'><a name="p44" id="p44">p. 44</a></span></p> + +<p><span class="smcap">The Commutator.</span>—In Fig. <a href="#fig27">27</a> is shown, at 10, +a wooden cylinder, 1 inch long and 1¼ 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</p> +<p class="pn"><span class='pagenum'><a name="p45" id="p45">p. 45</a></span></p> + +<div class="figcenter" style="width: 355px;"> +<a id="fig28" name="fig28"></a><a href="#p45"> +<img src="images/illus-fig28.png" width="355" height="297" alt="Fig. 28. End View Armature, Mounted" title="Fig. 28. End View Armature, Mounted" /></a> +<span class="caption"><i>Fig. 28.</i><br /> <span class="smcap">End View Armature, Mounted</span></span> +</div> + +<p>These tubular sections are called the commutator +plates.</p> + +<div class="figcenter" style="width: 363px;"> +<a id="fig29" name="fig29"></a><a href="#p45"> +<img src="images/illus-fig29.png" width="363" height="338" alt="Fig. 29. Top View of Armature on Base" title="Fig. 29. Top View of Armature on Base" /></a> +<span class="caption"><i>Fig. 29.</i><br /><span class="smcap">Top View of Armature on Base</span></span> +</div> + +<p>In order to mount this armature, two bearings +are provided, each comprising a bar of brass (15, +Fig. <a href="#fig28">28</a>), each ¼ inch thick, ½ inch wide and 4½ +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<span class='pagenum'><a name="p46" id="p46">p. 46</a></span> +(I) and enter the base (J). Midway between the +ends, each bar (15) has an iron bearing block (17), +¾" × ½" and 1½ inches high, the ¼-inch hole for the +journal (7) being midway between its ends.</p> + +<p><span class="smcap">Commutator Brushes.</span>—Fig. <a href="#fig28">28</a> 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 2½ 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.</p> + +<p><span class="smcap">Dynamo Windings.</span>—There are several ways to +wind the dynamos. These can be shown better by +the following diagrams (Figs. <a href="#fig30-31">30</a>, <a href="#fig30-31">31</a>, <a href="#fig32-33">32</a>, <a href="#fig32-33">33</a>):</p> + +<p><span class="smcap">The Field.</span>—If the field (A, Fig. <a href="#fig30-31">30</a>) 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.<span class='pagenum'><a name="p47" id="p47">p. 47</a></span> +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').</p> + +<div class="figcenter" style="width: 348px;"> +<a id="fig30-31" name="fig30-31"></a><a href="#p47"> +<img src="images/illus-fig30-31.png" width="348" height="169" alt="Fig. 30-31. Field Winding, Series-wound" +title="Fig. 30-31. Field Winding, Series-wound" /></a> +<span class="caption"><i>Figs. 30-31.</i> <span class="smcap">Field Winding, Series-wound</span></span> +</div> + + +<p><span class="smcap">Series-wound Field.</span>—Fig. <a href="#fig30-31">31</a> 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. <a href="#fig32-33">32</a> and <a href="#fig32-33">33</a>, 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.</p> + +<p><span class="smcap">Shunt-wound Field.</span>—Fig. <a href="#fig32-33">32</a> represents what +is known as a "shunt-wound" dynamo. Here the<span class='pagenum'><a name="p48" id="p48">p. 48</a></span> +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.</p> + +<div class="figcenter" style="width: 343px;"> +<a id="fig32-33" name="fig32-33"></a><a href="#p48"> +<img src="images/illus-fig32-33.png" width="343" height="162" alt="Figs. 32-33. Shunt-wound, Compound-wound" +title="Figs. 32-33. Shunt-wound, Compound-wound" /></a> +<span class="caption"><i>Figs. 32-33.</i> <span class="smcap">Shunt-wound, Compound-wound</span></span> +</div> + +<p><span class="smcap">Compound-wound Field.</span>—Fig. <a href="#fig32-33">33</a> 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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p49" id="p49">p. 49</a></span></p> + +<h2><a name="CHAPTER_V" id="CHAPTER_V"></a>CHAPTER V<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>HOW TO DETECT AND MEASURE ELECTRICITY</h3> + + +<p><span class="smcap">Measuring Instruments.</span>—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.</p> + +<p>As electricity cannot be seen by the human eye, +some mechanism must be made which will reveal +its movements.</p> + +<p><span class="smcap">The Detector.</span>—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 <i>galvanometer</i>. 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.</p> + +<p>For example, the wire (A, Fig. <a href="#fig34-36">35</a>) is connected<span class='pagenum'><a name="p50" id="p50">p. 50</a></span> +up in an electric circuit with a permanent magnet +(B) suspended by a fine wire (C), so that +the magnet (B) may freely revolve.</p> + +<div class="figcenter" style="width: 354px;"> +<a id="fig34-36" name="fig34-36"></a><a href="#p50"> +<img src="images/illus-fig34-36.png" width="354" height="86" alt="Figs. 34-36. +To the right, Compass Magnet, To the left" title="Figs. 34-36. +To the right, Compass Magnet, To the left" /></a> +<span class="caption"><i>Figs. 34-36.</i><br /> +To the right, <span class="smcap">Compass Magnet</span>, To the left</span> +</div> + +<p>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. <a href="#fig34-36">35</a> shows the normal condition of +the magnetized bar (B) parallel with the wire +(A) when a current is not passing through the +latter.</p> + +<p><span class="smcap">Direction of Current.</span>—If the current should +go through the wire (A) from right to left, +as shown in Fig. <a href="#fig34-36">34</a>, the magnet (B) would +swing in the direction taken by the hands +of a clock and assume the position shown<span class='pagenum'><a name="p51" id="p51">p. 51</a></span> +in Fig. <a href="#fig34-36">34</a>. 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. <a href="#fig34-36">36</a>. The little pointer (G) would, in either +case, point in the direction of the flow of the current +through the wire (A).</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig37" name="fig37"></a><a href="#p51"> +<img src="images/illus-fig37.png" width="351" height="364" alt="Fig. 37. Indicating Direction of Current" title="Fig. 37. Indicating Direction of Current" /></a> +<span class="caption"><i>Fig. 37.</i> <span class="smcap">Indicating Direction of Current</span></span> +</div> +<p class="pn"><span class='pagenum'><a name="p52" id="p52">p. 52</a></span></p> + +<p><span class="smcap">Simple Current Detector.</span>—A simple current +detector may be made as follows:</p> + +<p>Prepare a base 3' × 4' in size and 1 inch thick. +At each corner of one end fix a binding post, as at +A, A', Fig. <a href="#fig37">37</a>. 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" × 1" × 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.</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig38" name="fig38"></a><a href="#p52"> +<img src="images/illus-fig38.png" width="349" height="68" alt="Fig. 38. The Bridge" title="Fig. 38. The Bridge" /></a> +<span class="caption"><i>Fig. 38.</i> <span class="smcap">The Bridge</span></span> +</div> + +<p>Now make a bridge (E, Fig. <a href="#fig38">38</a>) of a strip of +brass ½ 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.</p> + +<p>Midway between the ends this bridge has a transverse +slot (H) in one edge, to receive therein the<span class='pagenum'><a name="p53" id="p53">p. 53</a></span> +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).</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig39" name="fig39"></a><a href="#p53"> +<img src="images/illus-fig39.png" width="351" height="97" alt="Fig. 39. Details of Detector" title="Fig. 39. Details of Detector" /></a> +<span class="caption"><i>Fig. 39.</i> <span class="smcap">Details of Detector</span></span> +</div> + +<p>The magnet is made of a bar of steel (K, Fig. +<a href="#fig39">39</a>) 1½ inches long, ⅜ 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<span class='pagenum'><a name="p54" id="p54">p. 54</a></span> +to have a metal socket for the lower end of the +pin. When these parts are put together, as shown +in Fig. <a href="#fig37">37</a>, a removable glass top, or cover, should +be provided.</p> + +<p>This is shown in Fig. <a href="#fig40">40</a>, 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.</p> + +<div class="figcenter" style="width: 343px;"> +<a id="fig40" name="fig40"></a><a href="#p54"> +<img src="images/illus-fig40.png" width="343" height="116" alt="Fig. 40. Cross Section of Detector" title="Fig. 40. Cross Section of Detector" /></a> +<span class="caption"><i>Fig. 40.</i> <span class="smcap">Cross Section of Detector</span></span> +</div> + +<p><span class="smcap">How to Place the Detector.</span>—If the detector +is placed north and south, as shown by the two +markings, N and S (Fig. <a href="#fig37">37</a>), 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<span class='pagenum'><a name="p55" id="p55">p. 55</a></span> +current is flowing through the wire (R) which +you are testing.</p> + +<p>The next step of importance is to <i>measure</i> the +current, that is, to determine its strength or intensity, +as well as the flow or quantity.</p> + +<p><span class="smcap">Different Ways of Measuring a Current.</span>—There +are several ways to measure the properties +of a current, which may be defined as follows:</p> + +<p>1. <span class="smcap">The Sulphuric Acid Voltameter.</span>—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.</p> + +<p>2. <span class="smcap">The Copper Voltameter.</span>—By electro-chemical +means, in which the current passes through +plates immersed in a solution of copper sulphate.</p> + +<p>3. <span class="smcap">The Galvanoscope.</span>—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.</p> + +<p>4. <span class="smcap">Electro-magnetic Method.</span>—By using a +pair of magnets and sending a current through +the coils, and then measuring the pull on the armature.</p> + +<p>5. <span class="smcap">The Power or Speed Method.</span>—By using an +electric fan, and noting the revolutions produced +by the current</p> +<p class="pn"><span class='pagenum'><a name="p56" id="p56">p. 56</a></span></p> + +<p>6. <span class="smcap">The Calorimeter.</span>—By using a coil of bare +wire, immersed in paraffine oil, and then measuring +the temperature by means of a thermometer.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> + <td align="center"> +<a id="fig41" name="fig41"></a><a href="#p56"> +<img src="images/illus-fig41.png" width="178" height="330" alt="Fig. 41. Acid Voltameter" title="Fig. 41. Acid Voltameter" /></a> +</td> + <td align="center"> +<a id="fig42" name="fig42"></a><a href="#p56"> +<img src="images/illus-fig42.png" width="175" height="326" alt="Fig. 42. Copper Voltameter" title="Fig. 42. Copper Voltameter" /></a> + </td> + </tr> + <tr> + <td class="tdnwc"> +<span class="caption"><i>Fig. 41.</i><br /><span class="smcap">Acid Voltameter</span></span> + </td> + <td class="tdnwc"> +<span class="caption"><i>Fig. 42.</i><br /><span class="smcap">Copper Voltameter</span></span> + </td> + </tr> +</tbody> +</table> + +</div> + +<p>7. <span class="smcap">The Light Method.</span>—Lastly, by means of +an electric light, which shows, by its brightness, a +greater or less current.</p> + +<p><span class="smcap">The Preferred Methods.</span>—It has been found +that the first and second methods are the only<span class='pagenum'><a name="p57" id="p57">p. 57</a></span> +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.</p> + +<p><span class="smcap">How to Make a Sulphuric Acid Voltameter.</span>—In +Fig. <a href="#fig41">41</a> 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.</p> + +<p><span class="smcap">How to Make a Copper Voltameter.</span>—The second, +or copper voltameter, is shown in Fig. <a href="#fig42">42</a>. +The glass jar (A) contains a solution of copper +sulphate, known in commerce as blue vitriol. A<span class='pagenum'><a name="p58" id="p58">p. 58</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="smcap">Disadvantages of the Galvanoscope.</span>—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<span class='pagenum'><a name="p59" id="p59">p. 59</a></span> +selecting the sizes of wire used and in the number +of turns made in the coils.</p> + +<p>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.</p> + +<p><span class="smcap">Objections to the Calorimeter.</span>—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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p60" id="p60">p. 60</a></span></p> + +<h2><a name="CHAPTER_VI" id="CHAPTER_VI"></a>CHAPTER VI<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>VOLTS, AMPERES, OHMS AND WATTS</h3> + + +<p><span class="smcap">Understanding Terms.</span>—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 <i>bushel</i> or the measurement +<i>yard</i> means.</p> + +<p><span class="smcap">Intensity and Quantity.</span>—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 <i>resistance</i>.</p> + +<p><span class="smcap">Voltage.</span>—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<span class='pagenum'><a name="p61" id="p61">p. 61</a></span> +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 <i>amperage</i>.</p> + +<p>In the case of water, a column 1" × 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.</p> + +<p><span class="smcap">Amperage.</span>—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.</p> + +<p><span class="smcap">Meaning of Watts.</span>—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.</p> + +<p>Here are two examples:</p> + +<ol style="margin: 0 15% 0 15%"> +<li> +<span class='pagenum'><a name="p62" id="p62">p. 62</a></span>28 inches = height of the water in the reservoir.<br /> +2 square inches = size of the pipe.<br /> +Multiply 28 × 2 = 56.</li> +<li>56 = height of the water in the reservoir.<br /> +1 square inch = size of the pipe.<br /> +Multiply 56 × 1 = 56.</li> +</ol> + +<p>Thus the two problems are equal.</p> + +<p><span class="smcap">A Kilowatt.</span>—Now, in electricity, remembering +that the height of the water corresponds with <i>voltage</i> +in electricity, and the size of the pipe with +<i>amperage</i>, if we multiply volts by amperes, or amperes +by volts, we get a result which is indicated +by the term <i>watts</i>. 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.</p> + +<p>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.</p> + +<p><span class="smcap">A Standard of Measurement.</span>—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:</p> + +<p><span class="smcap">The Ampere Standard.</span>—It is necessary, first, +to determine what an ampere is. For this purpose +a standard solution of nitrate of silver is<span class='pagenum'><a name="p63" id="p63">p. 63</a></span> +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.</p> + +<p><span class="smcap">The Voltage Standard.</span>—In order to determine +the voltage we must know something of <i>resistance</i>. +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 <i>ohm</i>, which is the measure +of resistance.</p> + +<p><span class="smcap">The Ohm.</span>—It is calculated in this way: There +are several standards, but the one most generally +employed is the <i>International Ohm</i>. 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.</p> + +<p><span class="smcap">Calculating the Voltage.</span>—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</p> +<p class="pn"><span class='pagenum'><a name="p64" id="p64">p. 64</a></span></p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p65" id="p65">p. 65</a></span></p> + +<h2><a name="CHAPTER_VII" id="CHAPTER_VII"></a>CHAPTER VII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>PUSH BUTTONS, SWITCHES, ANNUNCIATORS, BELLS AND LIKE APPARATUS</h3> + + +<p><span class="smcap">Simple Switches.</span>—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.</p> + +<p><span class="smcap">A Two-Pole Switch.</span>—A simple two-pole switch +for a single line is made as follows:</p> + +<p>A base block (A, Fig. <a href="#fig43">43</a>) 3 inches long, 2 inches +wide and ¾ 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).</p> + +<p><span class="smcap">Double-Pole Switch.</span>—A double-pole switch +or a switch for a double line is shown in Fig. <a href="#fig44">44</a>.<span class='pagenum'><a name="p66" id="p66">p. 66</a></span> +This is made similar in all respects to the one +shown in Fig. <a href="#fig43">43</a>, 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).</p> + +<div class="figcenter" style="width: 345px;"> +<a id="fig43" name="fig43"></a><a href="#p66"> +<img src="images/illus-fig43.png" width="345" height="130" alt="Fig. 43. Two-Pole Switch" title="Fig. 43. Two-Pole Switch" /></a> +<span class="caption"><i>Fig. 43.</i> <span class="smcap">Two-Pole Switch</span></span> +</div> + +<div class="figcenter" style="width: 342px;"> +<a id="fig44" name="fig44"></a><a href="#p66"> +<img src="images/illus-fig44.png" width="342" height="151" alt="Fig. 44. Double-Pole Switch" title="Fig. 44. Double-Pole Switch" /></a> +<span class="caption"><i>Fig. 44.</i> <span class="smcap">Double-Pole Switch</span></span> +</div> + +<p>Other types of switch will be found very useful. +In Fig. <a href="#fig45">45</a> 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<span class='pagenum'><a name="p67" id="p67">p. 67</a></span> +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).</p> + +<div class="figcenter" style="width: 378px;"> +<a id="fig45" name="fig45"></a><a href="#p67"> +<img src="images/illus-fig45.png" width="378" height="188" alt="Fig. 45. Sliding Switch" title="Fig. 45. Sliding Switch" /></a> +<span class="caption"><i>Fig. 45.</i> <span class="smcap">Sliding Switch</span></span> +</div> + +<p><span class="smcap">Sliding Switch.</span>—This sliding switch form may +have the contact plates (A, B and C, Fig. <a href="#fig46">46</a>) 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.</p> + +<p><span class="smcap">Reversing Switch.</span>—A reversing switch is +shown in Fig. <a href="#fig47">47</a>. 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<span class='pagenum'><a name="p68" id="p68">p. 68</a></span> +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.</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig46" name="fig46"></a><a href="#p68"> +<img src="images/illus-fig46.png" width="349" height="184" alt="Fig. 46. Rheostat Form of Switch" title="Fig. 46. Rheostat Form of Switch" /></a> +<span class="caption"><i>Fig. 46.</i> <span class="smcap">Rheostat Form of Switch</span></span> +</div> + +<p><span class="smcap">Push Buttons.</span>—A push button is but a modified +structure of a switch, and they are serviceable<span class='pagenum'><a name="p69" id="p69">p. 69</a></span> +because they are operating, or the circuit is +formed only while the finger is on the button.</p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig47" name="fig47"></a><a href="#p69"> +<img src="images/illus-fig47.png" width="350" height="186" alt="Fig. 47. Reversing Switch" title="Fig. 47. Reversing Switch" /></a> +<span class="caption"><i>Fig. 47.</i> <span class="smcap">Reversing Switch</span></span> +</div> + +<p>In its simplest form (Fig. <a href="#fig48">48</a>) 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.</p> + +<p><span class="smcap">Electric Bell.</span>—One of the first things the boy<span class='pagenum'><a name="p70" id="p70">p. 70</a></span> +wants to make, and one which is also an interesting +piece of work, is an electric bell.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 359px;"> +<a id="fig48" name="fig48"></a><a href="#p70"> +<img src="images/illus-fig48.png" width="359" height="127" alt="Fig. 48. Push Button" title="Fig. 48. Push Button" /></a> +<span class="caption"><i>Fig. 48.</i> <span class="smcap">Push Button</span></span> +</div> + +<p><span class="smcap">How Made.</span>—In Fig. <a href="#fig49">49</a> 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<span class='pagenum'><a name="p71" id="p71">p. 71</a></span> +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'.</p> + +<div class="figcenter" style="width: 354px;"> +<a id="fig49" name="fig49"></a><a href="#p71"> +<img src="images/illus-fig49.png" width="354" height="371" alt="Fig. 49. Electric Bell" title="Fig. 49. Electric Bell" /></a> +<span class="caption"><i>Fig. 49.</i> <span class="smcap">Electric Bell</span></span> +</div> + +<p>The principle of the electric bell is this: In +looking at Fig. <a href="#fig49">49</a>, you will note that the armature +bar D is held against the end of the adjusting<span class='pagenum'><a name="p72" id="p72">p. 72</a></span> +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'.</p> + +<div class="figcenter" style="width: 364px;"> +<a id="fig50" name="fig50"></a><a href="#p72"> +<img src="images/illus-fig50.png" width="364" height="179" alt="Fig. 50. Armature of Electric Bell" title="Fig. 50. Armature of Electric Bell" /></a> +<span class="caption"><i>Fig. 50.</i> <span class="smcap">Armature of Electric Bell</span></span> +</div> + +<p><span class="smcap">Electric Bell—How Operated.</span>—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<span class='pagenum'><a name="p73" id="p73">p. 73</a></span> +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.</p> + +<p>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').</p> + +<p>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.</p> + +<p>It is better, in practice, to have a small spring +(P, Fig. <a href="#fig50">50</a>) 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.</p> + +<p>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.</p> + +<p>An easily removable cap or cover is usually<span class='pagenum'><a name="p74" id="p74">p. 74</a></span> +placed over the coils and armature, to keep out +dust.</p> + +<p>A very simple annunciator may be attached to +the bell, as shown in the following figures:</p> + +<div class="figcenter" style="width: 365px;"> +<a id="fig51-54" name="fig51-54"></a><a href="#p74"> +<img src="images/illus-fig51-54.png" width="365" height="367" alt="Figs. 51-54. Annunciator" title="Figs. 51-54. Annunciator" /></a> +<span class="caption"><i>Figs. 51-54.</i> <span class="smcap">Annunciator</span></span> +</div> + +<p><span class="smcap">Annunciators.</span>—Make a box of wood, with a +base (A) 4" × 5" and ½ inch thick. On this you +can permanently mount the two side pieces (B) +and two top and bottom pieces (C), respectively,<span class='pagenum'><a name="p75" id="p75">p. 75</a></span> +so they project outwardly 4½ inches from the base. +On the open front place a wood or metal plate +(D), provided with a square opening (D), as in +Fig. <a href="#fig51-54">54</a>, near its lower end. This plate is held +to the box by screws (E).</p> + +<p>Within is a magnet (F), screwed into the base +(A), as shown in Fig. <a href="#fig51-54">51</a>; 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. <a href="#fig51-54">51</a>, +a vertical trigger (M) passes up through the bottom, +its upper end being within range of one of +the limbs of the stirrup.</p> + +<p>This is easily made by the ingenious boy, and<span class='pagenum'><a name="p76" id="p76">p. 76</a></span> +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.</p> + +<div class="figcenter" style="width: 358px;"> +<a id="fig55" name="fig55"></a><a href="#p76"> +<img src="images/illus-fig55.png" width="358" height="180" alt="Fig. 55. Alarm Switch on Window" title="Fig. 55. Alarm Switch on Window" /></a> +<span class="caption"><i>Fig. 55.</i> <span class="smcap">Alarm Switch on Window</span></span> +</div> + +<div class="figcenter" style="width: 359px;"> +<a id="fig56" name="fig56"></a><a href="#p76"> +<img src="images/illus-fig56.png" width="359" height="205" alt="Fig. 56. Burglar Alarm Attachment to Window" +title="Fig. 56. Burglar Alarm Attachment to Window" /></a> +<span class="caption"><i>Fig. 56.</i> <span class="smcap">Burglar Alarm Attachment to Window</span></span> +</div> + +<p><span class="smcap">Burglar Alarm.</span>—In order to make a burglar +alarm connection with a bell, push buttons or +switches may be put in circuit to connect with the<span class='pagenum'><a name="p77" id="p77">p. 77</a></span> +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:</p> + +<p>The base piece (A), which may be of hard rubber +or fiber, is ¼ inch thick and 1" × 1½" in size.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig57" name="fig57"></a><a href="#p77"> +<img src="images/illus-fig57.png" width="344" height="213" alt="Fig. 57. Burglar Alarm Contact" title="Fig. 57. Burglar Alarm Contact" /></a> +<span class="caption"><i>Fig. 57.</i> <span class="smcap">Burglar Alarm Contact</span></span> +</div> + +<p>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)</p> +<p class="pn"><span class='pagenum'><a name="p78" id="p78">p. 78</a></span></p> + +<p>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).</p> + +<div class="figcenter" style="width: 360px;"> +<a id="fig58" name="fig58"></a><a href="#p78"> +<img src="images/illus-fig58.png" width="360" height="176" alt="Fig. 58. Neutral Position of Contact" title="Fig. 58. Neutral Position of Contact" /></a> +<span class="caption"><i>Fig. 58.</i> <span class="smcap">Neutral Position of Contact</span></span> +</div> + +<p>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. <a href="#fig56">56</a>, 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. <a href="#fig57">57</a>. During the daytime the pin (H) may +be removed, and in order to protect the switch<span class='pagenum'><a name="p79" id="p79">p. 79</a></span> +the heart-shaped piece (D) is swung inwardly, +as shown in Fig. <a href="#fig58">58</a>, so that neither of the lobes +is in contact with the plate (E).</p> + +<p><span class="smcap">Wire Circuiting.</span>—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.</p> + +<div class="figcenter" style="width: 348px;"> +<a id="fig59" name="fig59"></a><a href="#p79"> +<img src="images/illus-fig59.png" width="348" height="172" alt="Fig. 59. Circuiting for Electric Bell" title="Fig. 59. Circuiting for Electric Bell" /></a> +<span class="caption"><i>Fig. 59.</i> <span class="smcap">Circuiting for Electric Bell</span></span> +</div> + +<p><span class="smcap">Circuiting System with a Bell and Two Push +Buttons.</span>—Fig. <a href="#fig59">59</a> 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.</p> + +<p><span class="smcap">The Push Buttons and the Annunciator +Bells.</span>—Fig. <a href="#fig60">60</a> shows three push buttons and an +annunciator for each button. These three circuits<span class='pagenum'><a name="p80" id="p80">p. 80</a></span> +are indicated by A, B and C, so that when +either button makes contact, a complete circuit is +formed through the corresponding annunciator.</p> + +<div class="figcenter" style="width: 401px;"> +<a id="fig60" name="fig60"></a><a href="#p80"> +<img src="images/illus-fig60.png" width="401" height="165" alt="Fig. 60. Annunciators" title="Fig. 60. Annunciators" /></a> +<span class="caption"><i>Fig. 60.</i> <span class="smcap">Annunciators</span></span> +</div> + +<div class="figcenter" style="width: 402px;"> +<a id="fig61" name="fig61"></a><a href="#p80"> +<img src="images/illus-fig61.png" width="402" height="177" alt="Fig. 61. Wiring System for a House" title="Fig. 61. Wiring System for a House" /></a> +<span class="caption"><i>Fig. 61.</i> <span class="smcap">Wiring System for a House</span></span> +</div> + +<p><span class="smcap">Wiring Up a House.</span>—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. <a href="#fig61">61</a>. It will be understood that, in practice, +the bell is mounted on or at the annunciator, and<span class='pagenum'><a name="p81" id="p81">p. 81</a></span> +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.</p> + +<p>A, B, C represent the circuit wires from the terminals +of the window and door switches, to the +annunciators.</p> + +<p>It is entirely immaterial which side of the battery +is connected up with the bell.</p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p82" id="p82">p. 82</a></span></p> + +<h2><a name="CHAPTER_VIII" id="CHAPTER_VIII"></a>CHAPTER VIII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>ACCUMULATORS. STORAGE OR SECONDARY BATTERIES</h3> + + +<p><span class="smcap">Storing Up Electricity.</span>—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.</p> + +<p><span class="smcap">The Accumulator.</span>—The term <i>accumulator</i> is, +strictly speaking, the more nearly correct, as electricity +is, in reality, "<i>stored</i>" 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<span class='pagenum'><a name="p83" id="p83">p. 83</a></span> +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.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig62" name="fig62"></a><a href="#p83"> +<img src="images/illus-fig62.png" width="351" height="229" alt="Fig. 62. Accumulator Grids" title="Fig. 62. Accumulator Grids" /></a> +<span class="caption"><i>Fig. 62.</i> <span class="smcap">Accumulator Grids</span></span> +</div> + +<p><span class="smcap">Accumulator Plates.</span>—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</p> +<p class="pn"><span class='pagenum'><a name="p84" id="p84">p. 84</a></span></p> + +<p>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.</p> + +<p><span class="smcap">The Grid.</span>—The open space, called the grid, +proper, comprises cross bars, integral with the +plate, made in a variety of shapes. Fig. <a href="#fig62">62</a> 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.</p> + +<p><span class="smcap">The Positive Plate.</span>—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.</p> + +<p>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.</p> + +<p><span class="smcap">The Negative Plate.</span>—The negative plate is<span class='pagenum'><a name="p85" id="p85">p. 85</a></span> +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.</p> + +<div class="figcenter" style="width: 345px;"> +<a id="fig63" name="fig63"></a><a href="#p85"> +<img src="images/illus-fig63.png" width="345" height="292" alt="Fig. 63. Assemblage of Accumulator Plates" +title="Fig. 63. Assemblage of Accumulator Plates" /></a> +<span class="caption"><i>Fig. 63.</i> <span class="smcap">Assemblage of Accumulator Plates</span></span> +</div> + +<p><span class="smcap">Connecting Up the Plates.</span>—The next step is +to put these plates in position to form a battery. +In Fig. <a href="#fig63">63</a> is shown a collection of plates connected +together</p> +<p class="pn"><span class='pagenum'><a name="p86" id="p86">p. 86</a></span></p> + +<p>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).</p> + +<p>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.</p> + +<p>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</p> +<p class="pn"><span class='pagenum'><a name="p87" id="p87">p. 87</a></span></p> + +<p>Put enough of this solution into the cell to cover +the tops of the plates, and the cell is ready.</p> + +<div class="figcenter" style="width: 354px;"> +<a id="fig64" name="fig64"></a><a href="#p85"> +<img src="images/illus-fig64.png" width="354" height="118" alt="Fig. 64. Connecting Up Storage Battery in Series" +title="Fig. 64. Connecting Up Storage Battery in Series" /></a> +<span class="caption"><i>Fig. 64.</i> <span class="smcap">Connecting Up Storage Battery in Series</span></span> +</div> + +<p><span class="smcap">Charging the Cells.</span>—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. <a href="#fig64">64</a>, or, instead of this, we may put them +into two parallel sets of 5 cells each, as shown in +Fig. <a href="#fig65">65</a>, 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.</p> + +<p>The positive pole of the dynamo should be +connected with the positive pole of the accumulator<span class='pagenum'><a name="p88" id="p88">p. 88</a></span> +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. <a href="#fig64">64</a>, at +least 125 volts will be required, and the excess +necessary should bring up the voltage in the dynamo +to 135 or 140 volts.</p> + +<div class="figcenter" style="width: 353px;"> +<a id="fig65" name="fig65"></a><a href="#p88"> +<img src="images/illus-fig65.png" width="353" height="129" alt="Fig. 65. Parallel Series" title="Fig. 65. Parallel Series" /></a> +<span class="caption"><i>Fig. 65.</i> <span class="smcap">Parallel Series</span></span> +</div> + +<div class="figcenter" style="width: 353px;"> +<a id="fig66" name="fig66"></a><a href="#p88"> +<img src="images/illus-fig66.png" width="353" height="144" alt="Fig. 66. Charging Circuit" title="Fig. 66. Charging Circuit" /></a> +<span class="caption"><i>Fig. 66.</i> <span class="smcap">Charging Circuit</span></span> +</div> + +<p><span class="smcap">The Initial Charge.</span>—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<span class='pagenum'><a name="p89" id="p89">p. 89</a></span> +plates to a slate or gray color, and both plates +give off large bubbles of gas.</p> + +<p>In charging, the temperature of the electrolyte +should not exceed 100° Fahrenheit.</p> + +<p>When using the accumulators they should never +be fully discharged.</p> + +<p><span class="smcap">The Charging Circuit.</span>—The diagram (Fig. +<a href="#fig66">66</a>) 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 ½ +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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p90" id="p90">p. 90</a></span></p> + +<h2><a name="CHAPTER_IX" id="CHAPTER_IX"></a>CHAPTER IX<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>THE TELEGRAPH</h3> + + +<p>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.</p> + +<p>The signals sent over the wires are simply the +audible sounds made by the armature, as it moves +to and from the magnets.</p> + +<p><span class="smcap">Mechanism in Telegraph Circuits.</span>—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.</p> + +<p><span class="smcap">The Sending Key.</span>—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<span class='pagenum'><a name="p91" id="p91">p. 91</a></span> +brass, one-half inch wide by one-sixteenth of an +inch thick.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 357px;"> +<a id="fig67" name="fig67"></a><a href="#p91"> +<img src="images/illus-fig67.png" width="357" height="138" alt="Fig. 67. Telegraph Sending Key" title="Fig. 67. Telegraph Sending Key" /></a> +<span class="caption"><i>Fig. 67.</i> <span class="smcap">Telegraph Sending Key</span></span> +</div> + +<p>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.</p> + +<p>When the key A contacts with the screw heads<span class='pagenum'><a name="p92" id="p92">p. 92</a></span> +G, J, a click is produced, one when the key is +pressed down and the other when the key is released.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 345px;"> +<a id="fig68" name="fig68"></a><a href="#p92"> +<img src="images/illus-fig68.png" width="345" height="182" alt="Fig. 68. Telegraph Sounder" title="Fig. 68. Telegraph Sounder" /></a> +<span class="caption"><i>Fig. 68.</i> <span class="smcap">Telegraph Sounder</span></span> +</div> + +<p>When the key A is depressed, the circuit of +course goes through plate C, key A and plate +F to the station signalled.</p> + +<p><span class="smcap">The Sounder.</span>—The sounder is the instrument +which carries the electro-magnet.</p> + +<p>In Fig. <a href="#fig68">68</a> this is shown in perspective. The +base is six inches long and four inches wide, being<span class='pagenum'><a name="p93" id="p93">p. 93</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="smcap">Connecting Up the Key and Sounder.</span>—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.</p> + +<p>In Fig. <a href="#fig69">69</a> 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<span class='pagenum'><a name="p94" id="p94">p. 94</a></span> +being attached so that one end connects with the +positive terminal of the battery, and the other end +with the negative terminal.</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig69" name="fig69"></a><a href="#p94"> +<img src="images/illus-fig69.png" width="351" height="171" alt="Fig. 69. A Telegraph Circuit" title="Fig. 69. A Telegraph Circuit" /></a> +<span class="caption"><i>Fig. 69.</i> <span class="smcap">A Telegraph Circuit</span></span> +</div> + +<p>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.</p> + +<p><span class="smcap">Two Stations in Circuit.</span>—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<span class='pagenum'><a name="p95" id="p95">p. 95</a></span> +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'.</p> + +<p>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'.</p> + +<p><span class="smcap">The Double Click.</span>—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. <a href="#fig62">62</a>), 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. <a href="#fig68">68</a>) 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</p> +<p class="pn"><span class='pagenum'><a name="p96" id="p96">p. 96</a></span></p> + +<p><span class="smcap">Illustrating the Dot and the Dash.</span>—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.</p> + +<p class="center"><i>The Morse Telegraph Code</i></p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/illus-p113-1.png" width="400" height="248" alt="Morse Code Table: A-Z, 0-9, &" title="Morse Code Table: A-Z, 0-9, &" /> +</div> + +<p><span class="smcap">Example in Use.</span>—Let us take an example in +the word "electrical."</p> + +<div class="figcenter" style="width: 400px;"> +<img src="images/illus-p113-2.png" width="400" height="47" alt="E L E C T R I C A L" title="E L E C T R I C A L" /> +</div> + +<p class="pn"><span class='pagenum'><a name="p97" id="p97">p. 97</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p98" id="p98">p. 98</a></span></p> + +<h2><a name="CHAPTER_X" id="CHAPTER_X"></a>CHAPTER X<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>HIGH TENSION APPARATUS, CONDENSERS, ETC.</h3> + + +<p><span class="smcap">Induction.</span>—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.</p> + +<p><span class="smcap">Low and High Tension.</span>—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.</p> + +<p>For an illustration of this examine Fig. <a href="#fig70">70</a>, 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,<span class='pagenum'><a name="p99" id="p99">p. 99</a></span> +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 <i>Induction Coils</i>, 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.</p> + +<div class="figcenter" style="width: 347px;"> +<a id="fig70" name="fig70"></a><a href="#p99"> +<img src="images/illus-fig70.png" width="347" height="110" alt="Fig. 70. Induction Coil and Circuit" title="Fig. 70. Induction Coil and Circuit" /></a> +<span class="caption"><i>Fig. 70.</i> <span class="smcap">Induction Coil and Circuit</span></span> +</div> + +<p>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.</p> + +<p><span class="smcap">Elastic Property of Electricity.</span>—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</p> +<p class="pn"><span class='pagenum'><a name="p100" id="p100">p. 100</a></span></p> + +<p>Referring to Fig. <a href="#fig71">71</a>, 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.</p> + +<div class="figcenter" style="width: 341px;"> +<a id="fig71" name="fig71"></a><a href="#p100"> +<img src="images/illus-fig71.png" width="341" height="126" alt="Fig. 71. Illustrating Elasticity" title="Fig. 71. Illustrating Elasticity" /></a> +<span class="caption"><i>Fig. 71.</i> <span class="smcap">Illustrating Elasticity</span></span> +</div> + +<p><span class="smcap">The Condenser.</span>—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),<span class='pagenum'><a name="p101" id="p101">p. 101</a></span> +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.</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig72" name="fig72"></a><a href="#p101"> +<img src="images/illus-fig72.png" width="349" height="172" alt="Fig. 72. Condenser" title="Fig. 72. Condenser" /></a> +<span class="caption"><i>Fig. 72.</i> <span class="smcap">Condenser</span></span> +</div> + +<p>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.</p> + +<p>Care should be exercised to leave the paraffine +sheets perfect or without holes. You can make<span class='pagenum'><a name="p102" id="p102">p. 102</a></span> +these sheets yourself by soaking them in melted +paraffine wax.</p> + +<p><span class="smcap">Connecting Up a Condenser.</span>—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.</p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig73" name="fig73"></a><a href="#p102"> +<img src="images/illus-fig73.png" width="350" height="121" alt="Fig. 73. High-tension Circuit" title="Fig. 73. High-tension Circuit" /></a> +<span class="caption"><i>Fig. 73.</i> <span class="smcap">High-tension Circuit</span></span> +</div> + +<p>In Fig. <a href="#fig73">73</a> 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.</p> + +<p><span class="smcap">The Interrupter.</span>—One other piece of mechanism +is necessary, and that is an <i>Interrupter</i>, +for the purpose of getting the effect of the pulsations +given out by the secondary coil.</p> + +<p>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<span class='pagenum'><a name="p103" id="p103">p. 103</a></span> +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.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig74" name="fig74"></a><a href="#p103"> +<img src="images/illus-fig74.png" width="344" height="157" alt="Fig. 74. Current Interrupter" title="Fig. 74. Current Interrupter" /></a> +<span class="caption"><i>Fig. 74.</i> <span class="smcap">Current Interrupter</span></span> +</div> + +<p><span class="smcap">Uses of High-tension Coils.</span>—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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p104" id="p104">p. 104</a></span></p> + +<h2><a name="CHAPTER_XI" id="CHAPTER_XI"></a>CHAPTER XI<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>WIRELESS TELEGRAPHY</h3> + + +<p><span class="smcap">Telegraphing Without Wires.</span>—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.</p> + +<p><span class="smcap">Surging Character of High-tension Currents.</span>—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,<span class='pagenum'><a name="p105" id="p105">p. 105</a></span> +that the ether can, therefore, convey an electrical +impulse as readily as does a wire.</p> + +<p>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.</p> + +<p><span class="smcap">The Coherer.</span>—The instrument for detecting +these impulses, or disturbances, in the ether is +generally called a <i>coherer</i>, although detector is +the term which is most satisfactory. The name +coherer comes from the first practical instrument +made for this purpose.</p> + +<div class="figcenter" style="width: 337px;"> +<a id="fig75" name="fig75"></a><a href="#p105"> +<img src="images/illus-fig75.png" width="337" height="125" alt="Fig. 75. Wireless Telegraphy Coherer" title="Fig. 75. Wireless Telegraphy Coherer" /></a> +<span class="caption"><i>Fig. 75.</i> <span class="smcap">Wireless Telegraphy Coherer</span></span> +</div> + +<p><span class="smcap">How Made.</span>—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<span class='pagenum'><a name="p106" id="p106">p. 106</a></span> +bringing together of the particles, under these +conditions, is called cohering.</p> + +<p>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.</p> + +<p><span class="smcap">The Decoherers.</span>—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.</p> + +<p>In practice, the coils and the parts directly connected +with it are put together on one base.</p> + +<p><span class="smcap">The Sending Apparatus.</span>—Fig. <a href="#fig76">76</a> 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.</p> + +<p>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<span class='pagenum'><a name="p107" id="p107">p. 107</a></span> +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.</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig76" name="fig76"></a><a href="#p107"> +<img src="images/illus-fig76.png" width="349" height="332" alt="Fig. 76. Wireless Sending Apparatus" title="Fig. 76. Wireless Sending Apparatus" /></a> +<span class="caption"><i>Fig. 76.</i> <span class="smcap">Wireless Sending Apparatus</span></span> +</div> + +<p>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<span class='pagenum'><a name="p108" id="p108">p. 108</a></span> +secondary coil, carries a similar adjusting rod +with a knob (H).</p> + +<p>From the post (E) is a wire (I), which extends +upwardly, and is called the aerial wire, or wire +for the antennæ, 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.</p> + +<div class="figcenter" style="width: 346px;"> +<a id="fig77" name="fig77"></a><a href="#p108"> +<img src="images/illus-fig77.png" width="346" height="150" alt="Fig. 77. Wireless Receiving Apparatus" title="Fig. 77. Wireless Receiving Apparatus" /></a> +<span class="caption"><i>Fig. 77.</i> <span class="smcap">Wireless Receiving Apparatus</span></span> +</div> + +<p><span class="smcap">The Receiving Apparatus.</span>—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.</p> + +<p>Of course, when the coherer switch is closed, +the battery operates the decoherer</p> +<p class="pn"><span class='pagenum'><a name="p109" id="p109">p. 109</a></span></p> + +<p><span class="smcap">How the Circuits are Formed.</span>—By referring +again to Fig. <a href="#fig76">76</a>, 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.</p> + +<p>It is this impulse, or disturbance, which is received +by the coherer at the receiving station, +and which is indicated by the telegraph sounder.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p110" id="p110">p. 110</a></span></p> + +<h2><a name="CHAPTER_XII" id="CHAPTER_XII"></a>CHAPTER XII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>THE TELEPHONE</h3> + + +<p><span class="smcap">Vibrations.</span>—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.</p> + +<p><span class="smcap">The Acoustic Telephone.</span>—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 <i>Acoustic Telephone</i>. The principle of this +may be illustrated as follows:</p> + +<p>Take two cups (A, B), as in Fig. <a href="#fig78">78</a>, 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<span class='pagenum'><a name="p111" id="p111">p. 111</a></span> +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.</p> + +<div class="figcenter" style="width: 353px;"> +<a id="fig78" name="fig78"></a><a href="#p111"> +<img src="images/illus-fig78.png" width="353" height="137" alt="Fig. 78. Acoustic Telephone" title="Fig. 78. Acoustic Telephone" /></a> +<span class="caption"><i>Fig. 78.</i> <span class="smcap">Acoustic Telephone</span></span> +</div> + +<div class="figcenter" style="width: 353px;"> +<a id="fig79" name="fig79"></a><a href="#p111"> +<img src="images/illus-fig79.png" width="353" height="100" alt="Fig. 79. Illustrating Vibrations" title="Fig. 79. Illustrating Vibrations" /></a> +<span class="caption"><i>Fig. 79.</i> <span class="smcap">Illustrating Vibrations</span></span> +</div> + +<p><span class="smcap">Sound Waves.</span>—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:</p> + +<p>Stretch a wire, as at B (Fig. <a href="#fig79">79</a>), 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<span class='pagenum'><a name="p112" id="p112">p. 112</a></span> +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.</p> + +<p><span class="smcap">Hearing Electricity.</span>—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.</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig80" name="fig80"></a><a href="#p112"> +<img src="images/illus-fig80.png" width="351" height="149" alt="Fig. 80 .The Magnetic Field" title="Fig. 80. The Magnetic Field" /></a> +<span class="caption"><i>Fig. 80.</i> <span class="smcap">The Magnetic Field</span></span> +</div> + +<p>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. <a href="#fig80">80</a>.</p> + +<p>The magnetic field is shown in Fig. <a href="#fig80">80</a> at only<span class='pagenum'><a name="p113" id="p113">p. 113</a></span> +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.</p> + +<p><span class="smcap">The Diaphragm in a Magnetic Field.</span>—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.</p> + +<p><span class="smcap">A Simple Telephone Circuit.</span>—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.</p> + +<p><span class="smcap">How to Make a Telephone.</span>—For experimental +and testing purposes two of these telephones<span class='pagenum'><a name="p114" id="p114">p. 114</a></span> +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, ⅜ 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).</p> + +<p>The enlarged end of the case should be, exteriorly, +2¼ inches in diameter, and the body of the +case 1 inch in diameter.</p> + +<div class="figcenter" style="width: 369px;"> +<a id="fig81" name="fig81"></a><a href="#p114"> +<img src="images/illus-fig81.png" width="369" height="172" alt="Fig. 81. Section of Telephone Receiver" title="Fig. 81. Section of Telephone Receiver" /></a> +<span class="caption"><i>Fig. 81.</i> <span class="smcap">Section of Telephone Receiver</span></span> +</div> + +<p>Interiorly, the large end of the case is provided +with a circular recess 1¾ 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<span class='pagenum'><a name="p115" id="p115">p. 115</a></span> +from the magnet may have room where they +emerge from the spool.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 352px;"> +<a id="fig82" name="fig82"></a><a href="#p115"> +<img src="images/illus-fig82.png" width="352" height="142" alt="Fig. 82. The Magnet and Receiver Head" title="Fig. 82. The Magnet and Receiver Head" /></a> +<span class="caption"><i>Fig. 82.</i> <span class="smcap">The Magnet and Receiver Head</span></span> +</div> + +<p>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)</p> +<p class="pn"><span class='pagenum'><a name="p116" id="p116">p. 116</a></span></p> + +<p>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.</p> + +<p><span class="smcap">Telephone Connections.</span>—The simplest form +of telephone connection is shown in Fig. <a href="#fig83">83</a>. 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.</p> + +<div class="figcenter" style="width: 350px;"> +<a id="fig83" name="fig83"></a><a href="#p116"> +<img src="images/illus-fig83.png" width="350" height="85" alt="Fig. 83. Simple Telephone Connection" title="Fig. 83. Simple Telephone Connection" /></a> +<span class="caption"><i>Fig. 83.</i> <span class="smcap">Simple Telephone Connection</span></span> +</div> + +<p><span class="smcap">Complete Installation.</span>—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.</p> + +<p>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<span class='pagenum'><a name="p117" id="p117">p. 117</a></span> +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').</p> + +<div class="figcenter" style="width: 349px;"> +<a id="fig84" name="fig84"></a><a href="#p117"> +<img src="images/illus-fig84.png" width="349" height="132" alt="Fig. 84. Telephone Stations in Circuit" title="Fig. 84. Telephone Stations in Circuit" /></a> +<span class="caption"><i>Fig. 84.</i> <span class="smcap">Telephone Stations in Circuit</span></span> +</div> + +<p>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,<span class='pagenum'><a name="p118" id="p118">p. 118</a></span> +where it flows up wire G' to the battery, thereby +completing the circuit.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig85" name="fig85"></a><a href="#p118"> +<img src="images/illus-fig85.png" width="344" height="87" alt="Fig. 85. Illustrating Light Contact Points" title="Fig. 85. Illustrating Light Contact Points" /></a> +<span class="caption"><i>Fig. 85.</i> <span class="smcap">Illustrating Light Contact Points</span></span> +</div> + +<p>The operator at station 2, having given the +signal, again throws his switch (D') back to the +position shown in Fig. <a href="#fig84">84</a>, 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.</p> + +<p><span class="smcap">Microphone.</span>—Originally this form of telephone +system was generally employed, but it was found +that for long distances a more sensitive instrument +was necessary.</p> + +<p><span class="smcap">Light Contact Points.</span>—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<span class='pagenum'><a name="p119" id="p119">p. 119</a></span> +light pin, or a nail (A, Fig. <a href="#fig85">85</a>) 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. <a href="#fig86">86</a>.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> + <td align="center"> +<a id="fig86" name="fig86"></a><a href="#p119"> +<img src="images/illus-fig86.png" width="210" height="197" alt="Fig. 86. Microphone" title="Fig. 86. Microphone" /></a></td> + <td align="center"> +<a id="fig87" name="fig87"></a><a href="#p119"> +<img src="images/illus-fig87.png" width="134" height="196" alt="Fig. 87. Transmitter" title="Fig. 87. Transmitter" /></a> + </td> + </tr> + <tr> + <td class="tdnwc"> +<span class="caption"><i>Fig. 86.</i> <span class="smcap">Microphone</span></span> + </td> + <td class="tdnwc"> +<span class="caption"><i>Fig. 87.</i> <span class="smcap">Transmitter</span></span> + </td> + </tr> +</tbody> +</table> + +</div> + +<p><span class="smcap">How to Make a Microphone.</span>—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<span class='pagenum'><a name="p120" id="p120">p. 120</a></span> +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.</p> + +<p><span class="smcap">Microphone the Father of the Transmitter.</span>—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. <a href="#fig85">85</a>.</p> + +<p><span class="smcap">Automatic Cut-outs for Telephones.</span>—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.</p> + +<p>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.</p> + +<p>Before describing the circuiting required for +these improvements, we show, in Fig. <a href="#fig87">87</a>, a section +of a transmitter.</p> + +<p>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<span class='pagenum'><a name="p121" id="p121">p. 121</a></span> +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).</p> + +<p><span class="smcap">Complete Circuiting with Transmitter.</span>—In +showing the circuiting (Fig. <a href="#fig88">88</a>) 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.</p> + +<div class="figcenter" style="width: 347px;"> +<a id="fig88" name="fig88"></a><a href="#p121"> +<img src="images/illus-fig88.png" width="347" height="140" alt="Fig. 88. Complete Telephonic Circuit" title="Fig. 88. Complete Telephonic Circuit" /></a> +<span class="caption"><i>Fig. 88.</i> <span class="smcap">Complete Telephonic Circuit</span></span> +</div> + +<p>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<span class='pagenum'><a name="p122" id="p122">p. 122</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p123" id="p123">p. 123</a></span></p> + +<h2><a name="CHAPTER_XIII" id="CHAPTER_XIII"></a>CHAPTER XIII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>ELECTROLYSIS, WATER PURIFICATION, ELECTROPLATING</h3> + + +<p><span class="smcap">Decomposing Liquids.</span>—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.</p> + +<p><span class="smcap">Making Hydrogen and Oxygen.</span>—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. <a href="#fig89">89</a>.</p> + +<p>It is constructed of a glass or earthen jar (A), +preferably square, to which is fitted a wooden top<span class='pagenum'><a name="p124" id="p124">p. 124</a></span> +(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.</p> + +<div class="figcenter" style="width: 343px;"> +<a id="fig89" name="fig89"></a><a href="#p124"> +<img src="images/illus-fig89.png" width="343" height="216" alt="Fig. 89. Device for Making Hydrogen and Oxygen" +title="Fig. 89. Device for Making Hydrogen and Oxygen" /></a> +<span class="caption"><i>Fig. 89.</i> <span class="smcap">Device for Making Hydrogen and Oxygen</span></span> +</div> + +<p>If a current of electricity is passed through the +wires and the electrodes, in the direction shown<span class='pagenum'><a name="p125" id="p125">p. 125</a></span> +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.</p> + +<p><span class="smcap">Purifying Water.</span>—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, <i>oxy</i> and <i>gen</i>; one denoting +oxydation, and the other that it generates. +In other words, it is the <i>generator of oxides</i>. It +is the element which, when united with any other +element, produces an acid, an alkali or a neutral +compound.</p> + +<p><span class="smcap">Rust.</span>—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.</p> + +<p><span class="smcap">Oxygen as a Purifier</span>.—But oxygen is also a +purifier. All low forms of animal life, like bacteria +or germs in water, succumb to free oxygen. +By <i>free oxygen</i> is meant oxygen in the form of +gas.</p> + +<p><span class="smcap">Composition of Water.</span>—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<span class='pagenum'><a name="p126" id="p126">p. 126</a></span> +an active agent. But if oxygen, in the form of +gas, can be forced through water, it will attack the +germs, and destroy them.</p> + +<p><span class="smcap">Common Air Not a Good Purifier.</span>—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.</p> + +<p><span class="smcap">Pure Oxygen.</span>—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.</p> + +<p>The mechanism usually employed for purifying +water is shown in Fig. <a href="#fig90">90</a>.</p> + +<p><span class="smcap">A Water Purifier.</span>—The case (A, Fig. <a href="#fig90">90</a>) 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<span class='pagenum'><a name="p127" id="p127">p. 127</a></span> +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).</p> + +<div class="figcenter" style="width: 351px;"> +<a id="fig90" name="fig90"></a><a href="#p127"> +<img src="images/illus-fig90.png" width="351" height="389" alt="Fig. 90. Electric Water Purifier" title="Fig. 90. Electric Water Purifier" /></a> +<span class="caption"><i>Fig. 90.</i> <span class="smcap">Electric Water Purifier</span></span> +</div> +<p class="pn"><span class='pagenum'><a name="p128" id="p128">p. 128</a></span></p> + +<p>When the water passes upwardly, the decomposed +or gaseous oxygen percolates through the +water and thus attacks the germs and destroys +them.</p> + +<p><span class="smcap">The Use of Hydrogen in Purification.</span>—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.</p> + +<p><span class="smcap">Aluminum Electrodes.</span>—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.</p> + +<p>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<span class='pagenum'><a name="p129" id="p129">p. 129</a></span> +by the oxygen, which has become entangled +in the aluminum hydrate.</p> + +<p><span class="smcap">Electric Hand Purifier.</span>—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).</p> + +<div class="figcenter" style="width: 346px;"> +<a id="fig91" name="fig91"></a><a href="#p129"> +<img src="images/illus-fig91.png" width="346" height="294" alt="Fig. 91. Portable Electric Purifier" title="Fig. 91. Portable Electric Purifier" /></a> +<span class="caption"><i>Fig. 91.</i> <span class="smcap">Portable Electric Purifier</span></span> +</div> + +<p>Let each sheet be 1½ inches wide and 5½ inches +thick. One-half inch from the upper ends of the<span class='pagenum'><a name="p130" id="p130">p. 130</a></span> +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), ½ inch wide +and ½ inch long, provided with a small hole for a +bolt. Next cut out two hard-rubber blocks (F), +each 1½ inches long, 1 inch wide and ⅜ 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 ⅛ inch thick and the outer +plates each 1/16 inch thick, use two small eighth-inch<span class='pagenum'><a name="p131" id="p131">p. 131</a></span> +bolts 1¼ 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).</p> + +<div class="figcenter" style="width: 388px;"> +<a id="fig92-95" name="fig92-95"></a><a href="#p130"> +<img src="images/illus-fig92-95.png" width="388" height="226" alt="Figs. 92-95. Details of Portable Purifier" +title="Figs. 92-95. Details of Portable Purifier" /></a> +<span class="caption"><i>Figs. 92-95.</i> <span class="smcap">Details of Portable Purifier</span></span> +</div> + +<p>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.</p> + +<p><span class="smcap">Purification and Separation of Metals.</span>—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<span class='pagenum'><a name="p132" id="p132">p. 132</a></span> +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.</p> + +<p>Other metals are treated in the same way, and +this treatment has a very wide range of usefulness.</p> + +<p><span class="smcap">Electroplating.</span>—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.</p> + +<p><span class="smcap">Plating Iron with Copper.</span>—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</p> +<p class="pn"><span class='pagenum'><a name="p133" id="p133">p. 133</a></span></p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p134" id="p134">p. 134</a></span> +to remain until it has deposited the proper thickness +of copper.</p> + +<p><span class="smcap">Direction of Current.</span>—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.</p> + +<p>The action of electroplating reverses this process +and causes the current to flow from the copper +to the iron (in this instance, the cathode).</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p135" id="p135">p. 135</a></span></p> + +<h2><a name="CHAPTER_XIV" id="CHAPTER_XIV"></a>CHAPTER XIV<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>ELECTRIC HEATING, THERMO ELECTRICITY</h3> + + +<p><span class="smcap">Generating Heat in a Wire.</span>—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.</p> + +<p><span class="smcap">Resistance of Substances.</span>—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.</p> + +<p>The following is a partial list of metals, showing +their relative conductivity:</p> + +<div class="center" style="font-size:90%"> +<table border="0" width="50%" cellpadding="1" cellspacing="0"> + <col style="width:50%;" /><col style="width:50%;" /> +<tbody valign="top"> + <tr> <td align="left">Silver</td> <td align="left"> 1.</td></tr> + <tr> <td align="left">Copper</td> <td align="left"> 1.04 to 1.09</td></tr> + <tr> <td align="left">Gold</td> <td align="left"> 1.38 to 1.41</td></tr> + <tr> <td align="left">Aluminum</td> <td align="left"> 1.64<span class='pagenum'><a name="p136" id="p136">p. 136</a></span></td></tr> + <tr> <td align="left">Zinc</td> <td align="left"> 3.79</td></tr> + <tr> <td align="left">Nickel</td> <td align="left"> 4.69</td></tr> + <tr> <td align="left">Iron</td> <td align="left"> 6.56</td></tr> + <tr> <td align="left">Tin</td> <td align="left"> 8.9</td></tr> + <tr> <td align="left">Lead</td> <td align="left">13.2</td></tr> + <tr> <td align="left">German Silver</td> <td align="left">12.2 to 15</td></tr> +</tbody> +</table> +</div> + +<p>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.</p> + +<p>This table is made up of strands of the different +metals of the same diameters and lengths, so as +to obtain their relative values.</p> + +<p><span class="smcap">Sizes of Conductors.</span>—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.</p> + +<p><span class="smcap">Comparison of Metals.</span>—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<span class='pagenum'><a name="p137" id="p137">p. 137</a></span> +the cheaper, particularly as aluminum costs fully +three times as much as copper.</p> + +<div class="figcenter" style="width: 338px;"> +<a id="fig96" name="fig96"></a><a href="#p137"> +<img src="images/illus-fig96.png" width="338" height="310" alt="Fig. 96. Simple Electric Heater" title="Fig. 96. Simple Electric Heater" /></a> +<span class="caption"><i>Fig. 96.</i> <span class="smcap">Simple Electric Heater</span></span> +</div> + +<p>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.</p> + +<p>The principle of all electric heaters is the same,<span class='pagenum'><a name="p138" id="p138">p. 138</a></span> +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.</p> + +<p><span class="smcap">A Simple Electric Heater</span>.—In Fig. <a href="#fig96">96</a> 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 ½ inch thick. +Two holes are bored through the rubber cup, and +through them are screwed two round-headed +screws (C, D), each screw being 1½ 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.</p> + +<p>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).</p> + +<p>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.</p> + + +<div class="figcenter" style="width: 331px;"> +<a id="fig97" name="fig97"></a><a href="#p138"> +<img src="images/illus-fig97.png" width="331" height="113" alt="Fig. 97. Side view of resistance device" title="Fig. 97. Side view of resistance device" /></a> +<span class="caption"><i>Fig. 97.</i> <span class="smcap">Resistance Device</span></span> +</div> + +<div class="figcenter" style="width: 328px;"> +<a id="fig98" name="fig98"></a><a href="#p138"> +<img src="images/illus-fig98.png" width="328" height="107" alt="Fig. 98. Top view of resistance device" title="Fig. 98. Top view of resistance device" /></a> +<span class="caption"><i>Fig. 98.</i> <span class="smcap">Resistance Device</span></span> +</div> + +<p><span class="smcap">How to Arrange for Quantity of Current<span class='pagenum'><a name="p139" id="p139">p. 139</a></span></span> +<span class="smcap">Used.</span>—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<span class='pagenum'><a name="p140" id="p140">p. 140</a></span> +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.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig99" name="fig99"></a><a href="#p140"> +<img src="images/illus-fig99.png" width="344" height="183" alt="Fig. 99. Plan View of Electric Iron" title="Fig. 99. Plan View of Electric Iron" /></a> +<span class="caption"><i>Fig. 99.</i> <span class="smcap">Plan View of Electric Iron</span></span> +</div> + + +<p><span class="smcap">An Electric Iron.</span>—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<span class='pagenum'><a name="p141" id="p141">p. 141</a></span> +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.</p> + +<div class="figcenter" style="width: 347px;"> +<a id="fig100" name="fig100"></a><a href="#p141"> +<img src="images/illus-fig100.png" width="347" height="188" alt="Fig. 100. Section of Electric Iron" title="Fig. 100. Section of Electric Iron" /></a> +<span class="caption"><i>Fig. 100.</i> <span class="smcap">Section of Electric Iron</span></span> +</div> + +<p>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.</p> + +<p><span class="smcap">Thermo Electricity.</span>—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<span class='pagenum'><a name="p142" id="p142">p. 142</a></span> +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.</p> + +<p><span class="smcap">Converting Heat Directly Into Electricity.</span>—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.</p> + +<p><span class="smcap">Metals; Electric Positive-Negative.</span>—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.</p> + +<p>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<span class='pagenum'><a name="p143" id="p143">p. 143</a></span> +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.</p> + +<p>The two metals most available, which are thus +farthest apart in the scale of positive-negative +relation, are bismuth and antimony.</p> + +<div class="figcenter" style="width: 345px;"> +<a id="fig101" name="fig101"></a><a href="#p143"> +<img src="images/illus-fig101.png" width="345" height="112" alt="Fig. 101. Thermo-Electric Couple" title="Fig. 101. Thermo-Electric Couple" /></a> +<span class="caption"><i>Fig. 101.</i> <span class="smcap">Thermo-Electric Couple</span></span> +</div> + +<p>In Fig. <a href="#fig101">101</a> 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.</p> + +<p><span class="smcap">Thermo-Electric Couples.</span>—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.</p> + +<p>One thing must be observed: A current will<span class='pagenum'><a name="p144" id="p144">p. 144</a></span> +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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p145" id="p145">p. 145</a></span></p> + +<h2><a name="CHAPTER_XV" id="CHAPTER_XV"></a>CHAPTER XV<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>ALTERNATING CURRENTS, CHOKING COILS, TRANSFORMERS, CONVERTERS AND RECTIFIERS</h3> + + +<p><span class="smcap">Direct Current.</span>—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 <i>direct</i> current. This direct +current is a natural one if generated by a +cell.</p> + +<p><span class="smcap">Alternating Current.</span>—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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p146" id="p146">p. 146</a></span> +coil, transformers, rectifiers and converters, +may be explained.</p> + +<p><span class="smcap">The Magnetic Field.</span>—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.</p> + +<div class="figcenter" style="width: 341px;"> +<a id="fig102" name="fig102"></a><a href="#p146"> +<img src="images/illus-fig102.png" width="341" height="89" alt="Fig. 102. Cutting a Magnetic Field" title="Fig. 102. Cutting a Magnetic Field" /></a> +<span class="caption"><i>Fig. 102.</i> <span class="smcap">Cutting a Magnetic Field</span></span> +</div> + +<p>To explain this, study Fig. <a href="#fig102">102</a>, 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).</p> + +<p><span class="smcap">Action of the Magnetized Wire.</span>—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<span class='pagenum'><a name="p147" id="p147">p. 147</a></span> +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.</p> + +<p><span class="smcap">The Movement of a Current in a Charged Wire.</span>—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.</p> + +<p>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.</p> + +<p>Let us illustrate this by showing the four positions +of the revolving loop. In Fig. <a href="#fig103-106">103</a> 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<span class='pagenum'><a name="p148" id="p148">p. 148</a></span> +electrical impulse, is the most intense. The current +used flows in the direction of the darts (C) +or to the left.</p> + +<p>In Fig. <a href="#fig103-106">104</a>, 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. <a href="#fig103-106">105</a>, there is no current in +the loop, or, if there is any, it moves faintly in the +direction of the dart (E).</p> + +<div class="figcenter" style="width: 360px;"> +<a id="fig103-106" name="fig103-106"></a><a href="#p148"> +<img src="images/illus-fig103-106.png" width="360" height="174" alt="Fig. 13-106. Illustrating Alternations" title="Fig. 103-106. Illustrating Alternations" /></a> +<span class="caption"><i>Fig. 103-106.</i> <span class="smcap">Illustrating Alternations</span></span> +</div> + +<p><span class="smcap">Current Reversing Itself.</span>—When the loop +reaches its lowest point (Fig. <a href="#fig103-106">106</a>) it again comes +within the magnetic field and the current commences +to flow back to its original direction, as +shown by darts (C)</p> +<p class="pn"><span class='pagenum'><a name="p149" id="p149">p. 149</a></span></p> + +<p><span class="smcap">Self-Induction.</span>—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.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 353px;"> +<a id="fig107" name="fig107"></a><a href="#p149"> +<img src="images/illus-fig107.png" width="353" height="94" alt="Fig. 107. Form for Increasing Alternations" title="Fig. 107. Form for Increasing Alternations" /></a> +<span class="caption"><i>Fig. 107.</i> <span class="smcap">Form for Increasing Alternations</span></span> +</div> + +<div class="figcenter" style="width: 353px;"> +<a id="fig108" name="fig108"></a><a href="#p149"> +<img src="images/illus-fig108.png" width="353" height="107" alt="Fig. 108. Form for Increasing Alternations" title="Fig. 108. Form for Increasing Alternations" /></a> +<span class="caption"><i>Fig. 108.</i> <span class="smcap">Form for Increasing Alternations</span></span> +</div> + +<p>Instead, therefore, of using a single loop, we +may make four loops (Fig. <a href="#fig107">107</a>), 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,<span class='pagenum'><a name="p150" id="p150">p. 150</a></span> +as in Fig. <a href="#fig108">108</a>. 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.</p> + +<p>Let us now illustrate the manner of connecting +up and building the dynamo, so as to derive the +current from it. In Fig. <a href="#fig109">109</a>, 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).</p> + +<div class="figcenter" style="width: 346px;"> +<a id="fig109" name="fig109"></a><a href="#p150"> +<img src="images/illus-fig109.png" width="346" height="93" alt="Fig. 109. Connection of Alternating Dynamo Armature" title="Fig. 109. Connection of Alternating Dynamo Armature" /></a> +<span class="caption"><i>Fig. 109.</i> <span class="smcap">Connection of Alternating Dynamo Armature</span></span> +</div> + +<p><span class="smcap">Brushes in a Direct-Current Dynamo.</span>—The +object of the brushes in the direct-current dynamo, +in connection with a commutator, is to convert +this <i>inductance</i> of the wire, or this effort to reverse +itself into a current which will go in one<span class='pagenum'><a name="p151" id="p151">p. 151</a></span> +direction all the time, and not in both directions +alternately.</p> + +<p>To explain this more fully attention is directed +to Figs. <a href="#fig110">110</a> and <a href="#fig111">111</a>. 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. <a href="#fig110">110</a>, 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.</p> + +<div class="figcenter" style="width: 346px;"> +<a id="fig110" name="fig110"></a><a href="#p151"> +<img src="images/illus-fig110.png" width="346" height="214" alt="Fig. 110. Direct Current Dynamo" title="Fig. 110. Direct Current Dynamo" /></a> +<span class="caption"><i>Fig. 110.</i> <span class="smcap">Direct Current Dynamo</span></span> +</div> + +<p>One brush (D) contacts with the positive terminal +of the commutator and the other brush<span class='pagenum'><a name="p152" id="p152">p. 152</a></span> +(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. <a href="#fig110">110</a>). +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<span class='pagenum'><a name="p153" id="p153">p. 153</a></span> +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).</p> + +<div class="figcenter" style="width: 348px;"> +<a id="fig111" name="fig111"></a><a href="#p153"> +<img src="images/illus-fig111.png" width="348" height="210" alt="Fig. 111. Circuit Wires in Direct Current Dynamo" title="Fig. 111. Circuit Wires in Direct Current Dynamo" /></a> +<span class="caption"><i>Fig. 111.</i> <span class="smcap">Circuit Wires in Direct Current Dynamo</span></span> +</div> + +<p>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. <a href="#fig110">110</a>, 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. <a href="#fig111">111</a>. Here the current +in wire C flows <i>into</i> the negative (-) terminal, +and <i>from</i> 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).</p> + +<p>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.</p> + +<p><span class="smcap">Alternating Positive and Negative Poles.<span class='pagenum'><a name="p154" id="p154">p. 154</a></span></span>—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. <a href="#fig112">112</a>), 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.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig112" name="fig112"></a><a href="#p154"> +<img src="images/illus-fig112.png" width="344" height="105" alt="Fig. 112. Alternating Polarity Lines" title="Fig. 112. Alternating Polarity Lines" /></a> +<span class="caption"><i>Fig. 112.</i> <span class="smcap">Alternating Polarity Lines</span></span> +</div> + +<p class="pn"><span class='pagenum'><a name="p155" id="p155">p. 155</a></span></p> + +<p><span class="smcap">How an Alternating Dynamo Is Made.</span>—It is +now necessary to apply these principles in the construction +of an alternating-current machine. Fig. +<a href="#fig113">113</a> is a diagram representing the various elements, +and the circuiting.</p> + +<div class="figcenter" style="width: 341px;"> +<a id="fig113" name="fig113"></a><a href="#p155"> +<img src="images/illus-fig113.png" width="341" height="268" alt="Fig. 113. Alternating Current Dynamo" title="Fig. 113. Alternating Current Dynamo" /></a> +<span class="caption"><i>Fig. 113.</i> <span class="smcap">Alternating Current Dynamo</span></span> +</div> + +<p>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).</p> + +<p>The shaft (C) also carries two pulleys with +rings thereon. One of these rings (F) is for one<span class='pagenum'><a name="p156" id="p156">p. 156</a></span> +end of the armature winding, and the other ring +(G) for the other end of the armature wire.</p> + +<p><span class="smcap">The Windings.</span>—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.</p> + +<p><span class="smcap">The Armature Wires.</span>—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.</p> + +<p><span class="smcap">Choking Coil.</span>—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<span class='pagenum'><a name="p157" id="p157">p. 157</a></span> +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.</p> + +<div class="figcenter" style="width: 342px;"> +<a id="fig114" name="fig114"></a><a href="#p157"> +<img src="images/illus-fig114.png" width="342" height="116" alt="Fig. 114. Choking Coil" title="Fig. 114. Choking Coil" /></a> +<span class="caption"><i>Fig. 114.</i> <span class="smcap">Choking Coil</span></span> +</div> + +<p>In Fig. <a href="#fig114">114</a>, A is the choking coil and B an arc<span class='pagenum'><a name="p158" id="p158">p. 158</a></span> +lamp, connected up, in series, with the choking +coil.</p> + +<p><span class="smcap">The Transformer.</span>—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.</p> + +<div class="figcenter" style="width: 337px;"> +<a id="fig115" name="fig115"></a><a href="#p158"> +<img src="images/illus-fig115.png" width="337" height="165" alt="Fig. 115. A Transformer" title="Fig. 115. A Transformer" /></a> +<span class="caption"><i>Fig. 115.</i> <span class="smcap">A Transformer</span></span> +</div> + +<p>In Fig. <a href="#fig115">115</a> 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<span class='pagenum'><a name="p159" id="p159">p. 159</a></span> +(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.</p> + +<p><span class="smcap">How the Voltage Is Determined.</span>—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.</p> + +<p>If, on the other hand, 400 volts would be required, +the secondary should have 200 turns in +the winding.</p> + +<p><span class="smcap">Voltage and Amperage in Transformers.</span>—It +must not be understood that, by increasing the +voltage in this way, we are getting that much<span class='pagenum'><a name="p160" id="p160">p. 160</a></span> +more electricity. If the primary coil, with 100 +turns, produces a current of 200 volts and 50 amperes, +which would be 200 × 50 = 10,000 watts, +and the secondary coil has 50 turns, we shall have +100 volts and 100 amperes: 100 (V.) × 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) +× 25 (amperes) also gives 10,000 watts.</p> + +<p>Necessarily, there will be some loss, but the +foregoing is offered as the theoretical basis of +calculation.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p161" id="p161">p. 161</a></span></p> + + + + +<h2><a name="CHAPTER_XVI" id="CHAPTER_XVI"></a>CHAPTER XVI<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>ELECTRIC LIGHTING</h3> + + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>It would be difficult and tedious to follow out the<span class='pagenum'><a name="p162" id="p162">p. 162</a></span> +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.</p> + +<p>Reference has been made in a previous chapter +to what is called the <i>Electric Arc</i>, produced by +slightly separated conductors, across which the +electric current jumps, producing the brilliantly +lighted area.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p163" id="p163">p. 163</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p164" id="p164">p. 164</a></span> +earth, a form of which is shown in Fig. <a href="#fig116">116</a>.</p> + +<p>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.</p> + +<div class="figcenter" style="width: 344px;"> +<a id="fig116" name="fig116"></a><a href="#p164"> +<img src="images/illus-fig116.png" width="344" height="287" alt="Fig. 116. Parallel Carbons." title="Fig. 116. Parallel Carbons." /></a> +<span class="italcaption">Fig. 116. Parallel Carbons.</span> +</div> + +<p>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.</p> + +<p>In the direct or continuous current the movement<span class='pagenum'><a name="p165" id="p165">p. 165</a></span> +is in one direction only, and as a result the +positive electrode is eaten away twice as fast as +the negative.</p> + +<p>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.</p> + +<p>Arc lights are produced by what is called the +<i>series current</i>. This means that the lamps are all +connected in a single line. This is illustrated by +reference to Fig. <a href="#fig117">117</a>, 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.</p> + +<div class="figcenter" style="width: 356px;"> +<a id="fig117" name="fig117"></a><a href="#p165"> +<img src="images/illus-fig117.png" width="356" height="154" alt="Fig. 117. Arc-Lighting Circuit." title="Fig. 117. Arc-Lighting Circuit." /></a> +<span class="italcaption">Fig. 117. Arc-Lighting Circuit.</span> +</div> + +<p>A high voltage is necessary in order to cause the +current to leap across the gap made by the separation +of the electrodes</p> +<p class="pn"><span class='pagenum'><a name="p166" id="p166">p. 166</a></span></p> + +<p><span class="smcap">The Incandescent System.</span>—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.</p> + +<div class="figcenter" style="width: 352px;"> +<a id="fig118" name="fig118"></a><a href="#p166"> +<img src="images/illus-fig118.png" width="352" height="81" alt="Fig 118. Interrupted Conductor." title="Fig 118. Interrupted Conductor." /></a> +<span class="italcaption">Fig. 118. Interrupted Conductor.</span> +</div> + +<p>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.</p> + +<p>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. <a href="#fig118">118</a>, it +is obvious that the small wire would not be large +enough to carry the current.</p> + +<p>The result would be that the small connection<span class='pagenum'><a name="p167" id="p167">p. 167</a></span> +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. <a href="#fig117">117</a>.</p> + +<div class="figcenter" style="width: 348px;"> +<a id="fig119" name="fig119"></a><a href="#p167"> +<img src="images/illus-fig119.png" width="348" height="177" alt="Fig. 119. Incandescent Circuit." title="Fig. 119. Incandescent Circuit." /></a> +<span class="italcaption">Fig. 119. Incandescent Circuit.</span> +</div> + +<p>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.</p> + +<p>This knowledge resulted in an entirely new system +of wiring up the lamps in a circuit. This is +explained in Fig. <a href="#fig119">119</a>. In this figure A represents +the dynamo, B, B the brushes, C, D the two line<span class='pagenum'><a name="p168" id="p168">p. 168</a></span> +wires, E the lamps, and F the short-circuiting +wires between the two main conductors +C, D.</p> + +<p>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.</p> + +<p>This is called the <i>multiple</i> 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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p169" id="p169">p. 169</a></span> +metal there is a point at which it will fuse, and +thus the lamp is destroyed.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="smcap">Vapor Lamps</span>.—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<span class='pagenum'><a name="p170" id="p170">p. 170</a></span> +the vapor which produces a greenish light, and +owing to that peculiar color, has not met with much +success.</p> + +<p>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.</p> + +<p><span class="smcap">Directions for Improvements</span>.—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.</p> + +<p>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.</p> + +<p>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</p> +<p class="pn"><span class='pagenum'><a name="p171" id="p171">p. 171</a></span></p> + +<p class="center"><i>Curious Superstitions Concerning Electricity</i></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p172" id="p172">p. 172</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>Among the Romans Jupiter thus hurled forth +his wrath; and among many ancient people, even<span class='pagenum'><a name="p173" id="p173">p. 173</a></span> +down to the time of Charlemagne, any space +struck by lightning was considered sacred, and +made consecrated ground.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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:</p> + +<p>"Most men are ignorant of that secret, which, +by close observation of the heavens, deep scholars +and principal men of learning have found out,<span class='pagenum'><a name="p174" id="p174">p. 174</a></span> +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."</p> + + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p175" id="p175">p. 175</a></span></p> + +<h2><a name="CHAPTER_XVII" id="CHAPTER_XVII"></a>CHAPTER XVII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>POWER, AND VARIOUS OTHER ELECTRICAL MANIFESTATIONS</h3> + + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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,<span class='pagenum'><a name="p176" id="p176">p. 176</a></span> +one of them is turned, so that the north pole of +one is opposite the south pole of the other, they +will draw together.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>Attention is called to Figs. <a href="#fig120">120</a> and <a href="#fig121">121</a>. Let us +assume that the field magnets A, A are the positives,<span class='pagenum'><a name="p177" id="p177">p. 177</a></span> +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.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> +<td align="center"> +<a id="fig120" name="fig120"></a><a href="#p177"> +<img src="images/illus-fig120.png" width="179" height="182" alt="Fig. 120. Action of Magnets in a Dynamo" title="Fig. 120. Action of Magnets in a Dynamo" /></a> +</td> +<td align="center"> +<a id="fig121" name="fig121"></a><a href="#p177"> +<img src="images/illus-fig121.png" width="176" height="182" alt="Fig. 121. Action of Magnets in a Dynamo" title="Fig. 121. Action of Magnets in a Dynamo" /></a> +</td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 120-121.</i> <span class="smcap">Action of Magnets in a Dynamo</span></span> + </td> + </tr> +</tbody> +</table> + +</div> + +<p>Now in the particular position of the revolving +armature, in Fig. <a href="#fig120">120</a>, 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. <a href="#fig121">121</a>, 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</p> +<p class="pn"><span class='pagenum'><a name="p178" id="p178">p. 178</a></span></p> + +<p>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. <a href="#fig122">122</a>, 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. <a href="#fig123">123</a>, when the complete cycle is nearly finished, +the positives are again approaching each +other and the negatives moving together.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> +<td align="center"> +<a id="fig122" name="fig122"></a><a href="#p178"> +<img src="images/illus-fig122.png" width="179" height="183" alt="Fig. 122. Cycle Action in Dynamo" title="Fig. 122. Cycle Action in Dynamo" /></a> +</td> +<td align="center"> +<a id="fig123" name="fig123"></a><a href="#p178"> +<img src="images/illus-fig123.png" width="173" height="181" alt="Fig. 123. Cycle Action in Dynamo" title="Fig. 123. Cycle Action in Dynamo" /></a> +</td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 122-123.</i> <span class="smcap">Cycle Action in Dynamo</span></span> + </td> + </tr> +</tbody> +</table> + +</div> +<p>In this manner, at every point, the sets of magnets +are compelled to move against their magnetic +pull. This explains the dynamo.</p> + +<p>Now take up the cycle of the motor, and note in +Fig. <a href="#fig124">124</a> that the negative magnets D of the armature +are closely approaching the positive and negative<span class='pagenum'><a name="p179" id="p179">p. 179</a></span> +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. <a href="#fig120">120</a>.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> +<td align="center"> +<a id="fig124" name="fig124"></a><a href="#p179"> +<img src="images/illus-fig124.png" width="178" height="192" alt="Fig. 124. Action of Magnets in Motor" title="Fig. 124. Action of Magnets in Motor" /></a> +</td> +<td align="center"> +<a id="fig125" name="fig125"></a><a href="#p179"> +<img src="images/illus-fig125.png" width="175" height="192" alt="Fig. 125. Action of Magnets in Motor" title="Fig. 125. Action of Magnets in Motor" /></a> +</td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 124-125.</i> <span class="smcap">Action of Magnets in Motor</span></span> + </td> + </tr> +</tbody> +</table> +</div> +<p>When the pole pieces of the magnets C, D are +about to pass magnets A, B, as shown in Fig. <a href="#fig125">125</a>, +it is necessary to change the polarities of the armature +magnets C, D; so that by reference to Fig. +<a href="#fig126">126</a>, 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. +<a href="#fig125">125</a>), where the pull on one side, and the push on<span class='pagenum'><a name="p180" id="p180">p. 180</a></span> +the other are again the same, and the last Figure +127 shows the cycle nearly completed.</p> + +<p>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.</p> + +<div class="center"> +<table border="0" width="390" cellpadding="0" cellspacing="0"> +<tbody valign="top"> + <tr> +<td align="center"> +<a id="fig126" name="fig126"></a><a href="#p180"> +<img src="images/illus-fig126.png" width="179" height="181" alt="Fig. 126. Positions of Magnets in Motor" title="Fig. 126. Positions of Magnets in Motor" /></a> +</td> +<td align="center"> +<a id="fig127" name="fig127"></a><a href="#p180"> +<img src="images/illus-fig127.png" width="168" height="181" alt="Fig. 127. Positions of Magnets in Motor" title="Fig. 127. Positions of Magnets in Motor" /></a> +</td> + </tr> + <tr> + <td class="tdnwc" colspan="2"> +<span class="caption"><i>Figs. 126-127.</i> <span class="smcap"> Positions of Magnets in Motor</span></span> + </td> + </tr> +</tbody> +</table> +</div> +<p>The great advantage of electrical power is not in<span class='pagenum'><a name="p181" id="p181">p. 181</a></span> +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.</p> + + +<p class="center"><i>Transmission of Energy</i></p> + +<p>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.</p> + +<p>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.</p> + +<p><span class="smcap">The Transformer.</span>—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</p> +<p class="pn"><span class='pagenum'><a name="p182" id="p182">p. 182</a></span></p> + +<p>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.</p> + +<p><span class="smcap">Electric Furnaces.</span>—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.</p> + +<p>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.</p> + +<p><span class="smcap">Welding By Electricity.</span>—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<span class='pagenum'><a name="p183" id="p183">p. 183</a></span> +immense hammers, weighing tons, must be +employed.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p184" id="p184">p. 184</a></span></p> + +<h2><a name="CHAPTER_XVIII" id="CHAPTER_XVIII"></a>CHAPTER XVIII<span class="totoc"><a href="#toc">ToC</a></span></h2> +<h3>X-RAY, RADIUM, AND THE LIKE</h3> + + +<p>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 <i>Actinic</i> 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.</p> + +<p>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.</p> + +<p>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</p> +<p class="pn"><span class='pagenum'><a name="p185" id="p185">p. 185</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>This discovery was but the forerunner of a still +more important development, namely, the discovery +of <i>radium</i>. The actual finding of the metal<span class='pagenum'><a name="p186" id="p186">p. 186</a></span> +was preceded by the knowledge that certain minerals, +and water, as well, possessed the property +of radio-activity.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="p187" id="p187">p. 187</a></span> +turned to brown and others into violet or purple +tinges.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>It is not many years since the X-rays were discovered,<span class='pagenum'><a name="p188" id="p188">p. 188</a></span> +and the first announcement was concerning +its wonderful healing powers.</p> + +<p>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 <i>m</i> and the +<i>n</i> rays, as well as many others, each having some +peculiar qualification.</p> + +<p>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.</p> + +<p>It is, indeed, a study which is so broad that it +has no limitations, and a field which never will be +exhausted.</p> + +<p class="center">THE END</p> +<hr class="chapter" /> +<p class="chapter"><span class='pagenum'><a name="p189" id="p189">p. 189</a></span></p> + +<h3><a name="GLOSSARY_OF_WORDS" id="GLOSSARY_OF_WORDS"></a>GLOSSARY OF WORDS +USED IN TEXT OF THIS VOLUME<span class="totoc"><a href="#toc">ToC</a></span></h3> + +<div class="index"> +<table border="0" cellpadding="2" width="76%" cellspacing="0" summary="Glossary"> +<col style="width:15%;" /> +<col style="width:85%;" /> +<tbody valign="top"> + +<tr><td align='left'>Acid.</td><td align='left'>Accumulator material is sulphuric acid, diluted with +water.</td></tr> +<tr><td align='left'>Active Material.</td><td align='left'>That part of the material in accumulator plates +which is acted upon by the electric current.</td></tr> +<tr><td align='left'>Accumulator.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Aerial Wire, or Conductor.</td><td align='left'>The wire which, in wireless telegraphy, is carried up +into the air to connect the antennæ with the receiving and sending apparatus.</td></tr> +<tr><td align='left'>Alarm, Burglar.</td><td align='left'>A circulating system in a building, connected up +with a bell or other signaling means.</td></tr> +<tr><td align='left'>Alloy.</td><td align='left'>A mixture of two or more metals; as copper and +zinc to make brass; nickel and zinc to form German silver.</td></tr> +<tr><td align='left'>Alternating Current.</td><td align='left'>A current which goes back and forth in opposite directions, +unlike a direct current which flows continuously +in one direction over a wire.</td></tr> +<tr><td align='left'>Alternation.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Amber.</td><td align='left'>A resin, yellow in color, which when rubbed with a +cloth, becomes excited and gives forth negative +<span class='pagenum'><a name="p190" id="p190">p. 190</a></span>electricity.</td></tr> +<tr><td align='left'>Ammeter.</td><td align='left'>An instrument for measuring the quantity or flow of +electricity.</td></tr> +<tr><td align='left'>Ampere.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Annunciator.</td><td align='left'>A device which indicates or signals a call given +from some distant point.</td></tr> +<tr><td align='left'>Anode.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Arc.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Armature.</td><td align='left'>A body of iron, or other suitable metal, which is in +the magnetic field of a magnet.</td></tr> +<tr><td align='left'>Armature Bar.</td><td align='left'>The piece which holds the armature. Also one of a +series of bars which form the conductors in armature +windings.</td></tr> +<tr><td align='left'>Armature Coil.</td><td align='left'>The winding around an armature, or around the core +of an armature.</td></tr> +<tr><td align='left'>Armature Core.</td><td align='left'>The part in a dynamo or motor which revolves, and +on which the wire coils are wound.</td></tr> +<tr><td align='left'>Astatic (Galvanometer).</td><td align='left'>That which has no magnetic action to direct or divert +anything exterior to it.</td></tr> +<tr><td align='left'>Atom.</td><td align='left'>The ultimate particle of an elementary substance.</td></tr> +<tr><td align='left'>Attraction.</td><td align='left'>That property of matter which causes particles to +adhere, or cohere, to each other. It is known +<span class='pagenum'><a name="p191" id="p191">p. 191</a></span>under a variety of terms, such as gravitation, chemical +affinity, electro-magnetism and dynamic attraction.</td></tr> +<tr><td align='left'>Automatic Cut-out.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Bath.</td><td align='left'>In electroplating, the vessel or tank which holds the +electroplating solution.</td></tr> +<tr><td align='left'>Battery.</td><td align='left'>A combination of two or more cells.</td></tr> +<tr><td align='left'>Battery, Dry.</td><td align='left'>A primary battery in which the electrolyte is made +in a solid form.</td></tr> +<tr><td align='left'>Battery, Galvanic.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Battery, Storage.</td><td align='left'>A battery which accumulates electricity generated by +a primary battery or a generator.</td></tr> +<tr><td align='left'>Brush.</td><td align='left'>A term applied to the conducting medium that bears +against the cylindrical surface of a commutator.</td></tr> +<tr><td align='left'>Buzzer.</td><td align='left'>An electric call produced by a rapidly moving armature +of an electro-magnet.</td></tr> +<tr><td align='left'>Cable.</td><td align='left'>A number of wires or conductors assembled in one +strand.</td></tr> +<tr><td align='left'>Candle-power.</td><td align='left'>The amount of light given by the legal-standard candle. +This standard is a sperm candle, which burns +two grains a minute.</td></tr> +<tr><td align='left'>Capacity.</td><td align='left'>The carrying power of a wire or circuit, without +heating. When heated there is an overload, or the +<i>capacity</i> of the wire is overtaxed.</td></tr> +<tr><td align='left'>Capacity, Storage.</td><td align='left'>The quantity of electricity in a secondary battery +when fully charged, usually reckoned in ampere +<span class='pagenum'><a name="p192" id="p192">p. 192</a></span>hours.</td></tr> +<tr><td align='left'>Carbon.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Cell, Electrolytic.</td><td align='left'>A vessel containing an electrolyte for electroplating +purposes.</td></tr> +<tr><td align='left'>Charge.</td><td align='left'>The quantity of electricity on the surface of a body +or conductor.</td></tr> +<tr><td align='left'>Chemical Change.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Choking Coil.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Counter-electromotive Force.</td><td align='left'>Cells which are inserted in opposition to a battery +to reduce high voltage.</td></tr> +<tr><td align='left'>Circuit, Astatic.</td><td align='left'>A circuit in an instrument so wound that the earth's +magnetism will not affect it.</td></tr> +<tr><td align='left'>Circuit Breaker.</td><td align='left'>Any instrument in a circuit which cuts out or interrupts +the flow of a current.</td></tr> +<tr><td align='left'>Circuit, External.</td><td align='left'>A current flows through a wire or conductor, and +also along the air outside of the conductor, the +latter being the <i>external circuit.</i></td></tr> +<tr><td align='left'>Circuit Indicator.</td><td align='left'>An instrument, like a galvanometer, that shows the +direction in which a current is flowing through a +<span class='pagenum'><a name="p193" id="p193">p. 193</a></span>conductor.</td></tr> +<tr><td align='left'>Circuit, Return.</td><td align='left'>Usually the ground return, or the negative wire from +a battery.</td></tr> +<tr><td align='left'>Circuit, Short.</td><td align='left'>Any connection between the mains or parallel lines +of a circuit which does not go through the apparatus +for which the circuit is intended.</td></tr> +<tr><td align='left'>Coherer.</td><td align='left'>A tube, or other structure, containing normally high +resistance particles which form a path or bridge +between the opposite terminals of a circuit.</td></tr> +<tr><td align='left'>Coil.</td><td align='left'>A wire, usually insulated, wound around a spool.</td></tr> +<tr><td align='left'>Coil, Induction.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Coil, Resistance.</td><td align='left'>A coil so wound that it will offer a resistance to a +steady current, or reduce the flow of electricity.</td></tr> +<tr><td align='left'>Commutator.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Compass.</td><td align='left'>An apparatus which indicates the direction or flow +of the earth's magnetism.</td></tr> +<tr><td align='left'>Condenser.</td><td align='left'>A device for storing up electro-static charges.</td></tr> +<tr><td align='left'>Conductance.</td><td align='left'>That quality of a conductor to carry a current of +electricity, dependent on its shape for the best +results.</td></tr> +<tr><td align='left'>Conduction.</td><td align='left'>The transmission of a current through a rod, wire or +conductor.</td></tr> +<tr><td align='left'>Conductivity.</td><td align='left'>That quality which has reference to the capacity to +conduct a current.</td></tr> +<tr><td align='left'>Conductor.</td><td align='left'>Any body, such as a bar, rod, wire, or machine, +which will carry a current.</td></tr> +<tr><td align='left'>Connector.</td><td align='left'>A binding post, clamp, screw, or other means to hold +<span class='pagenum'><a name="p194" id="p194">p. 194</a></span>the end of a wire, or electric conductor.</td></tr> +<tr><td align='left'>Contact.</td><td align='left'>To unite any parts in an electric circuit.</td></tr> +<tr><td align='left'>Controller.</td><td align='left'>The handle of a switchboard, or other contact making +and breaking means in a circuit.</td></tr> +<tr><td align='left'>Converter.</td><td align='left'>An induction coil in an alternating circuit for changing +potential difference, such as high alternating +voltage into low direct current voltage.</td></tr> +<tr><td align='left'>Convolution.</td><td align='left'>To wind like a clock spring.</td></tr> +<tr><td align='left'>Core.</td><td align='left'>The inner portion of an electro-magnet. The inside +part of an armature wound with wire.</td></tr> +<tr><td align='left'>Core, Laminated.</td><td align='left'>When the core is built up of a number of separate +pieces of the same material, but not insulated from +each other.</td></tr> +<tr><td align='left'>Coulomb.</td><td align='left'>The unit of electrical quantity. It is the quantity +passed by a current of one ampere intensity in +one second of time.</td></tr> +<tr><td align='left'>Couple, Electric.</td><td align='left'>Two or more electrodes in a liquid to produce an +electric force.</td></tr> +<tr><td align='left'>Current, Alternating.</td><td align='left'>A natural current produced by the action of electro-magnets. +It is a succession of short impulses in +opposite directions.</td></tr> +<tr><td align='left'>Current, Constant.</td><td align='left'>A current which is uniformly maintained in a steady +stream.</td></tr> +<tr><td align='left'>Current, Induced.</td><td align='left'>A current produced by electro-dynamic induction.</td></tr> +<tr><td align='left'>Current Meter.</td><td align='left'>An apparatus for indicating the strength of a current. +An ammeter.</td></tr> +<tr><td align='left'>Current, Oscillating.</td><td align='left'>A current which periodically alternates.</td></tr> + +<tr><td align='left'>Current, Periodic.</td><td align='left'>A periodically varying current strength.</td></tr> + +<tr><td align='left'>Current, Undulating.</td><td align='left'>A current which has a constant direction, but has a +<span class='pagenum'><a name="p195" id="p195">p. 195</a></span>continuously varying strength.</td></tr> +<tr><td align='left'>Decomposition.</td><td align='left'>The separation of a liquid, such as an electrolyte, +into its prime elements, either electrically or otherwise.</td></tr> +<tr><td align='left'>Deflection.</td><td align='left'>The change of movement of a magnetic needle out of +its regular direction of movement.</td></tr> +<tr><td align='left'>Demagnetization.</td><td align='left'>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 <i>demagnetized</i>. 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.</td></tr> +<tr><td align='left'>Density.</td><td align='left'>The quantity of an electric charge in a conductor +or substance.</td></tr> +<tr><td align='left'>Depolarization.</td><td align='left'>The removal of magnetism from a permanent magnet, +or a horse-shoe magnet, for instance. It is +generally accomplished by applying heat.</td></tr> +<tr><td align='left'>Deposition, Electrolysis.</td><td align='left'>The act of carrying metal from one pole of a cell +to another pole, as in electroplating.</td></tr> +<tr><td align='left'>Detector.</td><td align='left'>Mechanism for indicating the presence of a current +in a circuit.</td></tr> +<tr><td align='left'>Diaphragm.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Dielectric.</td><td align='left'>A non-conductor for an electric current, but through +which electro-static induction will take place. For +example: glass and rubber are dielectrics.</td></tr> +<tr><td align='left'>Discharge.</td><td align='left'>The current flowing from an accumulator.</td></tr> +<tr><td align='left'>Disintegration.</td><td align='left'>The breaking up of the plate or active material.</td></tr> +<tr><td align='left'>Disruptive.</td><td align='left'>A static discharge passing through a dielectric.</td></tr> +<tr><td align='left'>Duplex Wire.</td><td align='left'>A pair of wires usually twisted together and insulated +from each other to form the conducting +<span class='pagenum'><a name="p196" id="p196">p. 196</a></span>circuit of a system.</td></tr> +<tr><td align='left'>Dynamic Electricity.</td><td align='left'>The term applied to a current flowing through a +wire.</td></tr> +<tr><td align='left'>Dynamo.</td><td align='left'>An apparatus, consisting of core and field magnets, +which, when the core is turned, will develop a +current of electricity.</td></tr> +<tr><td align='left'>Earth Returns.</td><td align='left'>Instead of using two wires to carry a circuit, the +earth is used for what is called the <i>return</i> circuit.</td></tr> +<tr><td align='left'>Efficiency.</td><td align='left'>The total electrical energy produced, in which that +wasted, as well as that used, is calculated.</td></tr> +<tr><td align='left'>Elasticity.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Electricity, Atmospheric.</td><td align='left'>Lightning, and, in short, any current or electrical +impulse, like wireless telegraphic waves, is called +<i>atmospheric</i>.</td></tr> +<tr><td align='left'>Electricity, Voltaic.</td><td align='left'>Electricity with a low potentiality and large current +density.</td></tr> +<tr><td align='left'>Electrification.</td><td align='left'>The process of imparting a charge of electricity to +any body.</td></tr> +<tr><td align='left'>Electro-chemistry.</td><td align='left'>The study of which treats of electric and chemical +forces, such as electric plating, electric fusing, +electrolysis, and the like.</td></tr> +<tr><td align='left'>Electrode.</td><td align='left'>The terminals of a battery, or of any circuit; as, for +instance, an arc light.</td></tr> +<tr><td align='left'>Electrolyte.</td><td align='left'>Any material which is capable of being decomposed by +an electric current.</td></tr> +<tr><td align='left'>Electro-magnetism.</td><td align='left'>Magnetism which is created by an electric current.</td></tr> +<tr><td align='left'>Electrometer.</td><td align='left'>An instrument for measuring static electricity, differing +from a galvanometer, which measures a current +in a wire that acts on the magnetic needle +<span class='pagenum'><a name="p197" id="p197">p. 197</a></span>of the galvanometer.</td></tr> +<tr><td align='left'>Electro-motive Force.</td><td align='left'>(E. M. F.) Voltage, which is the measure or unit +of e. m. f.</td></tr> +<tr><td align='left'>Electroscope.</td><td align='left'>A device for indicating not only the presence of +electricity, but whether it is positive or negative.</td></tr> +<tr><td align='left'>Electro-static Accumulator.</td><td align='left'>Surfaces separated by a dielectric for opposite charging +of the surface.</td></tr> +<tr><td align='left'>Element.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Excessive Charge.</td><td align='left'>A storage battery charged at too high a rate.</td></tr> +<tr><td align='left'>Excessive Discharge.</td><td align='left'>A storage battery discharged at too high a rate.</td></tr> +<tr><td align='left'>Excessive Overcharge.</td><td align='left'>Charging for too long a time.</td></tr> +<tr><td align='left'>Exciter.</td><td align='left'>A generator, either a dynamo or a battery, for exciting +the field of a dynamo.</td></tr> +<tr><td align='left'>Exhaustive Discharge.</td><td align='left'>An excessive over-discharge of an accumulator.</td></tr> +<tr><td align='left'>F.</td><td align='left'>The sign used to indicate the heat term Fahrenheit.</td></tr> +<tr><td align='left'>Fall of Voltage.</td><td align='left'>The difference between the initial and the final voltage +in a current.</td></tr> +<tr><td align='left'>Field.</td><td align='left'>The space or region near a magnet or charged wire. +Also the electro-magnets in a dynamo or motor.</td></tr> +<tr><td align='left'>Flow.</td><td align='left'>The volume of a current going through a conductor.</td></tr> +<tr><td align='left'>Force, Electro-magnetic.</td><td align='left'>The pull developed by an electro-magnet.</td></tr> +<tr><td align='left'>Frictional Electricity.</td><td align='left'>A current produced by rubbing dissimilar substances +together.</td></tr> +<tr><td align='left'>Full Load.</td><td align='left'>The greatest load a battery, accumulator or dynamo +<span class='pagenum'><a name="p198" id="p198">p. 198</a></span>will sustain.</td></tr> +<tr><td align='left'>Galvanic.</td><td align='left'>Pertaining to the electro-chemical relations of metals +toward each other.</td></tr> +<tr><td align='left'>Galvanizing.</td><td align='left'>The art of coating one metal with another, such, for +instance, as immersing iron in molten zinc.</td></tr> +<tr><td align='left'>Galvanometry.</td><td align='left'>An instrument having a permanently magnetized +needle, which is influenced by a coil or a wire in +close proximity to it.</td></tr> +<tr><td align='left'>Galvanoscope.</td><td align='left'>An instrument, like a galvanometer, which determines +whether or not a current is present in a +tested wire.</td></tr> +<tr><td align='left'>Generator.</td><td align='left'>A term used to generally indicate any device which +originates a current.</td></tr> +<tr><td align='left'>German Silver.</td><td align='left'>An alloy of copper, nickel and zinc.</td></tr> +<tr><td align='left'>Graphite.</td><td align='left'>One form of carbon. It is made artificially by the +electric current.</td></tr> +<tr><td align='left'>Grid.</td><td align='left'>The metallic frame of a plate used to hold the active +material of an accumulator.</td></tr> +<tr><td align='left'>Gravity.</td><td align='left'>The attraction of mass for mass. Weight. The accelerating +tendency of material to move toward +the earth.</td></tr> +<tr><td align='left'>Gutta Percha.</td><td align='left'>Caoutchouc, which has been treated with sulphur, to +harden it. It is produced from the sap of tropical +trees, and is a good insulator.</td></tr> +<tr><td align='left'>Harmonic Receiver.</td><td align='left'>A vibrating reed acted on by an electro-magnet, when +tuned to its pitch.</td></tr> +<tr><td align='left'>High E. M. F.</td><td align='left'>A term to indicate currents which have a high voltage, +and usually low amperage.</td></tr> +<tr><td align='left'>Igniter.</td><td align='left'>Mechanism composed of a battery, induction coil and +a vibrator, for making a jump spark, to ignite +gas, powder, etc.</td></tr> +<tr><td align='left'>I. H. P.</td><td align='left'>Abbreviation, which means Indicated Horse Power.</td></tr> +<tr><td align='left'>Impulse.</td><td align='left'>A sudden motion of one body acting against another. +<span class='pagenum'><a name="p199" id="p199">p. 199</a></span>An electro-magnetic wave magnetizing soft iron, +and this iron attracting another piece of iron, as an example.</td></tr> +<tr><td align='left'>Incandescence, Electric.</td><td align='left'>A conductor heated up by a current so it will glow.</td></tr> +<tr><td align='left'>Induced Current.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Induction, Magnetic.</td><td align='left'>A body within a magnetic field which is excited by +the magnetism.</td></tr> +<tr><td align='left'>Installation.</td><td align='left'>Everything belonging to an equipment of a building, +or a circuiting system to do a certain thing.</td></tr> +<tr><td align='left'>Insulation.</td><td align='left'>A material or substance which resists the passage of +a current placed around a conductor.</td></tr> +<tr><td align='left'>Intensity.</td><td align='left'>The strength of a magnetic field, or of a current flowing +over a wire.</td></tr> +<tr><td align='left'>Internal Resistance.</td><td align='left'>The current strength of electricity of a wire to resist +the passage.</td></tr> +<tr><td align='left'>Interrupter.</td><td align='left'>A device in a wire or circuit for checking a current. +It also refers to the vibrator of an induction coil.</td></tr> +<tr><td align='left'>Joint.</td><td align='left'>The place where two or more conductors are united.</td></tr> +<tr><td align='left'>Joint Resistance.</td><td align='left'>The combined resistance offered by two or more substances +or conductors.</td></tr> +<tr><td align='left'>Jump Spark.</td><td align='left'>A spark, disruptive in its character, between two +conducting points.</td></tr> +<tr><td align='left'>Initial Charge.</td><td align='left'>The charge required to start a battery.</td></tr> +<tr><td align='left'>Kathode, or Cathode.</td><td align='left'>The negative plate or side of a battery. The plate +on which the electro deposit is made.</td></tr> +<tr><td align='left'>Key.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Keyboard.</td><td align='left'>A switch-board; a board on which is mounted a number +<span class='pagenum'><a name="p200" id="p200">p. 200</a></span>of switches.</td></tr> +<tr><td align='left'>Kilowatt.</td><td align='left'>A unit, representing 1,000 watts. An electric current +measure, usually expressed thus: K.W.</td></tr> +<tr><td align='left'>Kilowatt Hour.</td><td align='left'>The computation of work equal to the exertion of +one kilowatt in one hour.</td></tr> +<tr><td align='left'>Knife Switch.</td><td align='left'>A bar of a blade-like form, adapted to move down +between two fingers, and thus establish metallic +connections.</td></tr> +<tr><td align='left'>Laminated.</td><td align='left'>Made up of thin plates of the same material, laid +together, but not insulated from each other.</td></tr> +<tr><td align='left'>Lamp Arc.</td><td align='left'>A voltaic arc lamp, using carbon electrodes, with +mechanism for feeding the electrodes regularly.</td></tr> +<tr><td align='left'>Lamp, Incandescent.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Leak.</td><td align='left'>Loss of electrical energy through a fault in wiring, +or in using bare wires.</td></tr> +<tr><td align='left'>Load.</td><td align='left'>The ampere current delivered by a dynamo under certain +conditions.</td></tr> +<tr><td align='left'>Low Frequency.</td><td align='left'>A current in which the vibrations are of few alternations +per second.</td></tr> +<tr><td align='left'>Magnet.</td><td align='left'>A metallic substance which has power to attract iron +and steel.</td></tr> +<tr><td align='left'>Magnet Bar.</td><td align='left'>A straight piece of metal.</td></tr> +<tr><td align='left'>Magnet Coil.</td><td align='left'>A coil of wire, insulated, surrounding a core of iron, +to receive a current of electricity.</td></tr> +<tr><td align='left'>Magnet Core.</td><td align='left'>A bar of iron adapted to receive a winding of wire.</td></tr> +<tr><td align='left'>Magnet, Field.</td><td align='left'>A magnet in a dynamo. A motor to produce electric +energy.</td></tr> +<tr><td align='left'>Magnet, Permanent.</td><td align='left'>A short steel form, to hold magnetism for a long +time.</td></tr> +<tr><td align='left'>Magnetic Adherence.</td><td align='left'>The adherence of particles to the poles of a magnet. +<span class='pagenum'><a name="p201" id="p201">p. 201</a></span></td></tr> +<tr><td align='left'>Magnetic Attraction and Repulsion.</td><td align='left'>That quality of a metal which draws metals. Also +the pulling action of unlike poles for each other, +and pushing away of like poles when brought together.</td></tr> +<tr><td align='left'>Magnetic Force.</td><td align='left'>The action exercised by a magnet of attracting or +repelling.</td></tr> +<tr><td align='left'>Magnetic Pole.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Magneto-generator.</td><td align='left'>A permanent magnet and a revolving armature for +generating a current.</td></tr> +<tr><td align='left'>Maximum Voltage.</td><td align='left'>The final voltage after charging.</td></tr> +<tr><td align='left'>Molecule.</td><td align='left'>Invisible particles made up of two or more atoms of +different matter. An atom is a particle of one substance only.</td></tr> +<tr><td align='left'>Morse Sounder.</td><td align='left'>An electric instrument designed to make a clicking +sound, when the armature is drawn down by a +magnet.</td></tr> +<tr><td align='left'>Motor-dynamo.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Motor-transformer.</td><td align='left'>A motor which delivers the current like a generator.</td></tr> +<tr><td align='left'>Needle.</td><td align='left'>A bar magnet horizontally poised on a vertical pivot +point, like the needle of a mariner's compass.</td></tr> +<tr><td align='left'>Negative Electricity.</td><td align='left'>Amber, when rubbed, produces negative electricity. +<span class='pagenum'><a name="p202" id="p202">p. 202</a></span>A battery has positive as well as negative electricity.</td></tr> +<tr><td align='left'>Negative Element.</td><td align='left'>That plate in the solution of a battery cell which is +not disintegrated.</td></tr> +<tr><td align='left'>Normal.</td><td align='left'>The usual, or ordinary. The average. In a current +the regular force required to do the work.</td></tr> +<tr><td align='left'>North Pole, Electric.</td><td align='left'>The term applied to the force located near the north +pole of the globe, to which a permanent magnet +will point if allowed to swing freely.</td></tr> +<tr><td align='left'>O.</td><td align='left'>Abbreviation for Ohm.</td></tr> +<tr><td align='left'>Ohm.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Ohm's Law.</td><td align='left'>It is expressed as follows: +<ol><li>The current strength is equal to the electro-motive +force divided by its resistance.</li> +<li>The electro-motive force is equal to the current +strength multiplied by the resistance.</li> +<li>The resistance is equal to the electro-motive +force divided by the current strength.</li> +</ol> +</td></tr> +<tr><td align='left'>Overload.</td><td align='left'>In a motor an excess of mechanical work which +causes the armature to turn too slowly and produces +heat.</td></tr> +<tr><td align='left'>Phase.</td><td align='left'>One complete oscillation. The special form of a wave +at any instant, or at any interval of time.</td></tr> +<tr><td align='left'>Plate, Condenser.</td><td align='left'>In a static machine it is usually a plate of glass and +revoluble.</td></tr> +<tr><td align='left'>Plate, Negative.</td><td align='left'>The plate in a battery, such as carbon, copper or +platinum, which is not attacked by the solution.</td></tr> +<tr><td align='left'>Plating, Electro-.</td><td align='left'>The method of coating one metal with another by +electrolysis.</td></tr> +<tr><td align='left'>Polarity.</td><td align='left'>The peculiarity, in a body, of arranging itself with +reference to magnetic influence.</td></tr> +<tr><td align='left'>Parallel.</td><td align='left'>When a number of cells are coupled so that their +<span class='pagenum'><a name="p203" id="p203">p. 203</a></span>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.</td></tr> +<tr><td align='left'>Polarization.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Porosity.</td><td align='left'>Having small interstices or holes.</td></tr> +<tr><td align='left'>Positive Current.</td><td align='left'>One which deflects a needle to the left.</td></tr> +<tr><td align='left'>Positive Electricity.</td><td align='left'>Any current flowing from the active element, such as +zinc, in a battery. The negative electricity flows +from the carbon to the zinc.</td></tr> +<tr><td align='left'>Potential, Electric.</td><td align='left'>The power which performs work in a circuit.</td></tr> +<tr><td align='left'>Potential Energy.</td><td align='left'>That form of force, which, when liberated, does or +performs work.</td></tr> +<tr><td align='left'>Power Unit.</td><td align='left'>The volt-amperes or watt.</td></tr> +<tr><td align='left'>Primary.</td><td align='left'>The induction coil in induction machines, or in a +transformer.</td></tr> +<tr><td align='left'>Push Button.</td><td align='left'>A thumb piece which serves as a switch to close a +circuit while being pressed inwardly.</td></tr> +<tr><td align='left'>Quantity.</td><td align='left'>Such arrangement of electrical connections which +give off the largest amount of current.</td></tr> +<tr><td align='left'>Receiver.</td><td align='left'>An instrument in telephony and telegraphy which +receives or takes in the sound or impulses.</td></tr> +<tr><td align='left'>Relay.</td><td align='left'>The device which opens or closes a circuit so as to +admit a new current which is sent to a more distant +point.</td></tr> +<tr><td align='left'>Repulsion, Electric.</td><td align='left'>That tendency in bodies to repel each other when +similarly charged.</td></tr> +<tr><td align='left'>Resilience.</td><td align='left'>The springing back to its former condition or position. +<span class='pagenum'><a name="p204" id="p204">p. 204</a></span>Electricity has resilience.</td></tr> +<tr><td align='left'>Resistance.</td><td align='left'>The quality in all conductors to oppose the passage +of a current.</td></tr> +<tr><td align='left'>Resistance Coil.</td><td align='left'>A coil made up of wire which prevents the passage +of a current to a greater or less degree.</td></tr> +<tr><td align='left'>Resistance, Electrolytic.</td><td align='left'>The counter force in an electrolyte which seeks to +prevent a decomposing current to pass through it.</td></tr> +<tr><td align='left'>Resistance: Internal, External.</td><td align='left'>The opposing force to the movement of a current +which is in the cell or generator. This is called +the <i>internal</i>. That opposite action outside of the +cell or generator is the <i>external</i>.</td></tr> +<tr><td align='left'>Resonator, Electric.</td><td align='left'>An open-circuited conductor for electrically resounding +or giving back a vibration, usually exhibited +by means of a spark.</td></tr> +<tr><td align='left'>Rheostat.</td><td align='left'>A device which has an adjustable resistance, so arranged +that while adjusting the same the circuit +will not be open.</td></tr> +<tr><td align='left'>Safety Fuse.</td><td align='left'>A piece of fusible metal of such resistance that it +breaks down at a certain current strength.</td></tr> +<tr><td align='left'>Saturated.</td><td align='left'>When a liquid has taken up a soluble material to the +fullest extent it is then completely saturated.</td></tr> +<tr><td align='left'>Secondary.</td><td align='left'>One of the two coils in a transformer, or induction +coil.</td></tr> +<tr><td align='left'>Secondary Plates.</td><td align='left'>The brown or deep red plates in a storage battery +when charged.</td></tr> +<tr><td align='left'>Self-excited.</td><td align='left'>Producing electricity by its own current.</td></tr> +<tr><td align='left'>Series.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Series, Multiple.</td><td align='left'>When lamps are grouped in sets in parallel, and +<span class='pagenum'><a name="p205" id="p205">p. 205</a></span>these sets are then connected up in series.</td></tr> +<tr><td align='left'>Series Windings.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Shunt.</td><td align='left'>Going around.</td></tr> +<tr><td align='left'>Shunt Winding.</td><td align='left'>A dynamo in which the field winding is parallel +with the winding of the armature.</td></tr> +<tr><td align='left'>Snap Switch.</td><td align='left'>A switch so arranged that it will quickly make a +break.</td></tr> +<tr><td align='left'>Sounder.</td><td align='left'>The apparatus at one end of a line actuated by a key +at the other end of the line.</td></tr> +<tr><td align='left'>Spark Coil.</td><td align='left'>A coil, to make a spark from a low electro-motive +force.</td></tr> +<tr><td align='left'>Spark, Electric.</td><td align='left'>The flash caused by drawing apart the ends of a conductor.</td></tr> +<tr><td align='left'>Specific Gravity.</td><td align='left'>The weight or density of a body.</td></tr> +<tr><td align='left'>Static Electricity.</td><td align='left'>Generated by friction. Also lightning. Any current +generated by a high electro-motive force.</td></tr> +<tr><td align='left'>Strength of Current.</td><td align='left'>The quantity of electricity in a circuit.</td></tr> +<tr><td align='left'>Synchronize.</td><td align='left'>Operating together; acting in unison.</td></tr> +<tr><td align='left'>Terminal.</td><td align='left'>The end of any electric circuit or of a body or machine +which has a current passing through it.</td></tr> +<tr><td align='left'>Thermostat, Electric.</td><td align='left'>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.</td></tr> +<tr><td align='left'>Transformer.</td><td align='left'>The induction coil with a high initial E. M. F. changes +into a low electro-motive force.</td></tr> +<tr><td align='left'>Unit.</td><td align='left'>A standard of light, heat, electricity, or of other +<span class='pagenum'><a name="p206" id="p206">p. 206</a></span>phenomena.</td></tr> +<tr><td align='left'>Vacuum.</td><td align='left'>A space from which all matter has been exhausted.</td></tr> +<tr><td align='left'>Vibrator.</td><td align='left'>Mechanism for making and breaking circuits in induction +coils or other apparatus.</td></tr> +<tr><td align='left'>Volt.</td><td align='left'>The unit of electro-motive force.</td></tr> +<tr><td align='left'>Voltage.</td><td align='left'>Electro-motive force which is expressed in volts.</td></tr> +<tr><td align='left'>Voltaic.</td><td align='left'>A term applied to electric currents and devices.</td></tr> +<tr><td align='left'>Volt-meter.</td><td align='left'>An apparatus for showing the difference of potential, +or E. M. F. in the term of volts.</td></tr> +<tr><td align='left'>Watt.</td><td align='left'>The unit of electrical activity. The product of amperes +multiplied by volts.</td></tr> +<tr><td align='left'>Watt Hour.</td><td align='left'>One watt maintained through one hour of time.</td></tr> +<tr><td align='left'>Waves, Electric Magnetic.</td><td align='left'>Waves in the ether caused by electro-magnetic disturbances.</td></tr> +<tr><td align='left'>X-rays.</td><td align='left'>The radiation of invisible rays of light, which penetrate +or pass through opaque substances.</td></tr> +<tr><td align='left'>Yoke, or Bar.</td><td align='left'>A soft iron body across the ends of a horseshoe magnet, +to enable the magnet to retain its magnetism +an indefinite time.</td></tr> +<tr><td align='left'>Zinc Battery.</td><td align='left'>A battery which uses zinc for one of its elements.</td></tr> +</tbody> +</table> +</div> + + +<hr class="chapter" /> +<p class="chapter"><span class="pagenum"><a name="p207" id="p207">p. 207</a></span></p> + +<h2><a name="INDEX" id="INDEX"></a>INDEX<span class="totoc"><a href="#toc">ToC</a></span></h2> + +<div class="index"> + +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<h4><a id="IX_A" name="IX_A"></a>A</h4> +<ul class="IX"> +<li>Accumulated, <a href="#p31">31</a>.</li> +<li>Accumulation, <a href="#p29">29</a>.</li> +<li>Accumulator cell, <a href="#p87">87</a>.</li> +<li>Accumulators, <a href="#p82">82</a>, <a href="#p88">88</a>, <a href="#p89">89</a>.</li> +<li>Accumulators, plates, <a href="#p83">83</a>.</li> +<li>Acid, <a href="#p34">34</a>, <a href="#p37">37</a>, <a href="#p125">125</a>.</li> +<li>Acid maker, <a href="#p125">125</a>.</li> +<li>Acid, sulphuric, <a href="#p31">31</a>, <a href="#p84">84</a>.</li> +<li>Acidulated, <a href="#p55">55</a>.</li> +<li>Acidulated water, <a href="#p34">34</a>.</li> +<li>Acoustics, <a href="#p110">110</a>.</li> +<li>Actinic rays, <a href="#p184">184</a>, <a href="#p185">185</a>.</li> +<li>Actinium, <a href="#p186">186</a>.</li> +<li>Active element, <a href="#p82">82</a>.</li> +<li>Adjustable rod, <a href="#p107">107</a>.</li> +<li>Adjusting screw, <a href="#p70">70</a>, <a href="#p71">71</a>, <a href="#p72">72</a>, <a href="#p73">73</a>, <a href="#p106">106</a>.</li> +<li>Aerial wire, <a href="#p108">108</a>.</li> +<li>Agents, <a href="#p13">13</a>, <a href="#p32">32</a>.</li> +<li>Alarms, burglar, <a href="#p11">11</a>, <a href="#p76">76</a>, <a href="#p80">80</a>.</li> + +<li>Alkali, <a href="#p125">125</a>.</li> + +<li>Alkaline, <a href="#p37">37</a>.</li> + +<li>Alternate, <a href="#p127">127</a>.</li> + +<li>Alternating, <a href="#p38">38</a>, <a href="#p149">149</a>, <a href="#p150">150</a>, <a href="#p153">153</a>, <a href="#p154">154</a>, <a href="#p155">155</a>, <a href="#p156">156</a>.</li> + +<li>Alternating current, <a href="#p145">145</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li><p></p></li> + +<li>Alternating periods, <a href="#p149">149</a>.</li> + +<li>Alternations, <a href="#p147">147</a>.</li> + +<li>Aluminum, <a href="#p128">128</a>, <a href="#p129">129</a>, <a href="#p135">135</a>, <a href="#p137">137</a>.</li> + +<li>Aluminum hydrate, <a href="#p129">129</a>.</li> + +<li>Amber, <a href="#p5">5</a>, <a href="#p171">171</a>.</li> + +<li>Ammeter, <a href="#p7">7</a>, <a href="#p88">88</a>.</li> + +<li>Amperage, <a href="#p38">38</a>, <a href="#p61">61</a>, <a href="#p62">62</a>, <a href="#p132">132</a>, <a href="#p159">159</a>, <a href="#p160">160</a>, <a href="#p168">168</a>.</li> + +<li>Ampere, <a href="#p7">7</a>, <a href="#p37">37</a>, <a href="#p60">60</a>, <a href="#p63">63</a>, <a href="#p139">139</a>, <a href="#p140">140</a>, <a href="#p167">167</a>.</li> + +<li>Amplitude, <a href="#p111">111</a>.</li> + +<li>Annunciator, <a href="#p65">65</a>, <a href="#p74">74</a>, <a href="#p76">76</a>, <a href="#p79">79</a>, <a href="#p80">80</a>, <a href="#p81">81</a>.</li> + +<li>Annunciator bells, <a href="#p11">11</a>.</li> + +<li>Anode, <a href="#p35">35</a>, <a href="#p133">133</a>, <a href="#p134">134</a>.</li> + +<li>Antennæ, <a href="#p108">108</a>.</li> + +<li>Antimony <a href="#p137">137</a>, <a href="#p143">143</a>.</li> + +<li>Anvil, <a href="#p13">13</a>, <a href="#p14">14</a>.</li> + +<li>Apparatus, <a href="#p11">11</a>, <a href="#p57">57</a>, <a href="#p106">106</a>, <a href="#p139">139</a>, <a href="#p145">145</a>.</li> + +<li>Arc, <a href="#p163">163</a>, <a href="#p182">182</a>.</li> + +<li>Arc lighting, <a href="#p38">38</a>, <a href="#p165">165</a>.</li> + +<li>Arc system, <a href="#p166">166</a>.</li> + +<li>Armature, <a href="#p18">18</a>, <a href="#p25">25</a>, <a href="#p38">38</a>, <a href="#p40">40</a>, <a href="#p42">42</a>, <a href="#p43">43</a>, <a href="#p45">45</a>, <a href="#p46">46</a>, <a href="#p47">47</a>, <a href="#p48">48</a>, <a href="#p53">53</a>, <a href="#p55">55</a>, <a href="#p70">70</a>, <a href="#p72">72</a>, <a href="#p73">73</a>, <a href="#p74">74</a>, <a href="#p90">90</a>, <a href="#p93">93</a>, <a href="#p112">112</a>, <a href="#p151">151</a>, <a href="#p152">152</a>, <a href="#p155">155</a>, <a href="#p163">163</a>, <a href="#p176">176</a>, <a href="#p177">177</a>, <a href="#p178">178</a>, <a href="#p179">179</a>, <a href="#p180">180</a>.</li> +</ul> +</td></tr> +</tbody> +</table> +<div><span class='pagenum'><a name="p208" id="p208">p. 208</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Armature brush, <a href="#p48">48</a>.</li> + +<li>Armature post, <a href="#p71">71</a>.</li> + +<li>Armature, vertical, <a href="#p75">75</a>.</li> + +<li>Armature winding, <a href="#p42">42</a>, <a href="#p43">43</a>, <a href="#p156">156</a>.</li> + +<li>Asbestos, <a href="#p140">140</a>.</li> + +<li>Astatic galvanometer, <a href="#p108">108</a>.</li> + +<li>Atmosphere, <a href="#p184">184</a>.</li> + +<li>Attract, <a href="#p30">30</a>.</li> + +<li>Attracted, <a href="#p72">72</a>.</li> + +<li>Attraction, <a href="#p21">21</a>, <a href="#p25">25</a>.</li> + +<li>Attractive, <a href="#p178">178</a>.</li> + +<li>Automatic, <a href="#p120">120</a>.</li> + +<li>Auxiliary, <a href="#p44">44</a>.</li> + +<li>Awls, <a href="#p14">14</a>.</li> +</ul> + +<h4><a id="IX_B" name="IX_B"></a>B</h4> +<ul class="IX"> +<li>Bacteria, <a href="#p126">126</a>, <a href="#p187">187</a>.</li> + +<li>Bar, cross, <a href="#p66">66</a>.</li> + +<li>Bar, horizontal, <a href="#p46">46</a>.</li> + +<li>Bar, parallel switch, <a href="#p67">67</a>.</li> + +<li>Bar, switch, <a href="#p65">65</a>, <a href="#p68">68</a>.</li> + +<li>Base block, <a href="#p66">66</a>.</li> + +<li>Batteries, <a href="#p11">11</a>, <a href="#p93">93</a>, <a href="#p122">122</a>.</li> + +<li>Battery, <a href="#p29">29</a>, <a href="#p30">30</a>, <a href="#p32">32</a>, <a href="#p35">35</a>, <a href="#p36">36</a>, <a href="#p46">46</a>, <a href="#p47">47</a>, <a href="#p80">80</a>, <a href="#p81">81</a>, <a href="#p82">82</a>, <a href="#p83">83</a>, <a href="#p85">85</a>, <a href="#p86">86</a>, <a href="#p88">88</a>, <a href="#p92">92</a>, <a href="#p94">94</a>, <a href="#p95">95</a>, <a href="#p107">107</a>, <a href="#p108">108</a>, <a href="#p116">116</a>, <a href="#p117">117</a>, <a href="#p118">118</a>, <a href="#p121">121</a>, <a href="#p134">134</a>, <a href="#p142">142</a>.</li> + +<li>Battery charging, <a href="#p82">82</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Bearings, <a href="#p45">45</a>, <a href="#p46">46</a>.</li> + +<li>Bells, <a href="#p65">65</a>, <a href="#p73">73</a>, <a href="#p76">76</a>, <a href="#p122">122</a>.</li> + +<li>Bells, electric, <a href="#p70">70</a>.</li> + +<li>Bench, <a href="#p13">13</a>, <a href="#p15">15</a>, <a href="#p17">17</a>.</li> + +<li>Binding post, <a href="#p52">52</a>, <a href="#p70">70</a>, <a href="#p71">71</a>, <a href="#p72">72</a>, <a href="#p103">103</a>, <a href="#p107">107</a>, <a href="#p108">108</a>, <a href="#p121">121</a>.</li> + +<li>Binding screw, <a href="#p65">65</a>, <a href="#p66">66</a>.</li> + +<li>Bismuth, <a href="#p18">18</a>, <a href="#p143">143</a>.</li> + +<li>Bit, <a href="#p13">13</a>.</li> + +<li>Blue vitriol, <a href="#p57">57</a>.</li> + +<li>Brass plate, <a href="#p77">77</a>, <a href="#p78">78</a>.</li> + +<li>Brazing, <a href="#p17">17</a>, <a href="#p65">65</a>.</li> + +<li>Bridge, <a href="#p52">52</a>.</li> + +<li>Brush holder, <a href="#p46">46</a>.</li> + +<li>Brushes, <a href="#p48">48</a>, <a href="#p150">150</a>, <a href="#p151">151</a>, <a href="#p153">153</a>, <a href="#p167">167</a>.</li> + +<li>Burglar, <a href="#p11">11</a>.</li> + +<li>Burglar alarm, <a href="#p76">76</a>, <a href="#p80">80</a>.</li> + +<li>Buttons, contact, <a href="#p80">80</a>.</li> + +<li>Buttons, push, <a href="#p65">65</a>, <a href="#p68">68</a>, <a href="#p69">69</a>, <a href="#p70">70</a>, <a href="#p76">76</a>, <a href="#p79">79</a>.</li> +</ul> + +<h4><a id="IX_C" name="IX_C"></a>C</h4> +<ul class="IX"> +<li>Calorimeter, <a href="#p56">56</a>.</li> + +<li>Cancerous, <a href="#p187">187</a>.</li> + +<li>Candle power, <a href="#p89">89</a>, <a href="#p139">139</a>.</li> + +<li>Cap, removable, <a href="#p73">73</a>.</li> + +<li>Cap screws, <a href="#p42">42</a>.</li> + +<li>Carbon, <a href="#p35">35</a>, <a href="#p119">119</a>, <a href="#p121">121</a>, <a href="#p162">162</a>, <a href="#p163">163</a>, <a href="#p169">169</a>.</li> +<li>Carbon block, <a href="#p120">120</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p209" id="p209">p. 209</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Carbon pencil, <a href="#p119">119</a>.</li> + +<li>Cathode, <a href="#p35">35</a>, <a href="#p36">36</a>, <a href="#p133">133</a>, <a href="#p134">134</a>.</li> + +<li>Cell, <a href="#p29">29</a>, <a href="#p33">33</a>.</li> + +<li>Cell, accumulator, <a href="#p87">87</a>.</li> + +<li>Cell, charging, <a href="#p87">87</a>.</li> + +<li>Channel, <a href="#p43">43</a>.</li> + +<li>Channel, concave, <a href="#p40">40</a>.</li> + +<li>Charged, <a href="#p120">120</a>.</li> + +<li>Charged battery, <a href="#p82">82</a>.</li> + +<li>Charging circuit, <a href="#p82">82</a>, <a href="#p89">89</a>.</li> + +<li>Charging source, <a href="#p83">83</a>.</li> + +<li>Charged wire, <a href="#p147">147</a>.</li> + +<li>Chemical, <a href="#p57">57</a>.</li> + +<li>Chisels, <a href="#p13">13</a>.</li> + +<li>Chloride of lime, <a href="#p84">84</a>.</li> + +<li>Choked, <a href="#p157">157</a>.</li> + +<li>Choking coils, <a href="#p145">145</a>, <a href="#p146">146</a>, <a href="#p156">156</a>, <a href="#p158">158</a>.</li> + +<li>Circuit, <a href="#p33">33</a>, <a href="#p69">69</a>, <a href="#p73">73</a>, <a href="#p76">76</a>, <a href="#p78">78</a>, <a href="#p80">80</a>, <a href="#p81">81</a>, <a href="#p90">90</a>, <a href="#p92">92</a>, <a href="#p93">93</a>, <a href="#p109">109</a>, <a href="#p113">113</a>, <a href="#p116">116</a>, <a href="#p121">121</a>, <a href="#p122">122</a>, <a href="#p131">131</a>, <a href="#p134">134</a>, <a href="#p143">143</a>, <a href="#p156">156</a>.</li> + +<li>Circuit, primary, <a href="#p99">99</a>.</li> + +<li>Circuit, secondary, <a href="#p99">99</a>.</li> + +<li>Circuiting, <a href="#p81">81</a>, <a href="#p155">155</a>.</li> + +<li>Circuiting system, <a href="#p79">79</a>.</li> + +<li>Clapper arm, <a href="#p70">70</a>.</li> + +<li>Closed rings, <a href="#p26">26</a>.</li> + +<li>Coherer, <a href="#p105">105</a>, <a href="#p108">108</a>, <a href="#p109">109</a>.</li> + +<li>Cohering, <a href="#p106">106</a>.</li> + +<li>Coils, <a href="#p18">18</a>, <a href="#p26">26</a>, <a href="#p52">52</a>, <a href="#p55">55</a>, <a href="#p74">74</a>, <a href="#p160">160</a>.</li> + +<li>Coils, choking, <a href="#p145">145</a>, <a href="#p146">146</a>, <a href="#p156">156</a>, <a href="#p158">158</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Coils, induction, <a href="#p99">99</a>, <a href="#p102">102</a>.</li> + +<li>Coils, primary, <a href="#p109">109</a>.</li> + +<li>Coils, secondary, <a href="#p102">102</a>, <a href="#p109">109</a>.</li> + +<li>Coincide, <a href="#p42">42</a>.</li> + +<li>Cold, <a href="#p14">14</a>.</li> + +<li>Collecting surfaces, <a href="#p30">30</a>.</li> + +<li>Collector, <a href="#p31">31</a>.</li> + +<li>Column, <a href="#p61">61</a>.</li> + +<li>Combustion, <a href="#p169">169</a>.</li> + +<li>Commutator, <a href="#p44">44</a>, <a href="#p46">46</a>, <a href="#p151">151</a>, <a href="#p152">152</a>.</li> + +<li>Commutator brushes, <a href="#p46">46</a>.</li> + +<li>Commutator plates, <a href="#p45">45</a>.</li> + +<li>Compass, <a href="#p22">22</a>, <a href="#p24">24</a>, <a href="#p172">172</a>.</li> + +<li>Composition, <a href="#p83">83</a>, <a href="#p124">124</a>.</li> + +<li>Compound wound, <a href="#p47">47</a>.</li> + +<li>Concave channel, <a href="#p40">40</a>.</li> + +<li>Condenser, <a href="#p98">98</a>, <a href="#p100">100</a>, <a href="#p101">101</a>, <a href="#p102">102</a>, <a href="#p108">108</a>.</li> + +<li>Conduct, <a href="#p6">6</a>, <a href="#p108">108</a>.</li> + +<li>Conduction, <a href="#p135">135</a>, <a href="#p136">136</a>, <a href="#p138">138</a>, <a href="#p166">166</a>, <a href="#p170">170</a>.</li> + +<li>Conduction current, <a href="#p27">27</a>.</li> + +<li>Conductor, <a href="#p21">21</a>, <a href="#p31">31</a>, <a href="#p33">33</a>, <a href="#p63">63</a>, <a href="#p98">98</a>, <a href="#p116">116</a>, <a href="#p161">161</a>, <a href="#p162">162</a>.</li> + +<li>Conduit, <a href="#p72">72</a>.</li> + +<li>Conically formed, <a href="#p126">126</a>.</li> + +<li>Conjunction, <a href="#p143">143</a>.</li> + +<li>Connecting wire, <a href="#p58">58</a>.</li> + +<li>Connection, <a href="#p72">72</a>, <a href="#p76">76</a>.</li> + +<li>Construction, magnet, <a href="#p39">39</a>.</li> + +<li>Consumption, <a href="#p180">180</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p210" id="p210">p. 210</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Contact, <a href="#p122">122</a>, <a href="#p123">123</a>, <a href="#p152">152</a>, <a href="#p162">162</a>.</li> + +<li>Contact finger, <a href="#p150">150</a>.</li> + +<li>Contact plate, <a href="#p67">67</a>, <a href="#p68">68</a>, <a href="#p79">79</a>.</li> + +<li>Contact screws, <a href="#p93">93</a>.</li> + +<li>Contact surface, <a href="#p66">66</a>.</li> + +<li>Continuous, <a href="#p145">145</a>.</li> + +<li>Converter, <a href="#p176">176</a>.</li> + +<li>Converting, <a href="#p142">142</a>, <a href="#p145">145</a>, <a href="#p146">146</a>.</li> + +<li>Copper, <a href="#p18">18</a>, <a href="#p34">34</a>, <a href="#p36">36</a>, <a href="#p65">65</a>, <a href="#p66">66</a>, <a href="#p132">132</a>, <a href="#p133">133</a>, <a href="#p134">134</a>, <a href="#p135">135</a>, <a href="#p136">136</a>, <a href="#p137">137</a>, <a href="#p142">142</a>, <a href="#p143">143</a>.</li> + +<li>Copper cyanide, <a href="#p133">133</a>.</li> + +<li>Copper plate, <a href="#p33">33</a>, <a href="#p35">35</a>, <a href="#p58">58</a>, <a href="#p67">67</a>.</li> + +<li>Copper sulphate, <a href="#p57">57</a>.</li> + +<li>Copper voltameter, <a href="#p55">55</a>, <a href="#p57">57</a>.</li> + +<li>Core, <a href="#p27">27</a>, <a href="#p28">28</a>, <a href="#p36">36</a>, <a href="#p39">39</a>, <a href="#p40">40</a>, <a href="#p115">115</a>.</li> + +<li>Core, magnet, <a href="#p75">75</a>, <a href="#p93">93</a>.</li> + +<li>Counter, clock-wise, <a href="#p51">51</a>.</li> + +<li>Coupled, <a href="#p36">36</a>.</li> + +<li>Crank, <a href="#p30">30</a>.</li> + +<li>Crookes' tube, <a href="#p184">184</a>.</li> + +<li>Cross bar, <a href="#p52">52</a>, <a href="#p66">66</a>.</li> + +<li>Crown of cups, <a href="#p32">32</a>.</li> + +<li>Crystal, <a href="#p85">85</a>.</li> + +<li>Current, <a href="#p6">6</a>, <a href="#p7">7</a>, <a href="#p13">13</a>, <a href="#p18">18</a>, <a href="#p26">26</a>, <a href="#p27">27</a>, <a href="#p28">28</a>, <a href="#p35">35</a>, <a href="#p36">36</a>, <a href="#p37">37</a>, <a href="#p38">38</a>, <a href="#p47">47</a>, <a href="#p50">50</a>, <a href="#p51">51</a>, <a href="#p52">52</a>, <a href="#p55">55</a>, <a href="#p56">56</a>, <a href="#p57">57</a>, <a href="#p58">58</a>, <a href="#p59">59</a>, <a href="#p62">62</a>, <a href="#p63">63</a>, <a href="#p70">70</a>, <a href="#p72">72</a>, <a href="#p73">73</a>, <a href="#p90">90</a>, <a href="#p95">95</a>, <a href="#p98">98</a>, <a href="#p105">105</a>, <a href="#p108">108</a>, +<a href="#p116">116</a>, <a href="#p133">133</a>, <a href="#p134">134</a>, <a href="#p135">135</a>, <a href="#p136">136</a>, <a href="#p138">138</a>, <a href="#p139">139</a>, <a href="#p140">140</a>, <a href="#p141">141</a>, <a href="#p142">142</a>, <a href="#p143">143</a>, <a href="#p147">147</a>, <a href="#p148">148</a>, <a href="#p149">149</a>, <a href="#p150">150</a>, <a href="#p152">152</a>, <a href="#p153">153</a>, <a href="#p157">157</a>, <a href="#p160">160</a>, <a href="#p161">161</a>, <a href="#p163">163</a>, <a href="#p165">165</a>, <a href="#p166">166</a>, <a href="#p170">170</a>.</li> +<li>Current, alternating, <a href="#p150">150</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Current changing, <a href="#p82">82</a>.</li> + +<li>Current conduction, <a href="#p27">27</a>.</li> + +<li>Current, continuous, <a href="#p164">164</a>.</li> + +<li>Current, direct, <a href="#p145">145</a>, <a href="#p150">150</a>.</li> + +<li>Current direction, <a href="#p50">50</a>.</li> + +<li>Current, exterior, <a href="#p50">50</a>, <a href="#p150">150</a>.</li> + +<li>Current, reversing, <a href="#p148">148</a>.</li> + +<li>Current strength, <a href="#p7">7</a>, <a href="#p57">57</a>.</li> + +<li>Current testing, <a href="#p143">143</a>.</li> + +<li>Cut-out, <a href="#p120">120</a>.</li> + +<li>Cutter, <a href="#p14">14</a>.</li> + +<li>Cutting, lines of force, <a href="#p38">38</a>.</li> + +<li>Cylinder, <a href="#p44">44</a>.</li> + +<li>Cylindrical, <a href="#p43">43</a>.</li> + + +</ul> +<h4><a id="IX_D" name="IX_D"></a>D</h4> +<ul class="IX"> + +<li>Dash, <a href="#p95">95</a>, <a href="#p97">97</a>.</li> + +<li>Decoherer, <a href="#p106">106</a>, <a href="#p108">108</a>.</li> + +<li>Decomposed, <a href="#p57">57</a>, <a href="#p128">128</a>.</li> + +<li>Decomposes, <a href="#p55">55</a>.</li> + +<li>Decomposing, <a href="#p123">123</a>.</li> + +<li>Decomposition, <a href="#p12">12</a>, <a href="#p35">35</a>, <a href="#p82">82</a>.</li> + +<li>Deflected, <a href="#p54">54</a>.</li> + +<li>Degree, <a href="#p135">135</a>, <a href="#p162">162</a>.</li> + +<li>Demagnetized, <a href="#p24">24</a>, <a href="#p72">72</a>.</li> + +<li>Deposited, <a href="#p58">58</a>, <a href="#p133">133</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p211" id="p211">p. 211</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Depression, <a href="#p15">15</a>, <a href="#p140">140</a>.</li> + +<li>Detecting current, <a href="#p49">49</a>.</li> + +<li>Detector, <a href="#p49">49</a>, <a href="#p52">52</a>, <a href="#p54">54</a>, <a href="#p105">105</a>.</li> + +<li>Devices, measuring, <a href="#p27">27</a>.</li> + +<li>Diagrams, <a href="#p46">46</a>, <a href="#p48">48</a>, <a href="#p79">79</a>, <a href="#p89">89</a>.</li> + +<li>Diagrammatically, <a href="#p81">81</a>.</li> + +<li>Diamagnetic, <a href="#p19">19</a>.</li> + +<li>Diametrically, <a href="#p114">114</a>.</li> + +<li>Diaphragm, <a href="#p112">112</a>, <a href="#p113">113</a>, <a href="#p116">116</a>, <a href="#p120">120</a>, <a href="#p122">122</a>.</li> + +<li>Diamonds, <a href="#p186">186</a>.</li> + +<li>Diluted, <a href="#p86">86</a>.</li> + +<li>Direct current, <a href="#p38">38</a>, <a href="#p140">140</a>.</li> + +<li>Direction of current, <a href="#p50">50</a>.</li> + +<li>Direction of flow, <a href="#p98">98</a>.</li> + +<li>Discharge, <a href="#p172">172</a>.</li> + +<li>Disintegrate, <a href="#p132">132</a>.</li> + +<li>Disk, <a href="#p43">43</a>.</li> + +<li>Dissimilar, <a href="#p37">37</a>.</li> + +<li>Disturbance, <a href="#p176">176</a>.</li> + +<li>Dividers, <a href="#p14">14</a>.</li> + +<li>Divisibility, <a href="#p168">168</a>.</li> + +<li>Dot, <a href="#p96">96</a>, <a href="#p97">97</a>.</li> + +<li>Dot and dash, <a href="#p96">96</a>.</li> + +<li>Double click, <a href="#p95">95</a>.</li> + +<li>Double line, <a href="#p65">65</a>.</li> + +<li>Double-pole switch, <a href="#p65">65</a>.</li> + +<li>Double-throw switch, <a href="#p117">117</a>.</li> + +<li>Drawing, <a href="#p20">20</a>.</li> + +<li>Drill, ratchet, <a href="#p13">13</a>.</li> + +<li>Drops, <a href="#p81">81</a>.</li> + +<li>Ductile, <a href="#p186">186</a>.</li> + +<li>Duplex wire, <a href="#p115">115</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Dynamo, <a href="#p7">7</a>, <a href="#p27">27</a>, <a href="#p38">38</a>, <a href="#p42">42</a>, <a href="#p46">46</a>, <a href="#p48">48</a>, <a href="#p62">62</a>, <a href="#p82">82</a>, <a href="#p83">83</a>, <a href="#p87">87</a>, <a href="#p89">89</a>, <a href="#p132">132</a>, <a href="#p141">141</a>, <a href="#p142">142</a>, <a href="#p145">145</a>, <a href="#p150">150</a>, <a href="#p155">155</a>, <a href="#p161">161</a>, <a href="#p165">165</a>, <a href="#p167">167</a>, <a href="#p175">175</a>, <a href="#p176">176</a>, <a href="#p180">180</a>, <a href="#p187">187</a>.</li> + +<li>Dynamo fields, <a href="#p40">40</a>, <a href="#p41">41</a>.</li> +</ul> +<h4><a id="IX_E" name="IX_E"></a>E</h4> +<ul class="IX"> + +<li>Earth, <a href="#p22">22</a>.</li> + +<li>Elasticity, <a href="#p100">100</a>, <a href="#p142">142</a>.</li> + +<li>Electric, <a href="#p6">6</a>, <a href="#p31">31</a>, <a href="#p49">49</a>, <a href="#p50">50</a>, <a href="#p76">76</a>, <a href="#p78">78</a>, <a href="#p81">81</a>, <a href="#p131">131</a>, <a href="#p142">142</a>, <a href="#p158">158</a>, <a href="#p162">162</a>, <a href="#p173">173</a>, <a href="#p176">176</a>.</li> + +<li>Electric arc, <a href="#p63">63</a>, <a href="#p163">163</a>.</li> + +<li>Electric bell, <a href="#p19">19</a>, <a href="#p69">69</a>, <a href="#p70">70</a>, <a href="#p71">71</a>, <a href="#p72">72</a>, <a href="#p106">106</a>, <a href="#p117">117</a>.</li> + +<li>Electric bulbs, <a href="#p167">167</a>.</li> + +<li>Electric circuit, <a href="#p118">118</a>.</li> + +<li>Electric fan, <a href="#p55">55</a>.</li> + +<li>Electric field, <a href="#p76">76</a>.</li> + +<li>Electric hand purifier, <a href="#p129">129</a>.</li> + +<li>Electric heating, <a href="#p135">135</a>, <a href="#p137">137</a>, <a href="#p161">161</a>.</li> + +<li>Electric iron, <a href="#p130">130</a>, <a href="#p141">141</a>.</li> + +<li>Electric lamp socket, <a href="#p139">139</a>.</li> + +<li>Electric light, <a href="#p56">56</a>, <a href="#p66">66</a>.</li> + +<li>Electric lighting, <a href="#p161">161</a>.</li> + +<li>Electric power, <a href="#p113">113</a>.</li> + +<li>Electric welding, <a href="#p183">183</a>.</li> + +<li>Electrical, <a href="#p8">8</a>, <a href="#p11">11</a>, <a href="#p65">65</a>, <a href="#p96">96</a>, <a href="#p98">98</a>, <a href="#p104">104</a>, <a href="#p141">141</a>, <a href="#p159">159</a>, <a href="#p180">180</a>, <a href="#p184">184</a>, <a href="#p187">187</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p212" id="p212">p. 212</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Electrical impulses, <a href="#p105">105</a>, <a href="#p147">147</a>, <a href="#p148">148</a>.</li> + +<li>Electrical manifestations, <a href="#p175">175</a>.</li> + +<li>Electrically, <a href="#p32">32</a>, <a href="#p70">70</a>.</li> + +<li>Electricity, <a href="#p5">5</a>, <a href="#p6">6</a>, <a href="#p7">7</a>, <a href="#p8">8</a>, <a href="#p9">9</a>, <a href="#p12">12</a>, <a href="#p13">13</a>, <a href="#p18">18</a>, <a href="#p21">21</a>, <a href="#p26">26</a>, <a href="#p27">27</a>, <a href="#p28">28</a>, <a href="#p29">29</a>, <a href="#p38">38</a>, <a href="#p49">49</a>, + <a href="#p54">54</a>, <a href="#p60">60</a>, <a href="#p61">61</a>, <a href="#p62">62</a>, <a href="#p82">82</a>, <a href="#p97">97</a>, <a href="#p98">98</a>, <a href="#p100">100</a>, <a href="#p104">104</a>, <a href="#p110">110</a>, <a href="#p112">112</a>, <a href="#p116">116</a>, <a href="#p123">123</a>, <a href="#p124">124</a>, + <a href="#p133">133</a>, <a href="#p134">134</a>, <a href="#p136">136</a>, <a href="#p138">138</a>, <a href="#p145">145</a>, <a href="#p146">146</a>, <a href="#p147">147</a>, <a href="#p154">154</a>, <a href="#p156">156</a>, <a href="#p160">160</a>, <a href="#p166">166</a>, <a href="#p170">170</a>, <a href="#p171">171</a>, <a href="#p172">172</a>, <a href="#p175">175</a>, <a href="#p182">182</a>, <a href="#p187">187</a>.</li> +<li>Electricity measuring, <a href="#p49">49</a>.</li> + +<li>Electricity, thermo-, <a href="#p142">142</a>.</li> + +<li>Electrified, <a href="#p37">37</a>, <a href="#p186">186</a>.</li> + +<li>Electro-chemical, <a href="#p55">55</a>.</li> + +<li>Electrode, <a href="#p35">35</a>, <a href="#p124">124</a>, <a href="#p127">127</a>, <a href="#p128">128</a>, <a href="#p161">161</a>, <a href="#p162">162</a>, <a href="#p163">163</a>, <a href="#p164">164</a>, <a href="#p165">165</a>, <a href="#p184">184</a>.</li> + +<li>Electrolysis, <a href="#p7">7</a>, <a href="#p123">123</a>, <a href="#p126">126</a>, <a href="#p132">132</a>.</li> + +<li>Electrolyte, <a href="#p33">33</a>, <a href="#p35">35</a>, <a href="#p36">36</a>, <a href="#p57">57</a>, <a href="#p86">86</a>, <a href="#p88">88</a>, <a href="#p123">123</a>, <a href="#p132">132</a>, <a href="#p142">142</a>.</li> + +<li>Electrolytic, <a href="#p55">55</a>, <a href="#p123">123</a>, <a href="#p125">125</a>.</li> + +<li>Electro-magnet, <a href="#p59">59</a>, <a href="#p78">78</a>.</li> + +<li>Electro-magnetic, <a href="#p7">7</a>, <a href="#p24">24</a>, <a href="#p25">25</a>, <a href="#p29">29</a>, <a href="#p37">37</a>, <a href="#p55">55</a>, <a href="#p92">92</a>, <a href="#p93">93</a>, <a href="#p94">94</a>.</li> + +<li>Electro-magnetic force, <a href="#p7">7</a>.</li> + +<li>Electro-magnetic rotation, <a href="#p7">7</a>.</li> + +<li>Electro-magnetic switch, <a href="#p116">116</a>.</li> + +<li>Electro-meter, <a href="#p7">7</a>.</li> + +<li>Electro-motive force, <a href="#p37">37</a>, <a href="#p63">63</a>, <a href="#p99">99</a>.</li> + +<li>Electroplate, <a href="#p12">12</a>, <a href="#p38">38</a>, <a href="#p48">48</a>, <a href="#p123">123</a>, <a href="#p132">132</a>, <a href="#p134">134</a>.</li> + +<li>Electro-positive-negative, <a href="#p142">142</a>, <a href="#p143">143</a>.</li> + +<li>Elements, <a href="#p36">36</a>, <a href="#p83">83</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Engine energy, <a href="#p170">170</a>, <a href="#p180">180</a>.</li> + +<li>Equidistant, <a href="#p127">127</a>.</li> + +<li>Ether, <a href="#p104">104</a>.</li> + +<li>Example, <a href="#p61">61</a>.</li> + +<li>Excited, <a href="#p47">47</a>.</li> + +<li>Extension plate, <a href="#p103">103</a>.</li> + +<li>Exterior, <a href="#p3">3</a>.</li> + +<li>Exterior magnetic, <a href="#p27">27</a>.</li> + +<li>External, <a href="#p37">37</a>.</li> + +<li>External circuit, <a href="#p153">153</a>.</li> + +<li>External current, <a href="#p50">50</a>.</li> + +<li>External resistance, <a href="#p37">37</a>.</li> + + +</ul> +<h4><a id="IX_F" name="IX_F"></a>F</h4> +<ul class="IX"> + +<li>Factor, <a href="#p61">61</a>.</li> + +<li>Ferrous oxide, <a href="#p125">125</a>.</li> + +<li>Field, <a href="#p46">46</a>, <a href="#p47">47</a>.</li> + +<li>Field, dynamo, <a href="#p40">40</a>, <a href="#p41">41</a>.</li> + +<li>Field magnet cores, <a href="#p155">155</a>.</li> + +<li>Field, magnetic, <a href="#p38">38</a>.</li> + +<li>Field of force, <a href="#p33">33</a>.</li> + +<li>Field wire, <a href="#p48">48</a>.</li> + +<li>Filament, <a href="#p168">168</a>, <a href="#p169">169</a>, <a href="#p170">170</a>.</li> + +<li>Filter, <a href="#p128">128</a>.</li> + +<li>Flat iron, <a href="#p140">140</a>.</li> + +<li>Flocculent, <a href="#p128">128</a>.</li> + +<li>Force, <a href="#p50">50</a>.</li> + +<li>Formulated, <a href="#p19">19</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p213" id="p213">p. 213</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Friction, <a href="#p32">32</a>.</li> + +<li>Frictional, <a href="#p6">6</a>, <a href="#p7">7</a>, <a href="#p29">29</a>.</li> + +<li>Fuse, <a href="#p169">169</a>.</li> + + +</ul> +<h4><a id="IX_G" name="IX_G"></a>G</h4> +<ul class="IX"> + +<li>Galvani, <a href="#p7">7</a>.</li> + +<li>Galvanic, <a href="#p7">7</a>, <a href="#p23">23</a>, <a href="#p30">30</a>.</li> + +<li>Galvanometer, <a href="#p7">7</a>, <a href="#p49">49</a>, <a href="#p108">108</a>, <a href="#p143">143</a>.</li> + +<li>Galvanoscope, <a href="#p55">55</a>, <a href="#p58">58</a>, <a href="#p59">59</a>.</li> + +<li>Gaseous, <a href="#p128">128</a>.</li> + +<li>Gasoline, <a href="#p99">99</a>.</li> + +<li>Gas stove, <a href="#p17">17</a>.</li> + +<li>Gelatine, <a href="#p128">128</a>.</li> + +<li>Generate, <a href="#p29">29</a>, <a href="#p38">38</a>, <a href="#p134">134</a>, <a href="#p136">136</a>, <a href="#p145">145</a>.</li> + +<li>Generated, <a href="#p55">55</a>.</li> + +<li>Generating, <a href="#p32">32</a>, <a href="#p134">134</a>.</li> + +<li>Generation, <a href="#p170">170</a>.</li> + +<li>Generator, <a href="#p32">32</a>, <a href="#p125">125</a>, <a href="#p147">147</a>.</li> + +<li>German silver, <a href="#p136">136</a>, <a href="#p137">137</a>.</li> + +<li>Germicide, <a href="#p187">187</a>.</li> + +<li>Gimlets, <a href="#p17">17</a>.</li> + +<li>Glass, <a href="#p30">30</a>, <a href="#p86">86</a>, <a href="#p126">126</a>, <a href="#p186">186</a>.</li> + +<li>Gold, <a href="#p135">135</a>.</li> + +<li>Grid, <a href="#p84">84</a>.</li> + +<li>Ground circuit, <a href="#p121">121</a>.</li> + +<li>Gunpowder, <a href="#p6">6</a>.</li> + + +</ul> +<h4><a id="IX_H" name="IX_H"></a>H</h4> +<ul class="IX"> + +<li>Hack-saw, <a href="#p14">14</a>.</li> + +<li>Hammer, <a href="#p13">13</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Heart-shaped switch, <a href="#p77">77</a>.</li> + +<li>Heater, <a href="#p136">136</a>.</li> + +<li>Heating, <a href="#p13">13</a>, <a href="#p38">38</a>.</li> + +<li>Hertzian rays, <a href="#p170">170</a>.</li> + +<li>Hertzian wave, <a href="#p184">184</a>.</li> + +<li>High tension, <a href="#p38">38</a>, <a href="#p102">102</a>, <a href="#p184">184</a>.</li> + +<li>High tension apparatus, <a href="#p98">98</a>.</li> + +<li>High tension coils, <a href="#p103">103</a>.</li> + +<li>High voltage, <a href="#p158">158</a>.</li> + +<li>Horizontal bar, <a href="#p46">46</a>.</li> + +<li>Horseshoe magnet, <a href="#p22">22</a>, <a href="#p24">24</a>, <a href="#p175">175</a>.</li> + +<li>Hydrate of aluminum, <a href="#p129">129</a>.</li> + +<li>Hydrogen, <a href="#p35">35</a>, <a href="#p123">123</a>, <a href="#p125">125</a>, <a href="#p128">128</a>.</li> + + +</ul> +<h4><a id="IX_I" name="IX_I"></a>I</h4> +<ul class="IX"> + +<li>Igniting, <a href="#p99">99</a>.</li> + +<li>Illumination, <a href="#p162">162</a>, <a href="#p163">163</a>, <a href="#p165">165</a>, <a href="#p167">167</a>, <a href="#p170">170</a>.</li> + +<li>Immersed, <a href="#p133">133</a>.</li> + +<li>Impulses, <a href="#p60">60</a>, <a href="#p62">62</a>, <a href="#p96">96</a>, <a href="#p104">104</a>, <a href="#p109">109</a>, <a href="#p152">152</a>, <a href="#p179">179</a>.</li> + +<li>Incandescent, <a href="#p166">166</a>, <a href="#p168">168</a>.</li> + +<li>Induced, <a href="#p28">28</a>.</li> + +<li>Inductance, <a href="#p149">149</a>, <a href="#p150">150</a>.</li> + +<li>Induction, <a href="#p27">27</a>, <a href="#p37">37</a>, <a href="#p98">98</a>, <a href="#p147">147</a>.</li> + +<li>Induction coils, <a href="#p99">99</a>, <a href="#p102">102</a>, <a href="#p106">106</a>.</li> + +<li>Influences, <a href="#p178">178</a>.</li> + +<li>Initial charge, <a href="#p88">88</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p214" id="p214">p. 214</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Insulated, 27, <a href="#p28">28</a>, <a href="#p40">40</a>, <a href="#p43">43</a>, <a href="#p52">52</a>, <a href="#p55">55</a>, <a href="#p73">73</a>, <a href="#p115">115</a>, <a href="#p151">151</a>, <a href="#p180">180</a>.</li> + +<li>Insulating, <a href="#p66">66</a>, <a href="#p69">69</a>, <a href="#p120">120</a>, <a href="#p140">140</a>, <a href="#p164">164</a>.</li> + +<li>Insulating material, <a href="#p114">114</a>.</li> + +<li>Insulation, <a href="#p40">40</a>, <a href="#p116">116</a>.</li> + +<li>Instruments, <a href="#p49">49</a>, <a href="#p94">94</a>, <a href="#p112">112</a>, <a href="#p118">118</a>, <a href="#p120">120</a>.</li> + +<li>Instruments, measuring, <a href="#p8">8</a>.</li> + +<li>Intensity, <a href="#p55">55</a>, <a href="#p60">60</a>, <a href="#p104">104</a>, <a href="#p154">154</a>.</li> + +<li>Interior, magnetic, <a href="#p23">23</a>.</li> + +<li>Internal resistance, <a href="#p37">37</a>.</li> + +<li>Interruption, <a href="#p102">102</a>, <a href="#p103">103</a>.</li> + +<li>Installation, <a href="#p168">168</a>.</li> + +<li>Ionize, <a href="#p186">186</a>.</li> + +<li>Iron, <a href="#p19">19</a>, <a href="#p132">132</a>, <a href="#p133">133</a>, <a href="#p136">136</a>, <a href="#p142">142</a>, <a href="#p171">171</a>.</li> + +<li>Isolated, <a href="#p186">186</a>.</li> + + +</ul> +<h4><a id="IX_J" name="IX_J"></a>J</h4> +<ul class="IX"> + +<li>Jar, <a href="#p29">29</a>, <a href="#p31">31</a>, <a href="#p32">32</a>.</li> + +<li>Journal, <a href="#p46">46</a>.</li> + +<li>Journal block, <a href="#p16">16</a>, <a href="#p146">146</a>.</li> + +<li>Jump spark, <a href="#p99">99</a>.</li> + + +</ul> +<h4><a id="IX_K" name="IX_K"></a>K</h4> +<ul class="IX"> + +<li>Key, <a href="#p90">90</a>, <a href="#p91">91</a>, <a href="#p95">95</a>.</li> + +<li>Key, sending, <a href="#p90">90</a>.</li> + +<li>Knob, <a href="#p32">32</a>.</li> + +<li>Knob, terminal, <a href="#p31">31</a>.</li> + + +</ul> +</td><td> + +<h4><a id="IX_L" name="IX_L"></a>L</h4> +<ul class="IX"> + +<li>Laboratory, <a href="#p9">9</a>.</li> + +<li>Lead, <a href="#p31">31</a>, <a href="#p136">136</a>.</li> + +<li>Lead, precipitated, <a href="#p83">83</a>, <a href="#p85">85</a>.</li> + +<li>Lead, red, <a href="#p83">83</a>, <a href="#p84">84</a>.</li> + +<li>Lever switching, <a href="#p67">67</a>.</li> + +<li>Light, <a href="#p104">104</a>.</li> + +<li>Light method, <a href="#p56">56</a>.</li> + +<li>Lighting, <a href="#p9">9</a>, <a href="#p38">38</a>.</li> + +<li>Lighting circuit, <a href="#p48">48</a>.</li> + +<li>Lighting system, <a href="#p82">82</a>.</li> + +<li>Lightning, <a href="#p6">6</a>, <a href="#p171">171</a>, <a href="#p172">172</a>, <a href="#p173">173</a>.</li> + +<li>Lightning rod, <a href="#p173">173</a>.</li> + +<li>Lime, chloride of, <a href="#p84">84</a>.</li> + +<li>Line of force, <a href="#p146">146</a>.</li> + +<li>Line wire, <a href="#p122">122</a>.</li> + +<li>Line, magnetic, <a href="#p22">22</a>, <a href="#p23">23</a>.</li> + +<li>Liquid, <a href="#p32">32</a>.</li> + +<li>Litharge, <a href="#p83">83</a>.</li> + +<li>Loadstone, <a href="#p17">17</a>.</li> + +<li>Locomotives, <a href="#p165">165</a>.</li> + +<li>Low tension, <a href="#p38">38</a>, <a href="#p98">98</a>, <a href="#p102">102</a>, <a href="#p179">179</a>.</li> + + +</ul> +<h4><a id="IX_M" name="IX_M"></a>M</h4> +<ul class="IX"> + +<li>Magnet bar, <a href="#p20">20</a>.</li> + +<li>Magnet core, <a href="#p16">16</a>, <a href="#p75">75</a>, <a href="#p93">93</a>.</li> + +<li>Magnet, electro, <a href="#p59">59</a>, <a href="#p78">78</a>.</li> + +<li>Magnet, horseshoe, <a href="#p22">22</a>, <a href="#p25">25</a>, <a href="#p175">175</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p215" id="p215">p. 215</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Magnet lines, <a href="#p22">22</a>, <a href="#p23">23</a>.</li> + +<li>Magnet, permanent, <a href="#p25">25</a>, <a href="#p38">38</a>, <a href="#p46">46</a>, <a href="#p50">50</a>, <a href="#p172">172</a>.</li> + +<li>Magnet, reversed, <a href="#p20">20</a>.</li> + +<li>Magnet, steel, <a href="#p53">53</a>.</li> + +<li>Magnet, swinging, <a href="#p53">53</a>.</li> + +<li>Magnetic, <a href="#p7">7</a>, <a href="#p19">19</a>, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p25">25</a>, <a href="#p113">113</a>, <a href="#p178">178</a>.</li> + +<li>Magnetic construction, <a href="#p39">39</a>.</li> + +<li>Magnetic exterior, <a href="#p27">27</a>.</li> + +<li>Magnetic field, <a href="#p22">22</a>, <a href="#p24">24</a>, <a href="#p27">27</a>, <a href="#p38">38</a>, <a href="#p50">50</a>, <a href="#p112">112</a>, <a href="#p146">146</a>, <a href="#p148">148</a>, <a href="#p155">155</a>.</li> + +<li>Magnetic interior, <a href="#p23">23</a>.</li> + +<li>Magnetic pull, <a href="#p59">59</a>.</li> + +<li>Magnetic radiator, <a href="#p37">37</a>.</li> + +<li>Magnetism, <a href="#p19">19</a>, <a href="#p54">54</a>, <a href="#p104">104</a>, <a href="#p110">110</a>, <a href="#p159">159</a>, <a href="#p171">171</a>.</li> + +<li>Magnetized, <a href="#p18">18</a>, <a href="#p25">25</a>, <a href="#p27">27</a>, <a href="#p50">50</a>.</li> + +<li>Magnetized wire, <a href="#p146">146</a>.</li> + +<li>Magnets, <a href="#p13">13</a>, <a href="#p14">14</a>, <a href="#p18">18</a>, <a href="#p19">19</a>, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p23">23</a>, <a href="#p24">24</a>, <a href="#p25">25</a>, <a href="#p39">39</a>, <a href="#p51">51</a>, <a href="#p53">53</a>, <a href="#p54">54</a>, <a href="#p70">70</a>, <a href="#p71">71</a>, <a href="#p73">73</a>, <a href="#p75">75</a>, <a href="#p81">81</a>, <a href="#p90">90</a>, <a href="#p93">93</a>, <a href="#p112">112</a>, <a href="#p113">113</a>, <a href="#p115">115</a>, <a href="#p147">147</a>, <a href="#p150">150</a>, <a href="#p163">163</a>, <a href="#p176">176</a>, <a href="#p177">177</a>, <a href="#p178">178</a>.</li> + +<li>Main conductor, <a href="#p31">31</a>.</li> + +<li>Mandrel, <a href="#p15">15</a>, <a href="#p16">16</a>.</li> + +<li>Manganese, <a href="#p19">19</a>.</li> + +<li>Manifestations, <a href="#p19">19</a>.</li> + +<li>Mariner, <a href="#p172">172</a>.</li> + +<li>Material, non-conducting, <a href="#p90">90</a>.</li> + +<li>Maximum, <a href="#p154">154</a>.</li> + +<li>Measure, <a href="#p55">55</a>, <a href="#p56">56</a>, <a href="#p60">60</a>, <a href="#p62">62</a>.</li> + +<li>Measurement, <a href="#p62">62</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Measuring devices, <a href="#p27">27</a>.</li> + +<li>Measuring instruments, <a href="#p8">8</a>.</li> + +<li>Mechanism, <a href="#p47">47</a>, <a href="#p180">180</a>.</li> + +<li>Medical batteries, <a href="#p99">99</a>.</li> + +<li>Mercury, <a href="#p63">63</a>, <a href="#p169">169</a>.</li> + +<li>Metal base, <a href="#p73">73</a>.</li> + +<li>Mica, <a href="#p186">186</a>.</li> + +<li>Microphone, <a href="#p118">118</a>, <a href="#p119">119</a>, <a href="#p120">120</a>.</li> + +<li>Millimeter, <a href="#p63">63</a>.</li> + +<li>Minus, <a href="#p34">34</a>.</li> + +<li>Minus sign, <a href="#p21">21</a>.</li> + +<li>Morse code, <a href="#p76">76</a>.</li> + +<li>Motor, <a href="#p7">7</a>, <a href="#p21">21</a>, <a href="#p27">27</a>, <a href="#p46">46</a>, <a href="#p47">47</a>, <a href="#p62">62</a>, <a href="#p82">82</a>, <a href="#p99">99</a>, <a href="#p150">150</a>, <a href="#p176">176</a>, <a href="#p180">180</a>.</li> + +<li>Mouthpiece, <a href="#p115">115</a>.</li> + +<li>Mouthpiece rays, <a href="#p188">188</a>.</li> + +<li>Moving field, <a href="#p117">117</a>.</li> + +<li>Multiple, <a href="#p168">168</a>.</li> + +<li>Musical scale, <a href="#p111">111</a>.</li> + + +</ul> +<h4><a id="IX_N" name="IX_N"></a>N</h4> +<ul class="IX"> + +<li>Negative, <a href="#p21">21</a>, <a href="#p35">35</a>, <a href="#p36">36</a>, <a href="#p68">68</a>, <a href="#p83">83</a>, <a href="#p86">86</a>, <a href="#p87">87</a>, <a href="#p94">94</a>, <a href="#p125">125</a>, <a href="#p151">151</a>, <a href="#p152">152</a>, <a href="#p154">154</a>, <a href="#p165">165</a>, <a href="#p177">177</a>, <a href="#p178">178</a>, <a href="#p179">179</a>.</li> + +<li>Neutral, <a href="#p125">125</a>.</li> + +<li>Neutral plate, <a href="#p84">84</a>.</li> + +<li>Nickel, <a href="#p136">136</a>.</li> + +<li>Nickel plating, <a href="#p132">132</a>.</li> + +<li>Nitrate of silver, <a href="#p62">62</a>.</li> + +<li>Nitrogen, <a href="#p126">126</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p216" id="p216">p. 216</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Non-conducting material, <a href="#p90">90</a>.</li> + +<li>Non-conductor, <a href="#p164">164</a>.</li> + +<li>Non-magnetic, <a href="#p19">19</a>.</li> + +<li>North pole, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p23">23</a>, <a href="#p25">25</a>, <a href="#p50">50</a>, <a href="#p54">54</a>, <a href="#p156">156</a>.</li> + +<li>Number plate, <a href="#p75">75</a>.</li> +<li>N-ray, <a href="#p188">188</a>.</li> +</ul> +<h4><a id="IX_O" name="IX_O"></a>O</h4> +<ul class="IX"> + +<li>Ohms, <a href="#p60">60</a>, <a href="#p63">63</a>.</li> + +<li>Ohms, international, <a href="#p63">63</a>.</li> + +<li>Ohms law, <a href="#p7">7</a>.</li> + +<li>Operator, <a href="#p95">95</a>, <a href="#p118">118</a>.</li> + +<li>Oscillating, <a href="#p99">99</a>, <a href="#p105">105</a>.</li> + +<li>Osmium, <a href="#p169">169</a>.</li> + +<li>Oxides, <a href="#p125">125</a>.</li> + +<li>Oxidizing, <a href="#p183">183</a>.</li> + +<li>Oxygen, <a href="#p35">35</a>, <a href="#p123">123</a>, <a href="#p125">125</a>, <a href="#p126">126</a>, <a href="#p128">128</a>, <a href="#p129">129</a>, <a href="#p169">169</a>.</li> + + +</ul> +<h4><a id="IX_P" name="IX_P"></a>P</h4> +<ul class="IX"> + +<li>Packing ring, <a href="#p124">124</a>.</li> + +<li>Paraffine, <a href="#p56">56</a>, <a href="#p100">100</a>, <a href="#p101">101</a>, <a href="#p102">102</a>.</li> + +<li>Paraffine wax, <a href="#p86">86</a>.</li> + +<li>Parallel, <a href="#p87">87</a>, <a href="#p88">88</a>, <a href="#p89">89</a>.</li> + +<li>Parallel switch bar, <a href="#p67">67</a>.</li> + +<li>Parallel wires, <a href="#p28">28</a>, <a href="#p49">49</a>.</li> + +<li>Partition, <a href="#p124">124</a>.</li> + +<li>Peon, <a href="#p13">13</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Percolate, <a href="#p128">128</a>.</li> + +<li>Periodicity, <a href="#p159">159</a>.</li> + +<li>Periods of alternations, <a href="#p149">149</a>.</li> + +<li>Permanent, <a href="#p18">18</a>, <a href="#p19">19</a>, <a href="#p50">50</a>.</li> + +<li>Permanent magnet, <a href="#p25">25</a>, <a href="#p38">38</a>, <a href="#p46">46</a>, <a href="#p50">50</a>, <a href="#p172">172</a>.</li> + +<li>Phase, <a href="#p19">19</a>.</li> + +<li>Phenomenon, <a href="#p27">27</a>, <a href="#p65">65</a>.</li> + +<li>Photograph, <a href="#p186">186</a>.</li> + +<li>Physical, <a href="#p21">21</a>.</li> + +<li>Pile, voltaic, <a href="#p33">33</a>.</li> + +<li>Pipe, <a href="#p61">61</a>.</li> + +<li>Pitchblende, <a href="#p186">186</a>.</li> + +<li>Pivot pin, <a href="#p53">53</a>.</li> + +<li>Pivotal, <a href="#p22">22</a>.</li> + +<li>Plane, <a href="#p13">13</a>.</li> + +<li>Plate, <a href="#p57">57</a>, <a href="#p93">93</a>.</li> + +<li>Plate, contact, <a href="#p67">67</a>, <a href="#p68">68</a>, <a href="#p79">79</a>.</li> + +<li>Plate, copper, <a href="#p33">33</a>, <a href="#p35">35</a>, <a href="#p58">58</a>, <a href="#p67">67</a>.</li> + +<li>Plate, negative, <a href="#p84">84</a>.</li> + +<li>Plate, number, <a href="#p75">75</a>.</li> + +<li>Plate, positive, <a href="#p84">84</a>, <a href="#p88">88</a>.</li> + +<li>Plate, zinc, <a href="#p33">33</a>.</li> + +<li>Platinum, <a href="#p13">13</a>, <a href="#p57">57</a>, <a href="#p137">137</a>.</li> + +<li>Pliers, <a href="#p14">14</a>.</li> + +<li>Plus sign, <a href="#p21">21</a>, <a href="#p24">24</a>.</li> + +<li>Pointer, <a href="#p53">53</a>.</li> + +<li>Polarity, <a href="#p154">154</a>, <a href="#p177">177</a>, <a href="#p178">178</a>, <a href="#p179">179</a>.</li> + +<li>Polarization, <a href="#p35">35</a>.</li> + +<li>Pole, north, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p23">23</a>, <a href="#p25">25</a>, <a href="#p50">50</a>, <a href="#p54">54</a>, <a href="#p156">156</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p217" id="p217">p. 217</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Pole piece, <a href="#p40">40</a>, <a href="#p42">42</a>.</li> + +<li>Pole, south, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p25">25</a>, <a href="#p50">50</a>, <a href="#p54">54</a>, <a href="#p156">156</a>.</li> + +<li>Poles, <a href="#p177">177</a>, <a href="#p179">179</a>.</li> + +<li>Polonium, <a href="#p186">186</a>.</li> + +<li>Porcelain, <a href="#p86">86</a>.</li> + +<li>Porous, <a href="#p85">85</a>.</li> + +<li>Positive, <a href="#p4">4</a>, <a href="#p21">21</a>, <a href="#p25">25</a>, <a href="#p36">36</a>, <a href="#p40">40</a>, <a href="#p68">68</a>, <a href="#p83">83</a>, <a href="#p86">86</a>, <a href="#p87">87</a>, <a href="#p94">94</a>, <a href="#p123">123</a>, <a href="#p125">125</a>, <a href="#p151">151</a>, <a href="#p152">152</a>, <a href="#p153">153</a>, <a href="#p155">155</a>, <a href="#p165">165</a>.</li> + +<li>Post, binding, <a href="#p52">52</a>, <a href="#p71">71</a>.</li> + +<li>Potentiality, <a href="#p105">105</a>, <a href="#p109">109</a>.</li> + +<li>Power, <a href="#p38">38</a>, <a href="#p186">186</a>.</li> + +<li>Power, candle, <a href="#p89">89</a>, <a href="#p139">139</a>.</li> + +<li>Precipitate of lead, <a href="#p83">83</a>, <a href="#p85">85</a>.</li> + +<li>Precision, <a href="#p7">7</a>.</li> + +<li>Pressure, <a href="#p87">87</a>.</li> + +<li>Primary, <a href="#p35">35</a>, <a href="#p62">62</a>, <a href="#p98">98</a>, <a href="#p134">134</a>, <a href="#p142">142</a>, <a href="#p159">159</a>, <a href="#p184">184</a>.</li> + +<li>Primary battery, <a href="#p7">7</a>, <a href="#p99">99</a>.</li> + +<li>Primary circuit, <a href="#p99">99</a>.</li> + +<li>Primary coil, <a href="#p106">106</a>, <a href="#p109">109</a>.</li> + +<li>Prime conductor, <a href="#p6">6</a>.</li> + +<li>Projected, <a href="#p185">185</a>.</li> + +<li>Propagated, <a href="#p105">105</a>, <a href="#p185">185</a>.</li> + +<li>Properties, <a href="#p55">55</a>.</li> + +<li>Purification, <a href="#p123">123</a>, <a href="#p128">128</a>.</li> + +<li>Purifier, <a href="#p126">126</a>, <a href="#p131">131</a>.</li> + +<li>Push button, <a href="#p65">65</a>, <a href="#p68">68</a>, <a href="#p69">69</a>, <a href="#p70">70</a>, <a href="#p76">76</a>, <a href="#p79">79</a>.</li> + + +</ul> +<h4><a id="IX_Q" name="IX_Q"></a>Q</h4> +<ul class="IX"> + +<li>Quantity, <a href="#p55">55</a>, <a href="#p60">60</a>, <a href="#p61">61</a>, <a href="#p138">138</a>.</li> + +<li>Quartz, <a href="#p186">186</a>.</li> + + +</ul> + +</td><td> +<h4><a id="IX_R" name="IX_R"></a>R</h4> +<ul class="IX"> + +<li>Radio-activity, <a href="#p186">186</a>.</li> + +<li>Radium, <a href="#p184">184</a>, <a href="#p185">185</a>, <a href="#p187">187</a>, <a href="#p188">188</a>.</li> + +<li>Ratchet drill, <a href="#p13">13</a>.</li> + +<li>Reaction, <a href="#p148">148</a>.</li> + +<li>Receiver, <a href="#p12">12</a>, <a href="#p90">90</a>, <a href="#p97">97</a>, <a href="#p121">121</a>, <a href="#p122">122</a>.</li> + +<li>Receiving station, <a href="#p109">109</a>.</li> + +<li>Rectangular, <a href="#p69">69</a>.</li> + +<li>Rectifiers, <a href="#p146">146</a>.</li> + +<li>Red lead, <a href="#p83">83</a>, <a href="#p84">84</a>.</li> + +<li>Reel, <a href="#p13">13</a>.</li> + +<li>Reflected, <a href="#p185">185</a>.</li> + +<li>Refraction, <a href="#p185">185</a>.</li> + +<li>Refractory, <a href="#p182">182</a>.</li> + +<li>Register, <a href="#p57">57</a>.</li> + +<li>Removable, <a href="#p54">54</a>.</li> + +<li>Removable cap, <a href="#p73">73</a>.</li> + +<li>Repel, <a href="#p20">20</a>.</li> + +<li>Repulsion, <a href="#p21">21</a>, <a href="#p128">128</a>.</li> + +<li>Reservoir, <a href="#p61">61</a>, <a href="#p62">62</a>.</li> + +<li>Resiliency, <a href="#p99">99</a>.</li> + +<li>Resistance, <a href="#p7">7</a>, <a href="#p36">36</a>, <a href="#p37">37</a>, <a href="#p60">60</a>, <a href="#p63">63</a>, <a href="#p99">99</a>, <a href="#p135">135</a>, <a href="#p136">136</a>, <a href="#p137">137</a>, <a href="#p138">138</a>, <a href="#p140">140</a>, <a href="#p141">141</a>, <a href="#p156">156</a>, <a href="#p157">157</a>, <a href="#p163">163</a>, <a href="#p166">166</a>, <a href="#p168">168</a>.</li> + +<li>Resistance bridge, <a href="#p7">7</a>.</li> + +<li>Resistance, external, <a href="#p37">37</a>.</li> + +<li>Resistance, internal, <a href="#p37">37</a>.</li> + +<li>Rheostat, <a href="#p7">7</a>.</li> + +<li>Reversed, <a href="#p20">20</a>, <a href="#p50">50</a>, <a href="#p153">153</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p218" id="p218">p. 218</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Reversible, <a href="#p163">163</a>.</li> + +<li>Reversing, <a href="#p176">176</a>.</li> + +<li>Reversing switch, <a href="#p67">67</a>.</li> + +<li>Revolubly, <a href="#p46">46</a>.</li> + +<li>Revolve, <a href="#p179">179</a>.</li> + +<li>Revolving, <a href="#p177">177</a>.</li> + +<li>Roentgen rays, <a href="#p184">184</a>.</li> + +<li>Roentgen tube, <a href="#p187">187</a>.</li> + +<li>Rotation, <a href="#p149">149</a>.</li> + +<li>Rubber, <a href="#p40">40</a>, <a href="#p46">46</a>, <a href="#p77">77</a>, <a href="#p115">115</a>, <a href="#p126">126</a>, <a href="#p130">130</a>, <a href="#p138">138</a>.</li> + + +</ul> +<h4><a id="IX_S" name="IX_S"></a>S</h4> +<ul class="IX"> + +<li>Sad-irons, <a href="#p13">13</a>.</li> + +<li>Saline, <a href="#p133">133</a>.</li> + +<li>Sanitation, <a href="#p12">12</a>.</li> + +<li>Saturated, <a href="#p85">85</a>.</li> + +<li>Screw, <a href="#p15">15</a>.</li> + +<li>Screw, binding, <a href="#p65">65</a>, <a href="#p66">66</a>.</li> + +<li>Screw-driver, <a href="#p14">14</a>.</li> + +<li>Screw, set, <a href="#p72">72</a>.</li> + +<li>Sealing wax, <a href="#p53">53</a>.</li> + +<li>Secondary, <a href="#p62">62</a>, <a href="#p98">98</a>, <a href="#p105">105</a>, <a href="#p158">158</a>, <a href="#p159">159</a>, <a href="#p160">160</a>.</li> + +<li>Secondary circuit, <a href="#p99">99</a>.</li> + +<li>Secondary coil, <a href="#p107">107</a>, <a href="#p108">108</a>.</li> + +<li>Self-induction, <a href="#p149">149</a>, <a href="#p156">156</a>.</li> + +<li>Sender, <a href="#p90">90</a>, <a href="#p97">97</a>.</li> + +<li>Sending apparatus, <a href="#p106">106</a>.</li> + +<li>Sending key, <a href="#p90">90</a>.</li> + +<li>Separately excited, <a href="#p46">46</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Series-wound, <a href="#p47">47</a>.</li> + +<li>Severed magnet, <a href="#p20">20</a>.</li> + +<li>Sewage, <a href="#p12">12</a>.</li> + +<li>Shaft, <a href="#p30">30</a>.</li> + +<li>Shears, <a href="#p14">14</a>, <a href="#p17">17</a>.</li> + +<li>Shellac, <a href="#p40">40</a>.</li> + +<li>Shunt-wound, <a href="#p47">47</a>.</li> + +<li>Signal, <a href="#p118">118</a>.</li> + +<li>Silver, <a href="#p19">19</a>, <a href="#p63">63</a>, <a href="#p125">125</a>.</li> + +<li>Silver nitrate, <a href="#p62">62</a>.</li> + +<li>Socket, <a href="#p54">54</a>, <a href="#p139">139</a>.</li> + +<li>Soldering, <a href="#p14">14</a>.</li> + +<li>Soldering iron, <a href="#p17">17</a>.</li> + +<li>Solution, <a href="#p55">55</a>, <a href="#p57">57</a>, <a href="#p62">62</a>, <a href="#p63">63</a>, <a href="#p84">84</a>, <a href="#p86">86</a>, <a href="#p133">133</a>, <a href="#p134">134</a>, <a href="#p142">142</a>.</li> + +<li>Sounder, <a href="#p90">90</a>, <a href="#p92">92</a>, <a href="#p95">95</a>, <a href="#p96">96</a>.</li> + +<li>Sounding board, <a href="#p119">119</a>.</li> + +<li>Source, charging, <a href="#p83">83</a>.</li> + +<li>South pole, <a href="#p20">20</a>, <a href="#p21">21</a>, <a href="#p22">22</a>, <a href="#p25">25</a>, <a href="#p50">50</a>, <a href="#p54">54</a>, <a href="#p156">156</a>.</li> + +<li>Spark gap, <a href="#p102">102</a>, <a href="#p106">106</a>.</li> + +<li>Spark jump, <a href="#p99">99</a>.</li> + +<li>Spring finger, <a href="#p69">69</a>.</li> + +<li>Square, <a href="#p14">14</a>, <a href="#p17">17</a>.</li> + +<li>Standard, <a href="#p62">62</a>, <a href="#p63">63</a>.</li> + +<li>Station, <a href="#p94">94</a>, <a href="#p95">95</a>, <a href="#p117">117</a>, <a href="#p122">122</a>.</li> + +<li>Steel, <a href="#p18">18</a>, <a href="#p19">19</a>.</li> + +<li>Steel magnet, <a href="#p53">53</a>.</li> + +<li>Sterilized, <a href="#p12">12</a>.</li> + +<li>Stirrup, <a href="#p75">75</a>.</li> + +<li>Stock bit, <a href="#p13">13</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p219" id="p219">p. 219</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Stock contact, <a href="#p121">121</a>.</li> + +<li>Storage, <a href="#p82">82</a>.</li> + +<li>Storage battery, <a href="#p107">107</a>.</li> + +<li>Storing, <a href="#p82">82</a>.</li> + +<li>Substances, <a href="#p135">135</a>.</li> + +<li>Sulphate, <a href="#p55">55</a>, <a href="#p128">128</a>, <a href="#p133">133</a>.</li> + +<li>Sulphur, <a href="#p19">19</a>.</li> + +<li>Sulphuric acid, <a href="#p31">31</a>, <a href="#p84">84</a>.</li> + +<li>Sulphuric acid voltameter, <a href="#p55">55</a>, <a href="#p57">57</a>.</li> + +<li>Superstition, <a href="#p171">171</a>, <a href="#p173">173</a>.</li> + +<li>Surging, <a href="#p153">153</a>, <a href="#p154">154</a>.</li> + +<li>Swinging magnet, <a href="#p53">53</a>.</li> + +<li>Swinging switch blade, <a href="#p67">67</a>.</li> + +<li>Switch blades, <a href="#p66">66</a>.</li> + +<li>Switches, <a href="#p65">65</a>, <a href="#p66">66</a>, <a href="#p70">70</a>, <a href="#p77">77</a>, <a href="#p78">78</a>, <a href="#p90">90</a>, <a href="#p117">117</a>.</li> + +<li>Switches, bar, <a href="#p65">65</a>, <a href="#p68">68</a>, <a href="#p90">90</a>, <a href="#p91">91</a>.</li> + +<li>Switches, bar, parallel, <a href="#p67">67</a>.</li> + +<li>Switches, heart-shaped, <a href="#p78">78</a>.</li> + +<li>Switches, piece, <a href="#p77">77</a>.</li> + +<li>Switches, reversing, <a href="#p67">67</a>.</li> + +<li>Switches, sliding, <a href="#p67">67</a>, <a href="#p80">80</a>.</li> + +<li>Switches, terminal, <a href="#p8">8</a>.</li> + +<li>Switches, two-pole, <a href="#p65">65</a>.</li> + +<li>System, circuiting, <a href="#p79">79</a>.</li> + + +</ul> +<h4><a id="IX_T" name="IX_T"></a>T</h4> +<ul class="IX"> + +<li>Tail-piece, <a href="#p16">16</a>.</li> + +<li>Tantalum, <a href="#p169">169</a>.</li> + +<li>Telegraph, <a href="#p11">11</a>, <a href="#p90">90</a>, <a href="#p96">96</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Telegraph key, <a href="#p106">106</a>.</li> + +<li>Telegraph sounder, <a href="#p108">108</a>, <a href="#p109">109</a>.</li> + +<li>Telegraphing, <a href="#p94">94</a>.</li> + +<li>Telephone, <a href="#p12">12</a>, <a href="#p110">110</a>, <a href="#p113">113</a>, <a href="#p117">117</a>, <a href="#p118">118</a>, <a href="#p119">119</a>, <a href="#p120">120</a>.</li> + +<li>Telephone circuit, <a href="#p118">118</a>.</li> + +<li>Telephone connections, <a href="#p116">116</a>.</li> + +<li>Telephone hook, <a href="#p122">122</a>.</li> + +<li>Temperature, <a href="#p56">56</a>, <a href="#p88">88</a>, <a href="#p134">134</a>, <a href="#p161">161</a>, <a href="#p170">170</a>.</li> + +<li>Tension, high, <a href="#p38">38</a>, <a href="#p102">102</a>, <a href="#p184">184</a>.</li> + +<li>Tension, low, <a href="#p38">38</a>, <a href="#p98">98</a>, <a href="#p102">102</a>, <a href="#p179">179</a>.</li> + +<li>Terminal, <a href="#p31">31</a>, <a href="#p34">34</a>, <a href="#p35">35</a>, <a href="#p40">40</a>, <a href="#p48">48</a>, <a href="#p82">82</a>, <a href="#p86">86</a>, <a href="#p93">93</a>, <a href="#p95">95</a>, <a href="#p107">107</a>, <a href="#p116">116</a>, <a href="#p121">121</a>, <a href="#p122">122</a>, <a href="#p151">151</a>, <a href="#p152">152</a>, <a href="#p153">153</a>, <a href="#p154">154</a>, <a href="#p156">156</a>.</li> + +<li>Terminal knob, <a href="#p31">31</a>.</li> + +<li>Terminal, secondary, <a href="#p102">102</a>.</li> + +<li>Terminal switch, <a href="#p81">81</a>.</li> + +<li>Theoretical, <a href="#p160">160</a>.</li> + +<li>Therapeutics, <a href="#p187">187</a>.</li> + +<li>Thermo-electric couples, <a href="#p146">146</a>.</li> + +<li>Thermo-electricity, <a href="#p135">135</a>.</li> + +<li>Thermometer, <a href="#p56">56</a>.</li> + +<li>Thorium, <a href="#p169">169</a>, <a href="#p186">186</a>.</li> + +<li>Thunderbolt, <a href="#p171">171</a>, <a href="#p173">173</a>.</li> + +<li>Tin, <a href="#p136">136</a>.</li> + +<li>Tinfoil, <a href="#p31">31</a>, <a href="#p101">101</a>.</li> + +<li>Tools, <a href="#p11">11</a>, <a href="#p13">13</a>, <a href="#p17">17</a>.</li> + +<li>Torch, brazing, <a href="#p17">17</a>.</li> + +<li>Transformer, <a href="#p145">145</a>, <a href="#p146">146</a>, <a href="#p158">158</a>, <a href="#p159">159</a>, <a href="#p180">180</a>, <a href="#p182">182</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p220" id="p220">p. 220</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Transformer, step-down, <a href="#p182">182</a>.</li> + +<li>Transmission, <a href="#p38">38</a>, <a href="#p187">187</a>.</li> + +<li>Transmit, <a href="#p63">63</a>, <a href="#p95">95</a>, <a href="#p157">157</a>.</li> + +<li>Transmitter, <a href="#p12">12</a>, <a href="#p120">120</a>, <a href="#p121">121</a>, <a href="#p122">122</a>, <a href="#p123">123</a>.</li> + +<li>Transverse, <a href="#p16">16</a>, <a href="#p52">52</a>.</li> + +<li>Transversely, <a href="#p43">43</a>.</li> + +<li>Trigger, <a href="#p75">75</a>.</li> + +<li>Tripod, <a href="#p31">31</a>.</li> + +<li>Tubular, <a href="#p44">44</a>, <a href="#p45">45</a>.</li> + +<li>Two-pole switch, <a href="#p65">65</a>.</li> + + +</ul> +<h4><a id="IX_U" name="IX_U"></a>U</h4> +<ul class="IX"> + +<li>Ultra-violet, <a href="#p185">185</a>.</li> + +<li>Uranium, <a href="#p186">186</a>.</li> + + +</ul> +<h4><a id="IX_V" name="IX_V"></a>V</h4> +<ul class="IX"> + +<li>Vacuum, <a href="#p184">184</a>.</li> + +<li>Vapor lamps, <a href="#p169">169</a>.</li> + +<li>Velocity, <a href="#p60">60</a>, <a href="#p73">73</a>.</li> + +<li>Vertical armature, <a href="#p75">75</a>.</li> + +<li>Vibration, <a href="#p110">110</a>, <a href="#p111">111</a>, <a href="#p113">113</a>.</li> + +<li>Vibratory, <a href="#p110">110</a>.</li> + +<li>Vise, <a href="#p13">13</a>.</li> + +<li>Voltage, <a href="#p37">37</a>, <a href="#p38">38</a>, <a href="#p60">60</a>, <a href="#p61">61</a>, <a href="#p62">62</a>, <a href="#p63">63</a>, <a href="#p87">87</a>, <a href="#p88">88</a>, <a href="#p99">99</a>, <a href="#p147">147</a>, <a href="#p154">154</a>, <a href="#p165">165</a>, <a href="#p180">180</a>, <a href="#p182">182</a>.</li> + +<li>Voltage, high, <a href="#p158">158</a>.</li> + +<li>Voltaic, <a href="#p29">29</a>, <a href="#p32">32</a>.</li> +</ul> +</td><td> +<ul class="IX"> +<li>Voltaic pile, <a href="#p33">33</a>.</li> + +<li>Voltameter, <a href="#p7">7</a>, <a href="#p58">58</a>, <a href="#p88">88</a>.</li> + +<li>Voltameter, sulphuric, acid, <a href="#p55">55</a>, <a href="#p57">57</a>.</li> + +<li>Volts, <a href="#p60">60</a>, <a href="#p62">62</a>, <a href="#p87">87</a>, <a href="#p89">89</a>, <a href="#p132">132</a>, <a href="#p158">158</a>, <a href="#p159">159</a>.</li> + + +</ul> +<h4><a id="IX_W" name="IX_W"></a>W</h4> +<ul class="IX"> + +<li>Water, <a href="#p123">123</a>, <a href="#p138">138</a>, <a href="#p144">144</a>.</li> + +<li>Water power, <a href="#p142">142</a>.</li> + +<li>Watts, <a href="#p60">60</a>, <a href="#p61">61</a>, <a href="#p160">160</a>.</li> + +<li>Wave lengths, <a href="#p104">104</a>, <a href="#p110">110</a>.</li> + +<li>Weight, <a href="#p49">49</a>.</li> + +<li>Welding, <a href="#p13">13</a>, <a href="#p182">182</a>.</li> + +<li>Winding, <a href="#p18">18</a>, <a href="#p40">40</a>, <a href="#p47">47</a>, <a href="#p58">58</a>, <a href="#p159">159</a>, <a href="#p196">196</a>.</li> + +<li>Winding reel, <a href="#p14">14</a>.</li> + +<li>Window connection, <a href="#p76">76</a>.</li> + +<li>Window frame, <a href="#p78">78</a>.</li> + +<li>Wire, <a href="#p6">6</a>, <a href="#p18">18</a>, <a href="#p21">21</a>, <a href="#p26">26</a>, <a href="#p28">28</a>, <a href="#p156">156</a>.</li> + +<li>Wire, circuiting, <a href="#p79">79</a>.</li> + +<li>Wire coil, <a href="#p40">40</a>.</li> + +<li>Wire lead, <a href="#p70">70</a>.</li> + +<li>Wire, parallel, <a href="#p28">28</a>, <a href="#p49">49</a>.</li> + +<li>Wireless, <a href="#p12">12</a>.</li> + +<li>Wireless telegraphy, <a href="#p103">103</a>, <a href="#p104">104</a>, <a href="#p184">184</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + +<div><span class='pagenum'><a name="p221" id="p221">p. 221</a></span></div> +<table border="0" width="76%" cellpadding="2" cellspacing="2"> + <col style="width:50%;" /><col style="width:50%;" /> + <tbody valign="top"> +<tr><td> +<ul class="IX"> +<li>Wiring, <a href="#p80">80</a>.</li> + +<li>Wiring, window, <a href="#p77">77</a>.</li> + +<li>Workshop, <a href="#p11">11</a>, <a href="#p17">17</a>.</li> + +<li>Wound, compound, <a href="#p48">48</a>.</li> + +<li>Wound-series, <a href="#p47">47</a>.</li> + +<li>Wound-shunt, <a href="#p47">47</a>.</li> + + +</ul> + +</td><td> +<h4><a id="IX_X" name="IX_X"></a>X</h4> +<ul class="IX"> +<li>X-ray, <a href="#p184">184</a>, <a href="#p185">185</a>, <a href="#p187">187</a>, <a href="#p188">188</a>.</li> +</ul> +<h4><a id="IX_Z" name="IX_Z"></a>Z</h4> +<ul class="IX"> +<li>Zinc, <a href="#p17">17</a>, <a href="#p34">34</a>, <a href="#p35">35</a>, <a href="#p85">85</a>, <a href="#p135">135</a>.</li> +<li>Zinc plates, <a href="#p33">33</a>.</li> +</ul> +</td></tr> +</tbody> +</table> + + +</div> + +<hr class="chapter" /> +<h2>THE "HOW-TO-DO-IT" BOOKS</h2> +<hr class="minor" /> +<h3><span class="smcap">Carpentry for Boys</span></h3> + +<p>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.</p> +<hr class="minor" /> +<h3><span class="smcap"><a href="#toc">Electricity for Boys</a></span></h3> + +<p>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.</p> +<hr class="minor" /> +<h3><span class="smcap">Practical Mechanics for Boys</span></h3> + +<p>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.</p> +<hr class="minor" /> + + +<p class="center"><i>Price 60 cents per volume</i></p> + +<p class="titleblock">THE NEW YORK BOOK COMPANY</p> +<p class="titleblock"><span class="smcap">147 Fourth Avenue New York</span></p> + +<div class="tr"> + +<p class="center" style="font-weight: bold;">Transcriber's Note:</p> + +<p>Every effort has been made to replicate this text as faithfully as possible, including obsolete and variant spellings and other inconsistencies. +Obvious spelling/typographical and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external +sources. Minor punctuation and printing errors have been amended without note.</p> + +<p>The first page of the original book is an advertisement. The page was moved to the end of the text.</p> +<p>Two occurrences of 'Colorimeter' for 'Calorimeter' repaired.</p> +<p>Some hyphenation inconsistencies in the text were retained:<br /> + 16-candle-power and 16-candlepower,<br /> + Electromotive and electro-motive,<br /> + Electro-meter and Electrometer,<br /> + Horseshoe and horse-shoe,<br /> + Switchboard and switch-board.</p> +</div> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of Electricity for Boys, by J. S. 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