Harper's electricity book for boys

Front matter

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Chapter Ii.— Cells And Batteries 12

Simple and Inexpensive Cells — How to Make Cells and Batteries — A Plunge-battery — A Storage-battery — Dry-cells and Batteries

CHAPTER III.— PUSH-BUTTONS AND SWITCHES .... 33 How to Make Push-buttons — Switches and Cut-outs — Table-jack Switches — -Binding-posts and Connectors — Lightning-arresters and Fuse-blocks — Some Practical Precautions

CHAPTER IV.— MAGNETS AND INDUCTION-COILS ... 54 Simple and Horseshoe Magnets — Induction-coils — An Electric Buzzer — Electric Bells — A Large Induction-coil — Circuit-interrupters

CHAPTER v.— ANNUNCIATORS AND BELLS ...... 78

A Drum-sounder — A Simple Annunciator — A Double Electric Bell — An Electric Horn — How to Make a Burglar-alarm — Electric Call-signals — Clock-alarms — A Dining-table Call

vii

CONTENTS

PAGE

CHAPTER VI.— CURRENT-DETECTORS AND GALVANOM- ETERS 102

How TO Make Detectors — An Astatic Current-detector — An Astatic Galvanometer — A Tangent Galvanometer

Part II CHAPTER VII.— ELECTRICAL RESISTANCE 125

Governing the Electric Current — Ohm's Law — Resistance - COILS AND Rheostats — How to Make Simple Apparatus — Liquid Resistance — Importance of Switches — Uses of a House-current — Running a Sewing-machine, Fan, or Toys — An Easy Method for a Boy's Use

CHAPTER VIIL— THE TELEPHONE . 156

Vibratory Waves — A Bladder Telephone — A Single (Receiver) Line — Plan of Installation — A Double-pole Receiver — The Transmitter — Another Form of Transmitter — The Wiring System^ — A Telephone Induction-coil — • An Installation Plan — A Portable Apparatus

CHAPTER IX.— LINE AND WIRELESS TELEGRAPHS . . 190 A Ground Telegraph — How to Talk from House to House — The Morse Telegraph Code — A Story of Edison — How Detectives Used the Code — Wireless Telegraphy — Its True Character — How a Boy Can Make a Practical Apparatus — Receiving and Sending Poles — Induction-coils, Batteries, Coherers and De-coherers, etc. — Working Plans in Detail — Aerograms Across the Atlantic and, perhaps, Around the World

CHAPTER X.— DYNAMOS AND MOTORS ' . 229

Dependence of Modern Electricity upon the Dynamo ■—A Field of Force Cutting another Field of Force—'

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CONTENTS

Varieties of Dynamos — Simpler Form^ of Generators AND Motors — How to Make a Uni-direction Current Machine — Permanent Magnet, Armature, Shafts, Wheels, etc. — A Small Dynamo — Machines to Light Lamps, Run Motors, etc. — A Split-ring Dynamo — A Small Motor — The Flat-bed Motor— Motors of Other Types

CHAPTER XI.— GALVANISM AND ELECTRO-PLATING . . 266

A Fascinating Use of Electricity — A Simple Electro-plating Outfit — The Sulphate of Copper Bath — How TO Make the Tank and Other Apparatus — A Variety of Beautiful and Useful Results — Explanations of Various Batteries — The Cleansing Process — The Plating-bath— Silver-plating — Gold- plating — Nickel- plating — • Finishing — Electrotyping — Practical Details of Interesting Work

CHAPTER XIL— MISCELLANEOUS APPARATUS 294

Making a Rotary Glass-cutter — To Smooth Glass Edges — Cutting Holes in Glass — Anti-hum Device for Metallic Lines — A Reel-car for Wire— Insulators — • Joints and Splices — "Grounds" — -The Edison Roach-killer — An Electric Mouse-killer

CHAPTER XIII.— FRICTIONAL ELECTRICITY 312

Its Nature — Limited Uses — Simplicity of Apparatus — A "WiMSHURST Influence Machine" — -Materials Required — -Glass, Tin -foil, Spindles, Uprights, Wheels, ETC. — -A Large Leyden-jar — Apparatus for Interesting Experiments — Necessity of Caution

CHAPTER XIV.— FORMULA 327

Acid-proof Cements — Hard Cement — Soft Cement — Very Hard Cement— Clark's Compound — Battery Fluid — Glass Rubbing — Acetic Glue — Insulators — Non-conductors — Insulating Varnish — Battery Wax

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CONTENTS

PAGE

CHAPTER XV.— ELECTRIC LIGHT, HEAT AND POWER . . 334 (By Joseph B. Baker)

The Work of the Dynamo — -The Electric Light — Uses OF the Arc-light — Incandescent and Other Lamps — Electric Heat — Electric Furnaces — Welding Metals — Electric Car-heaters — Household Uses — Electric Power — Power from Water-wheels — Transformers — Rotary Converters — Oil-switches — Electric Traction — ^The Trolley-car — ^The Continuous-current Motor — The Controller — Electric Locomotives — Other Forms of Electric Traction

A DICTIONARY OF ELECTRICAL TERMS 359

Introduction

IF a handy-book of electricity like this had fallen into the hands of Thomas A. Edison when he was a newsboy on the Grand Trunk Railway, or when he was a telegraph operator, he would have devoured it with the utmost eagerness. To be sure, at that time, in the early sixties, all that we knew of electricity and its applications could have been told in a very brief compass. It was an almost unknown field, and the crude form of the telegraph then in use represented its most important application. There were no electric lights; there was no telephone or phonograph; there were no electric motors. Telegraphing, itself, was a slow and difficult process. All the conditions were as far removed as possible from the broad field of applied electricity indicated in this book.

But this does not mean that we have now accomplished all that there is to be done. On the contrary, the next halfcentury will be full of wonderful advances. This makes it more than ever essential that we should become acquainted with the principles and present conditions of a science which is being applied more and more closely to the work of every-day life. It is necessary to know this from the inside, not simply from general descriptions. Theory is all very well, but there is nothing like mastering principles, and then applying them and working out results for one's self.

xi

INTRODUCTION

Any active and intelligent boy with an inquiring mind will find a new world opened to him in the satisfaction of making electrical devices for himself according to the suggestions given in this book. This will show him the reasons for things in concrete form, will familiarize him with principles, and will develop his mechanical ingenuity. He may be laying the foundation for inventions of his own or for professional success in some of the many fields which electricity now offers. Work of this kind brings out what is in one, and there is no satisfaction greater than that of winning success by one's own efforts.

The boy who makes a push-button for his ow^n home, or builds his own telephone line or wireless telegraph plant, or by his own ingenuity makes electricity run his mother's sewing-machine and do other home work, has learned applications of theory which he will never forget. The new world which he will enter is a modern fairyland of science, for in the use of electricity he has added to himself the control of a powerful genie, a willing and most useful servant, w^ho will do his errands or provide new pla3rthings, who will give him manual training and a vast increase in general knowledge. The contents of this book, ranging from the preparation of simple cells to the making of dynamos and motors, and the delightful possibilities of electro-plating, shows the richness of the field which is made accessible by Mr. Adams' practical explanations, his carefully tested working plans, and his numerous and admirable drawings — all of which have been made for this book.

It is in keeping with the practical character of the Electricity Book that pains are taken throughout to show the

xii

INTRODUCTION simplest and most inexpensive way of choosing materials and securing results. The actual working out of these directions can be done at very small expense. Furthermore, there need be no concern whatever as to possible danger if the book is read with reasonable intelligence. Mr. Adams has taken pains to place danger-signals wherever special precautions are advisable, and, as a father of boys who are constantly working with electricity in his laboratory, he may be relied upon as a safe and sure counsellor and guide.

While this book shows boys what they can do themselves, its scope has been enlarged by Mr. Baker's chapter explaining briefly the working of electricity all about us, in light and heat, in the trolley-car, and other daily applications. In addition, Mr. Adams has prepared a Dictionary of Electrical Terms, and these brief definitions will be found peculiarly helpful in the first reading of the book. It is believed that there is no book in this particular field comparable to Harper's Electricity Book in its comprehensiveness, practical character, and the number and usefulness of its illustrations. It follows the successful Out -door Book for Boys in Harper's series of Practical Books for Boys, and it will be followed by How to Understand Electrical Work, a book, not of instructions in making electrical apparatus, but of explanations of the commercial uses of electricity all about us.

Part I

Qiaptcr I

WE are living in the age of electricity, just as our fathers lived in the age of steam. Electricity is the world-power, the most powerful and terrible of nature's hidden forces. Yet, when man has learned how to harness its fiery energies, electricity becomes the most docile and useful of his servants. Unquestionably, electricity is to-day the most fascinating and the most profitable field for the investigator and the inventor. The best brains of the country are at work upon its problems. New discoveries are constantly being recorded, and no labor is thought too great if it but add its mite to the sum total of our knowledge. And yet, ridiculous as the statement may seem, we do not know what electricity is. We only know certain of its manifestations — what it can do. All we can say is that it does our bidding ; it propels our trains, lights our houses and streets, warms us, cooks for us, and performs a thousand and one other tasks at the turn of a button or at the thrust of a switch. But what it is, we do not know. Electricity has no weight, no bulk, no color. No one has seen it ; it cannot be classified, nor analyzed, nor resolved into its ultimate elements by any known process of science. We must content ourselves with describing it as one manifestation of the energy which fills the universe and appears in a variety of forms — such as heat, light, magnetism, chemical afifinity, and mechanical motion. In all probability it is one of those phenomena of nature that are destined to remain forever secret. Thus it stands in line with gravitation, magnetism, the active principle of radium, and the perpetual motion of the solar system.

Electricity was known to the early Greeks; indeed, it derives its name from the Greek word for amber (electron). For many centuries amber was credited with certain special or magical powers. When it was rubbed with a flannel cloth, "the hidden spirit" came out and laid hold of small detached objects, such as bits of paper, thread, chips, or pith-balls. No one could explain this phenomenon. It was looked upon with superstitious awe and the amber itself was regarded as possessing the special attributes of divinity. But as time went on, it was discovered that in various other substances this mysterious attractive power could be excited, at will, through the agency of friction. Rubbing a piece of glass rod with silk or leather generated an ''electricity ' ' identical with that of the amber ; or the same result could be obtained by exciting hard rubber with catskin. The conclusion followed that electricity was not a property of the special materials employed to generate it, but that it came from without, from that great reservoir of energy, the atmosphere. Then came Franklin with his experiment of the kite, and the invention of the Leyden-jar and the chemical production of the electric fluid by means of batteries. It was shown that the properties of the new and strange force were the same, whether it was produced by the static (frictional) process or by the galvanic (chemical) method. Electrical science as a science, had begun.

And yet, for many years, electricity was hardly more than a scientific toy. It was not supposed to possess any practical usefulness. The entertaining experiments with the static machine and the Leyden-jar (chapter xiii.) were confined to the laboratory and the lecture hall. Electricity was an amusing display of unknown energy, but no one ever dreamed that it could ever be made to serve the practical ends of life. It was not until about 1850 that electrical science became anything more than a name. The galvanic and voltaic batteries (chapter ii.) opened the way for ''current" electricity, which flowed continuously, instead of jumping and disappearing like the spark from a Leyden-jar. When the continuous current became an established fact, the telegraph and telephone headed the line of a long series of developments. Finally, the generation of electricity in greater volume, and cheaply, made possible the application of its power for heating, light, traction, and the other forms of activity in which it now does so large a share of the world's work.

How electricity works is a question often asked, but not easily answered. There are certain so-called laws, but we shall best arrive at a conclusion by simply stating a few of the facts that have been established through the observation and investigation of scientists and electrical engineers.^

For example, electricity is always alert, ready to move, and continually on the lookout for a chance to obtain its freedom. It will never go the longest way round if there is a short cut; and it will heat, light, or fuse anything in its path that is too weak to carry or resist it. For this reason, it must be generated in small volume — that is, just sufficient to do the work required of it. If produced in larger volume, it must be held in check by resistance, and only so much allowed to escape as may be needed for the specified work. Again, when electricity is generated this must be done in one of two ways — by friction or chemically. But in both processes there must be air surrounding the generators, and the fluid must be of a nature through which oxygen and hydrogen can circulate freely. Water fluids are suitable for this purpose, but oils cannot be used, as they contain hydrocarbon in large quantities and are non-conductors.

Batteries are chemical generators, dynamos are magneto-electric, and static machines are frictional. Now the theory is that electricity is drawn from the ether and, in its normal state, is quiet. If it be disturbed and collected by mechanical or chemical means, it is always on the alert to escape and again take its place in the atmosphere. As its volume is increased, so its energy to get away is multiplied, and this energy may be transformed, at will, into power, heat, or light. To express the idea in the simplest language,

* Explanations of any technical names or phrases used in the text will be found in the simple dictionary of electrical terms which appears as an appendix.

it wants to go home, and in its effort to do so it expresses itself in the form of stored-up power, precisely like water behind a dam. It is for man's cunning brain to devise all sorts of tasks that this power must perform before it can gain its release. It can't go home until its work is done.

Nearly every boy has experimented, at one time or another, with electricity and electrical apparatus, and whether it was with some of the simple frictional or galvanic toys, or with the more complicated induction-coils and motors, he has undoubtedly found it a most interesting amusement and an ever new and widening field for study. Then again, many boys would like to know something about simple electrical apparatus and how to make and use it. But his schoolbooks relating to the general subject of electricity are hardly definite enough to serve as a practical manual. And yet there are many things in the way of electrical machinery and equipment that a boy can easily construct and use. In this book it is my purpose to show him just what can be done with the aid of the tools that are usually in his possession. While some things may have to be purchased from an electrical supply -house or other sources, there is still much material to be found about the house that may be put to good use by the amateur electrician.

It is not possible or desirable to describe every variety of electrical equipment. We must confine ourselves to apparatus which can be readily understood and operated. The "practical" idea is the one to be borne in mind. This book shows a boy how to use his brains and the simple tools and material that may be at his command. Care and thought in the construction of the apparatus are the important qualifications for success. The instructions are given in the clearest possible language; the diagrams and drawings are intelligible to any one who will take the trouble to study them. If your finished apparatus does not work properly, read the description again and see if you have not made some error. A misplaced or broken wire, a wrong connection, or a short circuit will mean all the difference between success and failure.

Save in one short chapter, static or frictional electricity (see Appendix) is not considered ; for outside of laboratory experimenting and electro-medical apparatus, frictional electricity is but a toy — interesting and useful when generated in small volume, but very dangerous and difficult of control when in great volume. For example, the bolt of lightning is but the many times multiplied spark stored in the Leyden-jar by the static machine. For all practical purposes, galvanic electricity, in its various phases of direct and alternating current, meets the requirements of man. With the improved apparatus and the rapid advancement along the line of invention, electricity is as easily controlled to-day as steam — in fact, its economical use is even more fully under control and its adaptability more practical.

In the following pages there are probably illustrations and descriptions of many things that will seem strange to the boy who has not heard of them; but if a book were written each year on the subject of electricity, every new one would include principles and facts not known before. The field of electrical research is so broad and so many are working in it that new discoveries are being made continually.

To those familiar with the appHcation of electricity, it is clearly evident that, as yet, we are only beginning to deal with this unknown force. For generations to come, developments will take place and invention follow invention until electricity assumes its rightful place as the motive force of the world. To the boy interested in this subject a wide field is open, and the youth of to-day, who are taking up this study, are destined to become the successful electrical engineers and inventors of the future. There is no better education for any boy, in the application and principles of electricity, than to begin at the very bottom of the ladder and climb up, constructing and studying as he progresses. When he attempts to design more technical and difficult apparatus the lessons learned in a practical way will be of inestimable value, greater by far than any theoretical principles deduced from books; he knows his subject from the ground up ; he understands his machine because he has constructed it with his own hands.

As I have said already, the necessary tools are few in number and not expensive. They may include a hammer, a plane, awls, pliers, wire-cutters, and tin-shears. The raw material is also cheap — lead, tin, wire, wood, and simple chemicals. The laboratory may be a corner in the attic, or even in a boy's bedroom, so far as the finer work is concerned, while the hammering and sawing may be done in the cellar. The other best plan, of course, is to get the use of a spare room which may be fitted with shelves, drawers, and appliances for serious work. To enthusiastic beginners, as well as to those who have had some experience in electricity, a needed warning may be given in three words:

"Take no chances." Electricity, the subtle, stealthy, and ever-alert force, will often deal a blow when least expected. For that reason, a boy should never meddle with a high-tension current or with the mains from dynamos. The current in the house, used for lighting, cooking, or heating purposes, is always an attractive point for the young electrician, but the wires should never be touched in any way. Too many accidents have happened, and the conductors, lamp-sockets, and plugs should be carefully avoided.

The boy should keep strictly to his batteries, or small dynamos run by water-power from a faucet; in no case should the wire from power-houses be tampered with. One little knows what a current it may be carrying and what a death-dealing force it possesses. Always bear in mind that a naked wire falling from a trolley equipment carries enough force to kill anything it strikes.

Special attention is called to the dictionary of electrical terms given in the Appendix. The young student should never pass over a word or a term that he does not thoroughly understand. Always look it up at once and every time it occurs, until you are sure that its meaning is fixed in your mind. This is an education in itself, at least so far as the theoretical knowledge of our subject is concerned.

As a final word, I should like every boy interested in electricity to hear what Thomas A. Edison once said to me when I was a boy working in his laboratories. I often recall it when things do not go just right at first.

I asked the great inventor one day if invention was not made up largely of inspiration. He looked at me quizzically for a moment, and then repHed: " My boy, I have little use for a man who works on inspiration. Invention is two parts inspiration and ninety-eight per cent, perspiration."

You will never get what you are after unless you work hard for it. You must stick to it until you produce results. If the history of the world's most valuable inventions could be fully known, the fact would be clearly established that the vital spark of inspiration is but the starting-point. Then follow the days, weeks, and sometimes years of industrious toil, failures, and disappointments, until finally the desired end is attained. One must work for success; there is no other means of winning it.

As the table of contents shows, Part I. of this book explains principles and the simpler forms of electrical appliances. From this we advance to Part II., which deals with more complex forms of electrical work, most of which, however, are within the reach of intelligent boys who have followed the chapters carefully from the first. In a final chapter we have simple explanations of the great commercial uses of electricity, which we see all about us, although very few of us have a clear idea as to their operation.

Chapter II

Simple Cells

IN order to generate electricity it is necessary to employ cells, batteries, or dynamos. Since the construction and operation of a dynamo is somewhat intricate, it will be better to start with the simpler methods of electric generation, and so work up to the more complicated forms. For small apparatus, such as electric bells and light magnets and motors, the zinc-carbon-sal-ammoniac cell will answ^er very well; but for larger machinery, where more current is required, the bluestone and the bi-chromate batteries will be found necessary.

A simple and inexpensive cell may be made from electric-light carbons, with the copper coating removed, and. pencils of zinc, such as are used for electric-bell batteries and which can be purchased for five cents each. Copper wire is to be bound around the top of each pencil of carbon and zinc, and firmly fastened with the pliers, so that it will not pull off or become detached. It will be well to cut a groove with a file around the top of both the carbon and zinc, into which the wire will fit. The elements should then be

SIMPLE BATTERY ELEMENTS 13 clamped between two pieces of wood and held with screws, as shown in Fig. i . A more efficient carbon pole is made by strapping six or more short carbon pencils around one long one, as shown in Fig. 3. The short pieces of electric-light carbons are bound to the longest carbon with heavy elastic bands, or cotton string dipped in paraffine or wax, to make the cotton impervious to water and the sal-ammoniac solution.

Another arrangement of elements is shown in Fig. 2, where a zinc rod is suspended between two carbons, the carbons being connected by a wire that must not touch the zinc.

A fruit- jar, or a wide-necked pickle-bottle, may be employed for a cell, but before the solution is poured in, the upper edge of the glass should be coated with paraffine. This should be melted and applied with a brush, or the edge of the glass dipped in the paraffine.

The solution is made by dissolving four ounces of sal-ammoniac in a pint of water, and the jar should be filled three-fourths full. In this solution the carbons and zinc may be suspended, as shown in the illustration (Fig. 4) of the sal-ammoniac cell. The wood clamps keep the ca.rbon and zinc together, and the extending ends rest on the top of the jar and hold the poles in suspension. Plates of zinc and carbon may be clamped on either side of a square stick and suspended in the sal-ammoniac solution, as shown in Fig. 5 , taking care, however, that the screws used for clamping do not touch each other.

If one cell is not sufficiently powerful, several of them may be made and coupled up in series — that is, by carrying

J4 the wire from the zinc of one to the carbon of the next cell, and so on to the end, taking care that the wire from the carbon in the first cell and that from the zinc of the last cell will be the ones in hand, as shown in Fig. 6. This constitutes a battery. Be sure and keep the ends of the wire apart, to prevent galvanic action and to save the power of the batteries.

This battery is an excellent one for bells and small experimental work, and when inactive the zincs are not eaten away (as they would be if suspended in a bi-chromate solution), for corrosion takes place only as the electricity is required, or when the circuit is closed. A series of batteries of this description will last about twelve months, if used for a bell, and at the end of that time will only require a new zinc and fresh solution.

The cell in which the plates shown in Fig. 5 are used may contain a bi-chromate solution; and for experimental work, where electricity is required for a short time only, this will produce a stronger current. But remember that the solution eats the zinc rapidly, and the plates must be removed as soon as you have finished using them.

The bi-chromate solution is made by slowly pouring four ounces of commercial sulphuric acid into a quart of cold water. This should be done in an earthen jar, since the heat generated by adding acid to water is enough to crack a glass bottle. Never pour the water into the acid. When the solution is about cold, add four ounces of bi-chromate of potash, and shake or mix it occasionally until dissolved; then place it in a bottle and label it:

BI-CHROMATE BATTERY FLUID

POISON

Before the zincs are immersed in the bi-chromate solution they should be well amalgamated to prevent the acid from eating them too rapidly.

The amalgamating is done by immersing the zincs in a diluted solution of sulphuric acid for a few seconds, and then rubbing mercury (quicksilver) on the surfaces. The mercury will adhere to the chemically cleaned surfaces of any metal except iron and steel, and so prevent the corroding action of the acid. Do not get on too much mercury, but only enough to give the zinc a thin coat, so that it will present a silvery or shiny surface.

A two-fluid cell is made with an outer glass or porcelain jar and an inner porous cup through which the current can pass when the cup is wet. Fig. 7.

A porous cup is an unglazed earthen receptacle, similar to a flower-pot, through which moisture will pass slowly. The porous cup contains an amalgamated plate of zinc immersed in a solution of diluted sulphuric acid — one ounce to one pint of water. The outer cell contains a saturated solution of sulphate of copper in which a cylindrical piece of thin sheet-copper is held by a thin copper strap, bent over the edge of the outer cell. A few lumps or crystals of the copper sulphate, or bluestone, should be dropped to the bottom of the jar to keep the copper solution saturated at all times. When not in use, the zinc should be removed from the inner cell and washed off; and if the battery is not to be employed for several days, it would be well to

CELLS AND BATTE|^IES pour the solutions back into bottles and wash the several parts of the battery, so that it may be fresh and strong when next required. When in action, the solutions in both cups should be at the same level, ana be careful never to allow the solutions to get mixed or the copper solution to touch the zinc. Coat the top of 'he porous cell with paraffine to prevent crystallization, and also to keep it clean. Take great care, in handling the acid solutions, to wear old clothes, and do not let the liquids spatter, for they are strong enough to eat holes in almost anything, and even to char wood. The two-fluid cells are much stronger than the one-solution cells, and connected up in series they will develop considerable power.