Harper's Electricity Book for Boys

Some General Explanations

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 affinity, 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.[1]

[1] 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.

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 hydro-carbon 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, 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 school-books 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.