Elementary electricity up-to-date

Front matter

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Preface

Electricity presents a never ending field of research to the student who is inclined to delve among its mysteries. But a mere glance at the subject, with its apparently bewildering array of facts, and problems, both old and new, has a tendency to confuse, and at times to discourage rather than to excite interest, therefore the only correct and profitable method to be pursued in its study is to begin at the bottom, so to speak, and gradually work one's way up. It is with this end in view that the following pages are presented. Starting out with an explanation of the nature of electricity, and electrical experiments of the most simple form, the book gradually, but surely, guides the student in his pursuit of knowledge of this most wonderful science. First comes static electricity, with a clear explanation of the principles governing the various methods of its production. Condensers, what they are, and what they are for ; atmospheric electricity, and apparatus affected by it. Lightning arresters, and their auxiliary apparatus. Magnets, magnetic fields, magnetism, electro-magnetism, primary batteries, and how to make and care for them. Storage batteries of all types, together with a lengthened explanation of their construction, and the principles governing their action. Circuits, resistance and the laws by which it is controlled ; the induction coil, and its action; electrical measuring instruments, their construction, and the principles governing their action. The flow of current, and the laws by which it is controlled, also receive a large share of attention.

Qhm's law is clearly explained, and numerous problems

10 PREFACE

calculated according to its rulings, thus placing before the mind of the student the workings of this valuable law in a plain and simple manner. Rotary converters, and the principles of their action, together with the details of their construction and operation; transformers, what they are, and what they are for; transmission lines, and all of the various apparatus necessary in the transmission of current at a high voltage to locations at a distance from the central station, there to be transformed and made to do work, all are clearly and fully explained.

LESSON i.

Introduction

Exactly what electricity is we do not know, and indeed a practical man always dealing with the useful effects of electricity, applying these to the necessities and for the comfort of mankind, finds little time to wonder what electricity is.

We will omit the almost unanswerable question: — "What is electricity?" — and proceed to the question.

Question i. What is meant when a person talks about electricity ?

Answer. There are certain effects which we believe to be due to electricity, so that when a person observes any one of these things, he at once declares that there is electricity present.

Question 2. What are some of these effects?

Answer. Lightning during a thunder storm. Lighting gas with a spark from the finger tip.

Question 3. Are these effects due to electricity?

Answer. Yes, but by a kind which is different enough from other electricity to be called Static Electricity.

Question 4. Why is it called static electricity?

Answer. Because a quantity of this kind of electricity will remain on a body provided it is hung up by a dry silk thread. This electricity is at rest or stands still. Static means standing.

Question 5. What other effects are due to electricity ? 11

Answer. Ringing of an electric bell. Operation of an electric motor.

Question 6. Are these effects due to static electricity?

Answer. No, the bell and motor are operated by Dynamic Electricity.

Question 7. What is meant by dynamic electricity ?

Answer. Electricity in motion, because the word dynamic means force, giving the idea of motion.

Question 8. What is meant by a current of electricity?

Answer. Dynamic electricity is usually referred to as a current of electricity.

Question 9. Are there any other effects said to be due to electricity?

Answer. Yes ; the working of a wireless telegraphy instrument.

Question 10. What kind of electricity operates this instrument ?

Answer. Electrical waves.

Question 11. Are there still other kinds of electricity?

Answer. Practically no. All the effects we observe may be explained as being caused by either static electricity, a current of -electricity or electrical waves.

Question 12. What is static electricity?

Answer. It is electricity at rest.

Question 13. What is current electricity?

Answer. It is electricity in motion along a conductor.

Question 14. What are electrical waves?

Answer. They are electricity moving through the air, no conductor being required.

Question 15. Does the word electricity in the last three answers mean the same thing in each?

Answer. Yes; in each case it is electricity, either at

INTRODUCTION 13

rest, moving along a wire, or moving through the air without a wire.

Question 16. Give an example of static electricity.

Answer. If a brass ball be suspended by a silk thread and touched to one knob of an electrical machine (see Lesson 6) and then removed, it will be covered with a charge (see Lesson 2) of electricity. This electricity will be at rest and so is called a charge of static electricity.

Question 17. Give an example of a current of electricity.

Answer. If quantities of electricity are supplied at the end of a metal wire, they will quickly flow to the other end. Here the electricity is in motion and a current of electricity is flowing.

Question 18. Give an example of electrical waves.

Answer. If electricity is forced by a high pressure as in an electric machine or in an induction coil (see Lesson 2j) to jump a spark across an air space, while doing so it will send out in every direction a series of electrical waves which will travel long distances without the aid of wires.

Question 19. What are some of the common effects of current electricity?

Answer. Heat, light, magnetism, metal plating and refining, and medical effects.

Question 20. Explain about the heat effect.

Answer. If large quantities of electricity are forced through a conductor in a short time the wire is heated. The poorer the conductor the more heat is produced.

Question 21. Is there always some heat produced?

Answer. Yes. Electricity cannot flow through a conductor without producing some heat.

Question 22. Are the wires in a building heated, while carrying electricity?

Answer. Yes ; but the wire is large compared with the current carried; the material is copper, a good conductor, so that the heating is too small to be detected by feeling the wire.

Question 23. Does electricity produce light?

Answer. Yes. The heat produced in a very poor conductor by the current may be so great as to burn the conductor and the flame gives light; or it may make the conductor white or yellow hot, thus giving light.

The arc lamp gives light from flame and white hot carbon, while the incandescent lamp has no flame only the yellow hot carbon.

Question 24. Does electricity produce magnetism?

Answer. Yes. Electricity in motion will always affect the needle of a compass, usually pulling it aside from the north and south line, and keeping it out. This is described as "deflecting the needle ,, and whenever the "magnetic needle" is spoken of we mean a magnet of small weight and fairly long, pivoted so as to move freely in a horizontal direction. We speak of this effect as electro-magnetism.

Question 25. How does electricity plate metal?

Answer. Electricity in passing through solutions of chemicals takes the metal out of the solution and turns it into the solid form, thus making a layer of metal on the object placed in the solution. (See Lesson 17.)

Question 26. How does electricity refine metals ?

Answer. If a lot of metals and other chemicals are in a solution, by passing electricity through the solution the metals will be solidified and may be removed while the other chemicals remain dissolved in the solution*

INTRODUCTION 15

Question 27. What are the medical effects of electricity ?

Answer. They are not well understood; but the passage of current through the body seems to have a curative effect on some diseases.