HOW WE SECURE ELECTRICAL ENERGY 



241 



READINGS WHICH WILL HELP ANSWER THE 

 PROBLEM QUESTIONS 



What is electricity? Electricity has been known for 

 many centuries. Thales, an ancient Greek who lived 

 600 years before the birth of Christ, knew that when 

 amber was rubbed, it would draw bits of light sub- 

 stances like paper and cork to it. In Greek the word 

 for amber is electron, and so when it was later dis- 

 covered that other things than amber when rubbed 

 would also attract, people called the phenomenon 

 "electric." Little was really understood about this 

 peculiar attraction until about two hundred fifty years 

 ago when men began to experiment with it and lay 

 the foundations of modern electricity. 



There are two types of electric charge. Early in the 

 history of experimenting with electricity men dis- 

 covered that there were two kinds and gave them the 

 names of positive and negative. It became the custom 

 to think of an ebonite rod which had been rubbed with 

 fur or flannel as being negative and a glass rod rubbed 

 with silk as being positive. Your experiment has 

 taught you that if a negative electric charge is brought 

 near a negative charge on a balloon they push apart 

 or repel, but if a positive charge, like that of a glass 

 rod which has been rubbed with silk, is brought near 

 a negatively charged balloon they will draw together 

 or attract. 



Some substances conduct electricity while others 

 do not. Copper and aluminum are used to carry the 

 current in telephone and telegraph wires while glass, 

 porcelain, hard rubber, cloth, and other like sub- 

 stances are used to insulate electric wires. Things like 

 copper and aluminum which carry the electric cur- 

 rent readily are called conductors, while substances 

 like glass, rubber, and porcelain are called non-con- 

 ductors or insulators. 



How may electricity be obtained by friction? Al- 

 though the action of like and unlike electrical charges 

 has been known for many years, it remained for mod- 

 ern scientists to discover the reason back of it. Within 

 the past fifty years scientists have come to believe 

 that everything in the universe is made up of tiny 

 particles of electricity, so small that not even the most 

 powerful microscope could show them. Strange to 

 say, there are two kinds of these little particles, one 

 of which is negative and the other, positive. The nega- 

 tive particles are called electrons and the positive par- 

 ticles, protons. In conductors many of the electrons 

 are continually freeing themselves from some atoms 

 and entering others ; in non-conductors there seem 

 to be very few of the free electrons. 



An interesting thing about these electrical particles 

 of which everything is made is that the unlike par- 

 ticles attract one another while the like particles repel. 

 That is, protons attract electrons and repel protons, 



while electrons attract protons and repel electrons. 



All things are made of electrons and protons. The 

 stars, the moon, the earth, stone, wood, paper, dirt, 

 dust, metals, amber, glass, cloth, air, water, food, even 

 the flesh of the human body is built up of these tiny 

 electrical particles. It would seem that everything 

 would have an electric charge, but that is not true, 

 for bodies are positively or negatively charged only 

 when there are more protons than electrons on them 

 or the reverse. When there are the same number of 

 electrons as protons in a body, every proton is bal- 

 anced by an electron, and the body is neutral or un- 

 charged. If there are more protons than electrons, the 

 body is positively charged, while if there are more 

 electrons it is negatively charged. 



When you rubbed the balloon and fountain pen 

 with fur you rubbed some of the tiny electrons from 

 the fur over to the balloon and pen. When the glass 

 was rubbed with silk some of the electrons were 

 rubbed off on the silk, leaving the glass positively 

 charged. It is easy to make electrons stay on glass, 

 rubber, silk, porcelain, wax, or other non-conductors, 

 but as your experiment taught you, they cannot be 

 made to stay on iron or other metals that may be 

 rubbed. The electrons flow away through conductors. 

 An electric current flowing through a wire, a light, 

 or a toaster is just millions and millions of these tiny 

 electrons streaming past. 



Man has learned how to make electrons go where 

 he wishes and perform at his command. This has made 

 possible all the modern developments of electricity, 

 such as heating devices, motors, telephones, telegraph, 

 radio, and television. 



Exercise. From your study of this topic thus far, infer 

 a cause for each of the following: 



1. Your hair will follow a comb which is drawn through 

 it on a cold, dry day. 



2. Sparks may be drawn from a cat's fur by rubbing 

 it. 



3. A severe shock is often experienced after one walks 

 over a rug and then touches a radiator or waterpipe. 



4. Sometimes one gets a slight shock when a metal 

 filling in a tooth is touched with a silver fork or spoon. 



Lightning is a stream of electrons under a very 

 high voltage or electrical pressure, flowing from a 

 cloud either to the earth or to another cloud. It is the 

 result of the accumulation of static electric charges 

 in the clouds which scientists believe are caused by 

 the friction of air currents against the clouds. As these 

 charges increase, the electrical pressure rises often to 

 several million volts, and then just as water from a 

 bursting dam will run to lower levels, the electrons 

 from a charged cloud rush to the earth or to another 



