1. Energy

What is energy? A scientist would say that energy is the ability to do work. You use energy when you walk. You carry your books with you to the Institute. It takes energy to carry books. You can do nothing without using energy. You wash with water warmed by energy. You put on clothes washed and ironed with energy.

There are many forms of energy. Each of these is useful to us. For example, we use heat energy to do a lot of useful things, namely, to heat our homes, to transport us from one place to another, and so on. Automobiles, trams, trains and airplanes are moved by changing heat energy to other forms of energy.

Electrical energy does many things for us. It is changed to other forms, such as: light, mechanical, heat, chemical, and others. When you watch television, you hear the sound and see the picture. The television (TV) set gets warm. Thus, electrical energy changes to heat, light and sound.

Many machines use electrical energy. They change energy from one form to another. Devices that are operated with electrical energy help us to work. Indeed, electricity plays, an important part in modern life.

2. Electric fish

The electric fish is mentioned in the oldest writings of man. History tells us that the Greeks and the Romans knew about it. They knew, for example, that any man coming into contact with the electric fish could obtain an electric shock. In later years, experiments were made to find out the nature and amount of the shock given by one of them

called the electric eel. The so-called electric eel is found in the tropical waters of South America.

Small electric eels, only one inch long, can give a small shock. However, by the time they are 6 inches long their internal battery gives as much as 200 volts. When it is quite grown a good electric eel can generate 600 volts. When it is short circuited, a current of 1 ampere can be obtained. A two-metre long eel could light a dozen 50 watt lamps.

The electricity in the electric eel seems to be produced at will. Besides, the discharges take place at speeds from 10 to 100 per second. It is interesting to mention here that the eel's head end is positively charged and the opposite end is negatively charged. By the way, the electric eel has some ability for finding polarity. Thus, if two charged elec­trodes are placed in water, even in the dark, the electric fish which is somewhere near the electrodes, will move to­wards the positive electrode, possibly thinking that it is the head of a friend.

^{3. APPLICATIONS OF THE ELECTROMAGNET}

Electromagnets always find an application when it is , desirable to convert electrical energy into mechanical energy.

Telegraph systems and telephones, relays, motors and generators, radio sets and television sets, electrical measur­ing instruments as well as thousands of other valuable and necessary devices are known to contain electromagnets. They may be used, as well, to protect electrical circuits against overloads and underloads.

One of the first applications of the electromagnet was in telegraphy. Shilling, associate.member of the Petersburg Academy of Sciences, was the first to construct the electro­magnetic telegraph. He demonstrated his invention as far back as 1832.

As mentioned above, the telephone also uses electromag­nets, uses many of them, in fact. As soon as man learned to send word over the long wires of the telegraph circuit, the next problem to be solved was the telephone. Was it not pos­sible to send the spoken word over similar wires? As a matter of fact, the first practical telephone was invented by the American scientist Bell in 1876 ?.nd was further improved by Edison.

_HI