FROM THE HISTORY OF ELECTRICITY

There are two types of electricity: electricity at rest or in a static condition and electricity in motion, that is, the electric current .Both of them are made of electric charges, static charges being at rest, while electric current flows and does work.

Let us first turn our attention to static electricity. For a long time it was the only electrical

phenomenon to be observed by a man. As previously mentioned at least 2.500 years ago or so,

Greeks knew how to get electricity by rubbing substances. However, the electricity to be obtained by rubbing objects can not be used to light lamps, to boil water, to run electric trains and so on.

In 1753 Franklin made an important contribution to the science of electricity. He was the first to prove that the unlike charges are produced due to rubbing dissimilar objects .To show that

the charges are unlike and opposite, he decided to call the charge on the rubber-negative and that on the glass-positive.

We all know that the first scientist who got the electric current was Volta after whom the unit of pressure, the volt, was named. His discovery developed out of the Galvani’s experiments with a frog. Galvani observed that the legs of a dead frog jumped in the result of electric charge. He tried his experiment several times and every time he obtained the same result. He thought that electricity was generated within the leg itself .Volta began to carry on similar experiments and soon found that the electric source was not within the frog’s leg but was the result of the contact of both dissimilar metals used during his observations. He spent the next few years trying to invent a source of continuous current. To increase the effect obtained with one pair of metals, Volta increased the number of metal pairs. Thus the voltaic cell began to consist of a copper layer and a layer of zinc placed one above another with a piece of flannel moistened in salt water between them. A wire was connected first to the copper disc and then to the zinc disc.

The year 1800 is a date to be remembered: for the first time in the world history a continuous current was generated.

H. Answer the following questions to the text G and make up a short summary of it.

1. What types of electricity do you know?

2. What is the difference between electricity at rest and electricity in motion?

3. What experiments did Galvani carry on?

4. What did Franklin prove?

5. What kinds of charges do you know?

6. Who was the first to produce a continuous current?

7. What did the Volta’s discovery result in?

I. Read and translate the text, enumerate the most important inventions in the branch of

electrical technical units.

It is impossible to imagine our civilization without electricity: economic and social progress will

be turned to the past and our daily lives completely transformed. Electrical power has become universal. Thousands of applications of electricity such as lighting, electrochemistry and electro-metallurgy are unquestionable. With the appearance of the electrical motor, power cables replaced transmission shafts, gear wheels, belts and pulleys in the 19^th century workshops. And in the home a whole range of various time and labor saving appliances have become a part of our everyday lives. Other devices are based on specific properties of electricity: electrostatics

in the case of photocopying machine and electromagnetism in the case of radar and television.

The first industrial application was in the silver workshops in Paris. The generator - a new compact source of electricity - was also developed there. The generator replaced the batteries and other devices that had been used before. Electrical lighting came into wide use at the end of the last century with the development of the lamp by Thomas Edison. Then the transformer was invented, the first electric lines and networks were set up, dynamos and induction motors were designed. Since the beginning of the 20^th century the successful development of electricity has begun throughout the country. The consumption of electricity has doubled every ten years. Today consumption of electricity per capita is an indicator of the state development and economic health of a nation. Electricity replaced other sources of energy. One of the greatest advantages of electricity is that it is clean and generates no by-products. Applications of electricity cover all fields of human activity from house washing machines to the latest laser devices.

J. Make the sentences from two parts.

1. Electricity 1. have long ago become universal

2. The applications of electricity in the home 2. has completely transformed our

and in industry everyday life.

3. Electricity was used for the first time 3. per capita is an indicator of the

4. The generator, a new source of electricity state development of a nation

5. Since the beginning of the 20^th century 4. the wide industrial use of electri-

6. Today consumption of electricity city has begun throughout the

world

5. was also developed in Paris.

6. for industrial purposes in the silver

workshops.

Date: 2015-01-12; view: 1635