Text 5. From the History of Electricity

Do you know that the first ever man-made electric light illuminated the laboratory of the St. Petersburg physicist Vasily Petrov in 1802? He had discovered the electric arc, a form of the gas discharge. But in Petorv’s experiments the arc flame lasted for only a short time..

In 1876 Pavel Yablochkov invented an arc that burned like a candle for a long time and it was called “Yablochkov’s candle”. The source of light invented by Yablochkov won worldwide recognition. But while he and several other inventors were improving the arc light, some engineers were working along entirely different lines. They sought to develop an incandescent lamp¹. It was a young Russian engineer, Alexander Lodygin, who made the first successful incandescent lamp. The famous American inventor Thomas Edison improved the lamp having used a carbon filament. But it was again Lodygin who made another important improvement in the

incandescent lamp, having invented a lamp with a tungsten filament, the lamp we use today.

Automation, which is one of the main factors of technical progress today, is impossible without electricity.

Our life cannot be imagined without telephone, telegraph and radio communications. But it is also electricity that gives them life. In recent years electricity has made a great contribution to radio communication between the spaceships and also between the astronauts and the earth.

Little could be done in modern research laboratory without the aid of electricity. Nearly all of the measuring devices used in developing nuclear power for the use of mankind are electrically operated.

(1350 t.un.)

¹ incandescent lamp – лампочка накаливания

Text 6. Radar

The word “radar” is an abbreviation for the phrase “radio detection and ranging’, that is, the use of radio waves to detect the presence and determine the precise position of any stationary or moving object capable of reflecting them. Radio waves can be reflected by large solid objects in much the same manner as light. They are, however, able to travel greater distances than light in the Earth’s atmosphere, because they are not reflected or diffused by small dust particles in the atmosphere. Radar works on the so-called “echo” principle. It sends out radio waves and then measures the amount of time that it takes the waves to return.

Radar set includes a transmitter and a receiver. If a transmitter sends out a beam of waves, an adjacent receiver operating like a television receiver translates the echoed radio waves into a kind of picture. These radio waves can penetrate clouds and sea depths. They continue to move out in a straight line from a transmitter until they strike something solid. Then they are reflected back. The reflected waves moving back to the radar set are received and translated into a tiny spot on the cathode-ray-tube screen or display. The display may resemble a map of the surroundings and the objects are as bright spots on a dark background.

The most important uses of radar are known to be in ship and air navigation. Radar set on board a ship can provide the captain with complete information about the objects around the ship. It will show the distances and positions of other ships, islands or land so that a safe course can be steered.

There are many types of radar intended for use on ships and planes. The electrical features of radar for use in airplanes are similar to those used on ships. Special types of radar provide air-traffic control, “blond landing” and ground-controlled approach.¹ Radar provides information for meteorology and astronomy, such as detecting meteors and studying cosmic environments.

(1634 t.un.)

¹ ground-controlled approach – наземное управление при заходе на посадку

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