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ELECTRICITY. ELECTRICAL ENGINEERING

THE NATURE OF ELECTRICITY

The ancient Greeks knew that when a piece of amber is rubbed with wool or fur it achieves the power of attracting light objects. Later on the phenomenon was studied, and, the word electric, after the Greek word "electron", meaning amber was .used. Many scientists investigated electric phenomena, and during the nineteenth century many discoveries about the nature of electricity, and of magnetism, which is closely related to electricity, were made. It was found that if a sealing-wax rod is rubbed with a woolen cloth, and a rod of glass is rubbed with a silken cloth, an electric spark will pass between the sealing-wax rod and the glass rod when they are brought near one another. Moreover, it was found that a force of attraction operates between them. An electrified sealing-wax is repelled, however, by a wax rod, and also an electrified glass rod is repelled, by a similar glass rod.

The ideas were developed that there are two kinds of electricity, which were called resinous electricity, and that opposite kinds of electricity attract one another, whereas similar kinds repel one another.

Memorize the following words and word-combinations:

1.amber

2.to rub

3.wool

4.fur .

5.ttract

6.investigate

7.relate

8.spark

9.pposite

10.similar -

 

Answer the questions:

 

 

1.What did the ancient Greeks know?

2.What word was used for the word of electric?

3.Who investigated this phenomena?

4.Are there two kinds of electricity?

5.Were they called resinous electricity?

 

 

TEXT 7

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ELECTRONICS ELECTRON EMISSION

Electron emission is the liberation of electrons from sub stances under particular conditions. There are a number of ways in which the electrons of a substance can break through its surface, for example, the application of heat. If the metal is heated, the electrons move faster than their normal speed of motion. When electrons of a metal are freed by heating it is called thermionic emission.

Then there is the application of light. When electrons are liberated by the energy of the light rays it is called photoelectric emission.

The third type of emission is the liberation of electrons a-a result of the bombardment of the substance with fast-moving electrons.

The fourth method is called cold-cathode emission.In this case the electrons are liberated from a substance by the attracting power of a strong electric force.

Memorize the following words and word-combinations:

1.emission

2.liberation

3.substance

4.particular conditions

5.move

6.free

7.application

8.light

9.ray

10.force -

Answer the questions:

1.What is electron emission?

2.Are there a number of ways of emission?

3.What is in the result of heating?

4.What is called photoelectric emission?

5.What is called cold-cathode emission?

 

TEXT 8

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A WINDOW INTO THE INVISIBLE WORLD

Metals are as transparent as glass. Transparent are concrete, wood, oil and even living organisms.

All this and many more interesting things one may see with one's own eyes if one visits the electro-physics laboratory of the Metallurgy Institute under the USSR Academy of Sciences in Moscow.

Can the human eye see much? Of course it can, most people would answer. However, science and engineering have advanced to such a state that it has become necessary to find new means to see the invisible in order to explore and study the inner structure of things.

But neither X-rays nor supersound are capable of providing an adequate and precise picture of the inner structure of a material. Besides, these methods do not permit inspection of the objects while they are in motion, which is quite important for industry where the articles produced move along the conveyor.

Vision in non-transparent media is called "introscopy" and the instruments which accomplish this are called introscopes.

The scientists of the laboratory have created an intro-scope that permits one to see with the aid of infra-red rays in such materials as non-transparent plastics, ebonite, wood and others. Introscopes permit one to see defects in metal blanks moving on the conveyor, to see how the process of crystallization of melted metal proceeds. Tha scientists of the laboratory have already seen the work of an automobile motor on a TV screen, the motor looking on the screen as if it were made of glass of different tints.

But this is not ail. The scientists have succeeded in transforming the invisible-to-the-eye electromagnetic oscillations (infra-red, ultra-violet, X-rays, and even radio waves) into optically visible images.

The gamma-introscope makes it possible to watch the behaviour of different samples of metals under great pressures through the thick waits of a protective cylinder.

Thus we may say that the world that surrounds us will become as transparent to us as glass. AH this became possible thanks to the wonderful success of electronics.

Memorize the following words and word-combinations:

1.transparent

2.concrete

3.wood

4.oil

5.advance

6.means

7.invisible

8.inner

9.defects

10.screen -

Answer the questions:

1.Are the metals as transparent as glass?

2.Where can we see all these interesting things?

3.Can the human eye see much?

4.Are x-rays capable of providing precise picture of the inner structure of a material?

5.What is introscopy?

TEXT 9

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POWDER METALLURGY LOOKS TOWARDS

THE FUTURE

 

Developments and advances in powder metallurgy, a technology created some 50 years ago, can save manufacturing industry great amounts of valuable materials. Powder metallurgy is a cheap alternative to many conventional manufacturing processes.

When components, simple or complex, require precision and high quality at a comparatively low costpowder metallurgy can provide the solution of the problem. An important feature of powder metallurgy is that it can provide the industry with such material compositions which are not achievable by any other means.

Components produced by the powder metallurgy process can go straight into the manufacturing cycle or, if required, undergo further processing, including heat treatment. Powder metallurgy is finding new applications in various industriesin electronics, aviation, machine-building, etc.

The unique physical properties of powder metallurgy parts enable oil to be retained in minute porous cavities within the part. This self-lubricating characteristic * is long lasting and can eliminate other lubrication systems.

The Byelorussian research and production association for powder metallurgy has developed a number of processes for powder metallurgy components production. The source material there is metal powder which is subjected to high pressure to acquire a required shape and is then put to thermo-electric furnaces. The resultant parts are more durable and require no additional machining.

Future processes to be introduced by the association will produce self-lubricating bearings, metal and non-metal alloys and other materials with pre-set properties based on combinations of various powders. Metal powder with its unusual characteristic features and properties is listed in the category of new materials

Memorize the following words and word-combinations:

1.powder

2.towards

3.advance

4.create

5.amount ᒺ

6.cheap

7.provide

8.straight

9.processing

10.properties -

Answer the questions:

1.When was the powder metallurgy created?

2.Is it cheap?

3.What can it provide?

4.Is it finding a new application?

5.What are the unique physical properties of the powder metallurgy?

 

TEXT 10

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