Variant 2

Task 1

Variant 2

Task 1

I. Listen to the text:

FROM THE HISTORY OF TRANSISTORS

Scientists have invented very many electron devices serving us in various ways. Electronic (vacuum) valves are wonderful devices which serve to do jobs in radio and TV sets, in radars, for controlling manufacturing processes etc.

Still while using the mentioned vacuum valves scientists have noticed some drawbacks. They waste a good deal of electricity. One of the elements, the filament, is heated to such a degree that it gives off electrons. This heating requires electricity and produces unwanted heat. Scientists realized the drawbacks of electronic valves and began to search for other ways of doing the jobs that valves had done. Soon a new device, the transistor, appeared. It was so small that you had to look carefully to see it.

In recent years the art of semiconductor engineering has reached such a state of development that it rapidly replaces electron valves, previously considered the heart of modern radio.

For a long time had been no well-founded semiconductor theory although many cases of practical approach to the development of semiconductor circuits were recorded. The research carried out in 1922 by the engineer O.V. Losev was of great interest because his work showed that a semiconductor (a crystal) could be used as a generator of electromagnetic oscillations.

The engineers had designed a special crystal receiver and it showed its much higher sensitivity.

Semiconductor triodes, or transistors are at present widely used in various amplifiers, receivers, oscillators and countless electronic devices. Some transistors can replace electronic valves hundreds of times their size. Transistors need far less current and produce far less heat than comparable electronic valves. They are made of small germanium or silicon crystals.

II. Say whether the following statements are true or false:

1. Electronic (vacuum) valves serve to do jobs in radio and TV sets, in radars, for controlling manufacturing processes etc.

2. They waste poor deal of electricity.

3. Heating requires electricity and produces unwanted heat.

4. Losev’s research showed that a semiconductor could be used as an amplifier.

5. Transistors need far less current and produce far less heat than comparable electronic valves.

3. Complete the sentences:

1. While using the mentioned vacuum valves scientists have noticed …

2. The filament is heated to such a degree that it …

3. The engineers had designed a special crystal receiver and it showed…

4. Some transistors can replace electronic valves hundred of times…

5. Transistors are made of…

Variant 2

Task 1

Listening

Answer keys

II.

1.+

2.-

3.+

4.-

5.+

III.

1. …some drawbacks.

2. …gives off electrons.

3. …its much higher sensitivity.

4. …their size.

5. …small germanium or silicon crystals.