4. Complete the sentences with the proper words:

External influence, transistors, measuring instruments, photoresistance, thermal elements

1. …….are devices which consume very little power.

2. Transistors transform heat energy into electrical energy by means of……

3. They are extremely sensitive to…..and light.

4. Their property to decrease resistance was used as the basis of…….

5. At present this photoresistance is successfully used as the main elements for different….

5. Ask questions to the underlined words:

1. Transistors are used for direct transformation one kind of energy into another.

2. Light sources and lasers were built on the basis of transistors.

3. Transistors made needless the usage of vacuum tubes.

4. They are very sensitive to light, nuclear particles, pressure.

5. Some transistors act as insulators in the darkness.

6. Read the text below and translate it with the help of the given words:

Current gain-посилення по току, voltage-напруга, amplification-посилення, power gain-посилення по потужності, resistivity-здатність чинити опір, electrical charge carrier-носій електричного заряду, current flow-електричний струм, electronic valence-електровалентність

A transistor is an active semiconductor device with three or more electrodes. By active we mean that the transistor is capable of current gain, voltage, amplification and power gain. A transistor is an electron device in which electronic conduction takes place within a semiconductor.

A semiconductor is an electric conductor with resistivity in the range between metals and insulators, in which the electrical charge carrier concentration increases with increasing temperature over some temperature range.

The resistivities of semiconductors and insulators decrease rapidly with rising temperatures, while those of metals increase relatively slowly. Unlike metals and insulators, the resistivity of semiconductors depends upon the direction of current flow. The direction of easiest current flow or lowest resistivity is called the forward direction, the direction of restricted current flow or highest resistivity is known as the reverse or back direction.

Semiconductors, such as the elements germanium and silicon, possess two types of current carriers, namely, negative electrons and positive holes. A hole is a mobile vacancy in the electronic valence structure of a semiconductor which acts like a positive electronic charge with a positive mass.

TEXT B

1. Read and translate the text in a written form: Transistors

The bipolar junction transistor is the cornerstone of much of today's semiconductor electronics industry. This form of transistor has been in existence for many years and is still very widely used in electronic circuits. The bipolar transistor is very versatile and finds applications in many areas and at a wide range of frequencies. The bipolar transistor dates back to the middle of the twentieth century when three scientists named Bardeen, Brattain, and Shockley working at Bell Laboratories in the USA discovered it. They had been researching an idea for a semiconductor field effect device, but they had been unable to make it work. They had not succeeded in making this idea work and as a result they decided to follow other lines of research and in doing this they developed the bipolar transistor. They succeeded in making it work in late 1947, and only a week after their initial discovery they demonstrated it in front of a group of executives at Bell Laboratory. Today the semiconductor industry is enormous and vast quantities of money are being invested in new semiconductor device developments. Although there are many new types of transistor, the bipolar junction transistor is still in very widespread use. The bipolar transistor can be made from a variety of types of semiconductor. The original devices were made from germanium, but silicon is widely used today.

2. Make up a plan of the text in the form of questions.

TEXT C

1. Mind the following words:

1. bulky – громіздкий

2. inefficient – неефективний

3. spark – запалювати

4. manned – керований людиною

2. Listen to the text “The history of Transistors” and try to understand it.

3. Answer the following questions:

1. Where were transistors invented?

2. When was the first device developed?

3. What field of science were they awarded the Nobel Prize?

4. When did it happen?

5. Why was the need for transistor invention?

UNIT 7

TEXT A

Semiconductors

1. Read and remember the words and word combinations:

1. Conductivity-провідність

2. chemical compound-хімічна сполука

3. ore-руда

4. convert-перетворювати

5. thermocouple-термопара

6. solar energy-сонячна енергія

7. increase-збільшувати

8. decrease-зменшувати

9. accumulate-накопичувати

2. Read and translate the text:

The term ‘semiconductor’ means half-conductor that is a material whose conductivity ranges between that of conductors and non-conductors or insulators.

They include great variety of elements (silicon, germanium, selenium, phosphorus and others), many chemical compounds (oxides, sulphides) as well as numerous ores and minerals.

While the conductivity of metals is very little influenced by temperature, conductivity of semiconductors sharply increases with heating and falls with cooling. This dependence has opened great prospects for employing semiconductors in measuring techniques.

Light as well as heat, increases the conductivity of semiconducting materials, this principle being used in creating photo resistances. It is also widely applied for switching on engines, for counting on conveyer belts, as well as various systems of emergency signals and for reproducing sound in cinematography. Besides reacting to light, semiconductors react to all kinds of radiations and they are therefore employing in designing electronic counters.

Engineers and physicists turned their attention to semiconductors more that fifty years ago, seeing in them the way of solving complicated engineering problems. Converting heat into electricity without using boilers or other machines was one of them. This could be done as means of metal thermocouples, but in this way impossible to convert more one per cent of the heat into electricity. The thermocouples made later of conductors generated more than ten times as much electricity as the metal ones.

Sunlight like heat can feed our electric circuit. Photocells made of semiconducting materials are capable of transforming ten per cent of sunray energy into electric power. By burning wood, which has accumulated the same amount of solar energy, we obtained only heat fractions of one per cent of electric power.

The electricity generated by semiconductor thermocouples can produce not only heat but also cold, this principle being used in manufacturing refrigerators.

Semiconducting materials are also excellent means of maintaining a constant temperature irrespective of the surrounding temperature changes. The latter can vary over a wide range, for example, from 59C below 0C to 100C above 0C.

Semiconductors are the youngest field of physical science. Yet even now they are determining the process of radio engineering, automation, chemistry, electrical engineering and many other fields of science and technique.