6 Unit 9

Grammar: Gerund (forms and functions)

Reading Exercises.

1. Practise reading the following one-syllable words:

Sun, cold, light, ore, part, fall, switch, kind, turn, way, half, few, term, cent, branch.

2. Practise reading the following two-syllable words with the stress on the first syllable:

Metal, sharply, prospect, system, constant, progress, fraction, power, cover, sunlight.

3. Practise reading the following two-syllable words with the stress on the second syllable:

Include, between, employ, apply, design, convert, transform, obtain

4. Practise reading the following many syllable words:

Electricity, impossible, accumulate, numerous, resistance, temperature, emergency, photocell, complicated

5. Practise reading the following words with double stress:

Engineering, semiconductor, automation, conductivity, irrespective, reproduce

6. Memorize the spelling and pronunciation of the following words:

Vary ['vεərI] – міняти, змінювати

Variety [və’raIətI] – різноманітність

Technique [tek'ni:k] – метод

Design [dI'zaIn] – проект

Circuit ['sə:kIt] – схема

Determine [dI'tə:mIn] – визначати

Text 9 a semiconductors

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

They include a 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, the 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 is used in creating photo resistances. It is also widely applied for switching on engines, for counting parts on a conveyer belt, as well as for various systems of emergency signals and for reproducing sound in a cinematography. Besides reacting to light, semiconductors react to all kinds of radiations and are therefore employed in designing electronic counters.

Engineers and physicists turned their attention to semiconductors many 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 by means of metal thermocouples, but in this way it was impossible to convert more than a few tenths of one per cent of the heat into electricity. The thermocouples made later of semiconductors generated ten times as much electricity as the metal ones.

Sunlight like heat can feed our electric circuits. Photocells made of semi-conducting materials are capable of transforming ten per cent of sun-ray energy into electric power. By burning wood which has accumulated the same amount of solar energy, we obtain only fractions of one per cent of electric power.

The electricity generated by semiconductor thermocouples can produce not only heat but also cold, this principle is 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 50° below 0° to 100° above 0°.

Notes:

1. emergency signals – аварийні сигнали

2. to turn one’s attention to – звернути свою увагу

Answer the questions:

1. What does the term “semiconductor” mean?

2. What elements do they include?

3. When does the conductivity of semiconductors sharply increase and fall?

4. What principle is used in creating photoresistances?

5. Where is it also widely applied?

6. Why are semiconductors employed in designing electronic counters?

7. Why did engineers and physicists turn their attention to semiconductors?

8. What principle has been used in manufacturing refrigerators?

9. What temperature can semiconducting materials maintain irrespective of the surrounding temperature changes?