VI. Read the following abbreviations:

a.c, d.c, r.p.m., e.m.f., m.m.f., 317°F, 45°C, i.e.

VII. Define the following terms:

1. electromotive force; 2. electric circuit; 3. heating ef­fect of an electric current; 4. magnetic effect of an electric current; 5. electromagnet; 6. generator

VIII. Comrade Л., ask Comrade B.\ Comrade B.₉ answer Comrade A.'s questions:

1. if batteries can supply light, heat and power on a large scale.

2. if the electromagnet is a temporary magnet provided by electricity.

3. if the electromagnet is lifeless unless the electric cur­rent flows through the coil.

4. if the iron core will act as a magnet as long as the cur­rent continues to pass along the winding.

5. if the alternator provides a.c.

6. if the generator must be turned by some outside source of mechanical energy.

IX. Form five sentences combining suitable parts of the sentence given in columns I and II:

1 11

1. The electric circuit 1, is a temporary magnet provided by

electricity.

2. The e.m.f. 2. is an electrical appliance used in

daily life.

3. The heat engine 3. is a path to be followed by the cur-

rent from the source and back to the source.

4. The iron - 4. is the force that makes electrons

move along a conductor.

5. The electromagnet 5. is a device by means of which heat

is turned into work.

X. Look at Fig. 11, name a,b,c,d,e and describe the figure.

LESSON NINETEEN

PASSIVE AND IMPERSONAL CONSTRUCTIONS

POWER TRANSMISSION

They say that about a hundred years ago, power was nev­er carried far away from its source. Later on, the range of transmission was expanded to a few miles. And now, in a comparatively short period of time, electrical engineering has achieved so much that it is quite possible, at will, to convert mechanical energy into electrical energy and trans­mit the latter over hundreds of kilometres and more in any direction required. Then in a suitable locality the electric energy can be reconverted into mechanical energy whenever it is desirable. It is not difficult to understand that the above process has been made possible owing to generators, trans­formers, and motors as well as to other necessary electrical equipfnent. In this connection one cannot but mention the growth of electric power generation in this country. The long­est transmission line in pre-revolutionary Russia was that connecting the Klasson power station with Moscow. It is said to have been but 70 km long, w^rhile the present Kuiby­shev-Moscow high-tension transmission line is 900 kilometres long- (The reader is asked to note that the English terms "high-tension" and "high-voltage" are interchangeable). Gen­erally speaking, the length of high-tension transmission lines in the Soviet Union is so great that they could circle the globe six times, if not more.

It goes without saying that as soon as the electric energy is produced at the power station, it is to be transmitted over

wires to the consumer. However, the longer the wire, the greater is ils resistance to current flow. On the other hand, the higher the offered resistance, the greater are the heating losses in electric wires. One can reduce these undesirable losses in two ways, namely, one can reduce either the resist­ance or the current. It is easy for us to see how we can reduce resistance: it is necessary to make use of a better conducting material and as thick wires as possible. However, such wires are calculated to require too much material and, hence, they will be too expensive. Can the current be reduced? Yes, it is quite possible to reduce the current in the transmission line by employing transformers. In effect, the waste of useful energy has been greatly decreased due to high-voltage lines. It is well known that high voltage means low current, low current in its turn results in reduced heat­ing losses in electrical wires. It is dangerous, however, to use power at very high voltages for anything but transmission and distribution. For that reason, the voltage is always re­duced again before the power is made use of.

Lasers. Soviet scientists are successfully developing quan­tum generators, called lasers, for emitting light amplitude radio waves. Theoretical calculations have shown that lasers are very likely to transform the energy of light radio waves into electrical energy with an efficiency amounting to about 100 per cent. It means that electrical power might be transmit­ted over considerable distances with negligible losses and what is very important without the use of transmission lines.

Active Words and Expressions

to amount to, at will, considerable, distribution, equip­ment, expensive, growth, line, range, to reduce, successfully, transmission, tension, wave

Exercises

/. Translate the following sentences paying attention to the impersonal construction:

1. 1. It is easy to understand Ampere's rule. 2. It was desirable to compare the results obtained. 3. It is necessary to find new sources of energy. 4. It was difficult for Oers­ted to find out why the compass needle was deflected.

2. 1. One can say that there are unlimited sources of energy. 2. One could not obtain good results without repeating the test. 3. There are so many atoms in a water drop that

if one could count one atom a second, day and night, it would take one hundred milliard years. 3. One may mention here that the first industrial nuclear power plant in the world was constructed in this country.

• (с) 1. They employ different methods to obtain better re­sults. 2. They produce modern machines at our plant. 3. They say that lasers will be widely used in the nearest future.

(d) 1. It is supposed that people learnt to protect their houses from thunderstorms years ago. 2. It is said that these substances have similar properties. 3. It is well known that one form of energy can be converted into another form.

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