Exercises

I. Translate the following sentences:

1. When placing an iron core within the coil, we greatly increase the magnet's efficiency. 2. If suspended so that it :an rotate freely, the solenoid may be observed tq point north md south when the current flows. 3. This circuit can be

closed, if necessary. 4. When placed in a strong magnetic field, iron becomes magnetized. 5. When speaking about a direct current, we mean a continuous current.

II. Translate the following sentences and change them according to the model given below.

Model: It is the sun that is an unlimited source of almost all kinds of energy.

The sun is an unlimited source of almost all kinds of energy.

1. It is in the electrical appliance that the electric energy is changed into heat. 2. It is an increase in temperature that increases the molecular motion. 3. It was Ampere who showed the difference between the current and the charges. 4. It is at the power station that electricity is produced. 5. It is the magnetic effect of the current that is the subject of this ar­ticle. 6. It is the unit of current that is named after Ampere.

III. Fill in the blanks with where, which, when, who, that:

1. We know ... Oersted established the connection between an electric flow of current and a magnetic needle. 2. The great scientists Volta, Ampere and Yablochkov may be named among those ... have greatly contributed to electrical engi­neering. 3. The end ... the lines of force leave the coil after passing through its core will act like a north magnetic pole. 4. ... there is a certain connection between electricity and magnetism was proved by experiments. 5. ... he placed the wire parallel to the needle he" saw ... the needle deflected. 6. A wire ... is wound in the form of a solenoid acts like a magnet as long as it is carrying a current.

IV. Translate the following sentences paying special attention to the words in bold type:

1. Rubber is a very poor conductor of electricity. 2. This is the very appliance which I need for my experiment. 3. Lo-monosov was born in the family of a poor peasant. 4. All metals are poor insulators of an electric current. 5. The Soviet Union is a great country. 6. Next summer I shall have a rest in the country. 7. The rest of the story should be translated at home. 8. Electricity at rest or in a static condi­tion does no work. 9. Heat causes many chemical reactions. 10, What causes the electrons to flow along the wire? 11. Short circuit may be the cause of fire.

V. Fill in the blanks with either should or would:

1. The development of industry ... be impossible without electricity. 2. This research work ... never have been completed without help. 3. We ... like to read English articles on our specialty. 4. ... it be possible to live at a very low tempera­ture? 5. What ... you say, if you were late for the lesson? 6. Energy must be supplied to the circuit and this energy ,.. be equal in amount to that spent in the circuit.

VI. Fill in the blanks, with suitable prepositions, make up sentences with the following infinitives:

to equip ... ; to depend ... ; to compare ... ; to consist ... ; to contribute ... ; to be interested ... ; to be familiar ...

VII. Compare:

1. Potential energy and kinetic energy.

2. A series circuit and a parallel circuit.

3. A conductor and an insulator.

4. The magnetic effect of an electric current and the heating effect of an electric current.

VIII. Make up five questions using the verbs given below. Ask your comrades to answer them.

Model: How long does it take you (him, her) to get to the Institute? It takes me (him, her) 25 minutes to get there.

to go, to prepare, to translate, to learn, to do

IX. Form nouns from the following verbs and translate them:

to invent, to connect, to discover, to achieve, to observe, to state, to contribute, to conduct, to produce, to operate, to deflect

10. Give a short summary of the text.

11. Look at Fig. 10 and describe Oersted's discovery.

LESSON SEVENTEEN

GENERATORS

Great generators in our power stations, which rotate at a constant speed day and night, summer and winter, are able to generate electric energy only because of the electromagnets.

rt is calculated that these machines produce more than 99.99 per cent of all the world's electric power.

Although used to operate certain devices requiring small currents for their operation, batteries and cells are unlikely to supply light, heat, and power on our modern large scale. It is dynamo-electric machines that are used for this purpose. These are machines by means of which mechanical energy is

turned directly into electric energy with a loss of only a few per cent.

There are two types of dynamos, namely, the al­ternator and the generator (Fig. 11). The former pro­vides a. c. while the latter supplies d. c, similar to the current from a battery. Both of them must be turned by some outside source of me­chanical energy, such as , water power, for example. 'Where cities are far from water power, the mechanical

energy for the generator mostly comes from burning coal, which operates a steam turbine which turns the generator. Both-generators and alternators consist of the following principal parts: an armature and an electromagnet. The for­mer generally serves as a rotor in d. с generators while it is the magnetic system that serves this purpose in alternators. The latter is usually called a stator for it is in a static condi­tion "In order to get a strong e. m. f., the rotors in large alternators rotate at a speed of thousands of revolutions per minute (г. р. т.). In this connection one could add that the speed of rotation will control the output voltage of the gen­erator in the following manner:

1. The faster the armature is rotated, the more voltage the generator will produce.

2. The slower the rotation, the less the output voltage. Electric power stations which supply electricity over long

distances are at present always equipped with large alter­nators. These supply us with much greater quantities of cur­rent than anything ever supposed by Volta, Oersted and Ampere.

In order to produce electricity under the most economical con­ditions, the generators must be as large as possible. In addition to it, they should be kept as fully loaded as possible all the time. It is interesting to note here that the biggest generators ever installed at any hy­droelectric station in the world are those in­stalled in the USSR. As you are likely to remember, the Kuiby­shev and Volgograd sta-tions have 125,000 kil­owatt generators and the Bratsk hydroelec­tric station has twenty 225,000 kilowatt gener-

ators. Soviet scientists are known to develop 500,000 kilo­watt generators which are to be installed at the Kras­noyarsk station.

Large installations with turbo-generators of 200,000 to 300,000 kW power are being constructed in different parts of the Soviet Union. The eight generators of the Konakovo thermo-electric station not far from Moscow are planned to have 2,400,000 kW of rated capacity.

Our industry is most likely to produce even greater power installations for thermo-electric stations which play such an important part in the electrification plan of the USSR.

It goes without saying that the dynamo invented by Fa­raday in 1831 would seem to be a most primitive apparatus compared with the powerful, highly-efficient machines that are in use today. Nevertheless, these generators and alterna­tors work on the same principle as the one invented by the great English scientist. When asked what use his new inven­tion had, Faraday is said to have asked in his turn: "What is the use of a new-born child?" As a matter of fact, the "new-

born child" soon became an irreplaceable device we cannot do without^

Fig. 11 shows the principles the construction of an ele­mentary d. с generator is based upon. We see the armature, the electromagnet, the shunt winding, the commutator and the load.

Active Words and Expressions

Alternator генератор переменного тока

Armature якорь

Calculate считать

Equip оснащать, оборудовать

Operate работать, функционировать

revolutions per minute

(r_: p. m.) обороты в минуту

Rotate вращаться

shunt шунт, параллельная цепь

thermo-electric station термоэлектростанция

tur­bine турбина

winding обмотка