Fig. 11. Michael Faraday (1791–1867)

 

It goes without saying that the dynamo invented by Faraday in1831 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 i rreplaceable device we cannot do without.

 

Exercises

 

Translate the following sentences:

1. Heat developed in a transmission line or a generator is a needless waste of energy. 2. An electric lamp uses the light given off by its filament heated by the current. 3. The experiments made by Oersted attracted Ampere’s attention. 4. Electric power stations supplying power on a large scale are equipped with large alternators.

 

Translate the following sentences and combine the principal and subordinate clauses with suitable conjunctions.

1. There is a great number of engineering problems the Russian scientists work at. 2. It quite impossible to name a scientific problem Lomonosov did not turn his attention to. 3. There are many electric appliances we cannot do without. 4. The experiment I told you about will take much time.

 

Answer the following questions.

1. Do you want to translate this article. 2. Do you want me to translate this article. 3. Do you know this scientist? 4. Do you know this scientist to have explained the new phenomenon. 5. Did you hear my report? 6. Did you hear my friend make a report? 7. Did you see my brother? 8. Did you see my brother enter the room?

 

4. Form adjectives using the suffixes - able, -ful, -less, -ous.

control, continue, danger, value, replace, need, power, peace, use, life.

 

5. Form adverbs using the suffix - ly:

Exact, electrical, general, gradual, negative, natural, opposite, previous, usual, easy.

 

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.

 

Translate the following sentences.

1. Чем сильнее магнитное поле, тем больше ток. 2. Чем больше ток, текущий по проводнику, тем выше температура проводника. 3. Чем меньше труба, тем меньше воды проходит через нее. 4. Чем короче проводник, тем меньше сопротивление проходящему току. 5. Чем больше скорость движения между магнитным полем и проводниками, тем больше ток.

 

8. Form sentences combining suitable parts of the sentence given below:

 

I 1) electric circuit   2) e. m. f.   3) heat engine   4) iron   5) electromagnet

II 1) is a temporary magnet provided by electricity; 2) is an electrical appliance used in our everyday life; 3) is a path to be followed by the current from the source and back to the source; 4) is the force that makes electrons move along a conductor; 5) is a device by means of which heat is turned into work.

 

Look at Fig. 10 and describe it.

UNIT 15

The electric motor

Vocabulary

to employ |ɪmˈplɔɪ| – использовать	to add – прибавлять
machinery |məˈʃiːn(ə)ri| – техника, оборудование	to switch on – включать
appliances |əˈplaɪənsɪz| – бытовые приборы	starting torque |ˈstɑːtɪŋ tɔːk| – пусковой крутящий момент
to result |rɪˈzʌlt| – приводить к	series winding |ˈsɪəriːz| – обмотка с последовательным соединением
instead of |ɪnˈstɛd| – вместо	in series – последовательно
certainly |ˈsəːt(ə)nli|– конечно, несомненно	so far – пока, до сих пор
winding |ˈwʌɪndɪŋ| – обмотка, катушка	a wide range |reɪn(d)ʒ| – широкий диапазон
commutator |ˈkɒmjʊˌteɪtə| – коллектор	immersed |ɪˈmɜːst| – погруженный
brushes |ˈbrʌʃɪz| – щетки	countless |ˈkaʊntləs| – бесчисленный, несчетный, бесконечный, неисчислимый

 

 

The electric motor is a device employed for transforming one form of energy into another, that is to say, electrical into mechanical. We know it to produce the rotary motion which turns our machinery and various appliances.

We have already seen the generator convert mechanical energy into electrical one. Now the process is reverse. It is electricity that is supplied to the machine and it is motion that results. It is obvious that generators and motors are similar in certain respects. In case we put current into the dynamo instead of our taking current out, it will rotate as a motor. There are certainly some differences in detail but in both of them we find an armature with windings, a commutato r and brushes, combined with an electromagnet for producing the magnetic field. However in an electric motor one shunt winding is not sufficient and a second one called a series winding should be added. “Why is it necessary?”one might ask. The fact is that the motor is required to have a powerful effect at the very moment when the current is switched on, for instance, in an electric train or tram. Avery strong magnetic field is needed to obtain a so-called powerful starting torque. This is achieved by adding a series winding to the magnet coils. Is connected not in shunt with the armature but in series with it, so that all the heavy starting current passing through the armature winding, now passes through the serious field coil and provides a strong field necessary for starting while the shunt field winding provides the running conditions.

So far nothing was said of what a motor does in our homes. In a modern home there are many different electric motors in machines and devices utilized to meet our daily requirements: to tell the time, to wash clothes, to cool the refrigerator, to clean or brush various things, to shave, to circulate air in a warm room in a hot day work thanks to electric motors. It follows that in the electric motors we have a valuable and powerful appliance capable of fulfilling the required operations exactly and with just the desirable kind of motion, rate of speed and power. It is readily switched on, at will, and it continues running until we switch it off again. In our present-day wide use of the motor there are often cases when it is simply possible to replace it by any other suitable engine. Generally speaking, it revolutionized industry by making use of energy that can be transmitted from great distances.

 

 

Fig. 12. The electric motor

 

No appliance ever created by man has probably such a wide range of size and such a variety of application as a motor. In fact, on the one hand, there are all kinds of mighty giants in the motor world. These giants are known to perform innumerable operations in coal-mines, in steel mills, chemical factories and so on, in short, in great numbers of factories and works. On the other hand, there exist all kinds of small- sized and even minute motors which are able to power various complex machines. They operate equally well under any conditions: high in the air or immersed in water, lowered into a well or on the table of some famous scientist. Much of our farm equipment is also driven by means of electric motors. In short, they find the application wherever and whenever suitable, that is, in industry and science, in agriculture and transport.

Countless highly efficient and powerful motors constructed according to the latest achievements of science and engineering are widely employed in our country today.

 

Exercises