THE ELECTRIC MOTOR AND ITS NUMEROUS APPLICATIONS

The electric motor is a device employed for transforming one form of power 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 power into electric power. Now, the process is reversed. It is electricity that is supplied to the machine and it is motion that results. From all that has been said earlier in the previous articles about our getting magnetism from electricity and about the generation of the electric current by using magnet­ism, 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 commutator 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, as for instance, in an electric tram or a train. A very 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 (Fig. 15). It 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 series 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 on a hot summer day, and so on. In effect, vacuum-cleaners, washing machines, modern refrigerators,— all work thanks to electric motors. It follows that in the elec­tric motor 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 impossible to replace it by any other suitable engine. Generally speaking, it revolution­ized industry by making use of power that can be transmit­ted from great distances.

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 an 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

1. Learn the following active words:

brush щетка

coal-mine угольная шахта

commutator коммутатор

exist существовать

winding обмотка

fulfill выполнять

mighty мощный

perform выполнять

rate степень

replace заменять

rotary ротационный, вращательный

shunt переключение, ответвление

sufficient достаточный

torque вращающий момент

2. Translate the following sentences:

1. The flow of current being reduced, the speed of the motor is decreased. 2. It is on the above basis that all our power-plants are constructed at present. 3. We know of this substance having been used at first owing to its high quality. 4. Copper being a good conductor, we were asked to use it when carrying on our research work. 5. By changing the value of the resistance, we can increase the current. 6. Having been used for a long time, the instrument lost its former quality. 7. Were that so­lid substance heated, it would greatly expand. 8. To observe is the primary rule of any experiment. 9. The professor wants us to turn our attention to the problem of semiconductors. 10. The new invention proved to be of great practical impor­tance.

3. Define the function of the words in bold type:

1. The methods applied improved the quality of produc­tion. 2. The machine used showed good results. 3. The ex­periment described attracted everybody's attention. 4. The appliance received required some improvement. 5. The substances utilized neutralized each other. 6. The amount of electricity generated depended on the quality of the coal. 7. The scientists mentioned contributed greatly to the devel­opment of science.

4. Translate the following sentences:

1. Завтра будут получены приборы. 2. Студентам дали новые инструкции. 3. Об этих достижениях много говорят. 4. Меня попросили провести испытание. 5. Пример после­довал за правилом. 6. Нам показали новые материалы.7. Их учат иностранным языкам. 8. Вчера ответили на эти письма.

5. (a) Form verbs applying the suffix -ize:
civil, revolution, equal, neutral

(b) Form verbs applying the prefix over-: