Electric Motor

 

The electric motor is a device employed for transforming energy into mechanical energy. We know it to turn machinery and various appliances.

Speaking about the generation of electric current by using magnetism, it is necessary to mention that generators and motors are similar in certain respects. There is certainly some difference 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 should 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 magnetic coils. It is connected not in shunt with the armature but in the series with it. Thus, 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, the shunt field winding providing the running conditions.

No appliance ever created by man has probably had such a wide range of size and such a variety of application as the 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 wherever required. On the other hand, there exist all kinds of small-sized and even minute motors which are able to power various complex machines and operate equally well under any conditions. In a modern home there are many different electric motors in machines and devices utilized to meet our daily requirements. In effect, vacuum cleaners, washing machines, and modern refrigerators do 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 power and rate of motion. There are often cases when it is simply impossible to replace it by any other means. In short, the motor finds application in industry and engineering, in agriculture and transport, in medicine and our homes.

Notes on the text:

torque – момент, пусковой момент

сommutator – коллектор

 

VII. Письменно ответьте на вопросы по содержанию текста:

What is the motor employed for?

What is a very strong magnetic field needed for?

What does the shunt field winding provide?

 

Контрольная работа №4

 

Изучите следующие разделы грамматики по учебнику:

Неличные формы глагола: Participle I (Present Participle), Participle II (Past Participle) в функциях определения и обстоятельства. Причастные обороты: зависимый, независимый (самостоятельный), объектный.

Герундий (Gerund), простые и сложные формы. Основные способы перевода герундия на русский язык. Герундиальный оборот.

Сослагательное наклонение.

Три типа условных предложений.

 

 

Вариант I

I. Перепишите предложения. Переведите на русский язык, обращая

внимание на перевод герундия. Подчеркните герундий в предложениях.

 

Studying natural phenomenon without making observations is useless.

Russian scientists played an important part in solving this problem.

The lightning conductor, familiar to everybody at present, is a metal device protecting buildings from strokes of lightning by conducting the electrical charges to the earth.

We all know of their designing a new type of semiconductor radio set.

 

II. Перепишите предложения, подчеркните причастия. Переведите

предложения на русский язык. Укажите № предложения, в котором

употреблен независимый причастный оборот.

 

Having experimented with electricity and magnetism, Gilbert wrote a book on magnetism.

Many hydroelectric stations were built in our country, the one on the Angara being one of the largest.

This e-mail transmitted by using the Internet is very important for our professor.

Solar batteries converting the energy of the sun directly into electric current are sources of electric energy for radio and television equipment on spaceships and man-made satellites.

While using the Web you can start your program anywhere you want.

We saw the experiment worker operating a new very complex machine with great skill.

 

III. Перепишите предложения и переведите их на русский язык, обращая

внимание на глаголы в сослагательном наклонении.

 

It is highly desirable that more radio-electronic devices should be applied for astronomical observations and measurements.

If you watched a laser operate, you might be surprised at the simplicity of a device capable of such power.

It is necessary that highly sensitive reception devices be made for the radio telescope to achieve better results in observation.

If friction could be entirely eliminated, a body set in motion on a level surface would continue to move indefinitely.

 

IV. Перепишите предложения. Переведите на русский язык, обращая

внимание на условные придаточные предложения.

 

Provided electronic and radio navigation equipment had not been improved so radically in recent years, aircraft flying would not have become so reliable and efficient.

If some current flows through a thin wire and then the same amount of current is sent through a thicker one, a different amount of heat will be developed in both these wires.

If we solved the problem of controlled thermonuclear reactions, we could use oceans of fuels.

 

V. Прочитайте текст, перепишите его и письменно переведите на

русский язык.