II. Answer the following questions.

1. What is a transformer used for?

2. What does a transformer consist of

3. What is the function of the primary winding?

4. What is the function of the secondary winding?

5. What type of transformer is called a step up transformer?

6. What type of transformer is called a step down transformer?

7. What can you say about a transformer core?

8. What is the relation between the number of turns in the windings and the value of voltage?

III. Give a short summary of the text.

IV. Pick up pairs of synonyms.

to increase, to reduce, to convert, to decrease, lo transform, to transfer, to rise, lamination, winding, magnitude, layer, value, coil, to transmit

V. Translate the sentences paying attention to the words underlined.

1. This properly was demonstrated by a number of experiments.

2. This problem will be described in a number of articles.

3. The number of scientists taking part in the scientific conference at our institute is increased from year to year.

4. A great number of scientists has arrived in our country last week.

5. The number of power stations is increased in our country from year to year.

6. The number of electrons in atom depends on the kind of atom.

7. The number of tourists visiting our country has been increased.

 

                 TEST YOURSELF

Упр. 1. Подберите правильные переводы для слов левой колонки.

1. application         1. проводник

2. appliance           2. согласно

3. conductor          3. ряд

4. according to     4. изолятор

5.core                     5. применение

6. the number of    6. число

7. a number of     7. катушка

                                8. порядок

                                9. сердечник

                                10. прибор

 

Упр. 2. Подберите правильные переводы для слов левой колонки.

1. outside      1. обмотка

2. inside            2. слой

3. winding              3. составлять    

4. lamination         4. величина

5. size                     5. обнаруживать

6. side                     6. снаружи

7. magnitude          7. размер

                                8. сторона

                                9. внутри

                                10. представлять

 

Упр. 3. Подберите правильные переводы для слов левой колонки.

1. to induce        1. определять

2. to determine               2. влиять

3. to differ          3. считать

4. to affect         4. преобразовывать

5. to consider       5. наводить

6. to decrease       6. представлять

7. to convert      7. увеличивать

8. передавать

9. отличаться

10. уменьшать

Упр. 4. Подберите правильные переводы для слов левой колонки.

1. to transfer      1. повышать

2. to transform                2. понижать

3. to wind                     3. определение

4. to step up                        4. наматывать

5. to step down                 5. передавать

6. determination             6. преобразовывать

7. difference               7. разница

                                         8. повышение

                                         9. увеличение

                                         10. преобразование

 

Упр.5. Подберите синонимы для слов левой колонки.

1. to apply                       1. due to

2. to influence           2. to rise   

3. to receive                     3. value

4. because of                   4. to use

5. to increase                   5. to get

6. magnitude                   6. coil

7. winding                       7. to affect

 

Упр. 6. Подберите синонимы для слов левой колонки.

1. to convert                    1. strength

2. to reduce                     2. coil       

3. thanks to                     3. to transmit

4. force                            4. to define

5. turn                              5. to transform

6. to transfer                    6. due to

7. to determine             7. to decrease

 

Упр. 7. Подберите антонимы для слов левой колонки.

1. outside               1. step down

2. output                       2. low

3. weak                            3. strong

4. negative                       4. inside

5. increase              5. positive

6. step up               6. reduce

7. high                             7. input

 

Упр. 8. Переведите текст без словаря:

Suppose a transformer is wound with a proportion of ten to one, in the number of loops. Suppose there are one hundred turns on one side and one thousand turns on the other side. If fifty volts of alternating current were supplied to the coil with one hundred turns, the voltage in the other would be ten times that amount or five hundred volts. Of course, there would be some loss of current, but the actual voltage would be almost five hundred volts. Now, if the fifty volts were supplied to the opposite coil, the voltage would be stepped down one tenth, or to about five volts.

 

 

UNIT IV.

Kinds of Currents.

Lesson 1.

Text.

              Two kinds of currents.               

As you, certainly, know electric charges in motion constitute a current. There are two kinds of current, namely: direct and alternating.

A direct current (d.c. for short) flows through a conducting circuit in one direction only. It does not change in magnitude. It is measured by the quantity of electricity passing through any section of the conductor in one second. By the way, direct current generators produce a direct current.

A direct current is, of course, useful and we know the electrical systems in airplane, and in automobile to use direct current. It is also used in research work, in the telephone, in the telegraph, etc.

An alternating current (a.c. for short) is a current that changes its direction of flow through a circuit. To alternate means to move back and forth. The current flowing first in one direction and then in another, we name it an alternating current. An alternating current flows in cycles, the number of cycles per second being called the frequency of the current. The frequency of the current is known to be measured in cycles per second. The standard frequency in Russia is 50 c.p.s. (cycles per second).

From the above-mentioned, it is clear that a direct current system is useful. However, in spite of its usefulness a direct current system has one great disadvantage. Namely, there is no economical way by means of which one can increase or decrease its voltage. The alternating current does not know this disadvantage, alternating voltage increasing or decreasing with little loss owing to a transformer.

 Using a transformer, it is possible to convert power at low voltage into power at high voltage, power at high voltage being also transformed into power at low voltage.

Power being transmitted over long distances with less loss at high voltage, it is more economical to increase the voltage for transmission and to decrease it to the voltage which is best suited for the particular use.

An alternating current is widely used both in industry and in everyday life. A.c. generators produce alternating current.

It was Yablochkov, our great Russian scientist, who first widely applied the alternating current in practice. His electric candle was fed by the a.c.. Yablochkov's candle having given the first and most decisive stimulus to the development of the a,c. system, a number of plants began to turn out generators producing the alternating current.

Words and word combinations:

to constitute –составлять

section – часть, отрезок, разрез,

frequency –частота, частотность

cycle per second – герц,

advantage –преимущество

disadvantage –недостаток

to turn out – выпускать,

most decisive – самый решающий, окончательный

stimulus – стимул, воздействие

Assignment:

I. Find in the text the following words and word combinations:

Только в одном направлении, измеряется количеством,                        не изменяется по величине, используется в исследовательской работе, частота тока, большой недостаток, с меньшими потерями при высоком напряжении,   при высокомнапряжении, более экономично, ряд заводов.