Grammar Study

Laser

Text C

Notes

DIRECT CURRENT AND ALTERNATING CURRENT

Text B

When a cell or any other generator is connected so as to form a continuous path of conductors the electrons begin to move through conductors forming an electric current or an electric circuit. This phenomenon is known to be the electricity flow through a circuit. If broken anywhere, the electric circuit will stop carrying a current. There are two main types of current: direct and alternating. When electrons flow in one direction only, the current is called a direct current. When electrons flow first in one direction and then in another in a periodic manner, the current is called an alternating current.

Alternating current flows in cycles. The number of cycles per second is accepted to be termed the frequency of current. In a 60-cycle alternating current circuit, the current flows in one direction 60 times per second and in the other direction 60 times per second.

Two frequencies are in use nowadays: the standard for Europe is 50 cycles per second, while the standard for the USA is 60 cycles per second. A standard frequency has a great advantage since different electrical systems can be interconnected.

cell — элемент

circuit — электрическая цепь

to term — называть, выражать

frequency — частота, частотность

to interconnect —связывать, объединять энергосистемы

cycle per second — герц

II. Read the text and define whether the following statements are true or false.

1. If broken anywhere, the electric current will continue carrying a current.

2. When electrons flow first in one direction and then in another in a periodic manner, the current is called a direct current.

3. The standard frequency for the USA is 60 cycles per second.

III. Expand the sentences.

1. There are two main types of current.

2. Alternating current flows in cycles.

3. Two frequencies are in use nowadays.

IV. Now decide which of the following statements express important ideas or supporting details.

1. a) One of the main types of current is termed alternating.

b) The electrons moving through conductors form an electric current.

c) An alternating current is a current that changes its directions of flow through a circuit in a periodic manner.

2. a) The number of cycles per second is called the frequency of current.

b) The standard frequency for Europe is 50 cycles per second.

c) There are two frequencies in use nowadays.

V. Find the words – carriers of the primary and the secondary information in the text.

VI. Define the function of commas in the text.

VII. Find out the means of connection of simple, compound and complex sentences.

IX. Arrange the sentences in the logical order according to the text.

1. In a 60-cycle alternating current circuit, the current flows first in one direction and then in another 60 times per second.

2. A standard frequency has a great advantage.

3. When electrons flow in one direction only the current is called a direct current.

IX. Give the main points of the text in 4-5 sentences.

I. Translate from English into Russian.

In the “War of Worlds” written before the turn of the century H. Wells told a fantastic story of how Martians almost invaded our Earth. Their weapon was a mysterious “sword of heat”. Today Wells’ sword of heat has come to reality in the laser. The name stands for light amplification by stimulated emission of radiation.

Laser, one of the most sophisticated inventions of man, produces an intensive beam of light of a very pure single colour. It represents the fulfilment of one of the mankind’s oldest dreams of technology to provide a light beam intensive enough to vaporize the hardest and most heat-resistant materials. It can indeed make lead run like water, or, when focused, it can vaporize any substance on earth. There is no material unamenable to laser treatment and by the end of 2000 laser will have become one of the main technological tools.

The applications of laser in industry and science are so many and so varied as to suggest magic. Scientists in many countries are working at a very interesting problem: combining the two big technological discoveries of the second half of the 20-th century – laser and thermonuclear reaction – to produce a practically limitless source of energy. Physicists of this country have developed large installations to conduct physical experiments in heating thermonuclear fuel with laser beams. There also exists an idea to use laser for solving the problem of controlled thermonuclear reaction. The laser beam must heat the fuel to the required temperature so quickly that the plasma does not have time to disintegrate. According to current estimates, the duration of the pulse has to be approximately a thousand-millionth of a second. The light capacity of this pulse would be dozen of times greater than the capacity of all the world’s power plants. To meet such demands in practice scientists and engineers must work hard as it is clear that a lot of difficulties are to be encountered on route.

The laser’s most important potential may be its use in communications. The intensity of a laser can be rapidly changed to encode very complex signals. In principle, one laser beam, vibrating a billion times faster than ordinary radio waves, could carry the radio, TV and telephone messages of the world simultaneously. In just a fraction of a second, for example, one laser beam could transmit the entire text of the Encyclopaedia Britannica.

Besides, there are projects to use lasers for long distance communication and for transmission of energy to space stations, to the surface of the Moon or to planets in the solar system. Projects have also been suggested to place lasers aboard Earth satellites nearer to the Sun in order to transform the solar radiation into laser beams, with this transformed energy subsequently transmitted to the Earth or to other space bodies. These projects have not yet been put into effect, because of the great technological difficulties to be overcome and therefore the great cost involved. But there is no doubt that in time these projects will be realized and the laser beam will begin operating in outer space as well.

Модальные глаголы

(Modal Verbs)

Модальные глаголы не называют действие или состояние, а выражают лишь отношение лица (подлежащего) к действию или состоянию, выраженному инфинитивом, т.е. имеют значение возможности, вероятности или необходимости совершения этого действия или данного состояния.

Модальные глаголы отличаются от других глаголов следующими особенностями:

1) у модальных глаголов нет инфинитива, причастия, герундия;

2) они не изменяются по лицам и числам;

3) эти глаголы не употребляются в повелительном наклонении;

4) вопросительную и отрицательную формы они образуют без вспомогательных глаголов.

Наиболее употребительные

модальные глаголы и их эквиваленты

Таблица 1

Модальные глаголы и их эквиваленты	Present	Past	Future
Can	can The most powerful lasers can cut through metal and other materials. Самые мощные лазеры могут разрезать металл и другие материалы.	could Fifty years ago computers could store no more than thousand bytes. Пятьдесят лет назад компьютеры могли хранить не более тысячи байт информации.	-
To be able to	am/is/are able to Modern computers are able to recognize human speech. Современные компьютеры могут распознавать человеческую речь.	was/were able to In 1901 Marconi was able to senda radio message from Europe to America. В 1901г. Маркони смог отправить радиосообщения из Европы в Америку.	shall/will be able to Computers will be able to interact fully with their users. Компьютеры смогут полностью взаимодейст-вовать с поль-зователями.
Must (долженствование)	must We must take action to reduce environmental pollution. Мы должны принимать меры по уменьшению загрязнения окружающей среды.	-	-
Should	should The students should know the main laws of thermodynamics. Студенты должны знать основные законы термодинамики.	-	-
to have to (необходимость выполнения действия)	Have (has) to The water in this area has to be purified of undesirable chemicals. Вода в этом районе должна быть очищена от нежелательных химикатов.	had to The water in this area had to be purified of undesirable chemicals. Вода в этом районе должна была быть очищена от нежелательных химикатов.	shall (will) have to The water in this area will have to be purified of undesirable che-micals. Вода в этом районе должна будет очищаться от нежелательных химикатов
To be to (запланированность действия)	am (is, are) to The scientists are to launcha fundamental investigation next month. Ученые должны начать фундаментальное исследование в следующем месяце.	Was (were) to The scientists were to launch а fundamental investigation last month. Ученые должны были начать фундаментальное исследование в прошлом месяце.	-
May (разрешение, позволение)	May Our nuclear scientists may investigate this issue. Наши ученые – ядерщики могут исследовать эту проблему.	Might Our nuclear scientists might investigatethis issue. Наши ученые – ядер-щики могли исследовать эту проблему.	-

В языке научной литературы действие, выраженное перфектным инфинитивом, обычно относится к прошедшему времени. Глагол must с последующим Perfect Infinitive переводится должен был, должно быть, вероятно, глагол could – возможно, мог, мог бы, may – возможно, может быть, might – мог бы.

The explosion must have occurred long ago.

Взрыв, вероятно, произошел давно.

I could have gone to the conference, but I lost my invitation.

Я мог бы поехать на конференцию, но потерял пригласительный билет.

You might have proved that supposition by experiment.

Вы могли бы доказать эту гипотезу путем эксперимента.

Глаголы can и could в отрицательной форме в сочетании c Perfect Infinitive выражают сомнение в возможности совершении действия в прошлом и обычно переводятся не может быть, чтобы + глагол в прошедшем времени, не мог + неопределенная форма глагола.

Life couldn’t have existed on that planet.

Не может быть, чтобы на той планете существовала жизнь.

I. Choose the correct word or phrase underlined in each sentence.

1. Look at those clouds. I think it can/might/must rain.

2. This is impossible! It can’t be/mustn’t be/may not be the answer.

3. Well done! You may be/must be/might be very pleased!

4. I’ve no idea where Jane is. She could be/must be anywhere!

5. I suppose it’s possible. I might/can/must come to your party.

6. I’m not sure. I must not/ may not be able to get there in time.

7. That can’t be/ mustn’t be/ may not be David. He hasn’t got a bike.

8. Lisa isn’t here yet. She can be/must be on her way.

9. There’s someone at the door. It can be/could be the postman.

10. Sorry, I can’t /may not come out. I have to do my homework.

II. Rewrite each sentence, using can, can’t, might or must, beginning and ending as shown.

1. Helen is really good at swimming. Helen can swim really well.

2. It’s possible that our team will win. Our team…………………….. win.

3. I’m sure this isn’t right road. This………………………….. the right road.

4. I’m sure you work very hard! You ………………………….. very hard.

5. Carol isn’t allowed to come to our party. Carol …………… to our party.

6. It’s possible that I’ll see you tomorrow, but I’m not sure. I ………….., but I’m not sure.

7. I’m afraid that your teacher is unable to come today. I’m afraid that ………………………….. today.

8. I’m sure it’s very hot here in summer. It ………….. here in summer.

9. Excuse me, is it all right if I open the window? Excuse me, ……….. the window?

10. I suppose you are Mrs. Perry. How do you do? You …………….. Mrs. Perry. How do you do?

III. Put one suitable modal auxiliary in each space.

1. Soldiers …… to obey orders.

2. I think you …………… take your umbrella.

3. Sorry, I …………… go now. I don’t want to be late.

4. I’m not sure, but I …………. to help you.

5. Helen isn’t at home, so she …………….. be on her way here.

6. We …………….. better not leave any windows open.

7. It ……………….. be a star, it’s too bright. Perhaps it’s an alien spaceship!

8. I don’t …………….. to go to work today. It’s a holiday.

9. Sorry, but I wasn’t ……………..to finish all the work you gave me.

10. I think you …………. to ask you teacher for some advice.

IV. Rewrite each sentence so that it has a similar meaning and contains the word given.

1. I'm sure you dropped your wallet at the bus-stop (must).

2. Maybe Joanna missed the last bus (might).

3. Peter knew how to skate when he was twelve (able).

4. Emma was wrong not to tell you the answer (should).

5. It wasn't necessary for us to pay to get in (didn't).

6. It wasn't necessary for me to buy any food yesterday (need).

7. I'm sure that Diana didn't take your books (can't).

8. Perhaps David didn't notice you (might).

9. Terry arrived early, but it wasn't necessary (needn't).

10. It was a bad idea for us to be rude to the policemen (shouldn't).

V. Complete each sentence so that it contains the words given.

1. I’m completely soaked! We are silly! We …. should have taken an umbrella.... (should/umbrella)

2. I’ve lost my bag. I think I ………(must/bus)……………………..…...

3. I tried to phone Sam, but I ……(couldn't/get through)…………....

4. I forgot Kate’s birthday. I ………(should/present)……………….....

5. The cat doesn’t like fruit! It ……(can't/orange)……………………...

6. Jo hasn’t turned up yet. I suppose she …(might/address)………...

7. I did badly in the test. I …………(ought/harder)…...

8. It’s a shame we didn’t go on holiday. We …(could/good time)…....

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