Varieties of Energy

1.There exist many sources of energy in the world both potential and kinetic. One source consists in water falling from a high level such as an upland lake. Another source is wind or moving air. Others consist in tides in the sea, heat from subterranean sources and coal deposits and oil wells yielding mineral oil..

2.But all these sources and stores of energy are not equally useful to mankind. Moreover some stores of energy such as coal and oil can never be replaced by us 27

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when once used up. On the other hand stores of water are continually being replaced by rain whereas wind and tides will not, as far as we know, ever cease to exit. A very

important matter is the conversion of energy from one form to another, the form most required by us being mechanical rotational energy.

3.Appliances for converting energy from one form to another are called engines. Thus a heat-engine is a machine for converting heat energy into mechanical energy of rotation by the combustion of coal or oil. A turbine or water engine can convert the kinetic energy of falling water into mechanical rotational energy.

4.The efficiency of an engine is the ratio of the energy obtained in the desired form to that given to the engine in the available form. Thus having given a heat-engine much energy by combusting coal or oil we take from it mechanical energy in kinetic form, either rotational or motional.

Пояснения к тексту

1.as far as we know – насколько мы знаем

2.matter – вопрос

6. Перепишите вопрос и выберите правильный ответ.

How does a heat-engine convert heat-energy into mechanical energy?

1. by the combustion of coal or oil.

2. by giving a heat-engine much rotational energy.

3. by using the kinetic energy of falling water.

Вариант2

1. Перепишите и устно переведите следующие условные предложения. Напротив каждого из них напишите тип условия (реальное , маловероятное, нереальное). Подчеркните предложение, для которого верно утверждение “The student didn't work hard."

1.If the student works hard he will pass his exam. 2. If the student hadn’t worked hard he wouldn’t have passed his exam. 3.If the student had worked hard he would have passed his exam.

2. Перепишите предложения и переведите, обращая внимание на различные значения should, would.

1.You shouldn’t believe everything you read in the newspapers. 2.You should have been here an hour ago. 3.In summer we would all get up early and go for a swim.

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3. Перепишите предложения и переведите их, принимая во внимание, что инфинитивные и причастные обороты соответствуют придаточным предложениям.

1.Concrete having reached its initial set, the workers shouldn’t disturb it. 2.If disturbed after it has reached its initial set, concrete should never be used. 3.They wanted the workers to improve the quality of prefab units. 4.Prefab units are known to be widely used in the construction of both residential and industrial buildings.

4. Перепишите предложения и переведите, обращая внимание на различные значения подчеркнутых слов.

1.We add steel to concrete in order to make it stronger. 2. In spite of bad weather the builders went on working on the construction site. 3.Go as far as the traffic lights then turn left. 4.I’ve known him since we met at Tom’s place.

5. I haven’t seen him since .

5.Прочитайте и устно переведите весь текст. Перепишите и переведите письменно 1-8 абзацы.