Контрольная работа №4 (5) по английскому языку
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Short circuits and danger from overheating in circuits
1. No electrical appliances and machines are designed for use at very high temperatures. Motors, generators and transformers all have coils of wire with current passing through them. Too much heat damages their insulation. In addition to it this heat is really lost energy.
2. The less resistance there is in a circuit, the greater the amount of current carried through it. Thus, the lines that carry large amounts of current are designed with large cross section areas so that the heat losse is reduced to a minimum.
3. Overloaded wires are subjected to overheat, and if the overload is too great, the rubber and cotton insulation bums up and then the circuit is readily shorted. In some cases short circuits only prevent proper operation of the equipment, at any rate, they are considered to be dangerous and damaging. A short circuit may be very damaging if a large amount of current is involved.
4. Frequently, if small diameter wires are heavily overloaded, the wire catches fire. In order to prevent overloading of a circuit which might cause a fire, we use a protective device by means of which the circuit is broken, at once in case it is overloaded.
II. Найдите в тексте ответы на следующие вопросы:
1. Why may a short circuit be very damaging?
2. What do we use in order to prevent overloading of a circuit?
III. Найдите в тексте производные от следующих слов, выпишите их, переведите на русский язык, укажите часть речи:
1. to insulate
2. to add
4. to prevent
5. to load
6. to connect
7. to heat
8. to operate
IV. Перепишите и переведите на русский язык следующие предложения. Подчеркните инфинитив и определите его функцию:
1. То strengthen the magnetic field a closed core of iron is generally used.
2. The oscilograph to be used for testing purposes is similar to that used in our laboratory.
3. To analyze this effect we shall consider all the elements of the circuit.
4. The instrument to be described here was developed several years ago.
V. Перепишите и переведите следующие предложения. Подчеркните причастия 1 и 2 и определите их функции:
1. Condensers made of tinfoil plates insulated with paraffin paper are widely used in telephone.
2. It has become the usual thing to speak of the current as flowing from positive to negative.
3. The international volt is the electrical pressure creating a current of one international ampere.
4. A Watt is the power produced by a current of one ampere under a pressure of one volt.
VI. Перепишите и переведите следующие предложения на русский язык, подчеркните герундий:
1. In addition to instruments for measuring current and voltage there are also devices for measuring electric power and energy.
2. The effect of heating of the current occurs in the electric circuit itself.
3. Petroff not only discovered the electric arc but also foretold the possibility of its application for lighting.
4. The rheostat is used to control current strength by changing its resistance.
VII. Перепишите и переведите следующие предложения с конструкцией it is (was) ... that (who, which):
1. It is rheostat that is used to control current strength by changing its resistance.
2. It is German physicist Ohm who deserved to rank among the most distinguished pioneers in the science of electricity.
3. It is rectifier that is the device for changing alternating current into direct current.