Examination №4 (5) in English

I. Read, and then set the writing 1, 2, 3 paragraphs of text. The English text on the left page rewrite notebooks, Russian - on the right:

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. Find the text of the answers to the following questions:

1. Why may a short circuit be very damaging?

2. What do we use in order to prevent overloading of a circuit?

III. Find the text of the derivatives of the following words, write them, translated into Russian, enter part of the speech:

1. to insulate

2. to add

3. real

4. to prevent

5. to load

6. to connect

7. to heat

8. to operate

9. danger

IV. Rewrite and translate into Russian the following suggestions. Emphasize the infinitive and determine its function:

1. That 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. Copy and move the following suggestions. Emphasize Communion 1 and 2 and to determine their functions:

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. Rewrite and translate the following sentences into Russian, emphasize the gerund:

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. Rewrite and translate the following sentences to the structure 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.