Translate the text into Russian. Conductors are materials having a low resistance so that current easily passes through them

Conductors are materials having a low resistance so that current easily passes through them. The lower the resistance of the material, the more current can pass through it.

The most common conductors are metals. Silver and copper are the best of them. The advantage of copper is that it is much cheaper than silver. Thus copper is widely used to produce wire conductors. One of the common functions of wire conductors is to connect a voltage source to a load resistance. Since copper wire conductors have a very low re­sistance a minimum voltage drop is produced in them. Thus, all of the applied voltage can produce current in the load resistance.

It should be taken into consideration that most materials change the value of resistance when their temperature changes.

Metals increase their resistance when the temperature increases while carbon decreases its resistance when the temperature increases. Thus metals have a positive temperature coefficient of resistance while carbon has a negative temperature coefficient. The smaller is the tem­perature coefficient or the less the change of resistance with the change of temperature, the more perfect is the resistance material.

Materials having a very high resistance are called insulators. Cur­rent passes through insulators with great difficulty.

The most common insulators are air, paper, rubber, plastics.

Any insulator can conduct current when a high enough voltage is applied to it. Currents of great value must be applied to insulators in or­der to make them conduct. The higher the resistance of an insulator, the greater the applied voltage must be.

When an insulator is connected to a voltage source, it stores electric charge and a potential is produced on the insulator. Thus, insulators have the two main functions:

to isolate conducting wires and thus to prevent a short between them and

to store electric charge when a voltage source is applied.

1. Find answers to these questions in the text above:

1. What materials are called conductors?

2. What is the advantage of copper compared with silver?

3. What is the most common function of wire conductors?

4. Why is a minimum voltage drop produced in copper conductors?

5. What is the relation between the value of resistance and the temperature in carbon?

6. What materials are called insulators?

7. What are the most common insulators?

8. What are the two main functions of insulators?

2. Complete the sentences using the correct variant:

1. Insulators are materials having a) low resistance.

b) high resistance.

2. Current passes through conductors a) easily.

b) with great difficulty.

3. Copper and silver are a) common conductors.

b) common insulators.

4. Air, paper and plastics are a) common insulators.

b) common conductors.

5. In case a high voltage is applied to. a) it does not conduct current

an insulator b) it conducts current.

6. Insulators are used a) to store electric charge.

b) to reduce voltage.

c) to prevent a short between conducting

wires

8. Carbon decreases its resistance a) when the temperature in­creases.

b) when the temperature de­creases.

9. Metals have a) a positive temperature coefficient of

resistance

b) a negative temperature coef­ficient of

resistance

Date: 2015-12-13; view: 3499; Нарушение авторских прав