Exercise 1. Answer the questions

Exercise 1. Answer the questions

1. What materials are called conductors?

2. What is the advantage of copper as compared to 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 tem- perature in carbon?

6. What materials are called insulators?

7. What are the most common insulators?

8. What are the main functions of insulators?

 

Exercise 2. Choose the correct answer

1. Insulators are materials having … a) low resistance

b) high resistance

2. Current passes through conduc- tors …

a) easily

b) with great difficulty

3. Copper and silver are …              a) common insulators

b) common conductors

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

b) common conductors

5. In case a high voltage is applied to an insulator …

a) it does not conduct current

b) it conducts current

6. Insulators are used …                  a) to reduce voltage

b) to store electric charge

7. Metals have …                            a) a positive temperature coefficient of resistance

b) a negative temperature coeffi- cient of resistance

8. Metals increase their resistance … a) when the temperature decreases

b) when the temperature increases

 

 

Unit 5. Electromotive force and resistance

Vocabulary

to consist (of)             состоять (из)

to depend (on)            зависеть (от)

electromotive force    электродвижущая сила

excess                         избыток, излишнее количество

to influence                 влиять

to measure                  измерять, мерить

movement                   движение

to offer resistance       оказывать сопротивление on the other hand                            с другой стороны photocell                                    фотоэлемент

potential difference    разность потенциалов

to provide                   предоставлять; обеспечивать; снабжать