3. Make up sentences, using words and word-combinations.

Silver, copper, coefficient, cheap, so that, widely, decrease, call, wire conductors, copper conductors

Additional material for card № 6

1. Read the text, translate it and answer the questions.

A capacitor

A capacitor is one of the main elements of a circuit. It is used to store electric energy. A capacitor stores electric energy provided that a voltage source is applied to it.

The main parts of a capacitor are metal plates and insulators. The function of insulators is to isolate the metal plates and in this way to prevent a short.

There are two common types of capacitor in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacity doesn’t change. The plates of a variable capacitor move; its capacity changes. The greater the distance between the plates the less is the capacity of a capacitor.

.

1. What is a capacitor used for?

2. What are the main parts of a capacitor?

3. What are the main types of a capacitor?

2. Find the correct variant.

1. Insulators are materials having

a) low resistance

b) low resistance

2. current passes through conductors

a) easily

b) with great difficulty

3. copper and silver

a) common conductors

b) common insulators

4. air, paper and plastic

a) common insulators

b) common conductors

5. in case a high voltage is applied to an insulator

a) it doesn’t conduct current

b) it conducts current

3. Make up sentences, using words and word-combinations.

Direct current, alternating current, flow, change, types of current, frequency, direction, conducting circuit, voltage source

Additional material for card № 7

1. Read the text, translate it and answer the questions.

Conductors

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, and 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.

1. What is a conductor?

2. What are the advantages of copper conductors?

3. What types of conductors do you know?

2. Find the correct variant.

1. 1. d.c. is a current that

1. Changes its direction of flow

2. Flows in one direction

2. a.c. flows provided

1. a direct voltage source is applied

2. an alternating voltage source is applied

3. in an alternating current circuit

a) current flows in one direction 60 times per second

b) current flows in one direction 60 times and in the other direction 60 times per second.

4. a.c.

a) can be change in to d.c.

b) cannot be changed into d.c.

5. there are

a) two main types of current

b) three main types of current

c) four main types of current