II. Read and translate the text.

When a cell or any other generator is connected and forms a continuous path of conductors, the electrons begin to move through conductors. This is called an electric current, an electric circuit. We know that current is the flow of electricity through a circuit. If broken anywhere, the electric circuit will stop carrying a current. There are two main types of current: direct and alternating. When electrons flow in one direction only, the current is called a direct current. When electrons flow first in one direction and then in another in a periodic manner, the current is called an alternating current. An alternating current is a current that changes its direction of flow through a circuit in a periodic manner. Alternating current flows in cycles. The number of cycles per second is termed the frequency of current. In a 60-cycle alternating current circuit, the current flows in one direction 60 times per second and in the other direction 60 times per second.

Two frequencies are in use nowadays: the standard for Europe is 50 cycles per second, while the standard for the USA is 60 cycles per second. A standard frequency has a great advantage since different electrical systems can be interconnected.

Vocabulary

III. Remember these words:

Grammar

IV. Translate into English:

standard frequency; advantages of standard frequency; regular overload; disadvantages of regular overload; control elements; electric field; under test.

V. Translate the following sentences and define the functions of the word provided.

1. Current starts flowing provided a voltage source is applied to the circuit.

2. The new equipment can be utilized provided a protection fuse is applied to it.

3. These electrical devices can work for a long time provided they are made of high quality material.

4. These electrical devices are provided with rubber insulators.

5. These electrical devices provided with rubber insulators were produced at a large factory.

VI. Test. Choose the correct variant:

1. Direct current …

a) changes its direction of flow; b) flows in one direction.

2. Alternating current flows provided…

a) a direct voltage source is applied; b) an alternating voltage source is applied.

3. The frequency of the circuit is …

a) the number of cycles per minute; b) the number of cycles per second.

4. A standard frequency has …

a) great advantages; b) disadvantages.

5. Different systems can be in interconnected…

a) due to various frequencies; b) due to the standard frequency.

Speaking

VII. Answer the following words:

1. What is current?

2. What is circuit?

3. What types of current do you know?

4. What type is termed a direct current (an alternating current)?

5. What is frequency?

Date: 2015-12-11; view: 1782