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 Types of Current

1. Изучите слова и выражения:

alternating – переменный

direct – прямой

direction – направление

flow – течение

necessary – необходимый

to consider – рассматривать

use – использовать

2. Переведите на русский:

cycle _________

type __________

per second _____

one time -______

five times ______

sixty times _____

direct voltage source _______

alternating voltage source ____

direction of flow ____________

3. Изучите текст:

Types of Current

        Current is a flow of electricity through a circuit. Let us consider two main types of current: direct and alternating. A direct current (d.c.) flows through a conducting circuit on one direction only. It flows provided a direct voltage source is applied to the circuit.

        An alternating current (a.c.) is a current that changes its direction of flow through a circuit. It flows provided an alternating voltage source is applied to the circuit. Alternating current flows in cycles. The number of cycles per second is called the frequency of the current. In a 60-cycle alternating current circuit the current flows in one direction 60 times and in the other direction 60 times per second.

        It is easy to transform a.c. power from one voltage to another by a transformer. Transformers are also used to step down the voltage at the receiving point of the line to the low values that are necessary for use.

When necessary a.c. can be changed into d.c. but this is seldom necessary.

4. Закончите предложения используя правильный вариант:

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

1. current flows in one direction 60 times per second
2. current flows in one direction 60 times and in the other direction 60 times per second

4. A.c.

1. can be changed into d.c.
2. cannot be changed into d.c.

5. Ответьте на вопросы:

1. What is current?
2. What types of current do you know?
3. When does a direct current flow?
4. What type of current is called an alternating current?
5. What type of current is called a direct current?
6. What is called the frequency of current?
7. What device is used to transform a.c. power from one voltage to another?
8. Is it often necessary to change a.c. into d.c.?