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

Inductance, inductor, definite, provide, mutual, unit, touch, coils, transformer, primary winding.

Additional material for card № 8

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

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 in 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.

1. What types of current do you know?

2. What is an alternating current?

3. What is a direct current?

2. Find the correct variant.

1. Any conductor has

1. Some definite value of resistance

2. Some definite value of inductance

2. Any conductor can provide

1. Electric power

2. Induced voltage

3. Elements with a definite value of inductance

1. Are called inductors

2. Are called coils

3. Are called sources

4. The inductance of a coil depends on

1. Its size

2. Its core

3. Its material

4. The number of turns

5. An iron core

1. Increases the value of inductance

2. Decrease the value of inductance

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

Couple, indirect, tight, loose, self-inductance, field, separate, close together, primary winding, secondary winding

Additional material for card № 9

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

Inductance

Any conductor has some definite value of inductance. The inductance of a conductor shows how well it can provide induced voltage. Elements of a circuit with a definite value of inductance are coils of wire called inductors. The inductance of a coil depends upon its size and material. The greater the number of turns of a coil the higher is its inductance.

An iron core also increases the value of inductance. Coils of this type are used for low frequency currents while coils with an air core are used for high frequency currents. The primary and the secondary coils have mutual inductance. Mutual inductance is measured in the same units as inductance, that is in henries.

1. What does an inductance show?

2. What does an inductance of a coil depend on?

3. What type of coils increases the value of inductance?

2. Find the correct variant.

1. The circuit connected to the voltage source is called

1. Secondary circuit

2. Primary circuit

2. The circuit receiving its energy through a coupling is

1. A primary circuit

2. A secondary circuit

3. The function of a coupling elements is

1. To separate the circuits

2. To transfer energy

3. To prevent a short between the circuits

4. When the coupling is tight

1. The coupling are separated

2. The coils are close together

5. When the coils are close together

1. The coupling is loose

2. Te coupling is tight