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

Filter, choke coil, by-pass, high-pass, low-pass, oppose, on the other hand, consist of, direct current, capacitor

Additional material for card № 10

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

Types of coupling

When circuits are indirect-actively coupled energy is transferred from one circuit to another using electromagnetic field of the inductance through which a varying current is flowing. The coupling device is a transformer. It is not in series with the elements of the circuit, therefore the coupling is indirect.

The transformer consists of two windings: the primary and the secondary. The primary circuit is connected to the voltage source, the secondary – to the load circuit. The coupling may be tight and loose. In case the coils of the coupling elements are close together, the coupling is tight. In case the coils are separated the coupling is loose. In the loose coupling the mutual inductance is small compared with the self-inductance.

1. What types of coupling do you know?

2. What kinds of windings are there in the transformer?

3. Which winding is connected to the voltage source?

2. Find the correct variant.

1. a filter is used in order

1. to separate d.c. from a.c.

2. to transfer energy from the primary to the secondary

3. to separate low frequencies from high frequencies

2. a filter consists of

1. a resistor and a transformer

2. a choke coil and a capacitor

3. an inductance coil and a capacitor

3. direct current easily passes

1. through a choke coil

2. through a capacitor

4. alternating current easily passes

1. through a capacitor

2. through a choke coil

5. low-pass filter is used

1. to pass high frequencies and to prevent the flow of low frequencies

2. to pass low frequencies and to prevent the flow of high frequencies

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

Electron tubes, are placed into a, contains, operates, the cathode, electrons, collects, controls the flow of electrons, oscillate, the function

Additional material for card № 11

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

Filters

This filter is used to separate direct current from alternating current. It consists of a capacitor and a choke coil. Direct current cannot flow through a capacitor since its insulators oppose the flow of direct current. Therefore, it flows through the choke coil. Its windings easily pass direct current through them. Alternating current, on the other current, passes through the capacitor, since it cannot easily pass through the choke coil. In this way the direct and the alternating currents are separated.

A high pass filter is to pass high frequencies and prevent the flow of low frequencies. It consists of a condenser and an inductance coil. The condenser passes currents of high frequencies and opposes the flow of low frequencies currents.

1. What is the main function of the filter?

2. What does a filter do when it operates?

3. What is the difference between high pass and low pass filters?