V. Complete the following sentences, using active vocabulary:

1. The filamentary cathode consists of a wire filament, usually bent in the form of …2. The indirectly heated cathode consists of a metallic … 3. Since the electron stream is determined by potentials of the other tube … 4. If alternating current is used for heating, as is most frequently the case today, the different parts of the cathode … 5. Another advantage is that the heater wires are so close together, that the current …

VI. Which of the following statements are true or false? If the statement is wrong, correct it:

1. Three types of cathodes are employed in vacuum tubes. 2. The electric pressure of lightening causes the current to pass through the air. 3. The electric current does not flow in metal part. 4. Vacuum tubes amplify the voltage and power. 4. The indirectly heated cathode consists of a ceramic sleeve coated with emitting substance.

VII. Answer the following questions:

1. What types of cathodes are employed in vacuum tubes? 2. What a common practice to reduce the fluctuations as much as possible? 3. Where is ceramic insulating core placed? 4. What is the advantage of the indirectly heated cathodes?

VIII. Put the questions to the following sentences:

1. Two types of cathodes are employed in vacuum tubes, the filamentary and the indirectly heated.2. Vacuum tubes perform such functions as rectification, amplification, detection, modulation. 3. Cosmic rays belong to two energy groups. 4. The finer the filament, the greater the resistance which it offers to an electric current. 5. A material which allows electricity to flow through it is called a conductor. 6. Electrons leaving the surface, the metal becomes positively changed.

IX. Translate the sentences. Explain the conditional sentences:

1. He would have connected these circuits much quicker. 2. This might cause fluctuations which would result in the development of hum in the tube output. 3. Where the temperature increased, the velocity of the molecular motion would be increased. 4. Had the filament been heated, we should have obtained the electron emission. 5. It is essential that the entire cathode should be at a uniform potential. 6. It is necessary that a means by provided for cooling the windings. 7. Provided all the requirements were met, the efficiency of the apparatus would be increased. 8. If alternating current were used for heating, the different parts of the cathode would not be at constant potential.

X. Retell the text; speak about the “Physical constructions of cathodes”

XI. Read the following supplementary text and translate it without a dictionary; entitle it.

SUPPLEMENTARY TEXT

The term "semiconductor" is formed by the prefix "semi-" which means «напів» and the word "conductor" — «провідник».

Semiconductor is an electric conductor with resistivity in the range between metals and insulators, in which the electric charge-carrier concentration increases with the increasing temperature range. There are semiconductor integrated circuits. They are the physical realization of a number of electric elements connected with each other on or within a substrate to perform the function of a circuit.

An integrated circuit is fabricated upon or within the supporting material, which is called substrate. Sometimes an integrated circuit is attached to it. Such a substrate which may serve as a physical support and heat-exchanger to a thin-film integrated circuit and exhibits no transistance is a passive substrate. Examples of a passive substrate are glass, ceramic, and similar materials. A substrate may be active, when parts of it display transistance. Examples of active substrates are single crystals of semiconductor materials within which transistors and diodes are formed.