Power Engineering. Соколова Е.В. - 38 стр.

       A Shall I help you?
       B. Will you give me some information about tetrodes?
       A. Certainly.
       B. First of all, what is a tetrode?
       A. A tetrode is a four element tube.
       B. And what is the difference between a tetrode and a triode?
       A. You see, a tetrode has a screen grid which is inserted between the control
grid and the plate.
       B. Oh, now I understand why sometimes a tetrode is called a screengrid tube!
       A. Quite right! B. For what purpose is the screen grid inserted between the con-
trol grid and the plate?
       A. In order to remove the influence of their parasitic capacitance and to avoid
the instability of the amplifier. By the way, shall I explain to you the term "parasitic"?
       B. No, thank you! I know that there exist parasitic oscillations and currents
which are very undesirable in radio engineering.

      14 Grammar exercises

    14.1 Переведите предложения, обращая внимание на видовременные
формы

       1. We have already learned that when we double the current, it will reduce four
times as much heat. 2. The use of this two-circuit system protects the turbine and the
workers from the radioactive radiations. 3. If the number of negative charges is unlike
the number of positive charges, the matter will produce electrical effects. 4. The elec-
trons are moving from the filament to the plate and through the circuit to the battery.
5. In the sixties of the last century electrical engineering was just making its first,
rather timid, steps. 6. In a normal atom there is an equal number of protons and elec-
trons; this produces an electrical balance. 7. The use of various substances as insula-
tors enabled the constructor to change the colour of the arc itself. 8. The precise fre-
quency control of the transmitter enables the receiver to select its station. 9. When the
ball was touching the surface of the rod, some of the static electricity passed to it. 10.
As long as the current is steady, the magnetic effect does not represent any continu-
ous expenditure of energy as does the heating effect. 11. Nowadays the incandescent
lamp has become the most common source of electric light. 12. A friend of mine will
have been working as a radio man for three years before he enters the Institute. 13.
By the beginning of the nineteenth century physicists had already been able to pro-
duce powerful "artificial" magnets. 14. Man has been using no more than a portion of
one per cent of the various forms of energy, which until recently he owed only to the
sun. 15. Plate current in a screen grid tube depends to a great degree on the screen
voltage and very little on the plate voltage. 16. Early transistors used point contacts.
Later, the junction types appeared and soon replaced the older types. 17. A direct cur-
rent generally remains at constant voltage, that is, the voltage does not rise and fall.
18. When we turn on the light and our electric lamp is burning, the tungsten filament

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