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(3) READING 41A

Внимательно изучите схему и постарайтесь по­нять, о чем говорится в тексте. Затем прочитайте текст и проверьте соответствие его содержания схе­ме. Озаглавьте текст.

valves - design - application

diode - cathode +• plate - rectifier

triode - . cathode + grid + plate - amplifier

tetrode - cathode + grid + screen-plate - multipurpose

The branch of electronics dealing with the emission of electrons from substances under the action of heat, particularly the study and design of thermionic valves or tubes is called thermionics.

A good high vacuum is practically a perfect noncon­ductor, since in it no carriers of electricity are present. If two metal plates or electrodes are enclosed in a vacuum by a glass tube, we have an open circuit and no current will flow. However, one of the electrodes being heated to a high temperature, the thermal velocity of some of the conduction electrons in the metal becomes high enough for these electrons to escape. In moving through a vacuum these electrons form an electric current.

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