Exercise 1. Translate into English

Exercise 1. Translate into English

1. Ток, проходящий через катушку реле, создает магнитное поле, которое притягивает рычаг и замыкает или размыкает контакты вы- ключателя.

2. Внутри реле нет электрического соединения между двумя це- пями.

3. Все реле имеют два положения переключателя.

4. Реле могут иметь много контактных групп переключения.

 

Exercise 2. Pair work. Make up a dialogue about principles of relay operation

Unit 6. Electron tubes

Vocabulary

amplification                        усиление

anode                                    анод

carrier                                   носитель (заряда)

cathode                                 катод

diode                                     диод

electrode                               электрод

electron tube                        электронная лампа

to emit                                  испускать, излучать

envelope                               баллон, колба

evacuated                             вакуумный, разреженный

field emission                      автоэлектронная эмиссия

filament                                нить накала

filament voltage                   напряжение накала

gas-filled                              газонаполненный

grid                                       сетка

to heat                                   нагревать(ся)

heater                                    нагреватель

operation                              работа

photoelectric emission         фотоэлектронная эмиссия

plate current                         ток анода, анодный ток

rectifier                                выпрямитель

to repel                                 отталкивать

secondary emission              вторичная эмиссия thermionic emission                                              термоэлектронная эмиссия triode                                              триод

velocity                                скорость

 

Text

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 envelope, we have an open circuit and no current will flow.

However, if one of the electrodes is heated to a high temperature, the velocity of some of the electrons in the metal becomes high enough for these electrons to escape. This process is called emission.

There are some methods of obtaining emission. They are thermionic, photoelectric, field and secondary. The operation of electron tubes or vac- uum tubes is based on the thermionic emission.

The electrode which emits the electrons is called a cathode. The elec- trode which acts as a collector of the electrons (positive potential) is called a plate or anode. The electrodes are mounted in an evacuated or gas-filled envelope. So any electron tube is a metal, glass or ceramic envelope con- taining electrodes.

Electron tubes are classified by the number of electrodes they con- tain. A tube with two electrodes is known as a diode, a tube with three electrodes is a triode, etc.