Power Engineering. Соколова Е.В. - 13 стр.

battery. Later on the electricity was supplied from the machine itself; in other words,
the machine, was made selfexciting.

      4 Lesson 4

      4.1 Прочтите слова согласно транскрипции

        giant filament, amplifier, inert, rectifier, voltmeter, overestimate, thermionic ,
kinetic , strontium ,barium , centigrade , however, rugged , nickel, evaporate, migra-
tion , alloy , tungsten., percent, layer, thorium , oxide , pure

      4.2 Сгруппируйте синонимы

      require, present-day, function , apply, demand ,hence, usually, use, modern,
operate , commonly; principally, mainly, consequently

      4.3 Сгруппируйте антонимы

      tiny, heat, light, raise, heavy, cool, giant, reduce

      4.4 Прочтите и переведите текст

                                 Electronic principles

       1. Of all the component parts used in modern systems radio communication,
the electron tube is the most important one. Many of the basic principles of radio
were well understood for years before, they could be applied in practice but their
development and practical use had to await discovery and improvement of the vac-
uum tube. Vacuum tubes are made in all sizes, from the tiny or to the giant 100-kW
water-cooled tubes used in large radio transmitters. They function as oscillators, am-
plifiers, detectors, rectifiers, modulators, as voltmeters, oscillographs, in any special
ways. The importance of having a good working knowledge of their properties and
application cannot be overestimated.
       2. Metallic conductors are composed of atoms and molecules, with a great
number of free electrons, in continual random motion, which are not bound closely to
particular atoms. If the temperature of a conductor is raised sufficiently, some of
these free electrons will acquire enough kinetic energy to permit their escape by
penetrating the surface of the conductor. This process is known as thermionic emis-
sion and it is found that various metals differ widely with respect to this property. In
present-day tubes, the most commonly used materials for the purpose are as follows
tungsten, thoriated tungsten, oxide-coated emitters.
       3. Emitters made of tungsten are used principally in large transmitting tubes,
where heavy emission current are required. Tungsten emitters must be operated at
2,500 К, and they require relatively large amounts of power for heating. The operat-
ing temperature is close to the melting point of tungsten, and consequently the heat-
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