Power Engineering. Соколова Е.В. - 20 стр.

      minute current, stream, head phones, coil, crystal detector, filament, grid,
screen, plate, addition, lighting circuit, positively charged, negative potential

     наушники, сетка, анод, дополнительный, катушка, нить, положительно
заряженный, небольшой ток, поток, кристаллический детектор, отрицательный
потенциал, экран, осветительная сеть

      7.4 Сгруппируйте синонимы

        end significant, filament, if, cover, come black, finally, terminal, differ, cath-
ode, release anode, plate , especially , important, take place, return, set free, particu-
larly , at last, occur, coat, provided , vary

      7.5 Прочтите и переведите текст

      The vacuum tube

       1. The most important device known to radio science is the vacuum tube. Al-
though it is true that some receivers exist which use no tubes or valves at all, and that
those which are within a very short distance of broadcasting stations and those which
use only head phones can get along with coil, a condenser, and a crystal detector.
The greater number of receivers use tubes, some of them one, some two, many as
high as high as twelve or more.
       2. As we know the tube today consists of a glass valve within which are three
metallic parts known as the elements. The filament which is in the corner may be
made of tungsten carbon, tungsten covered with thorium, platinum or nickel coated
with oxides of barium, strontium, caesium, and other chemical elements. Next to the
filament is the grid, an open mesh of molibdenum (frequently) wire screen; finally is
the plate which is a sheet or screen of metal, often of nickel. Some tubes have only
two elements, the filament and the plate; many have an additional grid; the mechani-
cal construction differs according to the type of a tube, its use, and its manufacture.
       3.After the various elements are placed within the tube, the glass valve is at-
tached to a pump and the gas is removed. During the pumping process the glass valve
is heated in an electric oven to drive out the gas from it, and later the elements are
heated by means of an induction "furnace" so that various gases bound up in these
metals may be pumped out. The modern tube is a high vacuum tube
       4. Electron, which is an elementary constituent of matter carries electricity.
Now electron again assumes an important role. The filament is the centre of the vac-
uum tube; the electrons which rush about in this filament are the life blood. When the
filament is dead — due to age or crossed wires — the electrons no longer move in the
proper manner the tube is dead and might as well be broken up. If a filament of tung-
sten is heated so that an individual electron gets up a speed of 108 centimeters per
second (620 miles per second) it can break through the surfacetension of the filament.
Since it is negatively charged it will be attracted toward any positive body nearby.
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