How Electrical Energy Is Produced

There are several methods of producing electricity for practical purposes. The battery of a pocket torch may be contrasted with the source of enormous energy represented by a larger power station. Both are examples of the application of electrical energy to a parti­cular purpose, and in general the purpose determines the nature of the method used to produce the energy.

Practical methods of producing electricity may be enumerated as follows:

Chemical, as represented by the various types of batteries or primary cells in which the electricity is produced by purely chemical actions.

Chemical energy to electrical energy

1. Electromagnetic, forming the basis of operation of rotating generators in which the electricity is produced by conductors moving through a magnetic field. This is the method employed in practice for generators of various sizes.

2. Thermo-electric, in which the heating of the junction between two different metals produces a very small voltage which may be used for purposes of temperature measurement and as a source of power.

3. Piezo-electric, in which a very small voltage is produced across certain faces of a crystal by application of mechanical pressure. This effect is used, for example, as a means of frequency control in radio oscillators or for gramophone pick-ups, but it is not sui­table for power supply.

4. Electronic, characterized by the flow of electrons through evacuated or gas-filled tubes, and having the following forms:

a) Thermionic emission, in which the electrons are produced by the heating of special materials.

b) Photo-electric emission, in which electrons are liberated at the surface of certain substances by the action of light.

c) Secondary emission, in which electrons are driven from a ma­terial by the impact of electrons or other particles on its surface.

d) Field emission, in which electrons are drawn from the sur­face of a metal by the application of very powerful electric fields.

Вправа 7. Доведіть, що подані слова належать до однієї частини мови. До якої саме.

Emission, revolution, compression, circulation, mixture, development, agriculture, inventor, movement, pressure, balance, application, temperature, conductor, station.

Вправа 8. До якої частини мови належать наведені нижче слова.

Various, gaseous, famous, numerous, electrical, structural, simultaneously, voltage, purely.

Вправа 9. Прочитайте та перекладіть текст.