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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.

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.

Thermoelectric, 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.

Piezoelectric, 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 but it is not suitable for power supply.

Electronic, characterized by the flow of electrons through evacuated or gasfilled tubes, and having the following forms:

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

Photoelectric emission, in which electrons are liberated at the sur­ face of certain substances by the action of light.

Revision exercises

I. Translate the following sentences into Ukrainian paying attention to the functions of the Participle I.

A.1. Carrying on an important research the engineer helped his plant to raise its output. 2. Applying this new method the operator received good results. 3. Using the most modern methods of calculations the designer improved his design.

B.1. The man replacing this device by a new one is our mechanic. 2. The engineer carrying on an important research has some inventions. 3. The worker applying the new method of work will obtain good results.

C.1. The man testing this engine belongs to the group exploring dam­ages (troubles) in motors. 2. When translating the article he used no dictionary. 3. The problem facing our designing bureau is of great significance for the development of aircraft. 4. Listening to this young scientist's report we improved in some way our knowledge in that field of science. 5. While reading the article the student looked up some words in the dictionary.

II. Translate the following sentences into Ukrainian paying attention to the functions of the Participle II.

1.The problem solved by this young scientist is of great interest for our Institute. 2. The engineers will discuss the quality of the machine tested. 3. The parts produced by our plant are reliable. 4. The material prepared by this research institute has some important data connected with the point of view developed by this famous scientist. 5. Let us see the results received.