Version 13 Thermocouple and Photocell

Translate into Ukrainian.

There are two means of producing small electric currents for special purposes. One of these is the thermocouple or a thermopile. The other is the photocell, sometimes called the electric eye.

The "iron-copper" thermocouple represents an iron wire and a copper wire, both being carefully cleaned at the end and making close contact with each other. At the point of contact between unlike metals, a current tends to flow from one metal to the other because the outer electrons in the atoms of one metal have more potential energy than those in the other metal. The measure of this potential energy difference is called potential difference. This potential difference de­pends both upon the nature of the metals and upon the tem­perature at the point of contact.

A number of thermocouples are sometimes connected in series. Such a combination called a thermopile is more sensi­tive than a single thermocouple.

The photocell generates a small electric current in response to the action of light. In one type, the light ejects electrons from a photosensitive surface upon which it falls.

Quiz

for the third-year students, 5^th term (EP, ES)

Prepared by A.V.Kosobokova

Version 14 Thermocouple and Photocell

Translate into Ukrainian.

A photo­sensitive electrode usually consists of a thin layer of caesium or a caesium compound on a surface of silver.

This is the pho­tocell cathode. The anode is a metal rod or a loop which, when the cell is in use, is connected to the positive terminal of a battery. It is the collector of electrons. The anode and the cathode are connected to short, light metal rods which extend through the base of the tube to form the support.

Electrons moving from the cathode to the anode consti­tute a small electric current whose magnitude is directly proportional to the amount of light falling upon the cathode.

Photocells perform a great number of very important ser­vices. Perhaps, the best known use is in connection with motion pictures, where they are used in the reproduction of sound. They are also employed in television where they function in the signal transmission.

"Electric eyes" are also used in factories to give auto­matic control of illumination, by turning lamps on or off as required.

Quiz

for the third-year students, 5^th term (EP, ES)

Prepared by A.V.Kosobokova