电气工程及其自动化专业本科毕业论文

discharge. 8) Effects Produced by an Electric Current

In this article , we shall discuss the important effects accompanying the motion of electric charges, You certainly ,remember that the current flow is detected and measured by any of the effects that it is producting ,There are three of them ,namely ,the heating, magnetic and chemical effects ,the latter being manifestic under special condition .Whenever and electric current flows in a circuit ,it produces a heating effect current ,a magnetic effect ,and in some cases a chemical effect too.

The heating effect of the current occurs in the electric circuit itself .It is detected owing to and in crease in the temperature of the circuit .Thus, this effect repersents a continual transforamation of electric energy into heat. We know that it occurs to a greater or lesser degree whenever a current flows .For instance, a metallic conductor developing heat as long as the current is sent through it. In the same way, the current flowing through the filament of an incandescent lamp heats that filament to a high temperature .On account of nearly all the electrical energy transferred to the incandescent lamp is a result of the heating effect.

Does an electric current manifest itself in any other way? It ,certainly ,does .One can demonstrate this by making a very simple experiment .Hang two parallel wires one close to the other and through each of them send a current in the same direction .What shall we observe ?We shall observe that the wires attract each other .Reversing the direction of the direction of the curreent in one of the wires ,will see that the wires will be repelled instead of their being attracted .All that we have just observed is due to the magnetic effects accompanying the current flow .In effect ,it is the motion of the electric charges that procuces the magnetic forces .A conductor of any kind being able to carry an electric current ,a magnetic field is set up around that conductor .An

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electric at rest does not manifest any magnetic effect. However although in many cases it is so weak that one neglects it in dealing with the circuit.

As ling as the current is steady, the magnetic effect dies not represent any continuous expenditure of energy as does the heating effect.

Let us turn our attention now to the chemical effect flows through a liquid Whilepassing through some liquids and electric current produces a chemical action called electrolysis, and this is used in electroplating.

Electroplating is a way of using electricity to cover objects with a thin coating of metal .It is also used to purify copper and other metals.

Any of the above-mentioned effects may be used for detecting and measuring current.

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