Electric fields

Electric fields

An electric charge sets up an electric field in the space surrounding it and an electric force is exerted on any charged body placed in the field. Electric fields may be represented by eLectric field lines. An electric field line is a line drawn in an electric field such that its direction at any point gives the direction of the electric field at that point. The direction of an electric field at any point is the direction of the force on a small positive charge placed at the point.

Michael Faraday went further than this in his idea of field lines and imagined them to have some kind of real existence. This does not mean that he thought of them as having a tangible existence like elastic cords or springs, but rather that they represent a state of strain in the electric field. To these electric field lines he ascribed the following properties:

(I) they begin and end on equal and opposite quantities of electric charge;
(2) they are in a state of tension which causes them to tend to shorten;
(3) they repel one another sideways.

Faraday used this mind-picture of field lines to give an explanation of various electrical experiments. Thus, the attraction between two unlike charges is explained by the tension of the field lines joining them. Likewise, the repulsion between two like charges is caused by the sideways repulsion between their field lines (Fig. 32.21).

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