Electric Field Lines

Michael Faraday (1791 - 1867) introduced the idea of lines of forces.

They are nothing but a way of pictorially mapping the electric field around a configuration of charges. It is the curve drawn in such a way that the tangent to it at each point is in the direction of the net field at the point. An arrow on the lines of force is a must to indicate the direction of the electric field.

Let us see the nature of the lines of force in the following cases :

Sub Topics

Case 1:
Case 2:
Case 3:
Like Charges (q
1
q
2
> 0)
Case 4:
1
q
2
< 0)
General Properties of Electric Lines of Force or Field Lines

Case 1:

If it is a positively charged body, then the electric lines of force are directed away from the body.

Case 2:

If the body is negatively charged, then the lines of force are directed towards the body.

Case 3:

When two positively charged bodies are involved, the electric lines of force gives a vivid picture of mutual repulsion.

Like Charges (q

1 q

2 > 0)

Case 4:

In the case of two equal and opposite charges, the lines of force clearly shows mutual attraction, the lines move from +ve to -ve.

Unlike Charges (q

1 q

2 < 0)

The figure below shows the lines of force due to an infinitely large sheet of positive.

General Properties of Electric Lines of Force or Field Lines

The lines of force or field lines

1) start from positive charges and end at negative charges. In the case of a single charge, they may start or end at infinity.

2) two field lines can never intersect each other.

3) contract longitudinally.

4) exert lateral pressure on one another.

5) are perpendicular to the surface of a charged conductor.

6) do not pass though the conductor.