Question

Explain the graphical representation of the electric field in terms of field lines.

Answer 1

Electric Field Lines:

1. The field lines due to a single positive charge have been shown. The field lines are directed radially outwards and end only at infinity.

2. The field lines due to a single negative charge, the field lines are directed radially inwards.

3. The field lines due to two equal and opposite charges have shown. These lines start from the positive charge and end at the negative charge. The shape of the lines suggests as if the two charges are bound together by stretched rubber strings and there exists a longitudinal tension in the field lines.

4. The field lines due to two equal positive charges have been shown. The field lines seem to exert lateral pressure on each other. This clearly brings out the repulsion between two positively (i.e., similarly) charged bodies. The neutral point, where the net field is zero lies midway between the two charges.

5. There are two unequal positive charges $(q_1>q_2)$. The general characteristics of the field lines are the same as in figure points. The only difference is that the neutral point is nearer to $q_2$ than $q_1$. This is due to the greater repulsive force of the field lines due to $q_1$ on the field lines due to $q_2$.