Two charges `2muC and -2muC` are placed at points A and B 6 cm apart.
(a) Identify an equipotenital surface of the system.
(b) What is the direction of the electric field at every point on this surface ?

Explanation

(a) As both the charges from an electric dipole of length 6 cm, the equatorial plane for this electric dipole, i.e plane perpendicular to line AB and passing through the midpoint of line AB, is an equipotential surface for the given system.

Electric potential of this equipotential surface is zero because both charges are equidistant. The above described equipotential surface is planar. Other equipotential surfaces are curved.
(b) Electric field at the equatorial plane is perpendicular to the plane and is in the direction opposite to that of the electric dipole moment. Thus, the direction of the electric field will be normal to the equipotential surface along AB, i.e. from `+2muC` to `-2muC`.