Question

(i) Define electric dipole moment. Is it a scalar or a vector quantity? Derive the expression for the electric field of a dipole at a point on the equatorial plane of the dipole. 

(ii) Draw the equipotential surfaces due to an electric dipole. Locate the points where the potential due to the dipole is zero.

Answer 1

(i) Electric dipole moment : The strength of an electric dipole is measured by the quantity of electric dipole moment. Its magnitude is equal to the product of the magnitude of either charge and the distance between the two charges.

The direction of E_+q and E_-q are shown in the figure. The components normal to the dipole axis cancel out. The components along the dipole axis add up.

(ii) Equipotential surface due to electric dipole :

The potential due to the dipole is zero at the line bisecting the dipole length.