Question

Obtain an expression for intensity of electric field at a point in end on position, i. e. axial position of an electric dipole.

Answer 1

Consider an electric dipole consisting of – q and + q charges separated by a distance 2a as shown in. figure below. Let P be the point of observation on the axial line where the electric field has to be found. Let it be at a distance r from the center O of the dipole. Let us suppose that the dipole is placed in vacuum. Let E_A and E_B be the electric fields at point P due to the charges at A and B respectively. Therefore

The two field at P are in opposite direction. Thus, the resultant electric field at P is given by

Since θ = 180° , Therefore, the resultant electric field is