# Electric Field Intensity on Equatorial Line and Axial Line of an Electric Dipole

Electric Field Intensity on the axial and equatorial line of an electric dipole.

### What is an Axial Line?

The axial line is the line that unites the centers of positive and negative charges that form an electric dipole. Consider an electric dipole consisting of +q and -q charges separated by a distance. Consider a point D at a distance ‘r’ from the center O of the dipole on the axial line of the dipole.

Let a unit positive charge be placed at point D.

First of all, we find the electric field at point D due to both the charges.

• Electric field intensity at D due to +q charge is given by

• Electric field intensity at D due to -q charge is given by

Applying principle of superposition, the net electric field intensity at point D is given by

If r >>>>>
then,

Electric Field Intensity at a point on the equatorial line of an electric dipole.

This position is also known as ‘Broad-side-on position’.

What is an Equatorial Line?
The line that is perpendicular to the axial line and passes through the center of the electric dipole length is called an Equatorial Line.

Consider an electric dipole AB consisting of +q and -q charges separated by a distance.

Let P be the point on the equatorial line at a distance r from the center O of the dipole. A unit positive charge is placed at P.

First of all, we find the electric field at point P due to both the charges

• Electric field intensity at P due to +q charge is given by

• Electric field intensity at P due to -q charge is given by

(E1) and (E2) are inclined at an angle of 2θ. Applying parallelogram law of vector addition. As

The net electric field intensity (E) due to the electric dipole at point P.

If r <<<<<
then,