Define the term electric field intensity. Write its SI unit. Derive an expression for the electric field intensity at a point on the axis of an electric dipole. 

The force experienced by a unit positive charge placed at a point is termed as the electric field intensity at that point. It is vector quantity it’s direction is in the force acting on +ive charge.
The SI unit of electric field intensity is NC^–1. Electric field at an axial point of electric dipole:
Assume point P is located at distance r from the centre of an electric dipole as shown in the figure.