Question

Define electric field intensity. Derive an expression for electric field intensity at a distance r from an electric dipole.

Answer 1

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 and it's direction is in the direction of force acting on +ve test charge.

Answer 2

Electric field intensity:

The electric field intensity is the quantity of the strength of an electric field at any specified point. It is equal to the electric force per unit charge practiced by a test charge which is placed at that point.

Expression of electric field intensity:

By Coulomb's law, E1= q/4πϵ0  r12  

Here q is the positive charge of the dipole, r1 is its distance from the specified point on the axis and ϵ0 is the electric permittivity of air or vacuum.

Likewise for the negative charge, E2= -q/4πϵ0$r2^{2}$

By adding both the equations, we get,

E= q/4πϵ0× 1/ $r1^{2}$−$r2^{2}$

This is the concluding equation.