Electric Field

  1. Electric field due to an electric dipole at a point on its axial line
  2. Electric field due to an electric dipole at a point on the
    equatorial line.
  3. Electric dipole in a uniform electric field

Electric field due to an electric dipole at a point on its axial line

AB = electric dipole

-q, +q = two point charges

2d = small distance separating the two opposite point charges

P = point along the axial line of the dipole  at a distance r from the midpoint O of the electric dipole

E1 and E2 = electric fields acting on the point P in opposite directions

Because,  electric dipolemoment, p = q x 2d

E acts in the direction of diplolemoment.


Electric field due to an electric dipole at a point on the equatorial line

  • The magnitudes of E1 and E2 are equal.
  • E1 and E2 are resoved into their horizontal and vertical components.
  • E1 sin θ and E2 sin θ are equal and opposite, therefore
    they cancel each other.
  • The horizontal components E1 cos θ and E2 cos θ will get added
    along PR.


Electric dipole in a uniforms electric field

AB = electric dipole

p = dipole moment

θ = angle of dipole kept in the electric field, E

  • The charge +q experiences a force qE in the direction of the field.
  • The charge –q experiences an equal force in the opposite direction.
  • The net force on the dipole is zero.
  • The two and unlike parallel forces are not passing through the same point.
  • It results in a torque (a twisting force) on the dipole.
  • It tends to set the dipole in the direction of the electric field.