Question

Find the expression for the torque acting on an electric dipole placed in an uniform electric field

Answer 1

Explanation:

Torque on a bar magnet placed in a uniform magnetic field



Consider a bar magnet NS of length 2l and pole strength m placed in a uniform magnetic field of induction B at an angle θ with the direction of the field (Fig.).

Torque on a bar magnet placed in a uniform magnetic field

Consider a bar magnet NS of length 2l and pole strength m placed in a uniform magnetic field of induction B at an angle θ with the direction of the field (Fig.).



Due to the magnetic field B, a force mB acts on the north pole along the direction of the field and a force mB acts on the south pole along the direction opposite to the magnetic field.

These two forces are equal and opposite, hence constitute a couple.

The torque τ due to the couple is

τ = one of the forces ? perpendicular distance between them