Question

An electric dipole with dipole moment 4 × 10⁻⁹ C m is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 10⁴ N C^−1. Calculate the magnitude of the torque acting on the dipole.

Answer 1

Electric dipole moment, p = 4 × 10⁻⁹ C m
Angle made by p with a uniform electric field, θ = 30°
Electric field, E = 5 × 10⁴ N C⁻¹
Torque acting on the dipole is given by the relation, τ = pE sinθ =4×10⁻⁹×5×10⁴×sin30=20×10⁻⁵×1/2=10⁻⁴ Nm
Therefore, the magnitude of the torque acting on the dipole is 10⁻⁴ N m.