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.