Question

An electric dipole with dipole moment \(4 × 10^{−9} Cm\) is aligned at \(30^0\) with the direction of a uniform electric field of magnitude \(5 × 10^4 N C^{−1}\) Calculate the magnitude of the torque acting on the dipole.

Answer 1

Electric dipole moment, \(p = 4 × 10^{−9}Cm\)
Angle made by p with a uniform electric field, \(\theta= 30^0\)
Electric field, \(E = 5 × 10 ^4 N C^{−1}\)
Torque acting on the dipole is given by the relation, \(\tau= pE sin\theta\)
\(= 4 × 10^{-9} × 5 × 10^4 × sin 30 = 20 × 10^{-5}×\frac{1}{2} = 10^{ -4 }Nm.\)
Therefore, the magnitude of the torque acting on the dipole is \(10^{−4} N m.\)