Question

An electric dipole with dipole moment $4\times {10}^{-9}$C m is aligned at ${30}^{\circ }$ with the direction of a uniform electric field of magnitude $5\times {10}^{4}N{C}^{-1}$. Calculate the magnitude of the torque acting on the dipole.

Answer 1

Electric dipole moment, $E=4\times {10}^{-9}N/C$

Angle made by p with a uniform electric field, θ = 30°

Electric field, $E=5\times {10}^{4}N/C$

Torque acting on the dipole:

$\tau =pE\sin \theta$

$=4\times {10}^{-9}\times 5\times {10}^4\times sin{30}^o$

$=20\times {10}^{-5}\times \frac{1}{2}$

$={10}^{-4}Nm$

Hence, the magnitude of the torque acting on the dipole is ${10}^{-4}$ N m.