Question

An electric dipole of momentum $3\times {10}^{-8}Cm$ is placed in an electric field of $6\times {10}^{4}N/C$ with is axis making an angle of ${30}^o$ with the field . Find the torque acting on the dipole.

• A. $(9\times {10}^{-5})N-m$
• B. $(9\times {10}^{-4})N-m$
• C. $(9\times {10}^{-3})N-m$
• D. $(90\times {10}^{-8})N-m$

Answer 1

The correct option is B $(9\times {10}^{-4})N-m$

We know that Torque $\left(\overrightarrow{\tau }\right)=\overrightarrow{p}\times \overrightarrow{E}$

$\tau =pE\sin \theta$

$=(3\times {10}^{-8})\times (6\times {10}^4)\sin {30}^0$

$=(9\times {10}^{-4})N-m$