An electric dipole of length $1\ cm$ aligned at $30^\circ$ to a field $2\times10^{5}\ N\,C^{-1}$ experiences a torque of $8\ N\,m$. The magnitude of each charge is

1. Torque on a dipole: $\tau = pE\sin\theta$ with $p = q\,l$. 2. $p = \dfrac{\tau}{E\sin\theta} = \dfrac{8}{2\times10^{5}\times\sin30^\circ} = \dfrac{8}{1\times10^{5}} = 8\times10^{-5}$ C m. 3. $q = \dfrac{p}{l} = \dfrac{8\times10^{-5}}{1\times10^{-2}} = 8\times10^{-3}$ C $= 8\ mC$. _Source: Samacheer Kalvi Class 12 Physics Vol.1, Unit 1 'Electrostatics', Evaluation Q.4_