Question

42. An electric dipole of moment 10 ^ - 8 cm is in an uniform electric field of 1000 V/m what is the maximum torque that can act on dipole? what is the work done in rotating the dipole through 30 degree from its equilibrium position

Answer 1

Dear Student,

$$\begin{gathered} \mathrm{maximum}\mathrm{torque},\mathrm{\tau }=\mathrm{pE} \\ \mathrm{\tau }={10}^{-8}\times 1000={10}^{-5}\mathrm{Nm} \\ \mathrm{Work}\mathrm{done},\mathrm{W}=-\mathrm{pE}\left({\mathrm{cos\theta }}_2-{\mathrm{cos\theta }}_1\right) \\ \mathrm{W}=-{10}^{-5}\left(\cos 30°-\cos 0\right) \\ \mathrm{W}=-{10}^{-5}\left(\frac{\sqrt{3}}{2}-1\right) \\ \mathrm{W}=-{10}^{-5}\left(0.86-1\right) \\ \mathrm{W}=-{10}^{-5}\times \left(-0.14\right)=1.4\times {10}^{-6}\mathrm{J} \end{gathered}$$