Question

An electric dipole of moment $\vec{p}$ is lying along a uniform electric field $\vec{E}$. The work done in rotating the dipole by 90$^{\circ}$ is :-

• A. p E
• B. $\sqrt 2$ pE
• C. pE/2
• D. 2pE

Answer 1

Answer: (A)

p E

Answer 2

Work done in rotating a dipole from $\theta_{1}$ to $\theta_{2}$ is
$W = pE\, \left(\cos \theta_{1}-\cos \theta_{2}\right)$
Here $\theta_{1}=0^{\circ} \text { and } \theta_{2}=90^{\circ}$ therefore $W = pE$