Electric Charges And Fields Ques 9
9. An electric dipole of dipole moment $p$ is aligned parallel to a uniform electric field $E$. The energy required to rotate the dipole by $90^{\circ}$ is
(a) $p E^{2}$
(b) $p^{2} E$
(c) $p E$
(d) infinity
[NEET Kar. 2013]
Show Answer
Answer:
Correct Answer: 9.(c)
Solution:
- (c) When electric dipole is aligned parallel $\theta=0^{\circ}$ and the dipole is rotated by $90^{\circ}$ i.e., $\theta=90^{\circ}$.
Energy required to rotate the dipole
$\begin{aligned} W & =U_f-U_i=(-p E \cos 90^{\circ})-(-p E \cos 0^{\circ}) \\ & =p E .\end{aligned}$
BETA
