Q. An electric dipole of length $1\ cm$ is placed with the axis making an angle of $30^{o}$ to an electric field of strength $10^{4}\ NC^{- 1}.$ If it experiences a torque of $10\sqrt{2}\ Nm,$ the potential energy of the dipole is
A) $0.245\ J$
B) $2.45\ J$
C) $0.0245\ J$
D) $24.5\ J$
Explanation
(d) $\delta = PE\sin\theta$
$\Rightarrow 10\sqrt{2} = P \times 10^{4}\sin 30{^\circ}$
$\Rightarrow P = 2\sqrt{2} \times 10^{- 3}$
$\therefore U = PE\cos\theta$
$\Rightarrow U = 2\sqrt{2} \times 10^{- 3} \times 10^{4}\cos{30{^\circ} = 24.5\ J}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.