Question

The potential energies associated with four orientation of an electric dipole in an electric field are :
(i) $-5U_0$ , (ii) $-7U_0$ (iii) $3U_0$ and (iv) $5U_0$ where $U_0$ is positive.
Rank the orientations according to the angle between the electric dipole moment $\overrightarrow{p}$ and the electric field $\overrightarrow{E}$ , greatest first

• A. (i), (ii), (iii), (iv)
• B. (ii), (iii), (i), (iv)
• C. (iv), (iii), (i), (ii)
• D. (iv), (i), (iii), (ii)

Answer 1

Answer: (C)

Potential energy for a dipole $U=-P.E$
$\therefore U=-PE\cos \theta$
$U\propto -\cos \theta$
For greater orientation value of $U$ will be more positive
$\therefore$ in decreasing order is as follow
$(iv)>(iii)>(i)>(ii)$