Question

The potential energies associated with four orientation of an electric dipole in an electric field are :
(i) $ -5 U_{0} $ , (ii) $ -7U_{0} $ (iii) $ 3 U_{0} $ and (iv) $ 5 U_{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
$(iv) >\, (iii) >\, (i) >\, (ii)$