Question

A current carrying loop is placed in a uniform magnetic field in four different orientations as shown in figure. Arrange them in the decreasing order of potential energy.

• A. $4,2,3,1$
• B. $1,4,2,3$
• C. $4,3,2,1$
• D. $1,2,3,4$

Answer 1

The correct option is B $1,4,2,3$

Potential energy, $U=-\overline{M}.\overline{B}=-MBcos\theta$
(1) $U=-MBcos{180}^0=MB$
(2) $U=-MBcos{90}^0=0$
(3) $U=-MBcos\theta$
(4) $U=+MBcos\theta$