Question

A short bar magnet of magnetic moment $0.4\, J\, T^{-1}$ is placed in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is

• A. $-0.064\,J$
• B. zero
• C. $-0.082\,J$
• D. $0.064\,J$

Answer 1

Answer: (A)

$-0.064\,J$

Answer 2

Here, $M=0.4\,J\,T^{-1}; B=0.16\,T$ For stable equilibrium, the potential energy (U) of bar magnet in the magnetic field is $U = -MB = -0.4 ? 0.16 = -0.064 \,J$