Question

A short bar magnet of magnetic moment 0.4J 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

given,

magnetic moment, μ= 0.4 J/T

magnetic field, B= 0.16 T

U=-μ•B

=-μBcosx

where x is angle between μ And B

for x=0°

the dipole is in stable equilibrium

thus..

U=-μBcos0°

U=-μB

U=-0.4×0.16

U=-0.064 J

your answer is (a)