The magnetic moment of a bar magnet is 0.5 A m². It is suspended in a uniform magnetic field of 8 × 10⁻² T. The work done in rotating it from its most stable to most unstable position is:
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The magnetic moment of a bar magnet is 0.5 A m². It is suspended in a uniform magnetic field of 8 × 10⁻² T. The work done in rotating it from its most stable to most unstable position is:

G1 Physics · Accepted Answer

Potential energy of a magnetic dipole: U = -mB cosθ At stable equilibrium: θ = 0° U(stable) = -mB At unstable equilibrium: θ = 180° U(unstable) = +mB Work done: W = ΔU = 2mB = 2 × 0.5 × 8 × 10⁻² = 8 × 10⁻² J