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The work required to rotate a magnetic dipole of moment m in a field B from θ = 0 to θ = 180° is
A2mB
B0
CmB
D−mB
Answer & Solution
Correct answer: A. 2mB
W = ΔU = (−mB cos 180°) − (−mB cos 0°) = mB − (−mB) = 2mB. Work is positive because we move from minimum to maximum potential energy.
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