alleryA magnetic dipole of moment m in field B has potential energy:
Am B
B-m · B (minimum -mB when aligned)
Cm B sin theta
Dm + B
Answer & Solution
Correct answer: B. -m · B (minimum -mB when aligned)
We have U = -m · B.
So U = -mB cos theta.
Minimum (most stable) when m parallel to B (U = -mB).
Maximum (least stable) when m anti-parallel (U = +mB).
Compass needle aligns to minimize PE.
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