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A current loop of magnetic moment m is placed in a uniform magnetic field B. The net force on the loop is:
Am B sin θ
BZero
Cm B
D2 m B
Answer & Solution
Correct answer: B. Zero
1. In a uniform field, the forces on opposite arms of the loop are equal and opposite.
2. These forces cancel pairwise, so the net force is zero.
3. They do, however, form a couple, producing a torque.
4. Hence force = 0 while torque $= mB\sin\theta$ may be non-zero.
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.155_
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