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Question: Answered & Verified by Expert
A conducting circular loop of radius \( \mathrm{r} \) carries a constant current i. It is placed in a uniform magnetic field \( \overrightarrow{\mathrm{B}_{0}} \) such that \( \overrightarrow{\mathrm{B}_{0}} \) is perpendicular to the plane of the loop. The magnetic force acting on the loop is
PhysicsMagnetic Properties of MatterJEE Main
Options:
  • A ir \( \overrightarrow{\mathrm{B}_{0}} \)
  • B \( 2 \pi \) ir \( \overrightarrow{\mathrm{B}_{0}} \)
  • C Zero
  • D \( \pi \) ir \( \overrightarrow{\mathrm{B}_{0}} \)
Solution:
1491 Upvotes Verified Answer
The correct answer is: Zero

The magnetic field is perpendicular to the plane of the paper. Let us consider two diametrically opposite elements on the loop. Applying Fleming’s left-hand rule on element AB, the direction of force will be leftwards and the magnitude will be
dF=Idl Bsin90o=IdlB

On element CD, the direction of force will be rightwards on the plane of the paper and the magnitude will be dF=IdlB.

Hence, the net force on the loop due to current elements will be zero, which implies that the total force on the loop will be zero.

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