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MHT CET 2026 (11 Apr, Shift 2) · Current Loop as a Magnetic Dipole

Current Loop as a Magnetic Dipole question from MHT CET 2026 (11 Apr, Shift 2)

Q11MHT CET 2026 · 11 APR · SHIFT 2Medium

Current Loop as a Magnetic Dipole

A circular coil of N turns and diameter D carries current I. It is unwound and rewound to make another coil of diameter 2D, current I remaining the same. The ratio of magnetic moments of the original coil to the new coil is

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Answer: (c)

  1. Fixed wire length: NπD=N′π(2D)⇒N′=N2N\pi D = N'\pi(2D) \Rightarrow N' = \frac{N}{2}.
  2. M∝ND2M \propto ND^2, so M′∝N2⋅4D2=2ND2M' \propto \frac{N}{2}\cdot 4D^2 = 2ND^2.
  3. MM′=12\frac{M}{M'} = \frac{1}{2}
  4. So the answer is (c) 1:21 : 2.
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