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MHT CET 2026 (15 Apr, Shift 1) · Current Loop as a Magnetic Dipole

Current Loop as a Magnetic Dipole question from MHT CET 2026 (15 Apr, Shift 1)

Q9MHT CET 2026 · 15 APR · SHIFT 1Medium

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 new coil to the original coil is

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Answer: (a)

Wire length is fixed: $N\pi d = N'\pi(2d) \Rightarrow N' = \frac{N}{2}$ .
$M = NI\frac{\pi d^2}{4} \propto Nd^2$ .
$\frac{M'}{M} = \frac{(N/2)(2d)^2}{Nd^2} = 2$
So the answer is (a) $2 : 1$ .

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