The magnetic moments associated with two closely wound circular coils A and B of radius rA = 10 cm and rB = 20 cm respectively are equal if (NA, IA and NB, IB are number of turns and current of A and B respectively) (a) 2NA IA = NB IB (b) NA = 2NB (c) NA IA = 4NB IB (d) 4NA IA = NB IB

Answer: (c). Magnetic moment of a coil M = NIπ r². NA IA π (0.1)² = NB IB π (0.2)² NA IA = 4 NB IB So the answer is (c).

The magnetic moments associated with two closely wound circular coils… | MHT CET 2024 (4 May, Shift 1)

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Bar Magnet & Magnetic Moment

The magnetic moments associated with two closely wound circular coils A and B of radius $r_A = 10\text{ cm}$ and $r_B = 20\text{ cm}$ respectively are equal if $(N_A, I_A$ and $N_B, I_B$ are number of turns and current of A and B respectively)

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Answer: (c)

Magnetic moment of a coil $M = NI\pi r^2$ .
$N_A I_A \pi (0.1)^2 = N_B I_B \pi (0.2)^2$
$N_A I_A = 4 N_B I_B$
So the answer is (c).

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