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A circular coil of N turns and radius R carries a current I. It is unwound and rewound to make another coil of radius R/2, current I remaining the same. Calculate the ratio of the magnetic moments of the new coil and the original coil. |
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Answer» Solution :Magnetic moment of original COIL of N turns and RADIUS R carrying a current I `m_1 = N_1 A_1 I = N.PI.R^2.I` When the coil is unwound and is rewound to make another coil of radius `R_2 = (R_1)/2 = R/2` , the TOTAL number of turns in the coil will CHANGE to `N_2 = 2 N_1 = 2N`. As same current I flows through the coil even now, hence new magnetic moment is given by `m_2 = N_2 A_2 I = 2 N . pi . (R/2)^(2) . I = 1/2 N pi R^2 I = (|vecm_1|)/(2)` |
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