A 100-turn closely wound circular coil of radius 5 cm has a magnetic field of 3.14 10^ -3 T at its centre. The current flowing through the coil, and the magnitude of the magnetic moment of this coil are, respectively : (Take _0 = 4 10^ -7 T m/A)
D. 2.5 A, 2 A m^2
The magnetic field at the centre of a circular coil is given by: B = _0 N I 2R Substituting the given values (B = 3.14 10^ -3 T, N = 100, R = 0.05 m, _0 = 4 10^ -7 T m/A): 3.14 10^ -3 = 4 10^ -7 100 I 2 0.05 Taking = 3.14: 3.14 10^ -3 = 4 3.14 10^ -5 I 0.1 10^ -3 = 4 10^ -4 I I = 10^ -3 4 10^ -4 = 2.5 A The magnetic moment of the coil is given by: M = N I A = N I ( R^2) M = 100 2.5 3.14 (0.05)^2 M = 250 3.14 0.0025 M = 1.9625 A m ^2 2 A m ^2 Answer: 2.5 A, 2 A m^2
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