Magnetic Effects & Magnetism

JEE Main level, single correct, medium

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Question 1 of 276

The magnetic field at the centre of a circular coil of radius RR carrying current II is B0B_0. At an axial point at distance x=R3x = R\sqrt{3} from the centre, the magnetic field is:

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Answer: (B) B0/8B_0/8

B(x)=μ0IR22(R2+x2)3/2=B0(R2R2+3R2)3/2=B0(14)3/2=B08B(x) = \frac{\mu_0 I R^2}{2(R^2+x^2)^{3/2}} = B_0 \left( \frac{R^2}{R^2+3R^2} \right)^{3/2} = B_0 \left(\frac{1}{4}\right)^{3/2} = \frac{B_0}{8}.

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