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Question

Physics Question on Moving charges and magnetism

AA circular coil of wire consisting of 100100 turns each of radius 9 cm9 \,cm carries a current of 0.4 A0.4 \,A. The magnitude of magnetic field at the centre of the coil is

A

2.4×10−4 T2.4 \times 10^{-4}\, T

B

3.5×10−4 T3.5 \times 10^{-4}\, T

C

2.79×10−4 T2.79 \times 10^{-4}\, T

D

3×10−4 T3 \times 10^{-4}\, T

Answer

2.79×10−4 T2.79 \times 10^{-4}\, T

Explanation

Solution

Here N=100N= 100 R=9 cm=9×10−2 mR=9\, cm =9\times10^{-2}\,m and I=0.4 AI=0.4\,A Now, B=μ0NI2R=2π×10−7×100×0.49×10−2B=\frac{\mu_{0}NI}{2R}=\frac{2\pi\times10^{-7}\times100\times0.4}{9\times10^{-2}} =2×3.14×0.49×10−3=0.279×10−3=\frac{2\times3.14\times0.4}{9}\times10^{-3} =0.279\times10^{-3} T=2.79×10−4 TT=2.79\times10^{-4}\, T