Question

What should be the amount of current through the ring of radius $5\, cm$ so that field in the centre is with earth?s magnetic field of $7 \times 10^{-9} \,Wb/m^2$ is

• A. 0.5 A
• B. 0.28 A
• C. 2.8 A
• D. none

Answer 1

Answer: (D)

none

Answer 2

Given that the field at the centre of the ring B = 7 ? 10 Wb/m We know that $B=\frac{\mu_{0}I}{2r}$ $\Rightarrow I=\frac{2Br}{\mu_{0}}$ $=\frac{2\times7\times 10^{-9}\times 0.05}{4\pi\times 10^{-7}}$ $=5.57\times 10^{-4}$ A