Question

What current would be maintained in a circular coil of wire of 1000 turns and 10 cm in radius in order to just cancel the earth's magnetic field at a place where the horizontal component of earth is $2\times {10}^{-4}T?$

Answer 1

$B=N\frac{{\mu }_{o}i}{2a}$

$⟹i=\frac{2Ba}{{\mu }_{o}N}=\frac{2\times 2\times {10}^{-4}\times 0.1}{4\pi \times {10}^{-7}\times 1000}$

$⟹i=3.18\times {10}^{-2}A$