Physics - Magnetism Question with Solution | TestHub

The magnetic field at the centre of a circular loop carrying current $I$ is given by $B=\frac{m_{0}I}{2r}$ where $r$ is the radius of the circular loop. Given that $r=5.0\mathrm{cm}=0.05\mathrm{m}$. Now, $B=\frac{{\mu }_{0}I}{2r}=0.5\times 10^{-5}$ $$\begin{array}{rl}\Rightarrow I& =\frac{0.5\times 10^{-5}\times 2\times 0.05}{{\mu }_0}=\frac{0.5\times 10^{-5}\times 0.1}{4\pi \times 10^{-7}}\\ & =0.3978\approx 0.4\mathring{A}\end{array}$$