Physics - Magnetism Question with Solution | TestHub

In a circular coil of $n$ turns, magnetic field is $\mathrm{B}=\frac{{\mu }_0\mathrm{nI}}{2\mathrm{r}}=\frac{4\pi \times 10^{-7}\times 250\times 20\times 10^{-3}}{2\times 40\times 10^{-3}}$ $(\because \mathrm{n}=$ no. of turns, $\mathrm{I}=$ current through coil, $\mathrm{r}=$ radius of coil) $\begin{array}{rl}\Rightarrow B& =\frac{4\pi \times 250\times 20\times 10^{-7-3+3}}{2\times 40}\\ & =250\times 3.14\times 10^{-7}\\ & =785\times 10^{-7}=0.785\times 10^{-4}\text{ tesla }\\ & =0.785\text{ gauss }\end{array}$