Physics - Magnetism Question with Solution | TestHub

The equivalent current $I$ due to the revolving charge is given by $I=qf$, where $q$ is the charge and $f$ is the frequency of revolution.

Given $q=50e=50\times 1.6\times 10^{-19}=8\times 10^{-18}$ C and $f=1$ r.p.s.

$I=8\times 10^{-18}\times 1=8\times 10^{-18}$ A

The magnetic field at the centre of a circular current loop is given by $B=\frac{{\mu }_{0}I}{2r}$

Substituting the values of $I$ and $r=0.4$ m:

$B=\frac{{\mu }_0\times 8\times 10^{-18}}{2\times 0.4}$

$B=\frac{{\mu }_0\times 8\times 10^{-18}}{0.8}$

$B=10\times 10^{-18}{\mu }_0=10^{-17}{\mu }_0$

Answer: $10^{-17}{\mu }_0$