A thin ring of 10 cm radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of 40 π rad s^-1 about its axis,…

A thin ring of $\displaystyle 10$ cm radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of $\displaystyle 40 \pi \mathrm{rad} \mathrm{s}^{-1}$ about its axis, perpendicular to its plane. If the magnetic field at its centre is $\displaystyle 3.8 \times 10^{-9} \mathrm{~T}$, then the charge carried by the ring is close to $\displaystyle \left(\mu_0=4 \pi \times 10^{-7} \mathrm{~N} / \mathrm{A}^2\right)$.