A thin ring of radius $R$ metre has charge $q$ coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of $f$ revolution/s. The value of magnetic induction in $\mathrm{Wb} \mathrm{m}^{-2}$ at the centre of the ring is

• A

  $\frac{\mu_0 q \mathrm{f}}{2 \pi \mathrm{R}}$
• B

  $\frac{\mu_0 \mathrm{q}}{2 \pi \mathrm{f} R}$
• C

  $\frac{\mu_0 q}{2 f \mathrm{f}}$
• Correct answer
  D

  $\frac{\mu_0 q f}{2 R}$

Hence, the correct answer is option: 'D'.