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

  • A
    $2 \times 10^{-6} \, C$
  • B
    $7 \times 10^{-6} \, C$
  • C
    $4 \times 10^{-5} \, C$
  • D
    $3 \times 10^{-5} \, C$

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