question_answer

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 \[({{\mu }_{0}}=4\pi \times {{10}^{7}}\text{ }N/{{A}^{2}})\] : [JEE Main Held on 12-4-2019 Morning]

A) \[2\times {{10}^{-6}}C\]

B) \[3\times {{10}^{-5}}C\]

C) \[4\times {{10}^{-5}}C\]

D) \[7\times {{10}^{-6}}C\]

Correct Answer: B

Solution :

[b]