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A thin non-conducting ring of mass m car...

A thin non-conducting ring of mass `m` carrying a charge `q` can freely rotate about its axis. At `t = 0`, the ring was at rest and no magnetic field was present. Then suddenly a magnetic field `B` was set perpendicular to the plane. Find the angular velocity acquired by the ring.

A

`(qB)/(m)`

B

`(2qB)/(m)`

C

`(qB)/(2m)`

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
C
`int Edl = - (d phi)/(dt) = - pi r^(2) (dB)/(dt)` , `tau = R int lambda Edl = - R lambda pi r^(2) (dB)/(dt)`
`int tau dt = - R lambda pi r^(2) int dB = R lambda r^(2) B = I omega` : `pi r^(2) B (qr)/(2 pi r) = mr^(2) omega`, `omega = (q^(B))/(2m)`
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