A nonconducting ring of radius r has charge Q. A magnetic field perpen

1.	A nonconducting ring of radius r has charge Q. A magnetic field perpendicular to the plane of the ring changes at the rate dB/dt .The torque experienced by the ring is(a) zero(b) Qr2 (dB/dt)(c) 1/2 Qr2 (dB/dt)(d) πr2Q (dB/dt)
Answer» Correct Answer is: (c) 1/2 Qr² (dB/dt) The same emf is induced in a conducting and a nonconducting ring, and it is equal to πr² dB/dt. At any point on ring, E = 1/2 r dB/dt . For any charge dQ on the ring, force = dF = EdQ, tangential to the ring Torque about the centre due to dF = dτ = rdF = rEdQ. Total torque = ΣrEdQ = r (1/2 r dB/dt) Q.

A nonconducting ring of radius r has charge Q. A magnetic field perpendicular to the plane of the ring changes at the rate dB/dt .The torque experienced by the ring is(a) zero(b) Qr2 (dB/dt)(c) 1/2 Qr2 (dB/dt)(d) πr2Q (dB/dt)

Answer»

Correct Answer is: (c) 1/2 Qr² (dB/dt)

The same emf is induced in a conducting and a nonconducting ring, and it is equal to πr² dB/dt.

At any point on ring, E = 1/2 r dB/dt .

For any charge dQ on the ring, force = dF = EdQ, tangential to the ring

Torque about the centre due to dF = dτ = rdF = rEdQ.

Total torque = ΣrEdQ = r (1/2 r dB/dt) Q.

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A nonconducting ring of radius r has charge Q. A magnetic field perpendicular to the plane of the ring changes at the rate dB/dt .The torque experienced by the ring is(a) zero(b) Qr2 (dB/dt)(c) 1/2 Qr2 (dB/dt)(d) πr2Q (dB/dt)

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