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Sahay Sir > Question Answers > Uncategorised (JEE Advanced Physics by BM Sharma + GMP Solutions) > The diagram shows a circuit having a coil of resistance R=2.5(Ω) and inductance L connected to a conducting rod PQ which can slide on perfectly conducting circular ring of radius 10 cm with its centre at ‘P’. Assume that friction and gravity are absent and a constant uniform magnetic field of 5 T exist as shown in Fig.At t = 0, the circuit is switched on and simultaneously a time varying external torque is applied on the rod so that it rotates about P with a constant angular velocity 40rad/s. Find magnitude of this torque (in milli Nm) when current reaches half of its maximum value. Neglect the self-inductance of the loop formed by the circuit.

The diagram shows a circuit having a coil of resistance R=2.5(Ω) and inductance L connected to a conducting rod PQ which can slide on perfectly conducting circular ring of radius 10 cm with its centre at ‘P’. Assume that friction and gravity are absent and a constant uniform magnetic field of 5 T exist as shown in Fig.At t = 0, the circuit is switched on and simultaneously a time varying external torque is applied on the rod so that it rotates about P with a constant angular velocity 40rad/s. Find magnitude of this torque (in milli Nm) when current reaches half of its maximum value. Neglect the self-inductance of the loop formed by the circuit.

In the given circuit what is the current I ( in A ) drawn from battery at time t = 0 .