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Question
An LR circuit with a battery is connected at t = 0. Which of the following quantities is not zero just after the connection?
Options
Current in the circuit
Magnetic field energy in the inductor
Power delivered by the battery
Emf induced in the inductor
Solution
Emf induced in the inductor
At time t = 0, the current in the L-R circuit is zero. The magnetic field energy is given by `U=1/2Li^2,` as the current is zero the magnetic field energy will also be zero. Thus, the power delivered by the battery will also be zero. As, the LR circuit is connected to the battery at t = 0, at this time the current is on the verge to start growing in the circuit. So, there will be an induced emf in the inductor at the same time to oppose this growing current.
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