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An L-R circuit is connected to a battery at t = 0. Immediately after the switch is closed, which of the following quantities is NOT zero?
- The emf induced in the inductor
- The current in the circuit
- The magnetic energy stored in the inductor
- The power delivered by the battery
Correct answer: The emf induced in the inductor
Solution
Just after closing, the inductor prevents an instantaneous jump in current, so current is zero; hence magnetic energy (proportional to i²) and battery power (V*i) are also zero at that instant. The full battery emf appears across the inductor as a back-emf, so the induced emf is non-zero (equal to the battery emf).
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