GATE 2023 EC – Question 35
In the circuit shown below, switch S was closed for a long time. If the switch is opened at $t=0$, the maximum magnitude of the voltage $V_R$, in volts, is ________ (rounded off to the nearest integer).
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Correct answer: 4
Explanation
With S closed for a long time, the inductor is a short across the 2 Ω resistor, so the inductor current is $2\text{ V}/1\ \Omega=2$ A. When S opens, the inductor current cannot change instantly and must flow through the 2 Ω resistor: $|V_R|=2\text{ A}\times2\ \Omega=4$ V at $t=0^+$, which is the maximum since it then decays exponentially.