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In the circuit shown, E = 25 V, L = 2 H, C = 60 microF, R1 = 5 ohm and R2 = 10 ohm. Switch S is closed at t = 0. Find the current through R2 at t = infinity (steady state).

1. 0
2. 5 A
3. 2.5 A
4. 4 A

Correct answer: 0

Solution

At t = infinity: the inductor L acts as a short circuit (wire) and the capacitor C acts as an open circuit. Current flows through the path E -> R1 -> L (short circuit). The capacitor C is open, so no current passes through R2 (since R2 is in the branch containing C). Therefore, current through R2 = 0.

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