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In an RC circuit with a battery, resistor R1 in series, and a parallel combination of resistor R2 and capacitor C, a switch is closed at time t = 0. Which of the following statements are correct immediately after the switch is closed (at t = 0+)?

1. The battery delivers maximum current at t = 0.
2. No current flows through C at t = 0.
3. Voltage drop across R2 is non-zero at t = 0.
4. The current through the battery decreases with time and finally becomes zero.

Correct answer: The battery delivers maximum current at t = 0.

Solution

At t = 0, the uncharged capacitor acts as a short circuit, so all current bypasses R2 (voltage across R2 = 0) and maximum current flows from the battery. At t -> infinity, the capacitor is fully charged and acts as open circuit — current still flows through R1 and R2, so it does not become zero.

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