Capacitors in DC Circuits & RC question from JEE Main 2020 (6 Sep, Shift 1)

Answer: (b)

1. $\tau = RC = 10^{3}\times10\times10^{-9} = 10\ \mu\text{s}$.
2. 0–5 $\mu$s: charges, $V = 5(1-e^{-0.5}) \approx 2\text{ V}$.
3. 5–10 $\mu$s (input 0): discharges, $V = 2e^{-0.5} \approx 1.2\text{ V}$, not to zero.
4. 10–15 $\mu$s: charges again, $V = 5-(5-1.2)e^{-0.5} \approx 2.7\text{ V}$, close to 3 V.
5. So the answer is (b).