An RC circuit as shown in the figure is driven by a AC source generating a square wave. The output wave pattern monitored by CRO would look close to :

Solution

Physics sir · 4 steps

The CRO reads the capacitor, and a capacitor's voltage never jumps: it rises and falls smoothly.

1. What the CRO reads. The CRO is connected in parallel with C, so it shows the capacitor voltage V_C. The current into C must pass through R, so it stays finite. A finite current changes the charge gradually, so V_C cannot jump suddenly.
2. High half of input. When the source is at V₀, the capacitor charges through R. V_C rises fast at first and then levels off, so the curve bends downward.

   V_C = V₀(1 - e^(-t/RC)) (charging), V_C = V₁ e^(-t/RC) (discharging)

3. Low half of input. When the source drops to zero, the capacitor discharges through R. V_C falls smoothly and exponentially, starting from the value it had reached. It does not drop straight to zero.
4. So. The output is a continuous wave of rising charging curves and falling exponential decays, with no vertical drops. That is option (d).

The idea to keep. Across a capacitor, voltage is continuous because q cannot change instantly. Square-wave input gives smooth exponential rise and fall, never a vertical jump.

Answer from the NTA final answer key. Solution by PrepWiser.