Question

In a diode rectifier, the capacitors with large values of $C$ are used in filter circuits in order to

• A. increase the ac ripple
• B. reduce the peak voltage at the output
• C. increase the time constant to high value
• D. discharge quickly the voltage across it
• E. double the input ac peak value

Hint:

Physics Tip: Bigger capacitor = stores more charge = smoother DC output.

Answer 1

The Correct Option is C

Concept:
In rectifier filter circuits, capacitor smooths pulsating DC output. Ripple decreases when capacitor discharges slowly through load resistance. Time constant: $$\tau = RC$$
Step 1: Effect of large capacitance.
If $C$ is large, then $$\tau = RC$$ also becomes large. Large time constant means capacitor loses charge slowly between peaks.
Step 2: Why useful in rectifier.
Slow discharge keeps output voltage more constant and reduces ripple. Hence capacitor acts as better filter.
Step 3: Check options.
(A) Ripple decreases, not increases.
(B) Peak voltage is not reduced mainly for this reason.
(C) Correct.
(D) Large capacitor discharges slowly, not quickly.
(E) False.
Hence correct option is (C). :contentReference[oaicite:1]{index=1}