Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 169 of 494
Increasing the capacitance \( C \) of a parallel shunt filter capacitor connected across the load resistor \( R_L \) of a full-wave rectifier causes the peak-to-peak ripple voltage to:
A
Increase proportionally
B
Decrease, making the output voltage smoother and closer to pure DC
C
Fluctuate with double the amplitude
D
Remain completely unchanged
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Decrease, making the output voltage smoother and closer to pure DC
Concept:

A larger filter capacitor stores more charge during conduction peaks, slowing its discharge through \( R_L \) between cycles and reducing the output ripple voltage.

Formula:

$$V_{\text{ripple (peak-to-peak)}} = \frac{I_{\text{dc}}}{2 f C} = \frac{V_{\text{dc}}}{2 f R_L C} \propto \frac{1}{C}$$

Solution:

  • The peak-to-peak ripple voltage \( V_r \) is inversely proportional to the filter capacitance \( C \).


  • Increasing \( C \) reduces ripple, delivering a smoother, more stable DC voltage to the load.


Why other options are incorrect:

  • Option A: Ripple voltage decreases with increasing capacitance; it does not increase.
  • Option C: Increasing capacitance damps fluctuations rather than doubling them.
  • Option D: Filtering performance depends strongly on capacitance \( C \).

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