Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 237 of 494
Why is the AC ripple produced by a full-wave rectifier easier to filter with a smaller capacitor than the ripple from a half-wave rectifier?
A
The full-wave output has a lower DC component
B
Full-wave rectifiers do not use semiconductor diodes
C
The full-wave output has zero peak voltage
D
The ripple frequency is doubled (\( 2f_{\text{in}} \)), meaning the capacitor has half the discharge time between peaks and lower capacitive reactance
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Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: The ripple frequency is doubled (\( 2f_{\text{in}} \)), meaning the capacitor has half the discharge time between peaks and lower capacitive reactance
Concept:

Because a full-wave rectifier operates at twice the ripple frequency (\( 2f_{\text{in}} \)), the time between charging peaks is halved, reducing the time available for the filter capacitor to discharge into the load.

Formula:

$$V_{\text{ripple}} = \frac{I_{\text{dc}}}{2 f_{\text{in}} C} \quad \text{vs} \quad V_{\text{ripple, half-wave}} = \frac{I_{\text{dc}}}{f_{\text{in}} C}$$

Solution:

  • Doubling the ripple frequency halves the discharge interval between peaks.


  • This means a capacitor of half the physical size can achieve the same ripple reduction as in a half-wave circuit.


Why other options are incorrect:

  • Option A: Full-wave rectifiers deliver twice the DC voltage and power of half-wave rectifiers.
  • Option B: Full-wave rectifiers use two or four semiconductor diodes.
  • Option C: Full-wave rectifiers reach the same peak voltage \( V_m \) as half-wave rectifiers.

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