Rectifier Ripple Comparison
Two rectifier circuits, one half-wave and one full-wave, are each built using identical diodes, the same smoothing capacitor, and the same load and supply frequency. Why does the full-wave circuit deliver a steadier output with smaller ripple?
Select the correct option:
Solution
Its output pulses arrive twice as often, leaving the capacitor less time to discharge
Ripple is the residual AC fluctuation superimposed on the rectified DC output, and a smoothing capacitor reduces it by charging during each output pulse and discharging into the load between pulses. The key difference is timing: a half-wave rectifier delivers one pulse per input cycle, while a full-wave rectifier delivers two, so its output ripple frequency is double. With pulses arriving twice as often, the capacitor has only half as long to discharge before the next pulse recharges it, so the output voltage sags much less between peaks, giving smaller ripple. The discharge between pulses is governed by the time constant of the capacitor and load, and shortening the available discharge interval directly limits how far the voltage can droop, which is the heart of why pulse spacing controls ripple. The option about diode forward resistance is irrelevant since identical diodes are specified. The option claiming complete removal of AC is wrong because a real capacitor filter always leaves some ripple. The option stating the output frequency equals the supply frequency describes the half-wave case, not the full-wave one. As a consistency check, the ripple factor of a full-wave rectifier is roughly half that of a half-wave rectifier under the same conditions, directly reflecting the doubled pulse rate.
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About This Question
- Subject
- physics
- Chapter
- semiconductor electronics
- Topic
- rectifier ripple comparison
- Difficulty
- Hard
- Year
- 2025
Solution
Correct Answer:
Its output pulses arrive twice as often, leaving the capacitor less time to discharge
Ripple is the residual AC fluctuation superimposed on the rectified DC output, and a smoothing capacitor reduces it by charging during each output pulse and discharging into the load between pulses. The key difference is timing: a half-wave rectifier delivers one pulse per input cycle, while a full-wave rectifier delivers two, so its output ripple frequency is double. With pulses arriving twice as often, the capacitor has only half as long to discharge before the next pulse recharges it, so the output voltage sags much less between peaks, giving smaller ripple. The discharge between pulses is governed by the time constant of the capacitor and load, and shortening the available discharge interval directly limits how far the voltage can droop, which is the heart of why pulse spacing controls ripple. The option about diode forward resistance is irrelevant since identical diodes are specified. The option claiming complete removal of AC is wrong because a real capacitor filter always leaves some ripple. The option stating the output frequency equals the supply frequency describes the half-wave case, not the full-wave one. As a consistency check, the ripple factor of a full-wave rectifier is roughly half that of a half-wave rectifier under the same conditions, directly reflecting the doubled pulse rate.
This hard difficulty physics question is from the chapter semiconductor electronics, covering the topic of rectifier ripple comparison. It appeared in the 2025 exam.
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