Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 394 of 494
In a bridge rectifier circuit, what is the consequence of one of the four diodes burning out into a permanent open-circuit failure?
A
The circuit continues operating as a normal full-wave rectifier without changes
B
The transformer secondary short-circuits, immediately blowing the AC mains fuse
C
The circuit begins functioning as a half-wave rectifier, conducting on only one half-cycle
D
The output DC voltage doubles because resistance is reduced
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: The circuit begins functioning as a half-wave rectifier, conducting on only one half-cycle
Concept:

A bridge rectifier requires two functioning diode pairs to conduct on alternate half-cycles. If one diode opens, its associated half-cycle conduction path is broken.

Formula:

Qualitative concept / No formula required.

Solution:

  • A bridge rectifier relies on diode pair \( D_1-D_3 \) during the positive half-cycle and pair \( D_2-D_4 \) during the negative half-cycle.


  • If one diode (e.g., \( D_1 \)) fails open, its pair cannot conduct during that half-cycle.


  • The remaining intact pair continues conducting during the opposite half-cycle.


  • As a result, current is delivered only during one half-cycle, converting the circuit into a half-wave rectifier.


Why other options are incorrect:

  • Option A: Full-wave operation is lost because conduction during one half-cycle is blocked.
  • Option B: Short-circuiting the transformer occurs if a diode fails short, not if it fails open.
  • Option D: Average DC output voltage drops by half because one half-cycle is lost.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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