Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 10 of 494
In a two-diode center-tapped full-wave rectifier, the two diodes \(D_1\) and \(D_2\) operate:
A
Simultaneously during both positive and negative half-cycles
B
Alternately, each conducting during opposite half-cycles of the AC input
C
Only when both transformer secondary terminals are at a positive potential
D
In reverse bias continuously to maintain constant output voltage
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Alternately, each conducting during opposite half-cycles of the AC input
Concept:

In a center-tapped transformer, the potentials of the two outer terminals are \(180^\circ\) out of phase with respect to the center tap. Consequently, when one diode is forward-biased and conducts, the other diode is reverse-biased and non-conducting.

Formula:

Qualitative concept / No formula required.

Solution:

  • During the positive half-cycle, diode \(D_1\) anode is positive (forward-biased) and conducts, while \(D_2\) is reverse-biased.


  • During the negative half-cycle, diode \(D_2\) anode becomes positive (forward-biased) and conducts, while \(D_1\) is reverse-biased.


  • Current passes through the load resistor in the identical direction during both half-cycles.


Why other options are incorrect:

  • Option A: The diodes are out of phase and cannot conduct at the same instant.
  • Option C: Because of the center tap, the two ends are in antiphase; they cannot be positive simultaneously.
  • Option D: Diodes must be forward-biased to conduct current to the load.

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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