Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 367 of 494
The output waveform produced by an unfiltered half-wave rectifier across a resistive load is best described as:
A
A pulsating, unidirectional waveform consisting of discrete positive voltage pulses separated by zero-voltage intervals
B
A pure, constant \( \text{DC} \) voltage line with zero ripple factor
C
A continuous sinusoidal waveform identical to the input AC signal
D
An inverted AC waveform oscillating symmetrically about the zero-volt axis
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: A pulsating, unidirectional waveform consisting of discrete positive voltage pulses separated by zero-voltage intervals
Concept:

A half-wave rectifier conducts only during the positive half-cycle of the input AC waveform and blocks conduction during the negative half-cycle.

Formula:

$$V_L(t) = \begin{cases} V_m \sin(\omega t) & 0 \le \omega t < \pi \\ 0 & \pi \le \omega t < 2\pi \end{cases}$$

Solution:

  • During the positive half-cycle (\( 0 \) to \( \pi \)), the diode conducts, reproducing the positive half-sine wave across the load.


  • During the negative half-cycle (\( \pi \) to \( 2\pi \)), the diode is reverse-biased, resulting in zero output across the load.


  • The resulting output consists of unidirectional positive pulses separated by zero-voltage intervals.


Why other options are incorrect:

  • Option B: Unfiltered rectifier output pulsates periodically; producing a steady DC line requires low-pass smoothing filters.
  • Option C: The negative half-cycle is blocked, so the output is not a continuous sinusoidal waveform.
  • Option D: The output does not cross zero into negative values; it is unidirectional.

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