Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 17 of 494
The form factor of a rectified waveform is defined as the ratio of its RMS value to its average (DC) value. What is the form factor of an unfiltered full-wave rectifier?
A
\(1.57\)
B
\(0.48\)
C
\(1.11\)
D
\(1.21\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \(1.11\)
Concept:

Form factor (\(k_f\)) is a standard measure of waveform shape, defined mathematically as the ratio of root-mean-square (RMS) current/voltage to the average (DC) current/voltage.

Formula:

$$\text{Form Factor } (k_f) = \frac{I_{\text{rms}}}{I_{\text{dc}}}$$

Solution:

  • For a full-wave rectifier: \(I_{\text{rms}} = \frac{I_0}{\sqrt{2}}\) and \(I_{\text{dc}} = \frac{2I_0}{\pi}\).


  • $$k_f = \frac{I_0 / \sqrt{2}}{2I_0 / \pi} = \frac{\pi}{2\sqrt{2}} = \frac{3.1416}{2.8284} \approx 1.11$$


Why other options are incorrect:

  • Option A: \(1.57\) is the form factor for a half-wave rectifier (\(\pi / 2\)).
  • Option B: \(0.48\) is the ripple factor of a full-wave rectifier.
  • Option D: \(1.21\) is the ripple factor of a half-wave rectifier.

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