Concept:The output of an unfiltered rectifier is pulsating direct current, which consists of a steady average DC level accompanied by unwanted fluctuating AC harmonics termed 'ripple'.
Formula:$$r = \frac{V_{\text{ac, rms}}}{V_{\text{dc}}} = \sqrt{\left(\frac{V_{\text{rms}}}{V_{\text{dc}}}\right)^2 - 1}$$
Solution:- A rectifier converts bidirectional AC into unidirectional pulsating DC.
- The time-varying fluctuations remaining in this unidirectional signal represent the AC ripple.
- Filter circuits are used to attenuate this ripple component.
Why other options are incorrect:- Option A: The constant component is the desired DC level, not the ripple.
- Option B: Thermal noise is random Johnson-Nyquist noise, distinct from periodic ripple harmonics.
- Option D: Leakage current is the reverse minority carrier current across the diode junction.
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