Q.Draw the circuit diagram of a half wave rectifier. Explain its working. What is the frequency of ripple in its output?

[!TLDR] A half wave rectifier uses one diode in series with the transformer secondary and load $R_L$; it conducts only during the half-cycle that forward biases it, giving pulsed DC at the SAME frequency as the AC input. [!ANSWER] Circuit: secondary coil AB -- diode D -- load $R_L$, in series. It conducts (forward biased) only during the positive half cycle, giving alternate output pulses; ripple frequency = input AC frequency (e.g. 50 Hz).

Circuit diagram: the transformer's secondary winding, with its two ends labelled A and B, is connected in series with a single diode D and the load resistor $R_L$, forming one complete loop -- secondary coil AB, through diode D, through $R_L$, and back to the coil (Fig. 16.2). Working: the AC voltage across AB varies sinusoidally, reversing polarity every half cycle. During the POSITIVE half cycle, when A is at a higher potential than B, the diode D is forward biased -- it conducts, behaving as a closed switch, and current flows around the loop through $R_L$. During the NEGATIVE half cycle, when A is at a lower potential than B, the diode is reverse biased -- it behaves as an open switch and blocks current entirely; no current flows through $R_L$ during this half. So the diode conducts only during alternate (positive) half cycles, giving an output across $R_L$ that consists of a series of separated positive pulses, each shaped exactly like the corresponding positive half cycle of the input, with a complete zero-output gap during every intervening negative half cycle (Fig. 16.3). Ripple frequency: since exactly ONE output pulse is produced for every ONE full cycle of the AC input (only the positive half of each cycle contributes), the ripple (and hence the output) frequency of a half wave rectifier is equal to the input AC frequency -- for standard 50 Hz Indian mains, the ripple frequency is also 50 Hz (as established in Example 16.1). [!ANSWER] Circuit: secondary coil AB -- diode D -- load $R_L$, in series. It conducts (forward biased) only during the positive half cycle, giving alternate output pulses; ripple frequency = input AC frequency (e.g. 50 Hz).

Describe the single-diode series circuit, work through forward/reverse conduction on alternate half cycles to explain the pulsed output waveform, and use the one-pulse-per-input-cycle fact (from Example 16.1) to state the ripple frequency.

Assuming (by analogy with a full wave rectifier) that the ripple frequency must be double the input frequency -- doubling only happens with TWO diodes conducting on alternate half cycles; a half wave rectifier's single diode produces exactly one pulse per input cycle, so its ripple frequency equals, not doubles, the input frequency.