Question

Explain the working of a diode as half wave rectifier.

Answer 1

A circuit which rectifies half of the a.c. wave is called half wave rectifier.

Working:
The figure shows the circuit for half wave rectification. The a.c. voltage $\left(V_S\right)$ to be rectified is obtained across the secondary ends $S_1{S}_2$ of the transformer. The $P$-end of the diode $D$ is connected to $S_1$ of the secondary coil of the transformer. The $N$-end of the diode is connected to the other end $S_2$ of the secondary coil of the transformer, through a load resistance $R_L$. The rectified output voltage $V_{dc}$ appears across the load resistance $R_L$.
During the positive half cycle of the input a.c. voltage $V_S$, $S_1$ will be positive and the diode is forward biased and hence it conducts. Therefore, current flows through the circuit and there is a voltage drop across $R_L$. This gives the output voltage.
During the negative half cycle of the input a.c. voltage $\left(V_S\right)$, $S_1$ will be negative and the diode $D$ is reverse biased. Hence, the diode does not conduct. No current flows through the circuit and the voltage drop across $R_L$ will be zero. Hence, no output voltage is obtained. Thus corresponding to an alternating input signal, unidirectional pulsating output is obtained.