Define Rectification. With the help a circuit diagram explain the working of p-n junction diode as a half wave rectifier.

Explanation

Rectification: The process of changing alternating current into direct current is known as rectification
Principle: p-n junction diode conducts only when it is forward biased.
Half wave rectifier:

Arrangement: The a.c. supply is fed across the primary coil P of a step-down transformer. The secondary coil S of the transformer is connected to the junction diode and a load resistance `R_(L)` as shown in Fig. The output d.c voltage is obtained across the load resistance `R_(L)`. Theory: Suppose that during the first half of the input cycle, the junction diode gets forward biased The conventional current will flow in the direction of the arrow-heads. The upper end of `R_(1)` will be at positive potential w.r.t the lower end. The magnitude of output across `R_(L)` during first half cycle at any time will be proportional to the magnitude of current through `R_(L)` i.e., proportional to the number of majority carriers crossing the junction, which in turn will be proportional to the magnitude of forward blas and which ultimately depends upon the value of a.c. input at that time. Hence, during the first half of the input cycle, when junction diode conducts, output across `R_(L)` will vary in accordance with a.c. input.
During the second half cycle, junction diode will get reverse biased and hence no output will be obtained across `R_(L)`. Critically, a small current will flow due to minority carriers and a negligible output will be obtained during this half cycle also. During the next half cycle, output is again obtained as the junction diode gets forward biased. Thus, a half wave rectifier gives discontinuous and pulsating d.c output across the load resistance as shown in Fig. Thus, half-wave rectification involves a lot of wastage of energy and hence it is not preferred.