(a) Circuit diagram to study the V-I Characteristics of p - n junction diode in
(i) Forward biasing:
(ii) Reverse biasing:
V−I Characteristics of Diode

(i) Minority carrier injection in forward bias:
In forward biased p-n junction, electrons from n-region diffuse into p-region where they are minority carriers. Holes are injected from p-side to n-side where they are minority carriers. This process is known as 'minority carrier injection'.
(ii) Breakdown voltage in reverse bias:
In reverse biased p-n junction, only minority carriers can cross the junction. Hence, a very small amount of current flows in reverse direction which is known as reverse saturation current. If the reverse voltage is increased to a very large value, a large reverse current flows through the diode due to zener diode breakdown. The voltage at which this happens is known as breakdown voltage.
OR
(b) Two processes involved in formation of p-n junction:
(i) Diffusion
(ii) Drift
Full wave rectifier:
A centre-tapped transformer and two p - n junction diodes are used for a full weave rectifier.
Input of the transformer is connected to the ac supply.
In secondary there are three terminals −A,B and CT. For positive half cycle, A is positive, B is negative. For the negative half cycle, A is negative, B is positive. CT is always at zero potential. It is always grounded.
Anode of one diode (D1) is connected to A and anode of other diode (D2) is connected to B.
Cathodes of both the diodes are joined together and ultimately connected to CT through a load resistance (RL).
When positive half cycle appears, A is at positive and B is at negative potential. So, diode D1 is forward biased and hence, it conducts.
When negative half cycle appears, B is at positive and A is at negative potential. So, diode D2 is forward biased and hence, it conducts.
The process repeats.
For both the half cycles current flowing through the load resistance is unidirectional. Hence, a DC voltage appears across it.
Thus, a full wave rectifier works.
Input and output wave forms:

Characteristic property of junction diode that makes it suitable for rectification:
An ideal p−n junction diode exhibits zero resistance when forward biased and infinite resistance when reversed biased.