P-n junction consists of a p-type and n-type semiconductor in contact. When forward bias (i.e. the P-semiconductor is connected to the positive terminal of a battery and the n-Semiconductor is connected to the negative terminal of a battery, it has a low resistance to current flow. When in reverse bias (i.e. the PSemiconductor is connected to the negative terminal of the battery and the nSemiconductor is connected to the positive terminal) it has a high resistance to current flow
The P-n junction device is only forward biased during one-half current flows during the period. It can be detected in the output resistance Rr. This is why the p-type is positive and n-type is negative. No current flows in the reverse cycle since the p-n junction is reversed biased. It exhibits high resistance to current flow. Current therefore flow in the resistance Rr as shown above in one direction only. This is called half wave rectification. For full wave ratification two p-n junction back to back are used.
