A rectifier is a device that converts alternating current into direct current.
Half wave rectifier:
In this rectifier, the PN junction diode is connected to an input AC supply with the help of a primary coil, which will induce an emf in the secondary coil and ultimately the output is taken across the load resistance (RL).
Let at any instant S1 is positive and S2 is negative. Due to this polarity the junction diode is forward biased so it will start conducting and output is obtained.
In the next half cycle, S1 will be –Ve and S2 will be +Ve. So, the diode will now be in the reversed biased position. So, it will not conduct and hence no output is taken.
In the similar pattern the output is obtained for that half-cycle in which the diode is forward biased so ultimately the output is a disturbed unidirectional pulsating d.c. but this discrepancy, we use a full wave rectifier.