If the a.c. input to a half-wave rectifier is an r.m.s value of $$\frac{{400}}{{\sqrt 2 }}$$   volts, then diode PIV rating is ___________

Vrms = Vm / √2 therefore, Vm = Vrms × √2
Vm = (400/√2 ) √2 = 400
In half wave rectifier, PIV = Vm = 400

Option (c) is correct Vrms =Vm/2

for half wave rectifier, PIV rating is Vm i.e peak max voltage
Here, Vrms= 400/sqrt2
Vrms=Vm/2 for half wave rectifier, therefore, Vm=800/sqrt2= 400 X( sqrt 2) i.e option (c)