27) If the input A.C. voltage is 30 volts, then output D.C. voltage of the half wave rectifier will be

28) If the input AC voltage of half wave rectifier is 12 V, then the output DC voltage will be

29) If the DC output voltage of half wave rectifier is 13.5 volt, then the input AC voltage is

30) In a bridge rectifier, No. of diodes conduct at a time is

31) In Bridge rectifier, how many times of ripple frequency at the output is greater than the input AC frequency ?