18) One of the diodes of a bridge rectifier connected to 100 V 50 Hz AC input is found to be damaged. The DC output of the circuit is 90 V. The minimum value of PIV of the diode required for replacement is

19) In a full wave rectifier one of the damaged diodes is replaced by a diode of PIV equal to input AC voltage. The newly replaced diode in the circuit

20) A 500 mA, 12 V eliminator power has bridge rectifier. The P.W. rating of diode is

21) A three phase halfwave rectifier has an AC input of 415 V 50 Hz. The ripple frequency of DC output in pulses/sec is

22) A 3-phase full wave rectifier has an AC input of 415 V, 50 Hz. The ripple frequency of D.C. output in pulses per second is