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

23) You have to measure the ripple voltage of a DC power supply to confirm with that of the manufacturer's specification. What is the instrument you need for this measurement ?