Power Electronics Multiple Choice Questions and Answers

31. In a UJT, the p-type emitter is ........................ doped

1. Heavily
2. Moderately
3. Lightly
4. None of the above

32. In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output

1. Switches between -1 / 2 and +1 / 2
2. Switches between -1 and +1
3. Zero
4. Switches between 0 and +1

33. In current commutated DC - DC choppers, the voltage spike appears across the load when

1. The capacitance voltage adds to the supply voltage
2. Both (a and b)
3. Voltage across the commutating inductances collapses
4. None of these

34. In EMCsignal, the source delivers maximum power to the input of transmissionline when the transmission line input impedance

1. Greater than the source resistance
2. Smaller than the source resistance
3. Is equal to the source resistance
4. None of these

35. In radiative coupling, the emitter radiation field

1. Decays as R, where R is the separation distance between the emitter and the receptor
2. Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor
3. Decays as 1 / R, where R is the separation distance between the emitter and the receptor
4. Decays as 2R, where R is the separation distance between the emitter and the receptor

36. In single phase VSI, the harmonic which is not present is

1. 3rd
2. 5th
3. 2nd
4. 7th

37. LISN is a device used to measure conducted emissions. LISN stands for

1. Line impedance stabilization network
2. Line integrated stored network
3. Line integrated stabilization network
4. Laser integrated stabilization networking

38. Power electronics essentially deals with control of a.c. power at .....................

1. Frequencies above 1000 kHz
2. Frequencies less than 10 Hz
3. Frequencies above 20 kHz
4. 50 Hz frequency

39. Silicon controlled rectifier can be turned on

1. And turned off by applying gate pulse
2. By applying a gate pulse and turned off by removing the gate pulse
3. By applying a gate pulse and turned off only when current becomes zero
4. By making current non zero and turned off by making current zero

40. Single phase VSI are mainly used in

1. Ups
2. Multilevel configuration
3. Power supplies
4. All of these