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Power electronics
1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
Q1 ⇒ Multiphase choppers are used in high power circuit [other wrong options] [Discuss in forum] low power circuits both low and high power circuits medium power circuits |
Q2 ⇒ In thermal ohm's law, temperature and power loss are analogous to I and V respectively of ohm's law [other wrong options] [Discuss in forum] V and I respectively of ohm's law R and V respectively of ohm's law I and R respectively of ohm's law |
Q3 ⇒ When an SCR is in forward blocking mode, the applied voltage appears across only one junction [other wrong options] [Discuss in forum] is equally shared by two junctions is equally shared by three junctions may appear across one or more junctions |
Q4 ⇒ In a 3 phase full converter, the instantaneous output voltage can have negative part if firing angle is more than 60° [other wrong options] [Discuss in forum] firing angle is less than 60° firing angle is less than 90° firing angle is more than 90° |
Q5 ⇒ The circuit in figure is self commutation [other wrong options] [Discuss in forum] resonant commutation load commutation auxiliary commutation |
Q6 ⇒ A chopper is a high efficiency circuit. TRUE [other wrong options] [Discuss in forum] FALSE |
Q7 ⇒ For an illumination control circuit it is advisable to use a matched TRIAC-DIAC pair. TRUE [other wrong options] [Discuss in forum] FALSE |
Q8 ⇒ Assertion (A): Chopper always requires forced commutation Reason (R): Morgan chopper uses a saturable reactor. Both A and R correct but R is not correct explanation of A [other wrong options] [Discuss in forum] Both A and R are correct and R is correct explanation of A A is correct but R is wrong A is wrong but R is correct |
Q9 ⇒ A UJT exhibits negative resistance characteristics when Current is more than peak current but less than valley current [other wrong options] [Discuss in forum] Current is less than valley current Current is less than peak current None of the above |
Q10 ⇒ A fully controlled bridge converter can operate in quadrants 1 and 4 [other wrong options] [Discuss in forum] 1 1 and 2 1 and 3 |
Q11 ⇒ Assertion (A): A GTO can be turned on and turned off by gate pulses Reason (R): A GTO can be turned off by negative gate pulse. Both A and R correct but R is not correct explanation of A [other wrong options] [Discuss in forum] Both A and R are correct and R is correct explanation of A A is correct but R is wrong A is wrong but R is correct |
Q12 ⇒ An SCR is triggered at 80° in the positive half cycle, only. The rms anode current is 25 A. If the firing angle is changed to 160°, the rms current is likely to be less than 12.5 A [other wrong options] [Discuss in forum] 25 A 12.5 A less than 25 A |
Q13 ⇒ A single phase full wave regulator feeds a resistive load. The firing angle of thyristors is 90°. The input power factor is 0.707 lagging [other wrong options] [Discuss in forum] 1 0.5 lagging 0.2 lagging |
Q14 ⇒ When a thyristor is conducting, the voltage drop across it increases slightly with increase in load current [other wrong options] [Discuss in forum] is absolutely constant decreases with increase in load current none of the above |
Q15 ⇒ A crowbar circuit is generally needed for protection under fault conditions. TRUE [other wrong options] [Discuss in forum] FALSE |
Q16 ⇒ In a modified series inverter with two inductors and two capacitors, the load current has 2 parallel paths [other wrong options] [Discuss in forum] has only one parallel path can have three parallel paths has four parallel paths |
Q17 ⇒ A dc series motor is coupled to a load whose torque is proportional to speed. It is fed by a single phase ac supply through a full converter. When speed is 500 rpm, firing angle is 45°. It is desired to raise the speed. It will be necessary to decrease the firing angle [other wrong options] [Discuss in forum] increase the firing angle either decrease or increase the firing angle depending on the required speed decrease the load torque |
Q18 ⇒ In disc mounting of SCR SCR is clamped between two disc shaped heat sinks [other wrong options] [Discuss in forum] SCR is clamped on one side of disc shaped heat sink The SCR has low current rating None of the above |
Q19 ⇒ In a full bridge circuit supplying an RLC under damped circuit the waveshapes of output voltage is square but the waveshape of load current is nearly sinusoidal [other wrong options] [Discuss in forum] the waveshapes of output voltage and load current are square the waveshapes of output voltage and load current are sinusoidal none of the above |
Q20 ⇒ Ripple factor RF and form factor FF are related as RF = (FF2 - 1)0.5 [other wrong options] [Discuss in forum] RF = FF2 - 1 RF = FF - 1 RF = (FF - 1)0.5 |
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