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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. |
Q21 ⇒ The amount of dielectric heating is inversely proportional to frequency. FALSE [other wrong options] [Discuss in forum] TRUE |
Q22 ⇒ Thyristors are suitable for dc circuit breakers but not for ac circuit breakers. FALSE [other wrong options] [Discuss in forum] TRUE |
Q23 ⇒ In single phase half wave regulator, the average current over one full cycle is always negative [other wrong options] [Discuss in forum] is always positive may be positive or negative may be negative |
Q24 ⇒ In a multiphase chopper, all choppers operate together. FALSE [other wrong options] [Discuss in forum] TRUE |
Q25 ⇒ Assertion (A): A TRIAC is a bidirectional SCR. Reason (R): A TRIAC is a four layers 3 terminal device and can conduct in both directions. Both A and R are correct and R is correct explanation of A [other wrong options] [Discuss in forum] Both A and R correct but R is not correct explanation of A A is correct but R is wrong A is wrong but R is correct |
Q26 ⇒ A DIAC has two terminals, anode and cathode. FALSE [other wrong options] [Discuss in forum] TRUE |
Q27 ⇒ A thyristor is reverse biased. A positive gate pulse is applied. The thyristor will not turn on [other wrong options] [Discuss in forum] will be turned on may or may not turn on will turn on after sometime |
Q28 ⇒ In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then both the average and rms thyristor currents will be less than 20 A [other wrong options] [Discuss in forum] average thyristor current will be less than 20 A but rms thyristor current will be more than 20 A both the average and rms thyristor currents will be more than 20 A rms thyristor current will be 20 A and average thyristor current will be 10 A |
Q29 ⇒ In an SCR, the anode current is controlled by external circuit only [other wrong options] [Discuss in forum] gate current only both gate current and external circuit none of the above |
Q30 ⇒ During forward blocking state of SCR, the voltage and current respectively are high and low [other wrong options] [Discuss in forum] high and high low and low low and high |
Q31 ⇒ A cycloconverter cannot give a frequency higher than input frequency. FALSE [other wrong options] [Discuss in forum] TRUE |
Q32 ⇒ Present day HVDC converters are all 12 pulse converters [other wrong options] [Discuss in forum] 3 pulse converters 6 pulse converters either 6 pulse or 12 converters |
Q33 ⇒ In a single phase full wave ac regulator, the firing angles in the two half cycles are always equal [other wrong options] [Discuss in forum] are sometimes equal are never equal may be equal or unequal |
Q34 ⇒ A thyristor has maximum allowable junction temperature of 110° C and the ambient temperature is 40°C, If the maximum internal power dissipation is 50 W, the thermal resistance is 1.4° C/W [other wrong options] [Discuss in forum] 2° C/W 0.7°C/W 2.2° C/W |
Q35 ⇒ A high frequency series inverter consists of a number of series inverters in parallel [other wrong options] [Discuss in forum] a number of series inverters in series a number of parallel inverters in parallel a number of parallel inverters in series |
Q36 ⇒ Natural commutation can be used in : AC circuits only [other wrong options] [Discuss in forum] DC circuits only both AC and DC circuits none of the above |
Q37 ⇒ Assertion (A): The turn on time of SCR is about 1 to 4 ms. Reason (R): The turn off time of SCR is about 10 to 300 ms. 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 |
Q38 ⇒ In a 3 phase semiconverter, the freewheeling diode comes into operation only if firing angle is more than 60° [other wrong options] [Discuss in forum] is zero is 60° is more than 90° |
Q39 ⇒ In pulse width modulation of chopper T is kept constant and Ton is varied [other wrong options] [Discuss in forum] Ton is kept constant T is varied both T and Ton are varied either T or Ton is varied |
Q40 ⇒ Which of the following devices exhibit negative resistance characteristics? Both UJT and PUT [other wrong options] [Discuss in forum] UJT PUT UJT, PUT and SBS |
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