electrical engineering MCQs – Page 2

Practise multiple-choice questions from electrical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
21. In forward blocking mode of a thyristor________?
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A. Junction J1, J3 is in reverse bias and J2 is in forward bias.

B. junction J2 is in reverse bias and J1, J3 is in forward bias.

C. Junction J1 and J2 is in forward bias and J3 is in reverse bias.

D. junction J3 is in forward bias and J1, J2 is in reverse bias.

22. For series connected SCRaEURs dynamic equalising circuit consists of___________?
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A. Series R and diode with C across R

B. R and C in series but with diode across R

C. R and C in series but with diode across C

D. Series R and diode with C across R

23. During which time maximum conduction spreading take place in the thyristor during turn ON?
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A. Same for every case

B. Rise time

C. Spread time

D. Delay time

24. The unit of resistivity is
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A. ? / m.

B. ? / metre.

C. ?.

D. ? metre.
25. What may happen high dV / dt____________?
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A. Unwanted turn ON

B. Breakdown of J2 junction

C. Both A and B

D. Anyone of these

26. An SCR has half cycle surge current rating of 3000 A for 50 Hz supply. One cycle surge current will be_____?
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A. 1500 A.

B. 4242.64 A.

C. 2121.32 A.

D. 6000 A.

27. Delay time is defined by the interval when_______________?
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A. all of these

B. gate current increases from 90 % to 100 % of its final value

C. anode current reaches 10 % from forward leakage current

D. anode voltage drops from 100 % to 90 % of its actual value

28. Dynamic equalizing circuit is used for________________?
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A. equal division of voltage across each thyristor in parallel

B. equal division of current through each thyristor in parallel

C. equal division of current through each thyristor in series

D. equal division of voltage across each thyristor
29. 4 thyristors rated 200 V in series. The operating voltage of the string is 600 V. Derating factor of the string is_____________________?
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A. 0.25

B. 0.75

C. 0.7

D. 0.2

30. Maximum di / dt in a SCR is________?
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A. Directly proportional to Vm of supply voltage

B. Inversely proportional to Vm of supply voltage

C. Inversely proportional to L in the circuit

D. Both A and C

31. Gate circuit or triggering circuit of a thyristor is
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A. high power circuit.

B. magnetic circuit.

C. may be low power or high power circuit

D. lower power circuit.
32. Switching frequency of SITH is____________?
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A. 60 KHz

B. 10 KHz

C. 5 KHz

D. 100 KHz
33. In a 3 phase bridge rectifier the ripple frequency is _____________?
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A. Three times the input frequency

B. Equal to the input frequency

C. Twice the input frequency

D. Six times the input frequency
34. How many coulombs of charge flow through a circuit carrying a current of 10 A in 1 minute?
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A. 1200

B. 60

C. 10

D. 600
35. A power semiconductor may undergo damage due to____________?
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A. Low dv/dt

B. High dv/dt

C. Low di/dt

D. High di/dt
36. What is the advantage of HRC fuses over Rewirable fuses?
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A. High rupturing capacity

B. No ageing effect

C. All of the above

D. High speed operation

37. AC power in a load can be controlled by using____________?
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A. Two SCRs in series

B. Three SCRs in series

C. Four SCRs in series

D. Two SCRs in parallel opposition
38. Under normal operating condition voltage clamping device offers impedance of_________?
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A. zero value.

B. low value.

C. moderate value.

D. high value.
39. Leakage current flows through the thyristor in_________?
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A. forward blocking mode

B. reverse blocking mode

C. both forward and reverse blocking mode

D. forward conduction mode

40. Rise time is defined by the interval when____________?
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A. gate current rises from 90 % to 100 % of it final value

B. anode voltage drops from 90 % to 10 % of its initial value

C. anode current rises 10 % to 90 % of its final value

D. both B and C