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
1. SITH is also known as___________?
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A. None of these

B. Silicon controlled rectifier

C. Filled controlled rectifier

D. Filled controlled diode
2. SCRs are used in series to meet_______________?
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A. low voltage demand

B. low current demand

C. high voltage demand

D. high current demand

3. As the breakdown voltage reached, the DIAC exhibits?
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A. All of these

B. Voltage drop snaps back

C. Negative resistance characteristics

D. Goes into avalanche condition

4. Internal resistance of ideal current source is ?
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A. finite

B. 100 ohms

C. zero

D. infinite
5. Which semiconductor device acts like a diode and two transistor?
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A. Triac

B. SCR

C. Diac

D. UJT

6. For similar carrier and modulating signals, the line current used in CSI is__________?
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A. Identical to line voltage in a VSI

B. Identical to line current in VSI

C. Identical to phase voltage in VSI

D. Identical to phase voltage in CSI

7. Thyristor is nothing but a____________?
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A. Amplifier with higher gain

B. Amplifier with large current gain

C. Controlled switch

D. Controlled transistor

8. The voltage induced in an inductor is represented as,
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A. ratio of the current through it to its inductance.

B. product of its inductance and current through it.

C. ratio of its inductance to the current through it.

D. product of its inductance and rate of change of current through it.
9. n a phase controlled 3 phase ac voltage controller, the harmonic present is__________?
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A. 5th

B. 3rd

C. 2nd

D. 7th

10. Materials used in heat sink should have_____________?
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A. large surface area

B. high thermal conductivity

C. high melting point

D. All of these
11. For swept frequency measurements, the input impedance of the mismatched transmission line would vary with frequency as the electrical length of the transmission line would
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A. Remains same with change in frequency

B. Either A. or B.

C. Decrease with frequency

D. Increase with frequency
12. Which of following devices has highest di/dt and dv/dt capability?
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A. GTO

B. SIT

C. SCR

D. SITH

13. Voltage commutation circuit can be converted into a current commutation by interchanging the positions of____________?
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A. Capacitor and SCR

B. Inductor and capacitor

C. Diode and capacitor

D. Capacitor and load

14. In EMC signal, the source delivers maximum power to the input of transmission line when the transmission line input impedance
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A. Greater than the source resistance

B. Is equal to the source resistance

C. None of these

D. Smaller than the source resistance

15. Which of the following is true about SIT?
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A. SIT is a high power, low frequency device

B. SIT is a high power, high frequency device

C. SIT is a low power, high frequency device

D. SIT is a high power, high voltage device

16. In BJT, the forward biased base emitter junction inject holes from base to emitter, the holes_______?
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A. Contribute to the collector current

B. Result in net current flow component into the base

C. Do not contribute to the collector current

D. Only (a) and (b)

E. Only (b) and (c)

17. During the commutation period in 3 phase converter, overlap time is_____________?
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A. Dependent on the load current

B. Dependent on the voltage

C. Dependent on both the load current and load voltage behind the short circuit current

D. Independent on both the load current and load voltage

18. Under harmonic free load voltages, the 3 phase VSI_____________?
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A. Does not contains fifth harmonic

B. Does not contains third harmonic

C. Does not contains seventh harmonic

D. Does not contains second harmonic
19. Power dissipation in ideal inductor is
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A. Zero

B. Minimum

C. A finite value

D. Maximum

20. Which of following is normally ON device?
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A. TRIAC

B. BJT

C. SIT

D. IGBT

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
41. Double fourier series analysis of PWM is_____________?
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A. Two dimensional functions

B. All of these

C. Three dimensional functions

D. One dimensional functions

42. The maximum firing angle in the half wave controlled regulator is_____________?
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A. 210 degree

B. 180 degree

C. 200 degree

D. 190 degree

43. A single phase full bridge inverter can operated in load commutation mode in case load consist of______?
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A. RLC overdamped.

B. RLC critically damped

C. RL.

D. RLC underdamped.
44. A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. value of n will be___________?
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A. 70

B. 60

C. 90

D. 80
45. The typical value of SCR for modern alternator is____________?
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A. 0.5.

B. 1.2.

C. 1.0.

D. 1.5.

46. If 1 A current flows in a circuit, the number of electrons flowing through this circuit is
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A. 0.625 1019

B. 0.625 10-<sup>19</sup>

C. 1.6 10<sup>19</sup>

D. 1.6 10-<sup>19</sup>

47. If the gate voltage of an SCR is removed, then the_______________?
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A. anode current increases

B. anode current does not decrease at all

C. cathode current increases

D. anode current decreases

48. A PNPN device having two gates is ___________?
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A. Triac

B. Diac

C. BCS

D. SUS

49. Maximum power loss occurs during_________________?
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A. rise time

B. spread time

C. all

D. delay time

50. A single phase ac dc converter is also known as____________?
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A. inverter

B. rectifier

C. regulator

D. chopper