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
51. If a shunt motor is started with its field winding open then?
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A. It will rotate at less speed as that with its field winding closed

B. It will rotate at dangerously high speed

C. It will rotate at the same speed as that with its field winding closed

D. None of these

52. The resistance of a conductor of diameter d and length l is R ?. If the diameter of the conductor is halved and its length is doubled, the resistance will be
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A. 2R ?

B. 8R ?

C. 4R ?

D. R ?

53. The turn-on time of an SCR with inductive load is 20 s. The puls train frequency is 2.5 KHz with a mark/space ratio of 1/10, then SCR will___________?
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A. Turn on

B. Turn on if pulse frequency us increased to two times

C. Not turn on

D. Turn on if inductance is removed

54. A Triac is a ______________?
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A. 3 terminal bilateral switch

B. 2 terminal bilateral switch

C. 3 terminal bidirectional switch

D. 2 terminal switch

55. In reverse blocking mode of a thyristor______?
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A. junction J1 and J2 is in forward bias and J3 is in reverse bias.

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

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

D. junction J1, J3 is in reverse bias and J2 is in forward bias.
56. A step up chopper has input voltage 110 V and output voltage 150 V. The value of duty cycle is_____?
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A. 0.27

B. 0.32

C. 0.67

D. 0.45

57. Capacitor does not allow the sudden change of ?
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A. current

B. power

C. voltage

D. None of the above

58. In single phase VSI, the harmonic which is not present is____________?
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A. 7th

B. 3rd

C. 2nd

D. 5th

59. Very large values of modulation index (greater than 3.24) lead to___________?
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A. Trapezoidal AC output voltage

B. Sine AC output voltage

C. Square AC output voltage

D. Triangular AC output voltage

60. The latching current of GTO should be of order
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A. 2:00 AM

B. 500 mA

C. 1:00 AM

D. 100 mA

61. IGBT combines the advantages of_____________?
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A. None of these

B. SITs and MOSFETs

C. BJTs and MOSFETs

D. BJTs and SITs

62. In a full wave rectifier, the rectification ratio is approximately equal to____________?
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A. 81%

B. 91%

C. 71%

D. 61%

63. The carrier which are commonly used in constant frequency PWM is______________?
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A. Triangle carrier

B. All of these

C. Inverted sawtooth carrier

D. Sawtooth carrier

64. For power output higher than 15 kW, the suitable rectifier is________________?
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A. Single phase

B. Only (b) and (c)

C. Poly phase

D. 3 phase

65. Which triggering is the most reliable____________?
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A. Gate triggering

B. Thermal triggering

C. Forward voltage triggering

D. dV / dt triggering

66. A single phase full bridge inverter can operate in load commutation mode in case load consists of____________?
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A. RLC underdamped.

B. RLC critically damped.

C. RL.

D. RLC overdamped.

67. The power MOSFET device is a___________?
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A. Voltage controlled bipolar device

B. Voltage controlled unipolar device

C. Current controlled unipolar device

D. Current controlled bipolar device

68. CB used for over current protection of thyristor operates when the fault current is__________?
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A. of long period

B. of short duration

C. both (A) and (B)

D. neither (A) nor (B)

69. Snubber circuit is used with SCR_________________?
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A. in parallel

B. either series or parallel

C. anti parallel

D. in series

70. If P is the power of a star connected system then what will be power of an equivalent delta connected system?
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A. 3P

B. None of the above

C. P

D. P/3

71. The power demand can be estimated approximately by___________?
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A. Statistical method

B. Economic parameters

C. Mathematical method

D. Load survey method

72. Which of the following quantities consists of SI unit as WATT ?
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A. Force

B. Charge

C. Current

D. Power
73. A thyristor can termed as__________?
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A. AC switch

B. DC switch

C. Both a and B

D. Square wave switch

74. After proper turn on of thyristor____________?
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A. gate signal is always present

B. gate signal should present but can be removed

C. none of the above.

D. gate signal must be removed
75. A capacitive load in voltage source inverters generates ________________?
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A. Small current spikes and can be reduced by using an inductive filter

B. Small current spikes and can be increased by using an inductive filter

C. Large current spikes and can be reduced by using an inductive filter

D. Large current spikes and can be increased by using an inductive filter

76. To meet high current demand we use SCRs in______________?
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A. series connection.

B. parallel connection.

C. anti parallel connection.

D. both B and C.

77. A power MOSFET has three terminals called___________?
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A. Collector, emitter and base

B. Drain, source and gate

C. Drain, source and base

D. Collector, emitter and gate

78. Any electrical signal present in a circuit other than the desired signal is known as______________?
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A. Interference

B. Distortion

C. All of these

D. Noise
79. 60 thyrsistors are connected in series and parallel to form a 10 KV and 5.5 KA switch. Each thyristor is rated for 1.2 KV, 1 KA. The no. of parallel path are 6. The efficiency of the switch is______________________?
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A. 83.30%

B. 76.3 %

C. 90.90%

D. 91.60%

80. Under over voltage condition impedance offered by the voltage clamping device is__________?
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A. moderate

B. High

C. low

D. infinity

81. In a load commutated DC DC chopper, the capacitor has a_____________?
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A. Symmetric sinusoidal voltage across itself

B. Symmetric triangular voltage across itself

C. Symmetric rectangular voltage across itself

D. Symmetric trapezoidal voltage across itself
82. Anode of an operational SCR is _______________?
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A. Always positive w.r.t cathode

B. Always negative w.r.t cathode

C. Always negative w.r.t anode

D. Always positive w.r.t anode

83. The average value of the output voltage in a step down dc chopper is given by__________?
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A. V 0 = V s

B. V 0 = V s / ( 1 D )

C. V 0 = V s / D

D. V 0 = D V s
84. In dual converters________________?
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A. Both rectifiers provides positive current to the load

B. Both rectifiers provide negative current to the load

C. One rectifiers provide positive current to the load and the other negative current

D. One rectifier provide positive current to the source and the other negative current to the load

85. The control method used for PWM dc dc converter is______________?
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A. Current mode control

B. Hysteric control

C. Voltage mode control

D. All of these
86. Which statement is true ?
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A. Reverse recovery time ( trr ) > gate recovery time (tgr)

B. All of these

C. Circuit turn OFF time > device turn OFF time ( tq )

D. Device turn OFF time ( tq ) > reverse recover time (trr)

87. The main objective of static power converters is to____________?
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A. Obtain an dc output waveform from a dc power supply

B. Obtain an dc output waveform from a dc power supply

C. Obtain an ac output waveform from a ac power suppl

D. Obtain an ac output waveform from a dc power supply
88. In a 3 phase CSI, if the required line output voltages are balanced and 120 degree out of phase, then the chopping angles are used to eliminate only the harmonics at frequencies
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A. All of these

B. 5

C. 7

D. 11

89. Which quantity should be measured by the voltmeter ?
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A. Power

B. Current

C. Voltage

D. Speed

90. In a three phase voltage source inverters____________?
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A. Only amplitude of voltage is controllable

B. Only phase is controllable

C. Both amplitude and phase is controllable

D. Amplitude, phase and frequency of voltages should always be controllable
91. The effects of EMI can be reduced by____________?
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A. Suppressing emissions

B. All of these

C. Reducing the susceptibility of the receptor

D. Reducing the efficiency of the coupling path

92. Typical range of thyristor turn OFF time is______________?
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A. 3 50 s

B. 3 10 s

C. 3 500 s

D. 3 100 s
93. Which of the followings is/are active element?
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A. Voltage source

B. None of these.

C. Both

D. Current source

94. The sum of all phase current in a star connected primary winding with no neutral connection is equal to___________?
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A. Three times the line current

B. Three times the phase current

C. Phase current

D. Zero at all times
95. The typical time of rising time lies between______________?
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A. 10 20 s

B. 90 100 s

C. 1 4 s

D. 40 60 s

96. Instantaneous power in inductor is proportional to the
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A. square of instantaneous current.

B. product of the instantaneous current and rate of change of current.

C. emperature of the inductor.

D. square of the rate of change of current.

97. Which of the following is used in SCR to protect from high dV / dt__________________?
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A. Fuse

B. Snubber circuit

C. Circuit breaker

D. Equalizing circuit

98. What is used to protect the SCR from over current ________________?
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A. Voltage clamping device.

B. CB and fuse.

C. Snubber circuit.

D. Heat sink.

99. Advantages of HVDC transmission over AC system is / are____________?
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A. Reversal of power can be controlled by firing angle

B. All of these

C. They can link two AC system operating unsynchronized

D. Very good dynamic behavior

100. How can we protect SCR from thermal conditions _____________?
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A. Using equalizing circuit

B. Use of snubber circuit.

C. Using heat sink.

D. Using CB and fuse.