MCQOPTIONS
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MCQOPTIONS
This section includes 204 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The on – state voltage drop of IGBT consists of__________? |
| A. | Drop across the collector junction |
| B. | Drop across the drift region |
| C. | Drop across MOSFET portion |
| D. | All of these |
| Answer» E. | |
| 52. |
The most suited gate pulses given to the AC regulator with R – L load can be in the form of____________? |
| A. | Continuous signal |
| B. | Large isolating pulse transformer |
| C. | A train of pulses |
| D. | None of these |
| Answer» D. None of these | |
| 53. |
The maximum firing angle in the half wave controlled regulator is_____________? |
| A. | 180 degree |
| B. | 190 degree |
| C. | 200 degree |
| D. | 210 degree |
| Answer» E. | |
| 54. |
The maximum di/dt in a SCR is____________? |
| A. | Directly proportional to supply voltage |
| B. | Directly proportional to inductance in the circuit |
| C. | Inversely proportional to supply voltage |
| D. | Both A and B |
| Answer» E. | |
| 55. |
The man made noise sources is / are_____________? |
| A. | Motors |
| B. | Switches, radio interferences |
| C. | Computers, digital electronics |
| D. | All of these |
| Answer» E. | |
| 56. |
The main objective of static power converters is to____________? |
| A. | Obtain an dc output waveform from a dc power supply |
| B. | Obtain an ac output waveform from a dc power supply |
| C. | Obtain an dc output waveform from a dc power supply |
| D. | Obtain an ac output waveform from a ac power supply |
| Answer» C. Obtain an dc output waveform from a dc power supply | |
| 57. |
The latching current of GTO should be of order |
| A. | 100 mA |
| B. | 500 mA |
| C. | 1 A |
| D. | 2 A |
| Answer» C. 1 A | |
| 58. |
The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is___________? |
| A. | Sine wave |
| B. | Square wave |
| C. | Saw – tooth wave |
| D. | Trapezoidal wave |
| Answer» C. Saw – tooth wave | |
| 59. |
The IGBT resulted in higher switching speed and lower energy losses. It can be used for___________? |
| A. | Uninterruptible power supplies |
| B. | Induction heating system |
| C. | Constant voltage and frequency power supplies |
| D. | All of these |
| Answer» E. | |
| 60. |
The Graetz bridge makes excellent use of ______________? |
| A. | Current transformer |
| B. | Potential transformer |
| C. | Power transformer |
| D. | SCR |
| Answer» D. SCR | |
| 61. |
The function of snubber circuit connected across the SCR is to___________? |
| A. | Suppress dV / dt. |
| B. | Increase dV / dt. |
| C. | Decrease dV / dt. |
| D. | Decrease di / dt. |
| Answer» B. Increase dV / dt. | |
| 62. |
The effects of EMI can be reduced by_____________? |
| A. | Suppressing emissions |
| B. | Reducing the efficiency of the coupling path |
| C. | Reducing the susceptibility of the receptor |
| D. | All of these |
| Answer» E. | |
| 63. |
The effects of EMI can be reduced by____________? |
| A. | Suppressing emissions |
| B. | Reducing the efficiency of the coupling path |
| C. | Reducing the susceptibility of the receptor |
| D. | All of these |
| Answer» E. | |
| 64. |
The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative w.r.t cathode are known as_____________________? |
| A. | both as forward characteristics |
| B. | both as reverse characteristics |
| C. | former as forward characteristics and later as reverse characteristics |
| D. | former as reverse characteristics and later as forward characteristics |
| Answer» D. former as reverse characteristics and later as forward characteristics | |
| 65. |
The control method used for PWM dc – dc converter is______________? |
| A. | Voltage mode control |
| B. | Current mode control |
| C. | Hysteric control |
| D. | All of these |
| Answer» E. | |
| 66. |
The conduction losses in IGBT is____________? |
| A. | More than that of MOSFET |
| B. | Lower than that of MOSFET |
| C. | Equal to that of MOSFET |
| D. | Equal to that of BJT |
| Answer» C. Equal to that of MOSFET | |
| 67. |
The carrier which are commonly used in constant – frequency PWM is______________? |
| A. | Sawtooth carrier |
| B. | Inverted sawtooth carrier |
| C. | Triangle carrier |
| D. | All of these |
| Answer» E. | |
| 68. |
The capacitance of reversed bised junction J2 in a thyristor is CJ2 = 20 pF and can be assumed to be independant of the off state voltage. The limiting value of the charging current to turn on the thyristor is 16 mA. What is the critical value of dv/dt? |
| A. | 600 V/µs |
| B. | 800 V/µs |
| C. | 1200 V/µs |
| D. | 1000 V/µs |
| Answer» C. 1200 V/µs | |
| 69. |
The average value of the output voltage in a step – down dc chopper is given by__________? |
| A. | V 0 = V s |
| B. | V 0 = D V s |
| C. | V 0 = V s / D |
| D. | V 0 = V s / ( 1 – D ) |
| Answer» C. V 0 = V s / D | |
| 70. |
The ac voltage controller can be used for ___________? |
| A. | Lighting and heating control |
| B. | On – line transformer tap changing |
| C. | Soft starting |
| D. | All of these |
| Answer» E. | |
| 71. |
The ac output voltage waveform of VSI and AC output current waveform of CSI respectively is composed of___________? |
| A. | High dv / dt, low di / dt |
| B. | Low dv / dt, low di / dt |
| C. | Low dv / dt, high di / dt |
| D. | High dv / dt, high di / dt |
| Answer» E. | |
| 72. |
SCRs are used in series to meet_______________? |
| A. | high current demand |
| B. | low voltage demand |
| C. | low current demand |
| D. | high voltage demand |
| Answer» E. | |
| 73. |
SCR will be turned off when anode current is_______________? |
| A. | < latching current but greater than holding current and gate signal is 0. |
| B. | less than holding current |
| C. | < latching current but greater than holding current and gate signal is present. |
| D. | both (A) and (B). |
| Answer» E. | |
| 74. |
Rise time is defined by the interval when____________? |
| 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 |
| Answer» E. | |
| 75. |
Ripple factor is the ratio of______________________? |
| A. | Rms value of the ac component of load voltage to the dc voltage |
| B. | Average value of the ac component of load voltage to the peak value of voltage |
| C. | Average value of the dc component of load voltage to the ac voltage |
| D. | Peak value of the dc component of load voltage to the ac voltage |
| Answer» B. Average value of the ac component of load voltage to the peak value of voltage | |
| 76. |
Regulator sampling PWM is usually used in___________? |
| A. | High power inverters |
| B. | Rectifiers |
| C. | Low power inverters |
| D. | Only A. and B. |
| Answer» E. | |
| 77. |
Practical way of obtaining static voltage equalization in series connected SCRs is by the use of____________? |
| A. | One resistor across the string |
| B. | Resistors of the same value across each SCR |
| C. | Resistors of different values across each SCR |
| D. | One resistor in series with each SCR |
| Answer» C. Resistors of different values across each SCR | |
| 78. |
Power transistor are type of___________? |
| A. | B.JTs |
| B. | MOSFETs |
| C. | IGBTs |
| D. | All of above |
| Answer» E. | |
| 79. |
Power electronics essentially deals with control of a.c. power at____________? |
| A. | Frequencies above 20 kHz |
| B. | Frequencies above 1000 kHz |
| C. | Frequencies less than 10 Hz |
| D. | 50 Hz frequency |
| Answer» E. | |
| 80. |
ON state voltage drop across SCR lie between the range_____________? |
| A. | 0 – 0.5 V. |
| B. | 0.5 – 1 V. |
| C. | 1 – 1.5 V. |
| D. | 1.5 – 2 V. |
| Answer» D. 1.5 – 2 V. | |
| 81. |
Number of PN junction in an SCR is____________? |
| A. | Two |
| B. | Three |
| C. | Four |
| D. | Five |
| Answer» C. Four | |
| 82. |
n a phase controlled 3 phase ac voltage controller, the harmonic present is__________? |
| A. | 2nd |
| B. | 3rd |
| C. | 5th |
| D. | 7th |
| Answer» B. 3rd | |
| 83. |
MOSFET stands for______________? |
| A. | Metal – oxide semiconductor field effect transistor |
| B. | Molybdenum – oxide semiconductor field effect transistor |
| C. | Metal – oxide silicon field effect transistor |
| D. | Metal – oxide semiconductor field effect transmitter |
| Answer» B. Molybdenum – oxide semiconductor field effect transistor | |
| 84. |
Maximum power loss occurs during_________________? |
| A. | delay time |
| B. | rise time |
| C. | spread time |
| D. | all |
| Answer» C. spread time | |
| 85. |
Maximum di / dt in a SCR is________? |
| 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 |
| Answer» B. Inversely proportional to Vm of supply voltage | |
| 86. |
Materials used in heat sink should have_____________? |
| A. | high thermal conductivity |
| B. | large surface area |
| C. | high melting point |
| D. | All of these |
| Answer» E. | |
| 87. |
LISN is a device used to measure conducted emissions. LISN stands for_____________? |
| A. | Line integrated stabilization network |
| B. | Line impedance stabilization network |
| C. | Line integrated stored network |
| D. | Laser integrated stabilization networking |
| Answer» C. Line integrated stored network | |
| 88. |
Let of a thyristor Vc1, Vc2, Vc3 are forward break over voltage for gate current Ig1, Ig2, Ig3 respectively. Then________________? |
| A. | Vc1 > Vc2 > Vc3 when Ig1 > Ig2 > Ig3. |
| B. | Vc1 > Vc2 > Vc3 when Ig1 < Ig2 < Ig3. |
| C. | Vc1 = Vc2 = Vc3 any value of Ig. |
| D. | Vc1 > Vc2 > Vc3 when Ig1 ≥ Ig2 &Atil |
| Answer» C. Vc1 = Vc2 = Vc3 any value of Ig. | |
| 89. |
Leakage current flows through the thyristor in_________? |
| A. | forward blocking mode |
| B. | reverse blocking mode |
| C. | both forward and reverse blocking mode |
| D. | forward conduction mode |
| Answer» D. forward conduction mode | |
| 90. |
In the SPWM, the modulating signal is___________? |
| A. | Square |
| B. | Sinusoidal |
| C. | Triangular |
| D. | Saw – tooth |
| Answer» C. Triangular | |
| 91. |
In the operation and control of both naturally commutated and forced commutated SCR base converter, commutation plays an important role. The converters is / are ___________? |
| A. | AC – DC |
| B. | DC – DC |
| C. | DC – AC |
| D. | All of these |
| Answer» E. | |
| 92. |
In single phase VSI, the harmonic which is not present is____________? |
| A. | 2nd |
| B. | 3rd |
| C. | 5th |
| D. | 7th |
| Answer» B. 3rd | |
| 93. |
In reverse blocking mode of a thyristor______? |
| A. | junction J2 is in reverse bias and J1, J3 is in forward bias |
| B. | junction J3 is in forward bias and J1, J2 in reverse bias |
| C. | junction J1, J3 is in reverse bias and J2 is in forward bias |
| D. | junction J1 and J2 is in forward bias and J3 is in reverse bias |
| Answer» D. junction J1 and J2 is in forward bias and J3 is in reverse bias | |
| 94. |
In rectifiers, load current flow is_________? |
| A. | Unidirectional |
| B. | Bidirectional |
| C. | Either (a) or (b) |
| D. | Non directional |
| Answer» B. Bidirectional | |
| 95. |
In radiative coupling, the emitter radiation field_____________? |
| A. | Decays as 1 / R, where R is the separation distance between the emitter and the receptor |
| B. | Decays as R, where R is the separation distance between the emitter and the receptor |
| C. | Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor |
| D. | Decays as 2R, where R is the separation distance between the emitter and the receptor |
| Answer» B. Decays as R, where R is the separation distance between the emitter and the receptor | |
| 96. |
In forward blocking mode of a thyristor________? |
| A. | junction J2 is in reverse bias and J1, J3 is in forward bias |
| B. | junction J3 is in forward bias and J1, J2 is in reverse bias |
| C. | Junction J1, J3 is in reverse bias and J2 is in forward bias |
| D. | Junction J1 and J2 is in forward bias and J3 is in reverse bias |
| Answer» B. junction J3 is in forward bias and J1, J2 is in reverse bias | |
| 97. |
In dual converters________________? |
| 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 |
| Answer» B. Both rectifiers provide negative current to the load | |
| 98. |
In current commutated DC-DC choppers, the voltage spike appears across the load when_____________? |
| A. | Voltage across the commutating inductances collapses |
| B. | The capacitance voltage adds to the supply voltage |
| C. | Both A. and B. |
| D. | None of these |
| Answer» D. None of these | |
| 99. |
In constant frequency PWM, at perturbation the amplitude of the sinusoidal component is a___________? |
| A. | Linear function |
| B. | Non linear function |
| C. | Constant function |
| D. | None of these |
| Answer» E. | |
| 100. |
In commutation PAC stands for_______? |
| A. | Permanent angle converter |
| B. | Phase angle converter |
| C. | Phase angle commutation |
| D. | Phase and commutation |
| Answer» C. Phase angle commutation | |