MCQOPTIONS
Saved Bookmarks
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.
| 101. |
In BJT, the forward biased base emitter junction inject holes from base to emitter, the holes_______? |
| A. | Do not contribute to the collector current |
| B. | Result in net current flow component into the base |
| C. | Contribute to the collector current |
| D. | Only (a) and (b) |
| E. | Only (b) and (c) |
| Answer» E. Only (b) and (c) | |
| 102. |
In BJT, switching losses occurs___________? |
| A. | Only at turn – on |
| B. | Only at turn – off |
| C. | Both at turn on and off |
| D. | None of these |
| Answer» D. None of these | |
| 103. |
In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output |
| A. | Zero |
| B. | Switches between – 1 / 2 and + 1 / 2 |
| C. | Switches between – 1 and + 1 |
| D. | Switches between 0 and + 1 |
| Answer» C. Switches between – 1 and + 1 | |
| 104. |
In ac – dc conversion, when the switch is closed then the sum of voltages around the loop is____________? |
| A. | Zero |
| B. | Non zero |
| C. | Equal to the sum of voltage when switch is open |
| D. | Twice of the voltage when switch is open |
| Answer» C. Equal to the sum of voltage when switch is open | |
| 105. |
In a three phase voltage source inverters____________? |
| 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 |
| Answer» E. | |
| 106. |
In a three phase converter, the number of notches per cycle is____________? |
| A. | One |
| B. | Three |
| C. | Six |
| D. | Nine |
| Answer» D. Nine | |
| 107. |
In a square – wave operation of 3 phase CSIs, the power values are on for___________? |
| A. | 60 degree |
| B. | 90 degree |
| C. | 120 degree |
| D. | 150 degree |
| Answer» D. 150 degree | |
| 108. |
In a single phase full wave rectifier, during blocking state the pea inverse voltage of diode is______________? |
| A. | V m |
| B. | 2 V m |
| C. | V m / 2 |
| D. | 4 V m |
| Answer» C. V m / 2 | |
| 109. |
In a silicon controlled rectifier, the load is connected___________? |
| A. | Across anode |
| B. | In series with anode |
| C. | Across cathode |
| D. | In series with cathode |
| Answer» C. Across cathode | |
| 110. |
In a push – pull converter, the filter capacitor can be obtained as____________? |
| A. | Cmin = V / ( Vr L f2 ) |
| B. | Cmin= ( 1 – D ) V / ( Vr L f2 ) |
| C. | Cmin= ( 1 – 2 D ) V / 32 ( Vr L f2 ) |
| D. | Cmin= ( 1 – 2 D ) V / 42 ( Vr L f2 ) |
| Answer» D. Cmin= ( 1 – 2 D ) V / 42 ( Vr L f2 ) | |
| 111. |
In a lossless inverter, the average power absorbed in one period by the load must be__________? |
| A. | Equal to the average power supplied by the dc source |
| B. | Greater than the average power supplied by the dc source |
| C. | Lesser than the average power supplied by the dc source |
| D. | Equal to the average power supplied by the ac source |
| Answer» B. Greater than the average power supplied by the dc source | |
| 112. |
In a load commutated DC – DC chopper, the capacitor has a_____________? |
| A. | Symmetric triangular voltage across itself |
| B. | Symmetric rectangular voltage across itself |
| C. | Symmetric trapezoidal voltage across itself |
| D. | Symmetric sinusoidal voltage across itself |
| Answer» D. Symmetric sinusoidal voltage across itself | |
| 113. |
In a full wave rectifier, the rectification ratio is approximately equal to____________? |
| A. | 61% |
| B. | 71% |
| C. | 81% |
| D. | 91% |
| Answer» D. 91% | |
| 114. |
In a full bridge VSI, in order to avoid the short circuit across the DC bus and the undefined AC output voltage condition, the modulating technique should ensure that___________? |
| A. | Top switch of each leg is on at any instant |
| B. | Bottom switch of each leg is on at any instant |
| C. | Either A. or B. |
| D. | None of these |
| Answer» D. None of these | |
| 115. |
In a flyback converter, the inductor of the buck-boost converter has been replaced by a_____________? |
| A. | Flyback capacitor |
| B. | Flyback resistor |
| C. | Flyback transformer |
| D. | Flyback transistor |
| Answer» D. Flyback transistor | |
| 116. |
In a 3 phase VSI SPWM to use a single carrier signal and preserve the features of PWM technique, the normalized carrier frequency should be____________? |
| A. | Multiple of two |
| B. | Odd multiple of three |
| C. | Odd multiple of five |
| D. | Odd multiple of seven |
| Answer» C. Odd multiple of five | |
| 117. |
In a 3 phase VSI out of eight valid states, the number of valid states that produce zero ac line voltages is/are_________? |
| A. | One |
| B. | two |
| C. | Three |
| D. | Four |
| Answer» C. Three | |
| 118. |
In a 3 phase half wave rectifier, when firing angle is less than 90 degree, then the average dc output voltage becomes__________________? |
| A. | Positive |
| B. | Negative |
| C. | Zero |
| D. | None of these |
| Answer» B. Negative | |
| 119. |
In a 3 phase bridge rectifier the ripple frequency is _____________? |
| A. | Equal to the input frequency |
| B. | Twice the input frequency |
| C. | Three times the input frequency |
| D. | Six times the input frequency |
| Answer» E. | |
| 120. |
IGBT stands for___________? |
| A. | Insulated gate bipolar transistor |
| B. | Insulated gate bidirectional transistor |
| C. | Inductive gate bipolar transistor |
| D. | Inductive gate bidirectional transistor |
| Answer» B. Insulated gate bidirectional transistor | |
| 121. |
IGBT combines the advantages of_____________? |
| A. | BJTs and SITs |
| B. | BJTs and MOSFETs |
| C. | SITs and MOSFETs |
| D. | None of these |
| Answer» C. SITs and MOSFETs | |
| 122. |
If the gate voltage of an SCR is removed, then the_______________? |
| A. | anode current decreases |
| B. | anode current does not decrease at all |
| C. | anode current increases |
| D. | cathode current increases |
| Answer» C. anode current increases | |
| 123. |
If the firing angle becomes negative, then the rectifier begins to work as_______________? |
| A. | A rectifier |
| B. | An inverter |
| C. | A chopper |
| D. | A regulator |
| Answer» C. A chopper | |
| 124. |
If the anode current is 800 A, then the amount of current required to turn off the GTO is about____________? |
| A. | 20 A |
| B. | 200 A |
| C. | 600 A |
| D. | 400 A |
| Answer» C. 600 A | |
| 125. |
If holding current of a thyristor is 2 mA then latching current should be_____? |
| A. | 0.01 A. |
| B. | 0.002 A. |
| C. | 0.009 A. |
| D. | 0.004 A. |
| Answer» E. | |
| 126. |
If energy is taken from the AC side of the inverter and sends it back into the DC side, then it is known as___________? |
| A. | Motoring mode operation |
| B. | Braking mode operation |
| C. | Regenerative mode operation |
| D. | None of these |
| Answer» D. None of these | |
| 127. |
If all the SCR’s of 3 phase PAC is replaced by diodes, they would be triggered_____________? |
| A. | 120 degree after the zero crossing of the corresponding line voltages |
| B. | 60 degree after the zero crossing of the corresponding line voltages |
| C. | 120 degree before the zero crossing of the corresponding line voltages |
| D. | 60 degree before the zero crossing of the corresponding line voltages |
| Answer» C. 120 degree before the zero crossing of the corresponding line voltages | |
| 128. |
If a shunt motor is started with its field winding open then___________? |
| A. | It will rotate at the same speed as that with its field winding closed |
| B. | It will rotate at less speed as that with its field winding closed |
| C. | It will rotate at dangerously high speed |
| D. | None of these |
| Answer» D. None of these | |
| 129. |
If a shunt motor is started with its field winding open then? |
| A. | It will rotate at the same speed as that with its field winding closed |
| B. | It will rotate at less speed as that with its field winding closed |
| C. | It will rotate at dangerously high speed |
| D. | None of these |
| Answer» D. None of these | |
| 130. |
How can we protect SCR from thermal conditions _____________? |
| A. | Use of snubber circuit |
| B. | Using heat sink |
| C. | Using CB and fuse |
| D. | Using equalizing circuit |
| Answer» C. Using CB and fuse | |
| 131. |
Harmonics in 3 phase inverters can be reduced by using___________? |
| A. | Passive filter |
| B. | Active filter |
| C. | Both passive and active filters |
| D. | None of these |
| Answer» D. None of these | |
| 132. |
Gate circuit or triggering circuit of a thyristor is |
| A. | lower power circuit |
| B. | high power circuit |
| C. | magnetic circuit |
| D. | may be low power or high power circuit |
| Answer» B. high power circuit | |
| 133. |
Form factor of a rectifier is the ratio of ______________? |
| A. | Root mean square value of voltage and current to its peak value |
| B. | Root mean square value of voltage and current to its average value |
| C. | Average value of current and voltage to its root mean square value |
| D. | Peak value of current and voltage to its root mean square value |
| Answer» C. Average value of current and voltage to its root mean square value | |
| 134. |
For similar carrier and modulating signals, the line current used in CSI is__________? |
| 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 |
| Answer» B. Identical to line current in VSI | |
| 135. |
For similar carrier and modulating signals, the line current used in CSI is_____________? |
| 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 |
| Answer» B. Identical to line current in VSI | |
| 136. |
For series connected SCR’s dynamic equalising circuit consists of___________? |
| A. | R and C in series but with diode across C |
| B. | R and C in series but with diode across R |
| C. | Series R and diode with C across R |
| D. | Series R and diode with C across R |
| Answer» C. Series R and diode with C across R | |
| 137. |
For power output higher than 15 kW, the suitable rectifier is________________? |
| A. | Single phase |
| B. | 3 phase |
| C. | Poly phase |
| D. | Only (b) and (c) |
| Answer» E. | |
| 138. |
For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are connected to the three legs of the converter via______________? |
| A. | Three inductances |
| B. | Three capacitances |
| C. | Three resistance |
| D. | Three transistors |
| Answer» B. Three capacitances | |
| 139. |
For bidirectional operation of converters____________? |
| A. | A parallel combination of controllable switch and a diode is used |
| B. | A parallel combination of controllable switch and capacitor is used |
| C. | A series combination of controllable switch and a diode is used |
| D. | A series combination of controllable switch and a capacitor is used |
| Answer» B. A parallel combination of controllable switch and capacitor is used | |
| 140. |
For an SCR gate – cathode characteristic is a straight line of 130. For triggered source volume of 15 V and allowable gate power dissipation of 0.5 W compute the gate source resistance_____? |
| A. | 111.9 Ω. |
| B. | 11.19 Ω. |
| C. | 108 Ω. |
| D. | 115 Ω |
| Answer» B. 11.19 Ω. | |
| 141. |
Example of a voltage clamping device______________? |
| A. | fast acting fuse |
| B. | snubber circuit |
| C. | metal oxide varistor |
| D. | aluminium block |
| Answer» D. aluminium block | |
| 142. |
Electrical power output in a d.c. generator is equal to____________? |
| A. | Electrical power developed in armature – copper losses |
| B. | Mechanical power input – iron and friction losses |
| C. | Electrical power developed in armature – iron and copper losses |
| D. | Mechanical power input – iron and friction losses – copper losses |
| Answer» E. | |
| 143. |
Electrical power output in a D.C. generator is equal to_____________? |
| A. | Electrical power developed in armature – copper losses |
| B. | Mechanical power input – iron and friction losses |
| C. | Electrical power developed in armature – iron and copper losses |
| D. | Mechanical power input – iron and friction losses – copper losses |
| Answer» E. | |
| 144. |
Dynamic equalising circuit is useful____________? |
| A. | To limit di / dt of SCR |
| B. | To limit dV / dt of SCR |
| C. | For voltage equalisation |
| D. | Both B and C |
| Answer» E. | |
| 145. |
Dynamic equalizing circuit is used for________________? |
| A. | equal division of voltage across each thyristor |
| B. | equal division of current through each thyristor in parallel |
| C. | equal division of voltage across each thyristor in parallel |
| D. | equal division of current through each thyristor in series |
| Answer» B. equal division of current through each thyristor in parallel | |
| 146. |
During which time maximum conduction spreading take place in the thyristor during turn ON? |
| A. | Delay time |
| B. | Spread time |
| C. | Rise time |
| D. | Same for every case |
| Answer» C. Rise time | |
| 147. |
During the commutation period in 3 phase converter, overlap time is____________? |
| 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 |
| Answer» D. Independent on both the load current and load voltage | |
| 148. |
During the commutation period in 3 phase converter, overlap time is_____________? |
| 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 |
| Answer» D. Independent on both the load current and load voltage | |
| 149. |
During reverse recovery time__________________? |
| A. | charge carrier of junction J2 recombined |
| B. | charge carrier of junction J1 is swept out |
| C. | charge carrier of junction J3 is swept out |
| D. | both B and C |
| Answer» E. | |
| 150. |
During gate recovery time_____________? |
| A. | charge carriers of J2 junction recombined |
| B. | charge carriers of J2 junction is swept out |
| C. | charge carrier of J1 junction removed |
| D. | charge carriers of J3 junction is removed |
| Answer» B. charge carriers of J2 junction is swept out | |