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MCQOPTIONS
This section includes 9294 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 6801. |
A static induction thyristor |
| A. | is a majority carrier device |
| B. | is a minority carrier device |
| C. | either a majority carrier or minority carrier device |
| D. | has a total number of 2 leads |
| Answer» C. either a majority carrier or minority carrier device | |
| 6802. |
A single phase step up cycloconverter changes 50 Hz to 100 Hz. Then one half wave of input will give rise to |
| A. | one half wave of output |
| B. | one full wave of output |
| C. | two full waves of output |
| D. | either (b) or (c) |
| Answer» C. two full waves of output | |
| 6803. |
Which of these triggering methods for series connected SCRs use LASCR in the gate circuit? |
| A. | Resistance triggering |
| B. | Simultaneous triggering |
| C. | Sequential triggering |
| D. | Optical triggering |
| Answer» E. | |
| 6804. |
A 3 phase ac regulator uses |
| A. | 3 thyristors |
| B. | 6 thyristors |
| C. | 9 thyristors |
| D. | 12 thyristors |
| Answer» C. 9 thyristors | |
| 6805. |
A capacitor C farads is charged to a voltage V. It discharges through a thyristor, a diode and an inductance L. The peak current in the circuit is |
| A. | VCL |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-3.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-330-1.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-330-2.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-330-1.png"> | |
| 6806. |
In a full bridge inverter fed by a battery of voltage V, the rms value of fundamental component of output voltage is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-310-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-310-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-310-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-310-4.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-310-3.png"> | |
| 6807. |
In a single phase full wave regulator feeding a resistive load, the average current over one full cycle |
| A. | is always zero |
| B. | cannot be zero |
| C. | may be sometimes zero |
| D. | is always positive |
| Answer» B. cannot be zero | |
| 6808. |
Which chopper circuit uses saturable reactor? |
| A. | Auxiliary commutated |
| B. | Jones chopper |
| C. | Morgan chopper |
| D. | Load commutated |
| Answer» D. Load commutated | |
| 6809. |
Thyristors connected in series need static and dynamic stabilizing circuits. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6810. |
In a controlled rectifier a freewheeling diode is necessary if the load is |
| A. | inductive |
| B. | resistive |
| C. | capacitive |
| D. | any of the above |
| Answer» B. resistive | |
| 6811. |
For an illumination control circuit it is advisable to use a matched TRIAC-DIAC pair. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6812. |
A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the starting torque is 100 N-m. At 25 Hz, the starting torque |
| A. | will be less than 100 N-m |
| B. | will be more than 100 N-m |
| C. | may be more or less than 100 N-m depending on motor parameters |
| D. | very small |
| Answer» C. may be more or less than 100 N-m depending on motor parameters | |
| 6813. |
In auxiliary commutated chopper fed by voltage V and having L and C commutating elements, the peak value of capacitor current is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-91-4.png"> | |
| 6814. |
In a single phase semiconverter feeding a highly inductive load, the load current is |
| A. | sinusoidal |
| B. | nearly constant |
| C. | absolutely constant |
| D. | rectangular |
| Answer» C. absolutely constant | |
| 6815. |
In a cycloconverter it is possible to vary |
| A. | only output frequency |
| B. | only output voltage |
| C. | both output voltage and frequency but not simultaneously |
| D. | both output voltage and output frequency simultaneously |
| Answer» E. | |
| 6816. |
Which of these devices is used in relaxation oscillator? |
| A. | UJT |
| B. | SCR |
| C. | DIAC |
| D. | TRIAC |
| Answer» B. SCR | |
| 6817. |
A single phase half wave converter is feeding-a resistor load. The input voltage is v = Vm sin t. If firing angle is zero, the output dc voltage Vdc and output rms voltage Vrms respectively |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-229-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-229-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-229-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-229-4.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-229-3.png"> | |
| 6818. |
In a three phase to single phase full wave bridge cycloconverter, the number of thyristors is |
| A. | 36 |
| B. | 18 |
| C. | 12 |
| D. | 8 |
| Answer» D. 8 | |
| 6819. |
If 0.5 T is the time period of oscillations and Toff is the time between turn off of one thyristor and turn on of second thyristor, the frequency of output f of a series inverter is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-294-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-294-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-294-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-294-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/278-294-2.png"> | |
| 6820. |
A thyristor circuit is feeding an R-L load. The turn on time can be reduced by |
| A. | decreasing R |
| B. | decreasing L |
| C. | increasing L |
| D. | decreasing R and L together |
| Answer» C. increasing L | |
| 6821. |
A single phase converter is fed by a source having an inductance L. If load current is I0, the decrease in output voltage due to overlap is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-55-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-55-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-55-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-55-4.png"> |
| Answer» D. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-55-4.png"> | |
| 6822. |
In a power diode the reverse recovery time is the time from the instant the forward current is zero to the instant when reverse recovery current has decayed to |
| A. | 50% of peak reverse current |
| B. | 25% of peak reverse current |
| C. | 10% of peak reverse current |
| D. | zero value |
| Answer» B. 25% of peak reverse current | |
| 6823. |
Assertion (A): McMurray Bredford half bridge inverter uses complementary commutationReason (R): Three phase inverter can have two modes of operation. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6824. |
Assertion (A): An ac regulator uses natural commutationReason (R): An ac regulator can be used for static on load tap changing of transformer. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6825. |
In auxiliary commutated chopper, the charging and discharging time of capacitor |
| A. | are constant |
| B. | depend on load current |
| C. | may be constant or may depend on load current |
| D. | none of the above |
| Answer» C. may be constant or may depend on load current | |
| 6826. |
Which inverter circuit uses coupled inductors? |
| A. | Modified McMurray full bridge inverter |
| B. | McMurray Bedford half bridge inverter |
| C. | Modified McMurray Bedford half bridge inverter |
| D. | Both (b) and (c) |
| Answer» E. | |
| 6827. |
If the frequency is less than the damped frequency in a series- inverter |
| A. | the distortion of output voltage waveform is low |
| B. | the distortion of output voltage waveform is high |
| C. | the distortion of output voltage may be high or low depending on the load impedance |
| D. | none of the above |
| Answer» C. the distortion of output voltage may be high or low depending on the load impedance | |
| 6828. |
Mc Murray full bridge inverter uses |
| A. | 4 thyristors and 2 diodes |
| B. | 4 thyristors and 4 diodes |
| C. | 8 thyristors and 4 diodes |
| D. | 8 thyristors and 8 diodes |
| Answer» D. 8 thyristors and 8 diodes | |
| 6829. |
Assertion (A): A DIAC has four layers but only two terminals. Reason (R): A DIAC can conduct in both directions. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6830. |
In a 3 phase full converter, the instantaneous output voltage can have negative part if |
| A. | firing angle is less than 60 |
| B. | firing angle is less than 90 |
| C. | firing angle is more than 60 |
| D. | firing angle is more than 90 |
| Answer» D. firing angle is more than 90 | |
| 6831. |
A class D chopper |
| A. | can operate in first quadrant only |
| B. | can operate in second quadrant only |
| C. | can operate in either first or fourth quadrant |
| D. | can operate in all the quadrants |
| Answer» D. can operate in all the quadrants | |
| 6832. |
The symbol in figure is for |
| A. | UJT |
| B. | PUT |
| C. | SCS |
| D. | SBS |
| Answer» C. SCS | |
| 6833. |
The efficiency of a chopper circuit is about |
| A. | 80% or more |
| B. | around 50% |
| C. | around 20% |
| D. | around 5% |
| Answer» B. around 50% | |
| 6834. |
A single phase cycloconverter feeds a resistance heating load. The heating power is provided by |
| A. | only the fundamental component of output wave |
| B. | only higher harmonics in the output wave |
| C. | both fundamental and higher harmonics in the output wave |
| D. | either (a) or (b) |
| Answer» D. either (a) or (b) | |
| 6835. |
Typical values of for an SCR are in the range of |
| A. | 1 to 10 |
| B. | 25 to 500 |
| C. | 0.1 to 1 |
| D. | 1000 to 2000 |
| Answer» C. 0.1 to 1 | |
| 6836. |
When a dc chopper feeds an RLE load, the load current, during steady state operation |
| A. | remains constant |
| B. | varies between maximum and minimum values |
| C. | may remain constant or vary |
| D. | is constant if R is constant |
| Answer» C. may remain constant or vary | |
| 6837. |
In a single phase full wave ac regulator using two thyristors only, the gate circuits of the two thyristors |
| A. | must be isolated |
| B. | may or may not be isolated |
| C. | should be preferably, isolated |
| D. | should not be isolated |
| Answer» B. may or may not be isolated | |
| 6838. |
A single phase half bridge inverter required to feed R-L loads needs |
| A. | 2 thyristors |
| B. | 4 thyristors |
| C. | 2 thyristors and two diodes |
| D. | 4 thyristors and 4 diodes |
| Answer» D. 4 thyristors and 4 diodes | |
| 6839. |
The total number of leads in SUS, SBS and SCS respectively are |
| A. | 3, 3, 4, |
| B. | 3, 3, 3 |
| C. | 2, 3, 3 |
| D. | 3, 3, 5 |
| Answer» B. 3, 3, 3 | |
| 6840. |
When an SCR is in forward blocking mode, the applied voltage |
| A. | appears across only one junction |
| B. | is equally shared by two junctions |
| C. | is equally shared by three junctions |
| D. | may appear across one or more junctions |
| Answer» B. is equally shared by two junctions | |
| 6841. |
In sinusoidal PWM for inverters the width of different pulses are not the same. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6842. |
Which converter is used in HVDC transmission? |
| A. | 3 pulse |
| B. | 6 pulse |
| C. | 12 pulse |
| D. | 24 pulse |
| Answer» D. 24 pulse | |
| 6843. |
Which of these commutation methods uses two leads? |
| A. | Class A |
| B. | Class B |
| C. | Class C |
| D. | Class D |
| Answer» E. | |
| 6844. |
Assertion (A): The turn on time of SCR is about 1 to 4 ms.Reason (R): The turn off time of SCR is about 10 to 300 ms. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6845. |
An n pulse rectifier is fed by a source having an inductance L. If load current is I0, the voltage drop due to overlap is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-56-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-56-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-56-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-56-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/267-56-2.png"> | |
| 6846. |
Which chopper circuit operates in all the 4 quadrants? |
| A. | A |
| B. | C |
| C. | D |
| D. | E |
| Answer» E. | |
| 6847. |
Multiphase choppers are used in |
| A. | low power circuits |
| B. | high power circuit |
| C. | both low and high power circuits |
| D. | medium power circuits |
| Answer» C. both low and high power circuits | |
| 6848. |
A step up chopper can give an output voltage |
| A. | higher than input voltage |
| B. | lower than input voltage |
| C. | both higher and lower input voltage |
| D. | all of the above |
| Answer» B. lower than input voltage | |
| 6849. |
The specified maximum junction temperature of thyristors is about |
| A. | 50 C |
| B. | 80 C |
| C. | 120 C |
| D. | 200 C |
| Answer» D. 200 C | |
| 6850. |
In a thyristor the gate lead is connected to the n layer near the p layer to which anode is connected. |
| A. | True |
| B. | False |
| Answer» C. | |