MCQOPTIONS
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MCQOPTIONS
This section includes 657 Mcqs, each offering curated multiple-choice questions to sharpen your Testing Subject knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The power factor at the input terminals of a cyclo- converter is generally |
| A. | low and leading |
| B. | low and lagging |
| C. | high and leading |
| D. | high and lagging |
| Answer» C. high and leading | |
| 2. |
A fully controlled bridge converter feeds a highly inductive load such that the load current can be assumed to be constant. The wave shape of input current is |
| A. | dc |
| B. | sinusoidal |
| C. | rectangular |
| D. | none of the above |
| Answer» D. none of the above | |
| 3. |
Padders are used in a receiver to |
| A. | discard the carrier |
| B. | facilitate tracking |
| C. | filter the input signal |
| D. | suppress noise |
| Answer» C. filter the input signal | |
| 4. |
An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The input resistance of the detector is |
| A. | 114 kW |
| B. | 336 kW |
| C. | 384 kW |
| D. | 455 kW |
| Answer» C. 384 kW | |
| 5. |
Modulated carrier power in FM |
| A. | increases with modulating signal power |
| B. | decreases with modulating signal power |
| C. | is independent of the modulating signal power |
| D. | none |
| Answer» D. none | |
| 6. |
In a FM waveform, the side bands are spaced at intervals equal to |
| A. | four times the modulating frequency |
| B. | twice the modulating frequency |
| C. | half the modulating frequency |
| D. | modulating frequency |
| Answer» D. modulating frequency | |
| 7. |
In a receiver, which of the following device has RF input but IF output? |
| A. | Loudspeaker |
| B. | Frequency changer |
| C. | Demodulator |
| D. | Audio amplifier |
| Answer» C. Demodulator | |
| 8. |
The IF stage of a receiver employs |
| A. | capacitive coupling |
| B. | impedance coupling |
| C. | double-tuned transformer coupling |
| D. | single-tuned transformer coupling |
| Answer» D. single-tuned transformer coupling | |
| 9. |
Double spotting in a receiver is due to |
| A. | poor sensitivity of RF amplifier |
| B. | high gain of IF amplifier |
| C. | inadequate image frequency rejection |
| D. | all of the above |
| Answer» D. all of the above | |
| 10. |
Which of the following circuit cannot be used to demodulate SSB? |
| A. | Phase discriminator |
| B. | Produce detector |
| C. | Balanced modulator |
| D. | Beat frequency oscillator |
| Answer» B. Produce detector | |
| 11. |
In a transistor receiver, the use of FET as the first stage amplifier is likely to |
| A. | improve selectivity of the receiver |
| B. | improve the effectiveness of the AGC |
| C. | reduce the effect of negative peak clipping |
| D. | reduce the effect of noise at all frequencies |
| Answer» D. reduce the effect of noise at all frequencies | |
| 12. |
The passband of the tuned circuits of a radio receiver should be equal to |
| A. | 20 kHz |
| B. | 455 kHz |
| C. | 1455 kHz |
| D. | more than 455 kHz |
| Answer» B. 455 kHz | |
| 13. |
The source of which of the following noise is different from that of the remaining? |
| A. | Solar noise |
| B. | Cosmic noise |
| C. | Galactic noise |
| D. | Atmospheric noise |
| Answer» E. | |
| 14. |
A communication channel with additive white Gaussian noise, has a bandwidth of 4 kHz and an SNR of 15. Its channel capacity is |
| A. | 1.6 kbps |
| B. | 16 kbps |
| C. | 32 kbps |
| D. | 256 kbps |
| Answer» C. 32 kbps | |
| 15. |
Match the following: List I List II A.BJT1.B.SCR2.C.UJT3.D.PUT4. |
| A. | A-1, B-2, C-3, D-4 |
| B. | A-2, B-3, C-1, D-4 |
| C. | A-1, B-3, C-4, D-2 |
| D. | A-4, B-2, C-1, D-3 |
| Answer» D. A-4, B-2, C-1, D-3 | |
| 16. |
Match the following: List I List II A.Mu Metal1.very high magnetic permeabilityB.Samrium/cobalt2.very high magnetic remanenceC.Sapphire3.very high thermal conductivityD.Ferrites4.very stable magnetic permeability |
| A. | A-1, B-2, C-3, D-4 |
| B. | A-3, B-4, C-1, D-2 |
| C. | A-2, B-3, C-4, D-1 |
| D. | A-4, B-1, C-2, D-3 |
| Answer» E. | |
| 17. |
Match the following: List I List II A.CLP1.Measure of P clock speedB.SHELL2.Double sided double densityC.DSDD3.Allows you to specify file as command processorD.Megahertz4.Microcode stored in ROM |
| A. | A-4, B-3, C-2, D-1 |
| B. | A-3, B-4, C-2, D-1 |
| C. | A-1, B-2, C-3, D-4 |
| D. | A-2, B-3, C-4, D-1 |
| Answer» B. A-3, B-4, C-2, D-1 | |
| 18. |
In a semi converter feeding a resistive load |
| A. | the waveshapes of output voltage and output current are exactly similar |
| B. | the waveshapes of output voltage and output current can not be similar |
| C. | the waveshapes of output voltage and output current are similar only for low values of firing angle |
| D. | the waveshapes of output voltage and output current may be similar or dissimilar |
| Answer» B. the waveshapes of output voltage and output current can not be similar | |
| 19. |
Assertion (A): SUS is a PUT and avalanche diode connected between gate and cathodeReason (R): SBS has two SUS inbuilt together and connected in anti-parallel |
| 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 | |
| 20. |
Match the following: List I (Characteristic equation) List II (Degree of damping)A.s2 + 15s + 56.251.UndampedB.s2 + 5s + 62.UnderdampedC.s2 + 20.253.Critically dampedD.s2 + 4.55s + 42.254.Overdamped |
| A. | A-1, B-2, C-3, D-4 |
| B. | A-2, B-3, C-1, D-4 |
| C. | A-3, B-4, C-1, D-2 |
| D. | A-1, B-2, C-4, D-3 |
| Answer» D. A-1, B-2, C-4, D-3 | |
| 21. |
Match the following: List I List II A.Ternary1.0, 1, 3B.Quaternary2.0, 1, 2, 3, 4, 5, 6 7, 8, 9, A, BC.Quinary3.0, 1, 2, 3, 4D.Duodecimal4.0, 1, 2 |
| A. | A-1, B-2, C-3, D-4 |
| B. | A-2, B-3, C-4, D-1 |
| C. | A-3, B-1, C-4, D-3 |
| D. | A-4, B-1, C-3, D-2 |
| Answer» E. | |
| 22. |
In an n stage high frequency series inverter having a time period T, each stage is active for a time interval of |
| A. | T |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-64-1.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-64-2.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-64-3.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-64-2.png"> | |
| 23. |
In a 3 phase semiconverter, the output voltage becomes discontinuous for |
| A. | firing angle > 30 |
| B. | firing angle > 60 |
| C. | firing angle > 90 |
| D. | firing angle > 120 |
| Answer» C. firing angle > 90 | |
| 24. |
The total number of leads in SCR, DIAC and TRIAC respectively are |
| A. | 3, 2, 3 |
| B. | 2, 3, 3 |
| C. | 3, 3, 2 |
| D. | 3, 2, 4 |
| Answer» B. 2, 3, 3 | |
| 25. |
A single phase semiconverter is feeding a highly inductive load and has a freewheeling diode across the load. The waveshape of input current is |
| A. | sinusoidal |
| B. | rectangular |
| C. | sinusoidal or rectangular |
| D. | triangular |
| Answer» C. sinusoidal or rectangular | |
| 26. |
Lead mounting for SCR is used for |
| A. | rating less than mA |
| B. | rating about 1 A or less |
| C. | rating of 20 A or less than 20 A |
| D. | rating 100 A or less |
| Answer» C. rating of 20 A or less than 20 A | |
| 27. |
A load commutated chopper circuit has |
| A. | one thyristor |
| B. | two thyristors |
| C. | four thyristors |
| D. | six thyristors |
| Answer» D. six thyristors | |
| 28. |
Assertion (A): The output voltage of an inverter can be controlled by PWM techniqueReason (R): In a current source inverter the input current is constant. |
| 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 | |
| 29. |
A TRIAC is equivalent to |
| A. | two thyristors in series |
| B. | two thyristors in parallel |
| C. | one thyristor and one diode |
| D. | one thyristor and one transistor |
| Answer» C. one thyristor and one diode | |
| 30. |
Which of the following commutation methods is the overall circuit under damped? |
| A. | Class A |
| B. | Class B |
| C. | Class C |
| D. | Both class A and Class B |
| Answer» E. | |
| 31. |
A single phase full wave regulator feeds a resistive load. The firing angle of thyristors is 90 . The input power factor is |
| A. | 1 |
| B. | 0.707 lagging |
| C. | 0.5 lagging |
| D. | 0.2 lagging |
| Answer» C. 0.5 lagging | |
| 32. |
The static equalisation circuit for thyristors connected in series is |
| A. | one resistor in series with each thyristor |
| B. | one resistor in parallel with each thyristor |
| C. | one resistor and one capacitor in parallel with each thyristor |
| D. | none of the above |
| Answer» C. one resistor and one capacitor in parallel with each thyristor | |
| 33. |
A step down cycloconverter has an input frequency f. If it uses natural commutation, the output frequency |
| A. | must be a sub-multiple of input frequency |
| B. | can be any frequency |
| C. | must be an even sub-multiple of input frequency |
| D. | must be an odd sub-multiple of input frequency |
| Answer» B. can be any frequency | |
| 34. |
Which of the following devices has two gates? |
| A. | SCR |
| B. | SCS |
| C. | SUS |
| D. | SBS |
| Answer» C. SUS | |
| 35. |
The symbol in figure is for |
| A. | SUS |
| B. | SBS |
| C. | SCS |
| D. | Shockley diode |
| Answer» C. SCS | |
| 36. |
If peak value of input voltage is Vm and firing angle is a, the average output voltage for single phase half wave and single phase full wave regulators are |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-336-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-336-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-336-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-336-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-336-2.png"> | |
| 37. |
An SUS is |
| A. | exactly similar to SCR but with higher rating |
| B. | similar to UJT |
| C. | PUT and avalanche diode connected in anti parallel |
| D. | SCR and avalanche diode connected in parallel |
| Answer» D. SCR and avalanche diode connected in parallel | |
| 38. |
In a certain inverter circuit each thyristor carries 26.67 A for 60 , 13.33 A for 120 and zero A for 180 of the cycle. The rms current of thyristor is |
| A. | 20 A |
| B. | 13.33 A |
| C. | 6.67 A |
| D. | 3.33 A |
| Answer» C. 6.67 A | |
| 39. |
The factor for a UJT is about |
| A. | 0.1 |
| B. | 0.2 |
| C. | 0.6 |
| D. | 0.9 |
| Answer» D. 0.9 | |
| 40. |
The symbol in figure is for |
| A. | UJT |
| B. | PUT |
| C. | Shockley diode |
| D. | TRIAC |
| Answer» B. PUT | |
| 41. |
An SCR is triggered at 80 in the positive half cycle, only. The rms anode current is 25 A. If the firing angle is changed to 160 , the rms current is likely to be |
| A. | 25 A |
| B. | 12.5 A |
| C. | less than 25 A |
| D. | less than 12.5 A |
| Answer» E. | |
| 42. |
The cut in voltages for germanium and silicon diodes respectively as |
| A. | 0.3 V and 0.7 V |
| B. | 0.7 V and 0.3 V |
| C. | 0.6 V and 0.9 V |
| D. | 0.5 V and 0.7 V |
| Answer» B. 0.7 V and 0.3 V | |
| 43. |
Assertion (A): Thyristors can be used in controlled heating, excitation systems of alternators, speed control of motors and HVDCReason (R): A static var system using thyristors is very commonly used in high voltage ac systems. |
| 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 | |
| 44. |
In a dual converter operated in circulating current mode, the circulating current flows |
| A. | when load current is zero |
| B. | when load current is non-zero |
| C. | even when load current is zero |
| D. | none of the above |
| Answer» D. none of the above | |
| 45. |
For a single phase half wave converter feeding a resistive load, the firing angle a. The waveshape in below figure is for |
| A. | output voltage |
| B. | input voltage |
| C. | voltage drop across thyristor |
| D. | none of the above |
| Answer» E. | |
| 46. |
A class B chopper operates in third quadrant. |
| A. | True |
| B. | False |
| Answer» C. | |
| 47. |
As compared to a p-n junction diode |
| A. | a schottky diode has lower cut in voltage and lower reverse saturation current |
| B. | a schottky diode has higher cut in voltage and higher reverse saturation current |
| C. | a Schottky diode has lower cut in voltage and higher reverse saturation current |
| D. | a schottky diode has higher cut in voltage and lower reverse saturation current |
| Answer» D. a schottky diode has higher cut in voltage and lower reverse saturation current | |
| 48. |
From which instant is the turn off time of a thyristor defined |
| A. | when anode voltage becomes zero |
| B. | when anode current becomes zero |
| C. | when both anode voltage and current become zero |
| D. | none of the above |
| Answer» C. when both anode voltage and current become zero | |
| 49. |
In a single phase cycloconverter with centre tapped transformer |
| A. | all thyristors carry currents for equal duration |
| B. | the durations of currents in all thyristors may or may not be equal |
| C. | the durations of currents in all thyristors cannot be equal |
| D. | the duration of currents in all thyristors must be equal for satisfactory operation |
| Answer» C. the durations of currents in all thyristors cannot be equal | |
| 50. |
The duty cycle of a step down chopper is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-78-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-78-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-78-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-78-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-78-2.png"> | |