In this section of Electronic Devices and Circuits.It contain Power Handling Devices and Circuits MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.

This Section covers below lists of topics :

  1. Power Electronics MCQs.
  2. SCR – Silicon controlled Rectifier MCQs
  3. Triac MCQs
  4. Four layer Diode or Shockley Diode MCQs
  5. Diac MCQs
  6. Fan Regulator MCQs
  7. UJT – Unijunction Transistor MCQs
  8. Three Phase Rectifier,Parallel Inverter MCQs
  9. Thyristors MCQs

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PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

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1. A thyristor can be used as

  • A resistor
  • An amplifier
  • A switch
  • A power source

2. Positive feedback means the returning signal

  • Opposes the original change
  • Aids the original change
  • Is equivalent to negative feedback
  • Is amplified

3. A latch always uses

  • Transistors
  • Feedback
  • Current
  • Positive feedback

4. To turn on a four-layer diode, you need

  • A positive trigger
  • low-current drop out
  • Breakover
  • Reverse-bias triggering

5. The minimum input current that can turn on a thyristor is called the

  • Holding current
  • Trigger current
  • Breakover current
  • Low-current drop out

6. The only way to stop a four-layer diode that is conducting is by

  • A positive trigger
  • Low-current drop out
  • Breakover
  • Reverse-bias triggering

7. The minimum anode current that keeps a thyristor turned on is called the

  • Holding current
  • Trigger current
  • Breakover current
  • Low-current drop out

8. A silicon controlled rectifier has

  • Two external leads
  • Three external leads
  • Four external leads
  • Three doped regions

9. A SCR is usually turned on by

  • Breakover
  • A gate trigger
  • Breakdown
  • Holding current

10. SCRs are

  • Low-power devices
  • Four-layer diodes
  • High-current devices
  • Bidirectional

11. The usual way to protect a load from excessive supply voltage is with a

  • Crowbar
  • Zener diode
  • Four-layer diode
  • Thyristor

12. An RC snubber protects an SCR against

  • Supply over voltages
  • False triggering
  • Breakover
  • Breakover

13. When a crowbar is used with a power supply, the supply needs to have a fuse or

  • Adequate trigger current
  • Holding current
  • Filtering
  • Current limiting

14. The photo-SCR responds to

  • Current
  • Voltage
  • Humidity
  • Light

15. The diac is a

  • Transistor
  • Unidirectional device
  • Three-layer device
  • Bidirectional device

16. The triac is equivalent to

  • A four-layer diode
  • Two diacs in parallel
  • A thyristor with a gate lead
  • Two SCRs in parallel

17. The unijunction transistor acts as a

  • Four-layer diode
  • Diac
  • Triac
  • Latch

18. Any thyristor can be turned on with

  • Breakover
  • Forward-bias triggering
  • Low-current dropout
  • Reverse-bias triggering

19. A Shockley diode is the same as a

  • four-layer diode
  • SCR
  • diac
  • triac

20. The trigger voltage of an SCR is closest to

  • 0
  • 0.7 V
  • 4 V
  • Breakover voltage

21. Any thyristor can be turned off with

  • Breakover
  • Forward-bias triggering
  • Low-current drop out
  • Reverse-bias triggering

22. Exceeding the critical rate of rise produces

  • Excessive power dissipation
  • Excessive power dissipation
  • Low-current drop out
  • Reverse-bias triggering

23. A four-layer diode is sometimes called a

  • Unijunction transistor
  • Diac
  • PNPN diode
  • Switch

24. A latch is based on

  • Negative feedback
  • Positive feedback
  • The four-layer diode
  • SCR action

25. AN SCR is not made of Germanium because

  • It is not easily available
  • It has poor conducting properties
  • It has more leakage current
  • It is costlier than silicon

26. AN SCR is also sometimes called thyristor because

  • We can conduct in one direction
  • It is analogous to thyratron
  • It has three Junctions
  • None of these

27. AN SCR is a

  • Current triggered device
  • Voltage triggered device
  • Power Trigger device
  • None of these

28. The maximum anode current, Gate being open, at which and SCR is turned off from on condition is called

  • Cutoff current
  • Switch off current
  • Forward current
  • Holding current

29. The maximum anode current that an SCR can handle without destruction is called

  • Holding current
  • Forward rating of an SCR
  • Working current of an SCR
  • None of these

30. triac is equivalent to

  • Two SCRs connected in Reverse parallel
  • Two SCR connected in series
  • Two diodes connected in Reverse parallel
  • None of these

31. A UJT contains

  • Four PN junctions
  • 3 PN junctions
  • Two PN junctions
  • One PN junctions

32. A Diac is a

  • Unidirectional two terminal device
  • Bidirectional two terminal device
  • Unidirectional three terminal device
  • Bidirectional three terminal device

33. in a diac

  • The firing angle is fixed
  • The firing angle can be changed by changing the supply voltage
  • Firing angle can be changed by changing the gate current
  • Firing angle can be changed by changing the gate voltage

34. A diac is is equivalent to

  • Two diodes connected in parallel
  • Two diodes connected in series
  • Two four layers Diodes (Shockley diode) connected in reverse parallel
  • Two transistors connected in parallel

35. Fabricated layers of SCR are

  • n–p–n–p
  • p–n–p–n
  • n–p–n
  • Either (a) or (b)

36. Fabricated layers of the TRIAC are:

  • n–p–n–p
  • p–n–p–n
  • n–p–n
  • p–n

37. Fabricated layers of SCR are:

  • n–p–n–p
  • n–p–n
  • n–p
  • None of the above

38. Holding current of a thyristor is:

  • Less than latching current
  • More than latching current
  • Equal to latching current
  • Zero

39. Anode current in a thyristor is made up of:

  • Electrons only
  • Electrons or holes
  • Electrons and holes
  • Holes only

40. For normal SCRs switching turn on depends on:

  • Gate current
  • Cathode current
  • Anode current
  • None of the above

41. A thyristor, when triggered, will change from forward-blocking state to conduction state if its anode to cathode voltage is equal to:

  • Peak repetitive off state forward voltage
  • Peak working off state reverse voltage
  • Peak working off state forward voltage
  • Peak non-repetitive off state forward voltage

42. A DIAC can be termed as:

  • Diode AC switch
  • Triode AC switch
  • Both (a) and (b)
  • None of the above

43. Turn-on time of an SCR can be reduced by using a:

  • Rectangular pulse of high amplitude and narrow width
  • Rectangular pulse of low amplitude and wide width
  • Triangular pulse
  • Trapezoidal pulse

44. For an SCR, dv/dt protection is achieved through the use of:

  • RL in series with SCR
  • RC across SCR
  • L in series with SCR
  • RC in series with SCR

45. A forward voltage can be applied to an SCR after its:

  • Anode current reduces to zero
  • Gate recovery time
  • Reverse recovery time
  • Anode voltage reduces to zero

46. In a UJT, with Vnn as the voltage across two base terminals, the emitter potential at peak point is given by:

  • VBB
  • V0
  • Vnn + VD
  • None of the above

47. A UJT exhibits negative resistance region:

  • Before the peak point
  • Between peak and valley points
  • After the valley point
  • Both (a) and (c)

48. In a UJT maximum value of charging resistance is associated with:

  • Peak point
  • Valley point
  • Any point between peak and valley point
  • After the valley point

49. A UJT is used for triggering an SCR then the wave shape of the voltage obtained from the UJT circuit is:

  • Swatooth wave
  • Sine wave
  • Trapezoidal wave
  • Square wave

50. In synchronized UJT triggering of an SCR voltage Vc across capacitor reaches UJT threshold voltage thrice in each half-cycle so that there are three firing pulses during each half-cycle. The firing angle of the SCR can be controlled:

  • Thrice in each half-cycle
  • Once in each half-cycle
  • Twice in each half- cycle
  • None of the above

51. A resistor connected across the gate and cathode of an SCR increases its:

  • Turn off time
  • Holding current
  • Noise immunity
  • dv/dt rating
  • All of the above

52. A TRIAC can be used only in:

  • Chopper
  • Inverter
  • Multi quadrant chopper
  • None of the above

53. SCR is a:

  • Unidirectional switch
  • Bidirectional switch
  • Four-directional
  • None of the above

54. TRIAC is a:

  • Unidirectional Switch
  • Bidirectional switch
  • Four-directional
  • None of the above

55. Inverter converts:

  • DC to AC
  • AC to DC
  • Both a and b
  • None of the above.

56. SCR is a:

  • Two-terminal device
  • Three-terminal device
  • Four-terminal device
  • None of the above
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