Physics chapter 18 Mcqs for ecat

Electronics Multiple Choice Question (MCQ) Notes

Both Bold and Underlined option is correct

1. The gate, which performs the operation of inversion is called:

• NOT gate
• AND gate
• OR gate
• XOR gate

2. The gate, which changes the logic level to its opposite level is called:

• NOR gate
• AND gate
• OR gate
• NOT gate

3. If both the inputs given to a gate are 1, such that the output is 0 then it is:

• NAND gate
• NOR gate
• XOR gate
• All of these

4. If both the inputs given to a gate are 0 such that the output is 1 then it is:

• NAND gate
• NOR gate
• XNOR gate
• All of these

5. XNOR gate can be made by combining:

• OR, NOR, NOT gate
• OR, AND, NOT gate
• OR, NAND, NOT gate
• NOR, AND, NOT gate

6. Breakdown voltage is:

• 25 V
• 15 V
• 35 V
• 5 V

7. The value of reverse current for Ge is:

• 1 micro Ampere
• 1 milli Ampere
• 1 Ampere
• 1 Mega Ampere

8. Device used for conversion of D.C. to A.C. is:

• Oscillator
• Rectifier
• Amplifier
• None

9. p-n junction when reversed biased acts as a:

• Capacitor
• On switch
• Off switch
• None

10. Pulsating D.C. can be made smooth by using a circuit known as:

• Filter
• Tank
• Accepter
• All

11. A photodiode can switch its current on Or off in:

• nano second
• milli second
• micro second
• centi second

12. Photodiode is used in:

• Automatic switch
• Optical communication equipment
• Light meters
• All

13. Current gain of a transistor which has collector current of 10 mA and a base current of 40 micro Ampere is:

• 25
• 250
• 2500
• 25000

14. In case of common emitter amplifier, phase difference between input and output:

• 0 degree
• 120 degree
• 180 degree
• 90 degree

15. When transistor acts as OFF switch then voltage across collector and emitter is _____ Vcc.

• Less than
• Greater than
• Equal to
• None

16. The photovoltaic cell is always:

• Forward biased
• Reverse biased
• No biasing is required
• None

17. Under ideal conditions, the collector current is:

• Equal to base current
• Nearly equal to emitter current
• Less than base current
• Always zero

18. One use of a single p-n junction semiconductor in an electrical circuit is a:

• Rectifier
• Transistor
• Battery
• Diode

19. The output from a full wave rectifier is:

• An AC voltage
• A DC voltage
• Zero
• A pulsating unidirectional voltage

20. When n-type semiconductor is heated:

• Number of electrons increases while holes decreases
• Number of holes increases while electrons decreases
• Holes and electrons remains same
• Holes and electrons increases equally

21. Zener diode is used for:

• Rectification
• Amplification
• Stabilization
• Modulation

22. In a semi-conducting diode, the reverse biased current is due to drift of free electrons and holes caused by:

• Thermal excitations only
• Impurity atoms only
• Both first and second
• Neither first nor second

23. In the reverse biased p-n junction, the current is of the order of:

• Ampere
• Milliampere
• Microampere
• Nanoampere

24. To measure light intensity we use:

• LED with forward bias
• LED with reverse bias
• Photodiode with reverse bias
• Photodiode with forward bias

25. On increasing the reverse bias to a large value in a p-n junction diode current:

• Increases slowly
• Remains fixed
• Suddenly increases
• Decreases slowly

26. Rectifier is used to convert:

• Electrical energy to mechanical energy
• Heat energy into electrical energy
• High voltage into low voltage
• AC into DC

27. In an n-p-n transistor p-type crystal acts as:

• Emitter only
• Base only
• Collector only
• Either emitter or collector

28. The emitter base junction in the transistor is:

• Forward biased
• Reverse biased
• Either forward or reverse biased
• Neither forward nor reverse biased

29. The current gain of common-base transistor amplifier is:

• Less than one
• More than one
• Equal to one
• Zero

30. In common-base transistor amplifier. the phase difference between output voltage and input voltage is:

• Zero
• 180 degree
• 90 degree
• 45 degree

31. For a common base transistor amplifier the numerical value is least for:

• Voltage gain
• Power gain
• Resistance gain
• Current gain

32. The base of the transistor is made thin and is doped with least impurity atoms, because:

• About 95% charge carriers may cross
• !00% charge carriers may cross
• the transistor may be saved from high currents
• None of these

33. A logic gate is an electronic circuit which:

• Makes logic decisions
• Allow electron flow only in one direction
• Allows hole flow only in one direction
• Alternates between 0 an 1 value

34. Digital circuits can be made by respective use of:

• AND gates
• OR gates
• NOT gates
• NAND gates

35. Which logic function has the output low only when inputs are high?

• OR
• NOR
• AND
• NAND

36. In a half wave rectifier the rms value of AC component of the waves:

• Zero
• Equal to DC value
• More than DC value
• Less than DC value

37. A PN junction has a thickness of the order of:

• 10(-12) m
• 10(-6) m
• 1 mm
• 1 cm

38. A hole in a p-type semi-conductor is:

• A donor level
• An excess electron
• Missing electron
• A missing atom

39. If PN junction is forward biased its resistance is:

• Zero
• Infinity
• A few ohm
• A few kilo ohms

40. A part of transistor which is heavily doped to produce large number of majority carriers is:

• Emitter
• Base
• Collector
• May be any one

41. How is emitter base junction in the transistor biased?

• Forward
• Reverse
• May be forward or reverse
• None

42. The potential barrier of silicon diode is:

• 0.3 V
• 0.5 V
• 0.7 V
• 0.9 V

43. If collector current is 10 mA and base current of 10 microA. What is the current gain of transistor?

• 250
• 500
• 1000
• None of these

44. An op-amplifier can be used as:

• Inverting amplifier
• Night switch
• Comparator
• All

45. The output of two input OR gate is zero only when:

• Both are one
• Both are zero
• Either input is 1
• None

46. The semi-conductor used for fast counting in electronic circuit is:

• Photodiode
• LED
• Photovoltaic cell
• Solar cell

47. For normal transistor operation Ie is given by:

• Ie = Ic
• Ie = Ic + Ib
• Ie = Ib
• None

48. The value of open loop gain value for the amplifier is:

• Zero
• Infinity
• Very high
• Very low

49. The gate will recognized the voltage as 1 if the applied voltage to gate is:

• 1.5 V
• 0.5 V
• 3.5 V
• 0.7 V

50. In the depletion region of an unbiased PN junction diode there are:

• Only electrons
• Only holes
• Both holes and electrons
• Ions

51. In a transistor, the conventional current flows from base to emitter. The transistor is:

• NPN
• PNP
• FET
• None of these

52. In full wave rectifier with input frequency 50 Hz the ripple in the output is mainly of frequency:

• 25 Hz
• 50 Hz
• 100 Hz
• Zero

53. What is the voltage gain in a common emitter amplifier where input resistance is 3 ohm and load resistance 24 ohm, β = 0.6?

• 8.4
• 4.8
• 2.4
• 480

54. How many NAND gates are used to form AND gate?

• 1
• 2
• 3
• 4

55. Photo diode operates when it is:

• Forward biased
• Reverse biased
• Unbiased
• None

56. The open loop gain of  op-amp is of the order of:

• 10(3)
• 10(4)
• 10(5)
• 10(6)

57. In  a forward biased p-n junction diode, current inside the junction diode is due to drift of:

• Free electrons
• Both types of majority carriers
• Both types of minority carriers
• Donor atoms

58. A p-n junction diode cannot be used for:

• Rectification
• Amplification
• Obtaining light radiation
• Detecting light intensity

59. In a semiconductor diode, p-side is earthed and to n-side is applied a potential of -2 volt; the diode shall:

• Conduct
• Not conduct
• Conduct partially
• Break down

60. In the symbol for a transistor, the arrow head points in the direction of flow of:

• Holes 
• Electrons
• Majority carriers
• Minority carriers

61. The current gain of common-emitter transistor amplifier is:

• Less than one
• More than one
• Equal to one
• Zero

62. In a common-emitter transistor amplifier, the phase difference between output voltage input voltage is:

• Zero
• 180 degree
• 90 degree
• 45 degree

63. The emitter of a transistor is doped the heaviest because it:

• Acts as a supplier of charge carriers
• Dissipates maximum power
• has a large resistance
• has a small resistance

64. At room temperature, potential difference develops across the depletion region in case of silicon:

• 0.3 V
• 0.7 V
• 0.8 V
• 0.9 V

65. Width of depletion region is:

• 10(-8) m
• 10(-7) m
• 10(-6) m
• 10(-4) m

66. In photovoltaic cell current is _______ proportional to intensity of light.

• Directly
• Inversely
• Both first and second
• None

67. Silicon transistors are preferred because:

• High operating temperature
• Low leakage current
• Suited to high frequency circuits
• All

68. If Rc = 10 kΩ , rie = 1kΩ , β = 50 then gain of common emitter amplifier:

• 500
• 50
• 5
• None

69. If R1 = 10 Ωk and R2 = 100kΩ then gain of inverting amplifier is:

• 10
• -10
• 100
• None

70. Electronic circuits which implement various logic operations are called:

• Logic gates
• Boolean algebra
• Amplifier gain
• None