# 100+ Capacitance and Capacitors Questions (Part 2)

Capacitance and Capacitors MCQs Questions

1. Potential drop in a dielectric is equal to _______
a) Electric field strength*thickness
b) Electric field strength*area of a cross section
c) Electric field strength
d) Zero

2. The electric field strength is 10N/C and the thickness of the dielectric is 3m. Calculate the potential drop in the dielectric.
a) 10V
b) 20V
c) 30V
d) 40V

3. The electric fields of dielectrics having the same cross sectional area in series are related to their relative permittivities in which way?
a) Directly proportional
b) Inversely proportional
c) Equal
d) Not related

4. What happens to the capacitance when a dielectric is introduced between its plates?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

5. Calculate the relative permittivity of the second dielectric if the relative permittivity of the first is 4. The electric field strength of the first dielectric is 8V/m and that of the second is 2V/m.
a) 32
b) 4
c) 16
d) 8

6. What happens to the potential drop between the two plates of a capacitor when a dielectric is introduced between the plates?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

7. If the potential difference across the plates of a capacitor is 10V and a dielectric having thickness 2m is introduced between the plates, calculate the potential difference after introducing the dielectric. The electric field strength is 2V/m.
a) 4V
b) 6V
c) 8V
d) 10V

8. Calculate the capacitance if the dielectric constant=4, area of cross section= 10m2 and the distance of separation between the plates is 5m.
a) 7.08*10-11F
b) 7.08*1011F
c) 7.08*10-12F
d) 7.08*10-10F

9. A dielectric is basically a ________
a) Capacitor
b) Conductor
c) Insulator
d) Semiconductor

Capacitance and Capacitors MCQs Questions

10. What happens to the potential difference between the plates of a capacitor as the thickness of the dielectric slab increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

11. Which of the following depends on charging and discharging rate of a capacitor?
a) Time constant
b) Current
c) Power
d) Voltage

12. What is the initial current while charging a capacitor?
a) High
b) Low
c) 0
d) Cannot be determined

13. What is the final current while charging a capacitor?
a) High
b) Zero
c) Infinity
d) Low

14. A capacitor is charged to a voltage of 400V and has a resistance of 20ohm. Calculate the initial value of charging current.
a) 10A
b) 0A
c) Infinity
d) 20A

15. A capacitor is charged to a voltage of 400V and has a resistance of 20ohm. Calculate the initial value of the discharge current.
a) 10A
b) 0A
c) Infinity
d) 20A

16. A capacitor is charged to a voltage of 400V and has a resistance of 20ohm. Calculate the final value of the discharge current.
a) 10A
b) 0A
c) Infinity
d) 20A

17. When will be capacitors fully charged?
a) When voltage is zero
b) When the supply voltage is equal to the capacitor voltage
c) When voltage is infinity
d) When capacitor voltage is equal to half the supply voltage

18. What happens to the capacitor when the capacitor voltage is equal to the source voltage?
a) The charging phase of the capacitor is over
b) The discharging phase of the capacitor is over
c) The capacitor is switched off
d) The capacitor is switched on

Capacitance and Capacitors MCQs Questions

19. A capacitor is charged to a voltage of 400V and has a resistance of 20ohm. Calculate the final value of charging current.
a) 10A
b) 0A
c) Infinity
d) 20A

20. The charging time constant of a circuit consisting of a capacitor is the time taken for the charge in the capacitor to become __________ % of the initial charge.
a) 33
b) 63
c) 37
d) 36

21. The discharging time constant of a circuit consisting of a capacitor is the time taken for the charge in the capacitor to become __________ % of the initial charge.
a) 33
b) 63
c) 37
d) 36

22. A circuit has a resistance of 2 ohm connected in series with a capacitance of 6F. Calculate the charging time constant.
a) 3
b) 1
c) 12
d) 8

23. A circuit has a resistance of 5 ohm connected in series with a capacitance of 10F. Calculate the discharging time constant.
a) 15
b) 50
c) 5
d) 10

24. What is the value of current in a discharging capacitive circuit if the initial current is 2A at time t=RC.
a) 0.74A
b) 1.26A
c) 3.67A
d) 2.89A

25. What is the value of current in a charging capacitive circuit if the initial current is 2A at time t=RC.
a) 0.74A
b) 1.26A
c) 3.67A
d) 2.89A

26. While discharging, what happens to the current in the capacitive circuit?
a) Decreases linearly
b) Increases linearly
c) Decreases exponentially
d) Increases exponentially

27. While discharging, what happens to the voltage in the capacitive circuit?
a) Decreases linearly
b) Increases linearly
c) Decreases exponentially
d) Increases exponentially

Capacitance and Capacitors MCQs Questions

28. While charging, what happens to the current in the capacitive circuit?
a) Decreases linearly
b) Increases linearly
c) Decreases exponentially
d) Increases exponentially

29. While charging, what happens to the voltage in the capacitive circuit?
a) Decreases linearly
b) Increases linearly
c) Decreases exponentially
d) Increases exponentially

30. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the time constant.
a) 1s
b) 2s
c) 3s
d) 4s

31. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the initial charging current.
a) 100 microA
b) 500 microA
c) 400 microA
d) 1000microA

32. A 8 microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the time taken for the potential difference across the capacitor to grow to 160V.
a) 6.93s
b) 7.77s
c) 2.33s
d) 3.22s

33. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the voltage in the capacitor 4s after the power is supplied.
a) 123.4V
b) 126.4V
c) 124.5V
d) 132.5V

34. An 8microF capacitor is connected in series with a 0.5 megaohm resistor. The DC voltage supply is 200V. Calculate the current in the capacitor 4s after the power is supplied.
a) 79 microA
b) 68 microA
c) 48 microA
d) 74 microA

35. A circuit has a resistance of 2 ohms connected in series with a capacitance of 6F. Calculate the discharging time constant.
a) 3
b) 1
c) 12
d) 8

36. What is the energy in a capacitor if the voltage is 5V and the charge is10C?
a) 25J
b) 35J
c) 54J
d) 55J

Capacitance and Capacitors MCQs Questions

37. A CR network is one which consists of _________
a) A capacitor and resistor connected in parallel
b) A capacitor and resistor connected in series
c) A network consisting of a capacitor only
d) A network consisting of a resistor only

38. At DC, capacitor acts as _________
a) Open circuit
b) Short circuit
c) Resistor
d) Inductor

39. In an RC series circuit, when the switch is closed and the circuit is complete, what is the response?
a) Response does not vary with time
b) Decays with time
c) Increases with time
d) First increases, then decrease

40. If the switch is closed at t=0, what is the current in the circuit?

a) 0A
b) 10A
c) 20A
d) Infinity

41. Calculate the voltage across the capacitor at t=0.

a) 0V
b) 10V
c) 20V
d) Infinity

42. Calculate di(0)/dt if the switch is closed at t=0.

a) -9.9A/s
b) -10A/s
c) 0A/s
d) -0.1A/s

43. Calculate d2i(0)/dt2 from the given circuit.

a) 10-6A/s2
b) 10-3A/s2
c) 106A/s2
d) 103A/s2

44. The current equation for the given circuit is?

a) i=10e(-0.01)t A
b) i=10e(0.01)t A
c) i=10e(-0.001)t A
d) i=100e(-0.01)t A

45. The expression for the current in an RC circuit is?
a) i=(V/R)et/RC
b) i=(V/R)e-t/RC
c) i=(V/R)(1-e-t/RC)
d) i=(V/R) (1-et/RC)

Capacitance and Capacitors MCQs Questions

46. What is the voltage in the resistor as soon as the switch is closed at t=0.

a) 0V
b) Infinity
c) 220V
d) Insufficient information provided

47. Work done in charging a capacitor is ____________
a) QV
b) 12QV
c) 2QV
d) QV2

48. Energy stored in 2000mF capacitor charged to a potential difference of 10V is?
a) 100J
b) 200J
c) 300J
d) 400J

49. When do we get maximum energy from a set of capacitors?
a) When they are connected in parallel
b) When they are connected in series
c) Both in series and parallel
d) Insufficient information provided

50. If the charge stored in a capacitor is 4C and the value of capacitance is 2F, calculate the energy stored in it.
a) 2J
b) 4J
c) 8J
d) 16J

51. If the charge in a capacitor is 4C and the energy stored in it is 4J, find the value of capacitance.
a) 2F
b) 4F
c) 8F
d) 16F

52. If the charge in a capacitor is 4C and the energy stored in it is 4J, calculate the voltage across its plates.
a) 2V
b) 4V
c) 8V
d) 16V

53. Calculate the energy in the 2F capacitor.

a) 8.6kJ
b) 64kJ
c) 64J
d) 6.4kJ

54. Calculate the energy in the 4F capacitor.

a) 128kJ
b) 1.28kJ
c) 12.8kJ
d) 1280J

Capacitance and Capacitors MCQs Questions

55. Calculate the energy stored in the combination of the capacitors.

a) 192kJ
b) 1.92kJ
c) 19.2kJ
d) 1920J

56. Which among the following is the correct expression for force between the plates of a parallel plate capacitor?
a) F=epsilon*A*(V/x)2/2
b) F=epsilon*A*(V/x)2/3
c) F=epsilon (V/x)2/2
d) F=epsilon (V/x)2/3

57. When the area of cross section of the plate increases, what happens to the force between the plates?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

58. When the potential gradient increases, what happens to the force between the plates?
a) Increases
b) Decreases
c) Remains the same
d) becomes zero

59. In which of the following mediums, will the force of attraction between the plates of a capacitor be greater?
a) Air
b) Water
c) Does not depend on the medium
d) Cannot be determined

60. A metal parallel plate capacitor has 100mm diameter and the distance between the plates is 1mm. The capacitor is placed in air. Calculate the force on each plate if the potential difference between the plates is 1kV.
a) 350N
b) 0.035kN
c) 0.035N
d) 3.35kN

61. A metal parallel plate capacitor has 100mm diameter and the distance between the plates is ‘a’ mm. The capacitor is placed in air. Force on each plate is 0.035N and the potential difference between the plates is 1kV. Find ‘a’.
a) 1m
b) 1cm
c) 10cm
d) 1mm

62. A metal parallel plate capacitor has ‘a’mm diameter and the distance between the plates is 1mm. The capacitor is placed in air. Force on each plate is 0.035N and the potential difference between the plates is 1kV. Find ‘a’.
a) 10mm
b) 100mm
c) 1000m
d) 1000cm

63. A metal parallel plate capacitor has 100mm diameter and the distance between the plates is 1mm. The capacitor is placed in air. Calculate the potential difference between the plates if the force on each plate is 0.035N.
a) 1kV
b) 1V
c) 2kV
d) 2V

Capacitance and Capacitors MCQs Questions

64. What happens to the force of attraction between the capacitors when the potential difference between the plates decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

65. What happens to the force of attraction between the capacitors when the distance of separation between the plates increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

66. The unit for dielectric strength is ____________
a) V/m2
b) MV/m2
c) MV/m
d) Vm

67. If the Voltage increases, what happens to dielectric strength?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

68. If the potential difference in a material is 4MV and the thickness of the material is 2m, calculate the dielectric strength.
a) 2MV/m
b) 4MV/m
c) 6MV/m
d) 8MV/m

69. If the dielectric strength of a material is 4MV/m and its potential difference is 28MV, calculate the thickness of the material.
a) 4m
b) 7m
c) 5m
d) 11m

70. If the thickness of the material increases, what happens to the dielectric strength?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

71. The thickness of a material having dielectric strength 10MV/m is 5m, calculate the potential difference.
a) 2MV
b) 10MV
c) 50MV
d) 100MV

72. Which medium has the highest dielectric strength?
a) Water
b) Mica
c) Air
d) Glass

Capacitance and Capacitors MCQs Questions

73. Leakage in capacitors is primarily caused by _________
a) Transistors
b) Resistors
c) Inductors
d) DC motors

74. What is the conduction current when a capacitor is fully charged?
a) Infinity
b) Zero
c) 100A
d) 1000A

75. The flow of electrons in dielectric is due to _________
a) Conduction
b) Potential difference
c) Breakdown
d) Resistance

76. The flow of electrons which does not pass through the battery is known as ________
a) Displacement current
b) Leakage current
c) Either displacement or leakage current
d) Neither displacement nor leakage current

77. The free electrons in practical dielectrics is due to _________
a) There are no free electrons
b) Conductors
c) Impurities
d) Both conductors and impurities

78. The current in conductors connecting the voltage source to the plates of a capacitor is ______
a) Conduction current
b) Leakage current
c) Charging current
d) Zero

79. What is the type of current where the electrons actually move?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

80. What is the type of current caused due to variations in the field?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

81. Under normal conditions capacitors have _________
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

Capacitance and Capacitors MCQs Questions

82. If a large amount of voltage is applied to a capacitor, what is the current that flows through it?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

83. The current in conductors connecting the voltage source to the plates of a capacitor is _______
a) Conduction current
b) Leakage current
c) Charging current
d) Displacement current

84. Under normal conditions capacitors have _______
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

85. What is the unit for displacement current?
a) No unit
b) Ampere
c) Coulomb
d) Ampere/coulomb

86. Displacement current depends on ___________
a) Moving charges
b) Change in time
c) Both moving charges and change in time
d) Neither moving charges nor change in time

87. Magnetic fields between the parallel plates of a capacitor are due to?
a) Displacement current
b) Conduction current
c) Both conduction and displacement current
d) Neither conduction nor displacement current

88. The free electrons in practical dielectrics are due to ________
a) There are no free electrons
b) Conductors
c) Impurities
d) Displacement currents

89. The flow of electrons which does not pass through the battery is known as ____________
a) Conduction current
b) Leakage current
c) Charging current
d) Displacement current

90. Paper capacitor is a type of _________
a) Fixed capacitor
b) Variable capacitor
c) Either fixed or variable depending on its usage
d) Neither fixed nor variable

Capacitance and Capacitors MCQs Questions

91. A capacitor using chemical reactions to store charge is _______
a) Paper capacitor
b) Ceramic capacitor
c) Polyester capacitor
d) Electrolyte capacitor

92. Which, among the following, is the odd one out?
a) Ceramic capacitor
b) Electrolyte capacitor
c) Tuning capacitor
d) Paper capacitor

93. In a variable capacitor, capacitance can be varied by ______
a) Turning the rotatable plates in or out
b) Sliding the rotatable plates
c) Changing the plates
d) Changing the material of plates

94. The simplest kind of capacitor is ________
a) Ceramic capacitor
b) Electrolyte capacitor
c) Tuning capacitor
d) Paper capacitor

95. Capacitor preferred when there is high frequency in the circuits is _______
a) Electrolyte capacitor
b) Mica capacitor
c) Air capacitor
d) Glass capacitor

96. The type of capacitors used in communication transmitters are?
a) Electrolyte capacitor
b) Variable capacitor
c) Air capacitor
d) Glass capacitor

97. Which capacitors relatively costly?
a) Electrolyte capacitor
b) Mica capacitor
c) Air capacitor
d) Glass capacitor

98. ____________ capacitors usually have a colour code to find its value.
a) Electrolyte capacitor
b) Variable capacitor
c) Polyester capacitor
d) Glass capacitor

99. ______________ capacitors have a high leakage voltage.
a) Electrolyte capacitor
b) Variable capacitor
c) Air capacitor
d) Polyester capacitor