100+ Capacitance and Capacitors Questions (Part 1)

                     

1. What is the relation between current and voltage in a capacitor?
a) I=1/C*integral(Vdt)
b) I=CdV/dt
c) I=1/CdV/dt
d) I=Ct
Answer: b

2. If 2V is supplied to a 3F capacitor, calculate the charge stored in the capacitor.
a) 1.5C
b) 6C
c) 2C
d) 3C
Answer: b

3. Calculate the current in the capacitor having 2V supply voltage and 3F capacitance in 2seconds.
a) 2A
b) 5A
c) 6A
d) 3A
Answer: d

4. A 4microF capacitor is charged to 120V, the charge in the capacitor would be?
a) 480C
b) 480microC
c) 30C
d) 30microC
Answer: b

5. For high frequencies, capacitor acts as _________
a) Open circuit
b) Short circuit
c) Amplifier
d) Rectifier
Answer: b

6. For very low frequencies, capacitor acts as ________
a) Open circuit
b) Short circuit
c) Amplifier
d) Rectifier
Answer: a

7. A capacitor consists of_________
a) Two conductors
b) Two semiconductors
c) Two dielectrics
d) Two insulators
Answer: a

8. Capacitor preferred when there is high frequency in the circuits is __________
a) Electrolyte capacitor
b) Mica capacitor
c) Air capacitor
d) Glass capacitor
Answer: b

9. Capacitance increases with ________
a) Increase in plate area
b) Decrease in plate area
c) Increase in distance between the plates
d) Increase in density of the material
Answer: a

10. Capacitance increases with __________
a) Increase in distance between the plates
b) Decrease in plate area
c) Decrease in distance between the plates
d) Increase in density of the material
Answer: c

11. Which among the following expressions relate charge, voltage and capacitance of a capacitor?
a) Q=C/V
b) Q=V/C
c) Q=CV
d) C=Q2V
Answer: c

12. If a 2F capacitor has 1C charge, calculate the voltage across its terminals.
a) 0.5V
b) 2V
c) 1.5V
d) 1V
Answer: a

13. What is the voltage across a capacitor at the time of switching, that is, when t=0?
a) Infinity
b) 0V
c) Cannot be determined
d) 1V
Answer: b

14. What is the voltage across the capacitor if the switch is closed and steady state is reached?

a) 8V
b) 0V
c) 10V
d) Infinity
Answer: c

15. If one plate of a parallel plate capacitor is charged to positive charge the other plate is charged to?
a) Positive
b) Negative
c) Positive or negative
d) Not charged
Answer: b

16. When the voltage across a capacitor increases, what happens to the charge stored in it?
a) Increases
b) Decreases
c) Becomes zero
d) Cannot be determined
Answer: a

17. When will capacitor fully charged?
a) When the voltage across its plates is half the voltage from ground to one of its plates
b) When the current through the capacitor is a 1/root2 time its value
c) When the supply voltage is equal to the capacitor voltage
d) Never
Answer: c

18. What happens to the current flow in a fully charged capacitor?
a) Current flow stops
b) Current flow doubles
c) Current flow becomes half its original value
d) Current flow becomes one-fourth its original value
Answer: a

19. Calculate the capacitance of a capacitor that stores 40microC of charge and has a voltage of 2V.
a) 20F
b) 20microF
c) 10F
d) 10microF
Answer: b

20. What happens to the capacitance when the voltage across the capacitor increases?
a) Decreases
b) Increases
c) Becomes 0
d) No effect
Answer: d

21. A power factor of a circuit can be improved by placing which, among the following, in a circuit?
a) Inductor
b) Capacitor
c) Resistor
d) Switch
Answer: b

22. When the supply frequency increases, what happens to the capacitive reactance in the circuit?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

23. Calculate the time constant of a series RC circuit consisting of a 100microF capacitor in series with a 100ohm resistor.
a) 0.1 sec
b) 0.1 msec
c) 0.01 sec
d) 0.01 msec
Answer: c

24. Capacitors charge and discharge in __________ manner.
a) Linear
b) Constant
c) Square
d) Exponential
Answer: d

25. Air has a dielectric constant of ___________
a) Unity
b) Zero
c) Infinity
d) Hundred
Answer: a

26. What is the value of capacitance of a capacitor which has a voltage of 4V and ha 8C of charge?
a) 2F
b) 4F
c) 6F
d) 8F
Answer: a

27. Unit of capacitance is___________
a) Volts
b) Farad
c) Henry
d) Newton
Answer: b

28. What will happen to the capacitor just after the source is removed?
a) It will not remain in its charged state
b) It will remain in its charged state
c) It will start discharging
d) It will become zero
Answer: b

29. Which among the following equations is incorrect?
a) Q=CV
b) Q=C/V
c) V=Q/C
d) C=Q/V
Answer: b

30. Capacitance is directly proportional to__________
a) Area of cross section between the plates
b) Distance of separation between the plates
c) Both area and distance
d) Neither area nor distance
Answer: a

31. What is the total capacitance when three capacitors, C1, C2 and C3 are connected in parallel?
a) C1/(C2+C3)
b) C1+C2+C3
c) C2/(C1+C3)
d) 1/C1+1/C2+1/C3
Answer: b

32. Calculate the total capacitance.

a) 10F
b) 15F
c) 13F
d) 20F
Answer: c

33. Calculate the voltage across AB if the total charge stored in the combination is 13C.

a) 1V
b) 2V
c) 3V
d) 4V
Answer: a

34. Calculate the charge in the 2F capacitor.

a) 200C
b) 100C
c) 300C
d) 400C
Answer: a

35. Calculate the charge in the 1F capacitor.

a) 200C
b) 100C
c) 300C
d) 400C
Answer: b

36. Calculate the total charge of the system.

a) 200C
b) 100C
c) 300C
d) 400C
Answer: c

37. When capacitors are connected in parallel, the total capacitance is always __________ the individual capacitance values.
a) Greater than
b) Less than
c) Equal to
d) Cannot be determined
Answer: a

38. When capacitors are connected in parallel, what happens to the effective plate area?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

39. Three capacitors having a capacitance equal to 2F, 4F and 6F are connected in parallel. Calculate the effective parallel.
a) 10F
b) 11F
c) 12F
d) 13F
Answer: c

40. Two capacitors having capacitance value 4F, three capacitors having capacitance value 2F and 5 capacitors having capacitance value 1F are connected in parallel, calculate the equivalent capacitance.
a) 20F
b) 19F
c) 18F
d) 17F
Answer: b

41. What is the total capacitance when two capacitors C1 and C2 are connected in series?
a) (C1+C2)/C1C2
b) 1/C1+1/C2
c) C1C2/(C1+C2)
d) C1+C2
Answer: c

42. N capacitors having capacitance C are connected in series, calculate the equivalent capacitance.
a) C/N
b) C
c) CN
d) N/C
Answer: d

43. When capacitors are connected in series, the equivalent capacitance is ___________ each individual capacitance.
a) Greater than
b) Less then
c) Equal to
d) Insufficient data provided
Answer: b

44. What is the equivalent capacitance?

a) 1.5F
b) 0.667F
c) 2.45F
d) 2.75F
Answer: b

45. When capacitors are connected in series ___________ remains the same.
a) Voltage across each capacitor
b) Charge
c) Capacitance
d) Resistance
Answer: b

46. When capacitors are connected in series _______________ Varies
a) Voltage across each capacitor
b) Charge
c) Capacitance
d) Resistance
Answer: a

47. Four 10F capacitors are connected in series, calculate the equivalent capacitance.
a) 1.5F
b) 2.5F
c) 3.5F
d) 0.5F
Answer: b

48. Calculate the charge in the circuit.

a) 66.67C
b) 20.34C
c) 25.45C
d) 30.45C
Answer: a

49. Calculate the voltage across the 1F capacitor.

a) 33.33V
b) 66.67V
c) 56.56V
d) 23.43V
Answer: b

50. Calculate the voltage across the 2F capacitor.

a) 33.33V
b) 66.67V
c) 56.56V
d) 23.43V
Answer: a

51. The total voltage drop across a series of capacitors is __________
a) The voltage drop across any one of the capacitors
b) The sum of the voltage drop across each of the capacitors
c) The product of the voltage drop across each of the capacitors
d) Zero
Answer: b

52. Capacitors C1, C2 and C3 have voltage drops 2V, 3V and 5V respectively. Calculate the total voltage in the circuit.
a) 10V
b) 2V
c) 5V
d) 0V
Answer: a

53. What is the voltage across the 2F capacitor?

a) 240V
b) 200V
c) 220V
d) 120V
Answer: d

54. What is the voltage across the 4F capacitor?

a) 120V
b) 60V
c) 100V
d) 220V
Answer: b

55. Calculate the voltage across the 6F capacitor.


a) 120V
b) 60V
c) 40V
d) 220V
Answer: c

56. When capacitors are connected in series, which of the following rules are applied?
a) Voltage divider
b) Current divider
c) Both voltage divider and current divider
d) Neither voltage divider nor current divider
Answer: a

57. A capacitor does not allow sudden changes in _________
a) Current
b) Voltage
c) Resistance
d) Inductance
Answer: b

58. Which of the following expressions is correct with respect to the voltage across capacitors in series?
a) V1/V2=C2/C1
b) V2/V1=C2/C1
c) V1*V2=C1*C2
d) V1/C1=V2/C2
Answer: a

59. Two 4F capacitors are connected in series, calculate the voltage across each if the total voltage is 20V.
a) 10V
b) 5V
c) 20V
d) 0V
Answer: a

60. Two capacitors having voltage 2F and 4F are connected in series. This combination is connected to a 100V supply, calculate the voltage across the 2F capacitor.
a) 66.67V
b) 33.33V
c) 100V
d) 0V
Answer: a

61. Capacitor is a device used to__________
a) store electrical energy
b) vary the resistance
c) store magnetic energy
d) dissipate energy
Answer: a

62. Capacitor stores which type of energy?
a) kinetic energy
b) vibrational energy
c) potential energy
d) heat energy
Answer: c

63. Capacitor blocks__________ after long time.
a) alternating current
b) direct current
c) both alternating and direct current
d) neither alternating nor direct current
Answer: b

64. Why does capacitor block dc signal at steady state?
a) due to high frequency of dc signal
b) due to zero frequency of dc signal
c) capacitor doesnot pass any current at steady state
d) due to zero frequency of dc signal
Answer: d

65. If a parallel plate capacitor of plate area 2m2 and plate separation 1m store the charge of 1.77*10-11 C. What is the voltage across the capacitor?
a) 1V
b) 2V
c) 3V
d) 4V
Answer: a

66. Which of the following is a passive device?
a) Transistor
b) Rectifier
c) Capacitor
d) Vaccuum Tubes
Answer: c

67. What is the value of capacitance of a capacitor which has a voltage of 4V and has 16C of charge?
a) 2F
b) 4F
c) 6F
d) 8F
Answer: b

68. For which medium capacitance is high?
a) Air
b) Mica
c) Water
d) Metal
Answer: d

69. The conventional direction of electric field is ________
a) Positive to negative
b) Negative to positive
c) No specific direction
d) Direction cannot be determined
Answer: a

70. Electric field originates at __________
a) Positive charge
b) Negative charge
c) Neither positive nor negative
d) Both positive and negative
Answer: a

71. Electric field terminates at ________
a) Positive charge
b) Negative charge
c) Neither positive nor negative
d) Both positive and negative
Answer: b

72. Which among the following statements is true with regard to electric field lines?
a) Electric field lines always intersect
b) Electric field lines may or may not intersect
c) Electric field lines can be seen
d) Electric field lines never intersect
Answer: d

73. Which, among the following, is the field where electric charge experiences a force?
a) Electric field
b) Magnetic field
c) Gravitational field
d) Electric, magnetic and gravitational field
Answer: a

74. A field that spreads outwards in all directions is __________
a) Linear
b) Radial
c) Weak
d) Strong
Answer: b

75. In uniform fields, all points have ________ field strength.
a) Zero
b) Same
c) Infinity
d) Different
Answer: b

76. Which, among the following is the correct expression for an electric field?
a) E=F/C
b) E=F*C
c) E=F/Q
d) E=F*Q
Answer: c

77. What happens when one material is rubbed against another?
a) The material becomes electrically neutral
b) The material becomes electrically charged
c) The material becomes negatively charged
d) The material becomes positively charged
Answer: b

78. The insulant between the two plates of a capacitor is called _______
a) Conductor
b) Semi-conductor
c) Dielectric
d) Superconductor
Answer: c

79. Gauss law is applicable for_________
a) Point charge
b) Sheet charge
c) Line charge
d) Point, sheet and line charge
Answer: d

80. “Total electric flux through any closed surface is equal to the charge enclosed by that surface divided by permittivity”. This is the statement for?
a) Gauss law
b) Lenz law
c) Coloumb’s law
d) Faraday’s law
Answer: a

81. Electric flux density is a function of_______
a) Volume
b) Charge
c) Current
d) Voltage
Answer: b

82. As charge increases, what happens to flux density?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: a

83. As area increases, what happens to electric flux density?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: b

84. Which, among the following, is the correct expression for electric flux density?
a) D=epsilon*E
b) D=epsilon/E
c) D2=epsilon*E
d) D=epsilon*E2
Answer: a

85. Strength of the electric field is ___________
a) Directly proportional to the force applied
b) Inversely proportional to the force applied
c) Directly proportional to the square of the force applied
d) Inversely proportional to the square of the force applied
Answer: a

86. The force applied to a conductor is 10N if the charge in the conductor is 5C, what is the electric field intensity?
a) 10V/m
b) 2V/m
c) 3V/m
d) 15V/m
Answer: b

87. What is the electric flux density in free space if the electric field intensity is 1V/m?
a) 7.76*10-12C/m2
b) 8.85*10-12C /m2
c) 1.23*10-12C /m2
d) 3.43*10-12C /m2
Answer: b

88. If the charge in a conductor is 16C and the area of cross section is 4m2. Calculate the electric flux density.
a) 64C/m2
b) 16C/m2
c) 4C/m2
d) 2C/m2
Answer: c

89. In order to obtain a high value for capacitance, the permittivity of the dielectric medium should be?
a) Low
b) High
c) Zero
d) Unity
Answer: b

90. Find the capacitance of a capacitor whose area of cross section of the plates is 4m2 and distance of separation between the plates is 2m. The capacitor is placed in vacuum.
a) 1.77*10-11F
b) 1.34*10-11F
c) 2.33*10-11F
d) 5.65*10-11F
Answer: a

91. What is relative permittivity?
a) Equal to the absolute permittivity
b) Ratio of actual permittivity to absolute permittivity
c) Ratio of absolute permittivity to actual permittivity
d) Equal to the actual permittivity
Answer: b

92. What happens to relative permittivity when actual permittivity decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

93. What is the relative permittivity when the actual permittivity is 4F/m?
a) 4.57*10-11
b) 4.57*1012
c) 4.57*1011
d) 4.57*10-12
Answer: c

94. What happens to absolute permittivity when relative permittivity increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: c

95. Calculate the actual permittivity of a medium whose relative permittivity is 5.
a) 4.43*10-11F/m
b) 4.43*10-12F/m
c) 4.43*1011F/m
d) 4.43*1012F/m
Answer: a

96. What is the unit for relative permittivity?
a) F/m
b) Fm
c) F/m2
d) No unit
Answer: d

97. Which, among the following, will be unity in free space?
a) Absolute permittivity
b) Relative permittivity
c) Actual permittivity
d) Both absolute and relative permittivity
Answer: b

98. Which, among the following, do not have any unit?
a) Absolute permittivity
b) Relative permittivity
c) Actual permittivity
d) Both absolute and relative permittivity
Answer: b

99. Which is the correct expression for capacitance of a multi plate capacitor?
a) C=absolute permittivity*A/d
b) C=Actual permittivity*(n-1)*A/d
c) C=Actual permittivity*(n)*A/d
d) Actual permittivity*(n+1)*A/d
Answer: b

100. What happens to the capacitance of a multi plate capacitor when the area of cross section of the plate decreases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: b

101. What happens to the capacitance of a multi plate capacitor when the distance of separation between the plate increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: b

102. What happens to the capacitance of a multi plate capacitor when the number of plates increases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: a

103. Find the capacitance of a multi plate capacitor whose actual permittivity= 5F/m, n=3, A=4m2and d=2m.
a) 10F
b) 20F
c) 30F
d) 40F
Answer: b

104. Find the capacitance of a multi plate capacitor whose relative permittivity=5, n=3, A=4m2 and d=2m.
a) 1.77*10-10 F
b) 1.77*1010 F
c) 1.77*10-11 F
d) 1.77*1011 F
Answer: a

105. Find the number of plates in the multi plate capacitor having C=20F absolute permittivity=5F/m, A=4m2 and d=2m.
a) 1
b) 2
c) 3
d) 4
Answer: c

106. Calculate the distance between the plates of the capacitor having C=20F, actual permittivity = 5F/m n=3 and A=4m2.
a) 1m
b) 2m
c) 3m
d) 4m
Answer: b

107. Calculate the area of cross section of the multi plate capacitor having C=20F, actual permittivity=5F/m n=3 and d=2m.
a) 1m2
b) 2m2
c) 3m2
d) 4m2
Answer: d

108. Calculate the number of plates in the multi plate capacitor having C=1.77*10-10F relative permittivity=5, A=4m2 and d=2m.
a) 1
b) 2
c) 3
d) 4
Answer: c