100+ Inductance in a DC Circuit Questions

1. In case of Inductive circuit, Frequency is ______________ to the inductance.
a) Directly proportional
b) Inversely proportional
c) Unrelated
d) Much greater than
Answer: b

2. In case of Inductive circuit, Frequency is ______________ to the current.
a) Directly proportional
b) Inversely proportional
c) Unrelated
d) Much greater than
Answer: b

3. In an inductive circuit, when the XL value increases, the circuit power factor?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

4. If the current and voltage are 90 degrees out of phase, the power factor will be?
a) 0
b) Infinity
c) 1
d) Insufficient information provided
Answer: a

5. In a pure inductive circuit, the power factor is __________
a) Maximum
b) Minimum
c) 0
d) Infinity
Answer: c

6. If the power factor is 1/10 and the value of impedance is 20 ohm, calculate the resistance in the circuit.
a) 1 ohm
b) 2 ohm
c) 3 ohm
d) 4 ohm
Answer: b

This is 100+ Inductance in a DC Circuit Questions

7. If the resistance in a circuit is 2 ohm and the impedance is 20 ohm, calculate the power factor.
a) 1/10
b) 1/20
c) 1/30
d) 1/40
Answer: a

8. If tan ϕ = 10 and the resistance is 2 ohm, calculate the inductive reactance.
a) 10 ohm
b) 20 ohm
c) 30 ohm
d) 40 ohm
Answer: b

9. What is the unit for inductive reactance?
a) Henry
b) Ohm
c) Farad
d) Volts
Answer: b

10. An induced emf is said to be ________
a) Inductive
b) Capacitive
c) Resistive
d) Cannot be determined
Answer: a

11. Among the following, which is the right formula for inductance?
a) L=emf*t/I
b) L=emf/t*I
c) L=emf*I/t
d) L=emf*t*I
Answer: a

12. Among the following, which is the right formula for inductance of N turns?
a) L=et/Ni
b) L=N*i *e*t
c) L=Ni/et
d) L=N/iet
Answer: a

13. For a coil having a magnetic circuit of constant reluctance, the flux is ___________ to the current.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Very large compared to
Answer: a

14. For a coil having a magnetic circuit of constant reluctance, if the flux increases, what happens to the current?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: a

15. The unit for inductance is ___________
a) Ohm
b) Henry
c) A/m
d) A/s
Answer: b

16. If either the inductance or the rate of change of current is doubled, the induced e.m.f?
a) Remains constant
b) Becomes zero
c) Doubles
d) Becomes half
Answer: c

17. If the current changes from 5A to 3A in 2 seconds and the inductance is 10H, calculate the emf.
a) 5V
b) 10V
c) 15V
d) 20V
Answer: b
This is 100+ Inductance in a DC Circuit Questions

18. If the current changes from 5A to 3A in x sec and inductance is 10H. The emf is 10V, calculate the value of x.
a) 2s
b) 3s
c) 4s
d) 5s
Answer: a

9. If the current changes from 3A to 5A in 2s and the emf is 10V. Calculate the inductance.
a) 10H
b) 20H
c) 30H
d) 40H
Answer: a

20. As the number of turns in the coil increases, what happens to the inductance of the coil?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

21. What happens to the inductance when the magnetic field strength decreases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

22. What happens to the inductance when the current in the coil becomes double its original value?
a) Becomes half
b) Becomes four times
c) Becomes double
d) Remains same
Answer: d

23. When the coil is wrapped around a ferromagnetic core, why is it difficult to determine the inductance?
a) The variation of flux is no longer proportional to the variation of current
b) Current does not exist in the coil
c) Flux does not exist in the coil
d) The value of current is too large to measure
Answer: a

24. What happens to the inductance as the area of the cross section of the coil increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

25. What happens to the inductance as the length of the magnetic circuit increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b
This is 100+ Inductance in a DC Circuit Questions

26. If the current changes from 20A to 10A in 5 seconds and the value of inductance is 1H, calculate the emf induced.
a) 8V
b) 6V
c) 4V
d) 2V
Answer: d

27. When a ferromagnetic core is inserted into an inductor, what happens to the flux linkage?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

28. What happens to the current when a ferromagnetic material is introduced within an inductor?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: c

29. What is the relation between the flux and the magnetizing current when a ferromagnetic core is introduced within the inductor?
a) Directly proportional
b) Inversely proportional
c) Not proportional
d) Current is double of flux
Answer: c

30. What happens to the effective inductance when a ferromagnetic core is introduced?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

31. A laminated steel ring is wound with 200 turns. When the magnetizing current varies between 5 and 7 A, the magnetic flux varies between 760 and 800 Wb. Calculate the inductance of the coil.
a) 40H
b) 4 H
c) 4000H
d) 0.004 H
Answer: c
This is 100+ Inductance in a DC Circuit Questions

32. Calculate the number of turns in an inductor with a ferromagnetic core when the inductance is 4000 H, the current changes from 5A to 7A and the flux changes from 760 to 800 Wb.
a) 100
b) 200
c) 300
d) 400
Answer: b

33. Calculate the change in current in an inductor having inductance 4000H, number of turns is 200 and the flux changes from 760 to 800 Wb.
a) 2A
b) 4A
c) 6A
d) 8A
Answer: a

34. Calculate the initial current in an inductor having inductance 4000 H, number of turns is 200 and the flux changes from 760 to 800 Wb. Current changes to 7A.
a) 10A
b) 2A
c) 3A
d) 5A
Answer: d

35. Calculate the change in flux of an inductor having inductance 4000 H, number of turns is 200 and the current changes from 5A to 7A.
a) 20 Wb
b) 40 Wb
c) 60 Wb
d) 80 Wb
Answer: b

36. Calculate the final flux in an inductor having inductance 4000 H, number of turns is 200 and the current changes from 5A to 7A. The initial flux is 760 Wb.
a) 200 Wb
b) 400 Wb
c) 600 Wb
d) 800 Wb
Answer: d

37. In a pure inductive circuit, the power factor is?
a) Maximum
b) Minimum
c) 0
d) Infinity
Answer: c

38. Among the following, which is the right formula for growth in an inductive circuit?
a) VL=V(1-e^-tR/L)
b) VL=(e^-tR/L)
c) VL=(1-e^-tR/L)
d) VL=V(e^-tR/L)
Answer: d
This is 100+ Inductance in a DC Circuit Questions

39. The charging time constant of a circuit consisting of an inductor is the time taken for the voltage in the inductor to become __________ % of the initial voltage.
a) 33
b) 63
c) 37
d) 36
Answer: c

40. What is the time constant of an inductive circuit?
a) LR
b) R/L
c) 1/LR
d) L/R
Answer: d

41. Calculate the time constant of an inductive circuit having resistance 5 ohm and inductance 10H.
a) 2s
b) 4s
c) 5s
d)10s
Answer: a

42. Calculate the resistance in an inductive circuit whose time constant is 2s and the inductance is 10H.
a) 7ohm
b) 10ohm
c) 2ohm
d) 5ohm
Answer: d

43. Calculate the inductance in an inductive circuit whose time constant is 2s and the resistance is 5 ohm.
a) 10H
b) 20H
c) 5H
d) 15H
Answer: a

44. The charging time constant of a circuit consisting of an inductor is the time taken for the current in the inductor to become __________% of the initial current.
a) 33
b) 63
c) 37
d) 36
Answer: b

45. What is the total applied voltage in an inductive circuit?
a) V=Ri+Ldi/dt
b) V=Ri+di/dt
c) V=i+Ldi/dt
d) V=R+Ldi/dt
Answer: a
This is 100+ Inductance in a DC Circuit Questions

46. What is Helmholtz equation?
a) i=I(e^Rt/L)
b) i=I(1-e^-Rt/L)
c) i=I(1+e^-Rt/L)
d) i=I(e^-Rt/L)
Answer: b

47. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the initial value of the current in the circuit.
a) 5A
b) 10A
c) 0 A
d) 20A
Answer: c

48. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of the current in the circuit.
a) 5A
b) 10A
c) 15A
d) 20A
Answer: a

49. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the value of current 1s after the switch is closed.
a) 5.44A
b) 4.32A
c) 6.56A
d) 2.34A
Answer: b

50. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the value of voltage 1s after the switch is closed.
a) 5.4V
b) 10.8V
c) 0 V
d) 2.7V
Answer: d

51. Among the following, which is the right formula for decay in an inductive circuit?
a) i=I(1-e^-t/time constant)
b) i=I(1-e^t /time constant)
c) i=(1-e^-t /time constant)
d) i=I(e^-t /time constant)
Answer: d

52. The discharging time constant of a circuit consisting of an inductor is the time taken for the voltage in the inductor to become __________ % of the initial voltage.
a) 33
b) 63
c) 37
d) 36
Answer: c

53. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the initial value of the voltage across the inductor.
a) 5V
b) 10V
c) 0 V
d) 20V
Answer: d

54. A coil has a resistance of 4 ohms and an inductance of 2H. It is connected to a 20V dc supply. Calculate the final value of the voltage across the inductor.
a) 5V
b) 10V
c) 0 V
d) 20V

55. An RL network is one which consists of ____________
a) Resistor and capacitor in parallel
b) Resistor and capacitor in series
c) Resistor and inductor in parallel
d) Resistor and inductor in series
Answer: d

This is 100+ Inductance in a DC Circuit Questions

56. If the switch is opened at t=0, what is the current in the circuit?

a) 0A
b) 1A
c) 2A
d) 3A
Answer: c

57. In an RL 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
Answer: b

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

a) 0A
b) 10A
c) 20A
d) 30A
Answer: a

59. What is the voltage across the inductor at t=0?

a) 0V
b) 20V
c) 60V
d) 58V
Answer: c

60. What is the expression for current in the given circuit?

a) i=2(e^-2t)A
b) i=2(1-e^-2t)A
c) i=2(e^2t)A
d) i=2(1+e^-2t)A
Answer: b

61. What is the expression for voltage in the given circuit?

a) V=60e^-0.5t
b) V=30e^-0.5t
c) V=60e^-2t
d) V=30e^-2t
Answer: c

62. At steady state, the current in the inductor is?
a) Maximum
b) Minimum
c) Zero
d) Infinity
Answer: a

63. Initially, when the switch in a series RL circuit is closed, the inductor acts as?
a) Open circuit
b) Short circuit
c) Resistor
d) Capacitor
Answer: a

This is 100+ Inductance in a DC Circuit Questions

64. Initially, when the switch in a series RL circuit is closed, the current in the inductor is?
a) Maximum
b) Minimum
c) Zero
d) Infinity
Answer: c

65. If the current in a coil having a constant inductance of L henrys grows at a uniform rate, what is the value of the average current?
a) I
b) I/2
c) I/4
d) 0
Answer: b

66. What is the power in the magnetic field if the current in a coil has a constant inductance of L henrys grows at a uniform rate?
a) LI/2t
b) LI²/2t
c) L/2It
d) L/2I²t
Answer: b

67. What is the energy stored in the magnetic field if the current in a coil has a constant inductance of L henrys grows at a uniform rate?
a) LI/2
b) LI²/2
c) L/2I
d) L/2I²
Answer: b

68. Find the average current in an inductor if the total current in the inductor is 26A.
a) 10A
b) 26A
c) 13A
d) 5A
Answer: c

69. Calculate the power in an inductive circuit if the inductance is 10H, the current flowing in the inductor is 2A in 4s.
a) 50W
b) 4W
c) 5W
d) 10W
Answer: c

70. Calculate the value of stored energy in an inductor if the value of inductance is 20H and 4A of current flows through it.
a) 220J
b) 150J
c) 190J
d) 160J
Answer: d

71. Calculate the emf induced in an inductor if the inductance is 10H and the current is 2A in 4s.
a) 2.5V
b) 1.5V
c) 3.5V
d) 5V
Answer: d

72. Calculate the value of emf in an inductor if the value of inductance is 15H and an average current of 5A flows through it in 10s.
a) 15V
b) 7.5V
c) 10V
d) 5.5V
Answer: b

73. Calculate the current in an inductor if the energy stored is 160J and the inductance is 20H.
a) 1A
b) 2A
c) 3A
d) 4A
Answer: d

This is 100+ Inductance in a DC Circuit Questions

74. Find the time taken for the current in an inductor to change to 2A from 0A if the power in the inductor is 5W. The value of inductance is 10H.
a) 1s
b) 2s
c) 3s
d) 4s
Answer: d

75. The phenomenon due to which there is an induced current in one coil due to the current in a neighbouring coil is?
a) Electromagnetism
b) Susceptance
c) Mutual inductance
d) Steady current
Answer: c

76. If the current in one coil becomes steady, the current in neighbouring coil is?
a) Zero
b) Infinity
c) Doubles
d) Halves
Answer: a

77. If the current in one coil is steady, what happens to the mutual inductance?
a) Zero
b) Infinity
c) Doubles
d) Halves
Answer: a

78. What is the SI unit of mutual inductance?
a) Ohm
b) Henry
c) Volt
d) Siemens
Answer: b

79. Which, among the following, is the correct expression for mutual inductance?
a) M=N2φ2/I2
b) M=N2φ2/I1
c) M=N1φ2/I2
d) M=N1φ1/I1
Answer: b

80. If the flux linkage in coil 1 is 3Wb and it has 500 turns and the current in coil 2 is 2A, calculate the mutual inductance.
a) 750H
b) 500H
c) 450H
d) 900H
Answer: a

81. The flux linkage in coil 1 is 3Wb and it has x turns and the current in coil 2 is 2A, calculate the value of x if the mutual inductance is 750H.
a) 300
b) 400
c) 500
d) 700
Answer: c

82. The flux linkage in coil 1 is x and it has 500 turns and the current in coil 2 is 2A, calculate the value of x if the mutual inductance is 750H.
a) 1Wb
b) 2Wb
c) 3Wb
d) 4Wb
Answer: c

83. The flux linkage in coil 1 is 3 Wb and it has 500 turns and the current in coil 2 is xA, calculate the value of x if the mutual inductance is 750H.
a) 1A
b) 2A
c) 3A
d) 4A
Answer: b

84. Practical application of mutual inductance is ____________
a) DC generator
b) AC generator
c) Transformer
d) Capacitor
Answer: c

85. The types of inductors are ____________
a) Fixed and variable
b) Only fixed
c) Only variable
d) Neither fixed nor variable
Answer: a

86. What is the coupling coefficient when all the flux of coil 1 links with coil 2?
a) 0
b) 100
c) 1
d) Insufficient information provided
Answer: c

87. What is the coupling coefficient when there is ideal coupling?
a) 0
b) 100
c) 1
d) Insufficient information provided
Answer: c

88. Can the coupling coefficient practically ever be equal to 1?
a) Yes
b) No
c) Depends on the current in coil 1
d) Depends on the current in coil 2
Answer: b

89. Mutual inductance between two coupled coils depend on?
a) Amount of flux linkage
b) Rate of change of flux linkage
c) Rate of change of current
d) Flux density
Answer: b
This is 100+ Inductance in a DC Circuit Questions

90. Which, among the following, is the correct formula to find the coupling coefficient?
a) k=M/sqrt(L1L2)
b) k=M/sqrt(L1²)
c) k=M/sqrt(L2²)
d) k=M/(L1L2)
Answer: a

91. What happens to the coupling coefficient when the flux linkage of coil 1 and coil 2 increases?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

92. What is the SI unit of coupling coefficient?
a) H
b) H^-1
c) No unit
d) H²
Answer: c

93. Find the coupling coefficient if the Mutual inductance is 20H, the inductance of coil 1 is 2H and the inductance of coil 2 is 8H.
a) 5
b) 20
c) 2
d) 8
Answer: a

94. Find the value of x if the Mutual inductance is x H, the inductance of coil 1 is 2H and the inductance of coil 2 is 8H. The coupling coefficient is 5.
a) 10H
b) 20H
c) 16H
d) 15H
Answer: b

95. Find the value of x if the Mutual inductance is 20H, the inductance of coil 1 is xH and the inductance of coil 2 is 8H. The coupling coefficient is 5.
a) 2H
b) 4H
c) 6H
d) 8H
Answer: a

96. What is the equivalent inductance when inductors are connected in series?
a) Sum of all the individual inductances
b) Product of all the individual inductances
c) Sum of the reciprocal of all the individual inductances
d) Product of the reciprocal of all the individual inductances
Answer: a

97. When inductances are connected in series, the equivalent inductance is ____________ the largest individual inductance.
a) Greater than
b) Less than
c) Equal to
d) Not related to
Answer: a
This is 100+ Inductance in a DC Circuit Questions

98. Three inductors having inductance values 3H, 4H and 5H are connected in series, calculate the equivalent inductance.
a) 10H
b) 12H
c) 3H
d) 5H
Answer: b

99. Calculate the equivalent inductance between A and B.

a) 30H
b) 54H
c) 44H
d) 60H
Answer: c

100. When inductors are connected in series, the voltage across each inductor is _________
a) Equal
b) Different
c) Zero
d) Infinity
Answer: b

101. In a series circuit, which of the parameters remain constant across all circuit elements such as resistor, capacitor, inductor etc?
a) Voltage
b) Current
c) Both voltage and current
d) Neither voltage nor current
Answer: b

102. Find voltage across 2H inductor.