Inductor MCQ | Inductance MCQ

31. If the self-inductance of a solenoid is 2 Henry and the current flowing through it is 2A, the energy in the electromagnetic field will be

  1. 8 J
  2. 2 J
  3. 16 J
  4. 4 J
Answer
Answer. d

32. When the current in a coil is increased from 2 A to 4 A in 0.05 seconds, the e.m.f. induced in the coil is 8V. The self-inductance of the coil is

  1. 0.8 H
  2. 0.4 H
  3. 0.2 H
  4. 0.1 H
Answer
Answer. c

33. Mutual inductance between two magnetically coupled coils depends on

  1. number of turns only
  2. permeability of the core only
  3. cross-sectional area of their common core only
  4. all of the above
Answer
Answer. d

34. The energy stored in the magnetic field of a solenoid 10 cm long and 2 cm diameter, with 1000 turns of carrying current of 10 A is

  1. 1.15 J
  2. 0.015 J
  3. 0.19 J
  4. 0.5 J
Answer
Answer. c

35. The rate of change of current in a 4 H inductor is 2 Amps/sec. Find the voltage across the inductor.

  1. 8 V
  2. 0.8 V
  3. 2 V
  4. 16 V
Answer
Answer. a

36. Mutual inductance between two coils is 4 H. If current in one coil changes at the rate of 2A/sec, then emf induced in the other coil is?

  1. 5 V
  2. 0.5 V
  3. 2 V
  4. 8 V
Answer
Answer. d

37. The mutual inductance between two unity coupled coils of 9H and 4H will be

  1. 6 H
  2. 13 H
  3. 36 H
  4. 2.2 H
Answer
Answer. a

38. If the co-efficient of coupling between two coils is increased, mutual inductance between the coils

  1. is increased
  2. changes depend on current
  3. is decreased
  4. remains unchanged
Answer
Answer. a

39. If the number of turns of a coil is increased, its inductance

  1. is increased
  2. remains the same
  3. is decreased
  4. none of the options
Answer
Answer. a

40. Two coupled coils with L1 = L2 = 0.6 have a coupling coefficient of K = 0.8. The turn ratio N1/N2 is

  1. 4
  2. 2
  3. 1
  4. 0.5
Answer
Answer. c

41. The magnetic field energy in an inductor changes from maximum value to minimum value in 5 msec when connected to an a.c. source. The frequency of the source is

  1. 50 Hz
  2. 200 Hz
  3. 500 Hz
  4. 20 Hz
Answer
Answer. a

42. The energy stored in the magnetic field of a solenoid 30 cm long and 3 cm diameter with 1000 turns of wire carrying current of 10A is

  1. 0.15 J
  2. 0.5 J
  3. 1.15 J
  4. 0.015 J
Answer
Answer. a

43. A circuit has inductance of 2 H. If the circuit current changes at the rate of 10 A/sec, then self-induced emf is

  1. 5 V
  2. 0.2 V
  3. 20 V
  4. 10 V
Answer
Answer. c

44. The principle of mutual induction is applied in the case of

  1. alternator
  2. synchronous motor
  3. wattmeter
  4. transformer
Answer
Answer. d

45. Which of the following expressions depicts the coefficient of self inductance?

(where l = length of magnetic circuit and a = area of cross-section of magnetic circuit through which flux is passing  and μ = permeability)

  1. N2μa/l
  2. N3μa/l
  3. N2a/μl
  4. N2μal
Answer
Answer. a

46. Energy stored in the magnetic field of inductor L carrying current is

  1. LI2
  2. (1/2)LI2
  3. 2LI
  4. (1/2)LI
Answer
Answer. b

47. A 100 mH coil carries a current of 1 A. Energy stored in the magnetic field

  1. 1 J
  2. 0.05 J
  3. 1.5 J
  4. 2.5 J
Answer
Answer. b

48. The induced e.m.f. in a coil of 0.08 mH carrying 2A current is reversed in 0.4 seconds

  1. 0.16 mV
  2. 0.4 mV
  3. 0.8 mV
  4. 0.064 mV
Answer
Answer. b

49. On a power grid the load is generally

  1. capacitive
  2. resistive
  3. inductive
  4. all of these
Answer
Answer. c

50. The current in an inductor changes 200 mA in 4ms and induces a voltage of 100 mV. The value of inductor is

  1. 2 mH
  2. 0.5 mH
  3. 8 mH
  4. 4 mH
Answer
Answer. a

51. A coil has an inductance of 1 henry if a current changing at the rate of 1 amp/sec.

  1. induces 1 volt in another coil
  2. causes a back emf of 1 volt
  3. causes an adding emf of 1 volt
  4. causes transformer action
Answer
Answer. b

52. Two uncoupled 3 H inductors are connected in parallel. Their total inductance is

  1. 1.5 H
  2. 6 H
  3. 2 H
  4. 3 H
Answer
Answer. a

53. A coil having an inductance of 150 mH is carrying a current of 5 Amp. If the current is reduced to zero in 1 milliseconds, the self-induced emf will be

  1. 125 V
  2. 375 V
  3. 500 V
  4. 750 V
Answer
Answer. d

54. The induction coil works on the principle of

  1. self-induction
  2. mutual induction
  3. ampere’s rule
  4. fleming right hand rule
Answer
Answer. b

55. At a particular instant an inductance of 1 H carries a current of 2 A while the voltage across it is 1V. The energy stored in the inductance in Joules is

  1. 1/2
  2. 1
  3. 3/2
  4. 2
Answer
Answer. d

56. The e.m.f. induced is 2 V when current is changing at the rate of 0.5 A/s. The self-inductance of coil is

  1. 4
  2. 2
  3. 1
  4. none of these
Answer
Answer. a

57. Inductance affects the direct current flows

  1. only at the time of turning off
  2. only at the time of turning on
  3. at the time of turning on and off
  4. at all the time of operations
Answer
Answer. c

58. Higher the self-inductance of a coil

  1. lesser its weber-turns
  2. lower the emf induced
  3. greater the flux produced by it
  4. longer the delay in establishing steady current through it
Answer
Answer. d

59. The differential coupling of two coils in series connection has self-inductance of 2 mH and 4 mH and a mutual inductance of 0.15 mH. The equivalent inductance of the combination is

  1. 5.7 mH
  2. 5.85 mH
  3. 6 mH
  4. 6.15 mH
Answer
Answer. a

60. A coil having 90 turns is connected to a 120 V, 60 Hz source. If the effective value of the magnetizing current is 4 A, then calculate the value of inductance of the coil.

  1. 79.6 mH
  2. 121.2 mH
  3. 32.2 mH
  4. 83.16 mH
Answer
Answer. a
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