electromagnetic induction Mcqs
51. An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is____________?
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A. 2 Wb

B. 0.2 Wb

C. 20 Wb

D. 0.02 Wb
52. Which of the following works on torque on the current carrying conductor placed in magnetic field ?
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A. ammeter

B. galvanometer

C. voltmeter

D. all of the above
53. Reversing the field or the current will reverse the force on the conductor
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A. Yes

B. No

54. The polarity of the induced voltage can be determined by using the left-hand generator rule
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A. Yes

B. No

55. For long distance transmission the transformer used is_____________?
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A. Input voltage and output voltage remain same

B. Step down

C. Step up

D. Amplifier is used

56. As per Faradays laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it_______________?
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A. lies in a magnetic field

B. lies perpendicular to the magnetic flux

C. cuts magnetic flux

D. moves parallel to the direction of the magnetic field

57. A.C can not be used for_______________?
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A. producing light

B. Producing magnetic field

C. Magnetizing iron

D. producing heat

58. A conductor 2 meters long moves at right angles to a magnetic field of flux density 1 tesla with a velocity of 12.5 m/s. The induced e.m.f. in the conductor will be____________?
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A. 25V

B. 15 V

C. 50V

D. 10 V

59. Which of the following uses electric energy and does not convert it into any other form ?
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A. motor

B. transformer

C. D.C generator

D. A.C generator

60. Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be______________?
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A. 38 mH

B. 40 mH

C. 48 mH

D. 32 mH

61. Weber is the unit of_____________?
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A. magnetic flux

B. Magnetic field intensity

C. self-inductance

D. magnetic induction

62. A 500 turns solenoid develops an average induced voltage of 60 V. Over what time interval must a flux change of 0.06 Wb occur to produce such a voltage ?
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A. 5 s

B. 0.1 s

C. 0.5 s

D. 0.01 s

63. Which of the following circuit elements will oppose the change in circuit current ?
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A. Inductance

B. All of the above

C. Capacitance

D. Resistance

64. A conductor carries 125 amperes of current under 60 to a magnetic field of 1.1 tesla. The force on the conductor will be nearly______________?
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A. 50 N

B. 120 N

C. 480 N

D. 240 N

65. The emf induced in a coil by a changing magnetic flux may have unit as______________?
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A. ms-1A

B. kgm2s-1A-1

C. kgms2A-1

D. ms-2A-1

66. An electric current induced within the body of a conductor when that conductor either moves through a non uniform magnetic field or in a region where there is a change in magnetic flux is called_____________?
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A. None of the above

B. Back emf

C. Induced current

D. Eddy current
67. For electroplating we use_________________?
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A. any source

B. A D.C source

C. an A.C source

D. all of the above

68. Higher the self-inductance of a coil_____________?
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A. lower the e.m.f. induced

B. lesser its weber-turns

C. greater the flux produced by it

D. longer the delay in establishing steady current through it
69. The alternating current has frequency of 106 Hz in such a way that time period for completion of cycle is_______________?
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A. 1.5Hzs

B. 1Hzs

C. 106sec

D. 1sec

70. In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will_____________?
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A. initially increase and then decrease

B. remain the same

C. increase

D. decrease
71. Self-inductance of a long solenoid is______________?
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A. ?oN2

B. BA

C. ?oN2A

D. ?oN2/A

72. Current changing from 8 A to 12 A in one second induced 20 volts in a coil. The value of inductance is___________?
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A. 10 mH

B. 5 mH

C. 5 H

D. 10 H

73. Self inductance of a coil depends upon________________?
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A. current flowing

B. voltage produce

C. all

D. number of turns per unit length

74. Lagging of changes in the magnetization of a substance behind changes in the magnetic field as the magnetic field is varied is known as magnetic_____________?
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A. Hysteresis

B. Flux

C. Permeability

D. Retaintivity

75. A.C cannot be used for_______________?
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A. magnetizing and electroplating

B. all the above

C. producing light

D. producing heat

76. If the coil is wound on an iron core the flux through it will_______________?
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A. remain the same

B. become zero

C. decrease

D. increase
77. A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is___________?
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A. 250 mH

B. 150 mH

C. 3500 mH

D. 350 mH
78. Inductors acts as a short circuit for_______________?
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A. AC

B. DC

C. Both A and B

D. none of these

79. For a purely inductive circuit which of the following is true ?
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A. Apparent power is zero

B. Actual power of the circuit is zero

C. Any capacitance even if present in the circuit will not be charged

D. Relative power is.zero

80. cmf generated by A.C dynamo depends upon_____________?
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A. number of turns in the coil

B. frequency of rotation

C. magnetic field strength

D. all of above
81. A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by________________?
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A. variation in coil current

B. variation in voltage to the coil

C. change of number of turns of coil

D. the resistance of magnetic path

82. The co-efficient of coupling between two air core coils depends on____________?
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A. self-inductance of two coils only

B. mutual inductance and self inductance of two coils

C. mutual inductance between two coils only

D. none of the above

83. The inductance of a coil will increase under all the following conditions except______________?
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A. when permeability of the core increases

B. when more area for each turn is provided

C. when more length for the same number of turns is provided

D. when the number of turns of the coil increase

84. If the secondary coil has Ns turns and the primary Np turns the relation between secondary and primary voltages is given by_____________?
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A. Vp/Vs = Ns/Np

B. Vp/Vs = Np/Ns

C. Vs/Vp = Ns/Np

D. Vs/Vp = Np/Ns

85. Lenzs law is a consequence of the law of conservation of__________?
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A. charge

B. induced e.m.f.

C. induced current

D. energy
86. Long distance transmission is easy for________________?
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A. Half D.C voltage

B. A.C voltage

C. Half A.C voltage

D. D.C voltage