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UNIT I - ELECTROMAGNETISM >> MCQs 1-50
51. The ability with which the magnetic material allows the flux to pass through a given medium is called
a. susceptibility
b. permeability
c. conductivity
d. reluctivity
ans: b
52. Unit of permeability is
a. A/m
b. H/m
c. I/m
d. m/H
ans: b
53. Permeability of free space or vacuum is defined as the ratio of
a. magnetic flux density in vacuum to magnetic field strength
b. Magnetic flux density in other medium to magnetic field strength
c. Magnetic field strength to magnetic flux density in vacuum
d. Magnetic field strength in medium to flux density in other medium
ans: a
54. Right hand thumb rule is used to find out
a. direction of induced emf
b. direction of magnetic field due to current carrying conductor
c. magnitude of force experienced
d. direction of force
ans: a
55. In left hand rule, thumb always represents
a. current
b. voltage
c. magnetic field
d. direction of force on conductor
ans: d
56. The force between two long current carrying conductor is inversely proportional to
a. current in one conductor
b. product of current in two conductors
c. distance between the two conductors.
d. radius of conductors
ans: c
57. While comparing magnetic and electric circuit, the point of dissimilarity exists while considering
a. mmf and emf
b. Reluctance and resistance
c. flux and current
d. permeance and conductance
ans: c
59. Permeance is to reluctance as conductance is to
a. inductance
b. resistance
c. capacitance
d. ampere turns
ans: b
60. A straight cylindrical solenoid has a flux of 12mwb and a flux density of 0.9T. The diameter of solenoid must be
a.130cm
b. 13cm
c.10cm
d.5cm
ans : b
61. 1 tesla is given as
a. 1wb/m2
b. 1wb/cm2
c.1mwb/cm2
d. 1wb/mm2
ans: a
62. Which part of the magnetic path requires largest mmf
a.coil
b.core
c.airgap
d. inductance
ans: c
63. Soft steel and iron alloy allow easy passage of a magnetic flux because
a. of its high elasticity
b. of its high permeability
c. of its high conductivity
d. of its high reluctance
ans: b
64. Magnitude of the magnetic field produced by a coil is proportional to
a. Permeability of the core material
b. the no. of turns of coil
c. the magnitude of current flow through the coil
d. the product of all above
ans:d
Following data should be used for solving 65 to 67
"A coil is wound uniformly with 300 turns over steel ring of relative permeability 900, having mean circumference of 40mm and cross sectional area of 50mm2. A current of 25A isnpassed through coil"
65. the mmf of ring is_____
a.5000AT
b. 7200AT
c.750AT
d. 7500AT
ans:d
66. The reluctance of ring is______
a.7×107 AT/Wb
b. 0.7×106 AT/Wb
c.6×107 AT/Wb
d. 6×105 AT/Wb
ans: b
67.The value of flux is _________
a.10.7 Wb
b.70 mWb
c.10.7mWb
d. 107 mwb
ans: c
68. The relative permeability of air is__________
a. 1
b. less than 1
c. greater than 1
d. 1000
ans: a
69. Relative permeability of all non magnetic materials is_____
a. 300
b. 0.7
c.1
d. 0
ans: c
70. Which of the following is non magnetic material?
a. iron
b. Mild steel
c. brass
d. Silicon steel
ans: c
71. Which of the following is magnetic material?
a. copper
b. silicon steel
c. aluminium
d. brass
ans: b
72. Flux in the air gap is called
a. leakage flux
b. total flux
c. useful flux
d. all of above
ans: c
73. A magnetic circuit has a mmf of 400AT and a reluctance of 2 × 105 AT/wb. The magnetic flux in the magnetic circuit is
a. 3 × 10-5Wb
b.2 × 10-3Wb
c.1.5 × 10-2Wb
d. 2.5 × 10-4Wb
ans: b
74. A 2cm long coil has 10 turns and carries a current of 750mA. The magnetizing force of the coil is
a. 225 AT/m
b. 675 AT/m
c.450 AT/m
d. 375 AT/m
ans: d
75. The reluctance of a magnetic circuit varies with
a. length × area
b. length / area
c. area/length
d. (length)2 + area
ans: b
76. A strength of an electromagnet is determined by
a. reluctance
b. permeability of the core
c.mmf
d. all of above
ans: d
77. The strength of the magnetic field around a conductor is directly proportional to
a. voltage across the conductor
b. current in the conductor
c. type of material of conductor
d. none of above
ans: b
78. Reluctance of magnetic material is
a. less than non magnetic material
b. more than non magnetic material
c. equal to that of non magnetic material
d. none of above
ans: a
79. The denser the flux
a. stronger is the magnetic field
b. weaker is the magnetic flux
c. no effect on the strength of field
d. none of above
ans: a
80. The direction of induced e.m.f. is given by
a. Flemings right hand rule
b. Flemings left hand rule
c. faradays law of electromagnetic induction
d. crock screw rule.
ans:a
81. Magnitude of induced e.m.f. in a generator depend on
a. flux density
b. magnitude of current
c. rate of cutting flux
d. Rate of current discharge.
ans:c
82. According to Lenz’s law direction of induced e.m.f. is.
a. Same as cause produced
b. Perpendicular to cause produced
c. opposite to cause produced
d. Non above
ans:c
83. According to Faraday’s Laws of electromagnetic induction, an e.m.f.is induced in a conductor whenever it
a. Lies in magnetic field
b. Cuts magnetic flux
c. moves parallel to the direction of the magnetic field
d. lies perpendicular to the magnetic flux.
ans:b
84. When a magnet moves past an object, it will produce eddy currents in the object if the object is
a. a solid
b. an insulator
c. a conductor
d. made from the magnetic material
ans:d
85. Electricity can be generated by rotating a wire loop between the poles of a magnet. In which of the following positions would induce the greatest current in the loop?
a. The plane of the loop is parallel to the magnetic field.
b. The plane of the loop is perpendicular to the magnetic field.
c. The plane of the loop makes an angle of 45° with the magnetic field.
d. The induced current is the same in all positions
ans:b
86. In which of the following situations a voltage is induced in a conductor?
a. The conductor moves through the air.
b. The conductor is connected to a battery.
c. The conductor is connected to a motor.
d. The conductor is moved in a magnetic field.
ans:d
89. In case of dynamically induced emf, direction of induced emf is given by
a. Fleming’s right hand rule
b. Lenz’s law
c. Faraday’s first law
d. Faraday’s second law
ans:a
90. Emf induced in a coil due to its own current is called __________Induction.
a. Mutual
b.Self
c. Dynamic
d. Static
ans:b
91. Emf induced in a coil due to current change in neighboring coil is called_________ induction.
a. Mutual
b. Self
c. Dynamic
d. Static
ans:a
92. Co-efficient of self induction is also called as__________
a. self- induction
b. Inductance
c. Self- inductance
d. Induction
ans:a
93. The property of a coil due to which it opposes the change of current flowing through itself is called_____ of the coil.
a. Static inductance
b. Dynamic inductance
c.Self inductance
d. Mutual inductance
ans:c
94. ____________is used to sense the flow of current in a electric circuit.
a. Ammeter
b. Voltmeter
c. Wattmeter
d. Galvanometer
ans:a
95. The phenomenon of the self induction is felt only when the current in the coil is
a. Changing
b. Increasing
c. Decreasing
d. All the above
ans:a
96. The negative sign in the induced emf of self induction indicates that energy is being absorbed from the electric circuit and stored as _______ energy in the coil.
a. mechanical
b. Electronic
c. electric
d. Magnetic
ans:d
97. Unit of co-efficient of self induction of the circuit is______
a. Volt
b. Ampere
c. Henry
d. Linkages
ans:c
98. Unit of induced emf is_________
a. Volt
b. Ampere
c. Henry
d. Linkages
ans:a
99. The property of one coil due to which it opposes the change in the other coil is called............. between two coils.
a. Dynamic inductance
b. Static inductance
c. Self inductance
d. Mutual inductance
ans:d
100. The unit of mutual inductance is_________
a. Volt
b. Ampere/ Volt
c. Henry
d. Linkages
ans:c
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