1. Acharge which when placed in vacuum from an equal and similar charge repels with a
force of 9 x 10 N, is known as
Correct : B. micro-coulomb
2. Dielectric strength of a medium is usually expressed in
Correct : C. kv/mm
3. A positive and a negative charge are initially 50 mm apart. When they are moved close
together so that they are now only 10 mm apart, the force between them will be
Correct : D. 25 times larger than before
4. Which is the most superior dielectric out of the following ?
Correct : C. bakelite
5. When a dielectric is placed in an electric field the field strength
Correct : A. decreases
6. To prevent the generation of static charges on rubber or flat leather
Correct : B. conductive dressing is done
7. Which of the following capacitor is preferred in case of single phase motor ?
Correct : C. electrolytic capacitor
8. A capacitance is a circuit component that opposes the change in circuit
Correct : A. current
9. A condenser suitable for D.C. only is
Correct : D. poled aluminium electrolytic condenser
10. In a capacitor, the electric charge is stored in
Correct : B. dielectric
11. Tesla is a unit of
Correct : C. flux density
12. The materials having low retentivity are suitable for making
Correct : B. temporary magnets
13. A magnetic field exists around
Correct : D. moving charges
14. Ferrites are materials.
Correct : C. ferromagnetic
15. Air gap has eluctance as compared to iron or steel path
Correct : B. lower
16. The direction of magnetic lines of force is
Correct : B. from north pole to south pole
17. Which of the following is a vector quantity ?
Correct : B. magnetic field intensity
18. The two conductors of a transmission line carry equal current I in opposite directions.
The force on each conductor is
Correct : B. proportional to x
19. A material which is slightly repelled by a magnetic field is known as
Correct : B. diamagnetic material
20. When an iron piece is placed in a magnetic field
Correct : B. the magnetic lines of force will bend away from their usual paths in order to pass through the piece
21. Fleming's left hand rule is used to find
Correct : C. direction of force on a current car¬rying conductor in a magnetic field
22. The ratio of intensity of magnetisation to the magnetisation force is known as
Correct : B. susceptibility
23. The left hand rule correlates to
Correct : D. current, magnetic field and direc¬tion of force on a conductor
24. The unit of relative permeability is
Correct : D. it is dimensionless
25. A conductor of length L has current I passing through it, when it is placed parallel to a
magnetic field. The force experienced by the conductor will be
Correct : A. zero
26. The force between two long parallel conductors is inversely proportional to
Correct : D. distance between the conductors
27. Materials subjected to rapid reversal of magnetism should have
Correct : B. high permeability and low hysteresis loss
28. The main constituent of permalloy is
Correct : C. nickel
29. Paramagnetic materials have relative permeability
Correct : C. slightly more than unity
30. Substances which have permeability less than the permeability of free space are known
as
Correct : C. diamagnetic
31. Two infinitely long parallel conductors in vacuum anf' separated 1 metre between
centres >rhen a current of 1 ampere flows thn. ugh each conductor, produce on each otLer a force of
Correct : D. 2x 1(t7 n/m)
32. In the left hand rule, forefinger always represents
Correct : C. magnetic field
33. Which of the following is a ferromagnetic material ?
Correct : D. nickel
34. Ferrites are a sub-group of
Correct : D. ferri-magnetic materials
35. Gilbert is a unit of
Correct : B. magnetomotive force
36. The working of a meter is based on the use of a permanent magnet. In order to protect
the meter functioning from stray magnetic fields
Correct : B. a soft iron shielding is used
37. Reciprocal of permeability is
Correct : A. reluctivity
38. The relative permeability is less than unity is case of
Correct : D. diamagnetic materials
39. Which of the following is the unit of magnetic flux density ?
Correct : C. tesla
40. The magnetism left in the iron after exciting field has been removed is known as
Correct : B. residual magnetism
41. Which of the following is not a unit of flux?
Correct : B. telsa
42. Which of the following is expected to have the maximum permeability ?
Correct : D. ebonite
43. One telsa is equal to
Correct : C. 1 wb/m2
44. Out of the following statements, concerning an electric field, which statement is not true
?
Correct : B. the electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point
45. When a magnet is in motion relative to a coil the induced e.m.f. does not depend upon
Correct : A. resistance of the coil
46. One maxwell is equal to
Correct : D. 10 webers
47. When two ends of a circular uniform wire are joined to the terminals of a battery, the
field at the centre of the circle
Correct : D. will depend on the radius of the circle
48. Susceptibility is positive for
Correct : C. ferromagnetic substances
49. Two long parallel conductors carry 100 A. If the conductors are separated by 20 mm,
the force per metre of length of each conductor will be
Correct : D. 0.1 n
50. The electromagnet has 50 turns and a current of 1A flows through the coil. If the length
of the magnet circuit is 200 mm, what is the magnetic field strength ?
Correct : B. 250 at/m
51. A square cross-sectional magnet has a pole strength of 1 x 10 Wb and cross sectional
area of 20 mm x 20 mm. What is the strength at a distance of 100 mm from the unit pole in air ?
Correct : C. 6338 n/wb
52. The unit of flux is the same as that of
Correct : D. pole strength
53. Unit for quantity of electricity is
Correct : D. coulomb
54. The Biot-savart's law is a general modification of
Correct : C. ampere\s law
55. The most effective and quickest may of making a magnet from soft iron is by
Correct : A. placing it inside a coil carrying current
56. The commonly used material for shielding or screening magnetism is
Correct : C. soft iron
57. If a copper disc is rotated rapidly below a freely suspended magnetic needle, the
magnetic needle shall start rotating with a velocity
Correct : D. less than that of disc and in the same direction
58. A permanent magnet
Correct : A. attracts some substances and repels others
59. The retentivity (a property) of material is useful for the construction of
Correct : A. permanent magnets
60. The relative permeability of materials is not constant.
Correct : C. ferromagnetic
61. The materials are a bit inferior conductors of magnetic flux than air.
Correct : C. diamagnetic
62. Hysteresis loop in case of magnetically hard materials is more in shape as compared to
magnetically soft materials.
Correct : C. rectangular
63. A keeper is used to
Correct : D. provide a closed path for flux
64. The change of cross-sectional area of conductor in magnetic field will affect
Correct : C. (a) and (b) b >th in the same way
65. The uniform magnetic field is
Correct : C. the field in which all lines of mag¬netic flux are parallel and equidis¬tant
66. The magneto-motive force is
Correct : C. the sum of all currents embraced by one line of magnetic field
67. What will be the current passing through the ring shaped air cored coil when number of
turns is 800 and ampere turns are 3200 ?
Correct : B. 4
68. What will be the magnetic potential difference across the air gap of 2 cm length in
magnetic field of 200 AT/m ?
Correct : B. 4 at
69. The initial permeability of an iron rod is
Correct : D. the permeability almost in non-magnetised state
70. How does the magnetic compass needle behave in a magnetic field ?
Correct : C. it assures a position which follows a line of magnetic flux
71. The stray line of magnetic flux is defined as
Correct : D. a line of magnetic flux which does not follow the designed path
72. The bar magnet has
Correct : A. the dipole moment
73. Which of the following materials are dia-magnetic ?
Correct : C. silver and copper
74. Which of the following type of materials are not very important for engineering
applications ?
Correct : C. diamagnetic
75. The susceptibility of paramagnetic materials generally lies between
Correct : A. kt3 and 1ct6
76. For which of the following materials the net magnetic moment should be zero ?
Correct : C. antiferromagnetic materials
77. The attraction capacity of electromagnet will increase if the
Correct : D. flux density increases
78. Which of the following statements is correct ?
Correct : A. the conductivity of ferrites is better than ferromagnetic materials
79. Temporary magnets are used in
Correct : D. all of the above
80. Main causes of noisy solenoid are
Correct : C. both of above
81. Magnetism of a magnet can be destroyed by
Correct : D. by all above methods
82. An air gap is usually inserted in magnetic circuits to
Correct : C. prevent saturation
83. The relative permeability of a ferromagnetic material is
Correct : D. more than 100 or 1000
84. The unit of magnetic flux is
Correct : B. weber
85. Permeability in a magnetic circuit corresponds to in an electric circuit.
Correct : C. conductivity
86. Point out the wrong statement.
Magnetic leakage is undesirable in electric machines because it
Correct : A. lowers their power efficiency
87. Relative permeability of vacuum is
Correct : A. 1
88. Permanent magnets are normally made of
Correct : A. alnico alloys
89. Those magnetic materials are best suited for making armature and transformer cores
which have permeability and hystersis loss.
Correct : C. high, low
90. The rate of rise of current through an inductive coil is maximum
Correct : B. at the start of the current flow
91. When both the inductance and resistance of a coil are doubled the value of
Correct : A. time constant remains unchanged
92. A material for good magnetic memory should have
Correct : D. high retentivity
93. Conductivity is analogous to
Correct : C. permeability
94. In a magnetic material hysteresis loss takes place primarily due to
Correct : D. it high retentivity
95. Those materials are well suited for making permanent magnets which
have retentivity and coercivity.
Correct : B. high, high
96. If the area of hysteresis loop of a material is large, the hysteresis loss in this material
will be
Correct : C. large
97. Hard steel is suitable for making permanent magnets because
Correct : A. it has good residual magnetism
98. Silicon steel is used in electrical machines because it has
Correct : C. low hysteresis loss
99. Conductance is analogous to
Correct : A. permeance
100. The property of a material which opposes the creation of magnetic flux in it is known as