4. A ferrite core has less eddy current loss than an iron core because
Correct : D. ferrites have high hysteresis
5. Hysteresis loss least depends on
Correct : D. ambient temperature
6. Laminated cores, in electrical machines, are used to reduce
Correct : B. eddy current loss
7. The property of coil by which a counter e.m.f. is induced in it when the current through
the coil changes is known as
Correct : A. self-inductance
8. Which of the following circuit element stores energy in the electromagnetic field ?
Correct : A. inductance
9. Higher the self-inductance of a coil,
Correct : D. longer the delay in establishing steady current through it
10. 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
Correct : B. decrease
11. Both the number of turns and the core length of an inductive coil are doubled.
Its self-inductance will be
Correct : B. doubled
12. If current in a conductor increases then according to Lenz's law self-induced voltage will
Correct : C. produce current opposite to the in-creasing current
13. The direction of incViced e.m.f. can be found by
Correct : B. lenz\s law
14. Air-core coils are practically free from
Correct : C. both (a) and (b)
15. The magnitude of the induced e.m.f. in a conductor depends on the
Correct : D. rate of change of flux-linkages
16. Mutually inductance between two magnetically-coupled coils depends on
Correct : D. all of the above
17. A laminated iron core has reduced eddy-current losses because
Correct : B. the laminations are insulated from each other
18. The law that the induced e.m.f. and current always oppose the cause producing them is
due to
Correct : B. lenz
19. Which of the following is not a unit of inductance ?
Correct : B. coulomb/volt ampere
20. In case of an inductance, current is proportional to
Correct : B. magnetic field
21. Which of the following circuit elements will oppose the change in circuit current ?
Correct : B. inductance
22. For a purely inductive circuit which of the following is true ?
Correct : C. actual power of the circuit is zero
23. Which of the following is unit of inductance ?
Correct : B. henry
24. An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of change of current
must be
Correct : D. 4 a/s
25. The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is
0.5, the mutual inductance of the coils is
Correct : C. 6 mh
26. 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
Correct : B. 38 mh
27. A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400
turns, all other quantities (area, length etc.) remaining the same, the inductance will be
Correct : D. 48 mh
28. Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If
the two coils are connected in series, the total inductance will be
Correct : C. 12 h
29. In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling
will be
Correct : B. 1.0
30. A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance
is
Correct : D. 5000 ohms
31. Lenz's law is a consequence of the law of conservation of
Correct : C. energy
32. 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
Correct : B. 120 n
33. Find the force acting on a conductor 3m long carrying a current of 50 amperes at right
angles to a magnetic field having a flux density of 0.67 tesla.
Correct : A. 100 n
34. The co-efficient of coupling between two air core coils depends on
Correct : C. mutual inductance and self inductance of two coils
35. 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
Correct : D. 0.02 wb
36. 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 ?
Correct : C. 0.5 s
37. Which of the fpllowing inductor will have the least eddy current losses ?
Correct : A. air core
38. A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of
inductance is
Correct : B. 350 mh
39. Two 300 uH coils in series without mutual coupling have a total inductance of
Correct : B. 600 uh
40. Current changing from 8 A to 12 A in one second induced 20 volts in a coil.
The value of inductance is
Correct : C. 5 h
41. Which circuit element(s) will oppose the change in circuit current ?
Correct : B. inductance only
42. A crack in the magnetic path of an inductor will result in
Correct : D. reduced inductance
43. A coil is wound on iron core which carries current I. The self-induced voltage in the coil
is not affected by
Correct : B. variation in voltage to the coil
44. Which of the following parameters is not a primary parameter?
Correct : B. attenuation constant
45. The networks in which the R, L, C parameters are individually concentrated or
lumped at discrete points in the circuit are called
Correct : A. lumped
46. The lines having R, L, C distributed along the circuit are called
Correct : B. distributed
47. Which primary parameter is uniformly distributed along the length of the
conductor?
Correct : D. r
48. The primary parameter that is associated with the magnetic flux linkage is
Correct : B. l
49. The primary parameter that is associated with the electric charges is
Correct : C. c
50. Find the receiving impedance of a transmission line having a voltage of 24V
and a conduction current of 1.2A is
Correct : D. 20
51. The characteristic impedance of a transmission line with impedance and
admittance of 16 and 9 respectively is
Correct : B. 1.33
52. Find the characteristic impedance expression in terms of the inductance and
capacitance parameters.
Correct : C. zo = √(l/c)
53. When a transmission line has a load impedance same as that of the
characteristic impedance, the line is said to be
Correct : D. matched
54. The wavelength of a line with a phase constant of 6.28 units is
Correct : B. 1
55. The wavelength of a wave with a frequency of 6 GHz in air is
Correct : D. 0.05
56. The phase constant of a wave with a wavelength of 2 units is given by
Correct : B. 3.14
57. The frequency of a wave travelling in a transmission line with velocity 4 x 108
and wavelength 3 units is
Correct : B. 0.133 ghz
58. The velocity and phase constant relation is given by
Correct : A. v = ω/β
59. The electrical length in a transmission line refers to the
Correct : A. product of attenuation constant and length
60. The unit of attenuation constant is
Correct : C. neper
61. The propagation constant of a wave with attenuation and phase constant
given by 2 and 3 respectively is
Correct : C. 2 + 3j
62. The velocity of wave in the air medium is
Correct : C. 3 x 108
63. Identify the secondary parameter from the options given below.
Correct : C. phase constant
64. Which of the following parameters does not exist in the transmission line
equation?
Correct : A. r
65. For an infinite transmission line, the characteristic impedance is given by 50
ohm. Find the input impedance.
Correct : D. 50
66. The best transmission length for effective transmission of power is
Correct : B. l = λ/8
67. When the length of the transmission line is same as that of the wavelength,
then which condition holds good?
Correct : D. zin = zl
68. The input impedance of a half wave transmission line with a load impedance
of 12.5 ohm is
Correct : D. 12.5
69. The condition for a quarter wave transformer is
Correct : A. zo2 = zin zl
70. Find the characteristic impedance of a quarter wave with input and load
impedances given by 50 and 25 respectively.
Correct : D. 35.35
71. Find the load impedance in a quarter line transformer with characteristic
impedance of 75 ohm and input impedance of 200 ohm.
Correct : A. 28.125
72. The reflection coefficient of a perfectly matched transmission line is
Correct : C. 0
73. The purpose of the transmission line equation is to
Correct : D. impedance matching
74. The quarter wave transformer can be considered as a
Correct : A. impedance inverter
75. Which transmission line is called as one to one transformer?
Correct : B. l = λ/2
76. The characteristic impedance of a quarter wave transformer with load and
input impedances given by 30 and 75 respectively is
Correct : A. 47.43
77. The input impedance of a quarter wave line 50 ohm and load impedance of
20 ohm is
Correct : D. 125
78. The reflection coefficient lies in the range of
Correct : A. 0 < τ < 1
79. When the ratio of load voltage to input voltage is 5, the ratio of the
characteristic impedance to the input impedance is
Correct : B. 5
80. The reflection coefficient of a wave with transmission coefficient 0.35 is
Correct : B. 0.65
81. The incident wave amplitude is 24 units. Find the reflected wave amplitude if
the reflection coefficient is 0.6.
Correct : A. 14.4
82. Find the reflection coefficient of the wave passing through two media having
intrinsic impedances of 4 and 9 respectively.
Correct : C. 0.38
83. The reflection coefficient of a wave travelling through two media having
permittivities 4 and 9 respectively is
Correct : D. 0.2
84. Calculate the transmission coefficient, when the incident and transmitted
amplitudes are 10 and 7 respectively.
Correct : D. 0.7
85. The transmission coefficient in a wave travelling through two media having
intrinsic impedances of 5.5 and 1.33 is
Correct : A. 0.389
86. The transmission coefficient in a wave travelling through two media having
permittivities 4 and 1 is
Correct : D. 2/3
87. The reflection coefficient of a transmission line having characteristic and load
impedances as 50 and 30 ohm respectively is
Correct : A. 1/4
88. In matched line, the transmission coefficient is
Correct : B. 1
89. Standing waves occurs due to
Correct : B. impedance mismatch
90. Standing wave ratio is defined as the
Correct : A. ratio of voltage maxima to voltage minima
91. Given that the reflection coefficient is 0.6. Find the SWR.
Correct : B. 4
92. The maxima and minima voltage of the standing wave are 6 and 2
respectively. The standing wave ratio is
Correct : B. 3
93. Find the standing wave ratio, when a load impedance of 250 ohm is
connected to a 75 ohm line.
Correct : D. 3.33
94. Find the reflection coefficient of the wave with SWR of 3.5.
Correct : A. 0.55
95. The range of the standing wave ratio is
Correct : C. 1 < s < ∞
96. For matched line, the standing wave ratio will be
Correct : D. 1
97. The maximum impedance of a 50 ohm transmission line with SWR of 3 is
Correct : C. 150
98. The minimum impedance of a 75 ohm transmission line with a SWR of 2.5 is
Correct : D. 30
99. The standing wave ratio of short circuited and open circuited lines will be
Correct : D. ∞
100. The current reflection coefficient of a line with voltage reflection coefficient of
0.65 is given by