BASIC ELECTRICALS PART -2
61. Ferrites are a sub-group of(a) non-magnetic materials
(b) ferro-magnetic materials
(c) paramagnetic materials
(d) ferri-magnetic materials
Ans: b
62. Gilbert is a unit of
(a) electromotive force
(b) magnetomotive force
(c) conductance
(d) permittivity
Ans: b
63. Which of the following is expected to have the maximum
permeability ?
(a) Brass
(b) Copper
(c) Zinc
(d) Ebonite
Ans: d
64. The Biot-savart’s law is a general modification of
(a) Kirchhoffs law
(b) Lenz’s law
(c) Ampere’s law
(d) Faraday’s laws
Ans: c
65. The commonly used material for shielding or screening magnetism is
(a) copper
(b) aluminium
(c) soft iron
(d) brass
Ans: c
67. A permanent magnet
(a) attracts some substances and repels others
(b) attracts all paramagnetic substances and repels others
(c) attracts only ferromagnetic substances
(d) attracts ferromagnetic substances and repels all others
Ans: a
68. A keeper is used to
(a) change the direction of magnetic lines
(b) amplify flux
(c) restore lost flux
(d) provide a closed path for flux
Ans: d
69. Magnetic moment is a
(a) pole strength
(b) universal constant
(c) scalar quantity
(d) vector quantity
Ans: d
70. Which of the following statements is correct ?
(a) The magnetic flux inside an exciting coil is lower than its outside
surface
(b) The magnetic flux inside an exciting coil is zero
(c) The magnetic flux inside the exciting coil is greater than its outside
surface
(d) The magnetic flux inside the exciting coil is same as on its outside
surface
Ans: d
71. The initial permeability of an iron rod is
(a) the highest permeability of the iron rod
(b) the lowest permeability of the iron rod
(c) the permeability at the end of the iron rod
(d) the permeability almost in non-magnetised state
Ans: d
72. How does the magnetic compass needle behave in a magnetic field ?
(a) It assures a position right angle to magnetic field
(b) It starts rotating
(c) It assures a position which follows a line of magnetic flux
(d) None of the above
Ans: c
73. The bar magnet has
(a) the dipole moment
(b) monopole moment
(c) (a) and (b) both
(d) none of the above
Ans: a
74. The magnetic materials exhibit the property of magnetisation because
of
(a) orbital motion of electrons
(b) spin of electrons
(c) spin of nucleus
(d) either of these
Ans: c
75. For which of the following materials the net magnetic moment should
be zero ?
(a) Diamagnetic materials
(b) Ferrimagnetic materials
(c) Antiferromagnetic materials
(d) Antiferrimagnetic materials
Ans: c
76. Which of the following statements is correct ?
(a) The conductivity of ferrites is better than ferromagnetic materials
(b) The conductivity of ferromagnetic materials is better than ferrites
(c) The conductivity of ferrites is very high
(d) The conductivity of ferrites is same as that of ferromagnetic materials
Ans: a
77. Which of the following type of materials are not very important for
engineering applications ?
(a) Ferromagnetic
(b) Paramagnetic
(c) Diamagnetic
(d) None of the above
Ans: c
78. For which of the following materials the saturation value is the highest
?
(a) Ferromagnetic materials
(b) Paramagnetic materials
(c) Diamagnetic materials
(d) Ferrites
Ans: d
79. Magnetism of a magnet can be destroyed by
(a) heating
(b) hammering
(c) by inductive action of another magnet
(d) by all above methods
Ans: d
80. Core of an electromagnet should have
(a) low coercivity
(b) high susceptibility
(c) both of the above
(d) none of the above
Ans: c
81. When an ac power is applied to a reactive load, then the voltage is
a. In phase with the current
b. 90 degree out of phase with the current
c. 180 degree out of phase with the current
d. 270 degree out of phase with the current
ANSWER:
B
82. The number of instantaneous values between zero and the peak
value is
a. Zero
b. One
c. Eleven
d. Infinity
ANSWER:
D
83. The peak value of a sine wave is 200 V. Its average value is
(a) 127.4 V
(b) 141.4 V
(c) 282.8 V
(d)200V
Ans: a
84. Two waves of the same frequency have opposite phase when the
phase angle between them is
(a) 360°
(b) 180°
(c) 90°
(d) 0°
Ans: b
85. The power consumed in a circuit element will be least when the phase
difference between the current and voltage is
(a) 180″
(b) 90°
(c) 60°
(d) 0°
Ans: b
86. The phase difference between voltage and current wave through a
circuit element is given as 30°. The essential condition is that
(a) both waves must have same frequency
(b) both waves must have identical peak values
(c) both waves must have zero value at the same time
(d) none of the above
Ans: a
87. The best place to install a capacitor is
(a) very near to inductive load
(b) across the terminals of the inductive load
(c) far away from the inductive load
(d) any where
Ans: b
88. Pure inductive circuit
(a) consumes some power on average
(b) does not take power at all from a line
(c) takes power from the line during some part of the cycle and then
returns back to it during other part of the cycle
(d) none of the above
Ans: c
89. Inductance affects the direct current flow
(a) only at the time of turning off
(b) only at the time of turning on
(c) at the time of turning on and off
(d) at all the time of operation
Ans: c
90. Power factor of the system is kept high
(a) to reduce line losses
(b) to maximise the utilization of the capacities of generators, lines and
transformers
(c) to reduce voltage regulation of the line
(d) due to all above reasons
Ans: d
91. In a loss-free R-L-C circuit the transient current is
(a) oscillating
(b) square wave
(c) sinusoidal
(d) non-oscillating
Ans: c
92. The r.m.s. value of alternating current is given by steady (D.C.) current
which when flowing through a given circuit for a given time produces
(a) the more heat than produced by A.C. when flowing through the same
circuit
(b) the same heat as produced by A.C. when flowing through the same
circuit
(c) the less heat than produced by A.C. flowing through the same circuit
(d) none of the above
Ans: b
93. The double energy transient occur in the
(a) purely inductive circuit
(b) R-L circuit
(c) R-C circuit
(d) R-L-C circuit
Ans: d
94. In the case of an unsymmetrical alternating current the average value
must always be taken over (a) unsymmetrical part of the wave form
(b) the quarter cycle
(c) the half cycle
(d) the whole cycle
Ans: d
95. Pure inductive circuit takes power from the A.C. line when
(a) applied voltage decreases but current increases
(b) applied voltage increases but current decreases
(c) both applied voltage and current increase
(d) both applied voltage and current decrease
Ans: a
96. In a R-L-C circuit
(a) power is consumed in resistance and is equal to I R
(b) exchange of power takes place between inductor and supply line
(c) exchange of power takes place between capacitor and supply line
(d) exchange of power does not take place between resistance and the
supply line
(e) all above are correct
Ans: e
97. A phasor is
(a) a line which represents the magnitude and phase of an alternating
quantity
(b) a line representing the magnitude and direction of an alternating
quantity
(c) a coloured tag or band for distinction between different phases of a 3-
phase supply
(d) an instrument used for measuring phases of an unbalanced 3-phase
load
Ans: a
98. Wire-wound resistors are unsuitable for use at high frequencies
because they
(a) create more electrical noise
(b) are likely to melt under excessive eddy current heat
(c) consume more power
(d) exhibit unwanted inductive and capacitive effects
Ans: d
99. A pure capacitor connected across an A.C. voltage consumed 50 W.
This is due to
(a) the capacitive reactance in ohms
(b) the current flowing in capacitor
(c) the size of the capacitor being quite big
(d) the statement is incorrect
Ans: d
100. In any linear network, the elements like inductor, resistor and
capacitor always_________
a. Exhibit changes due to change in temperature
b. Exhibit changes due to change in voltage
c. Exhibit changes due to change in time
d. Remains constant irrespective of change in temperature, voltage and
time
ANSWER: (d)
100. Which law plays a significant role in the loop analysis of the
network?
a. KCL
b. KVL
c. Law of Superposition Theorem
d. None of the above
ANSWER: (b)
101. How is the loop analysis different in application/functioning level as
compared to Kirchoff’s law?
a. Utilization of loop currents instead of branch currents for writing
equations
b. Capability of branch current to carry multiple networks
c. Reduction in the number of unknowns for complex networks
d. All of the above
ANSWER: (d)
102. Which theorem assists in replacement of an impedance branch over
the network by the other network comprising different circuit components,
without affecting the V-I relations throughout the entire network?
a. Superposition Theorem
b. Compensation Theorem
c. Substitution Theorem
d. Maximum Power Transfer Theorem
ANSWER: A
103. The time constant of a series R-C circuit is given by
(a) R/C
(b) RC2
(c) RC
(d) R2C
Ans: c
104. The safest value of current the human body can carry for more than 3
second is
(a) 4 mA
(b) 9 mA
(c) 15 mA
(d) 25 mA
Ans: b
105. The apparent power drawn by an A.C. circuit is 10 kVA and active
power is 8 kW. The reactive power in the circuit is
(a) 4 kVAR
(b) 6 kVAR
(c) 8 kVAR
(d) 16 kVAR
Ans: b
106. What should be done, if the dependent current and voltage sources
are present in a circuit while applying ‘Superposition Theorem’?
a. Replace them by open circuit
b. Replaced them by short circuit
c. Keep in their original form without replacing by either open or short
circuits
d. None of the above
ANSWER: C
107. Which is the correct sequential order of steps to be undertaken
while applying Thevenin’s theorem?
A. Calculation of Thevenin’s equivalent voltage
B. Removal of branch impedance through which required current is to be
estimated
C. Estimation of equivalent impedance between two terminals of the
branch
D. Estimation of branch current by schematic representation of
Thevenin’s equivalent circuit
a. A, C, B, D
b. B, A, C, D
c. D, A, C, B
d. B, C, D, A
ANSWER: B
108. Which method can be used for absolute measurement of resistance ?
(A) Ohm's law method
(B) Wheatstone bridge method
(C) Raleigh method
(D) Lortentz method.
Answer B
109. How many number of minimum end nodes or terminal nodes are
involved in a tree, according to its properties?
a. Only one
b. Two
c. Four
d. Infinite
ANSWER: (b)
110. What will be the value of a rectangular (complete incidence) matrix,
if an associated branch is oriented towards the node?
a. 1
b. -1
c. 0
d. Not defined (∞)
ANSWER: b
111. According to the linear graph theory, the number of possible trees is
always equal to the determinant of product of ______
a. Only complete incidence matrix
b. Reduced incidence matrix & its transpose
BASIC CONCEPT
c. Cut-Set matrix
d. Tie-set matrix
ANSWER: B
112. Consider the mathematical representation of nth order differential
equation given below. What does the notation v(t) indicate in it?
a. (dn i/dtn) + a1 (dn -1 i /dtn-1) + …… +a n-1 (di / dt) + an i = v(t)
a. Independent variable
b. Input or forcing function
c. Excitation
d. All of the above
ANSWER: D
113. Which elements behave as an open circuit especially under the
consideration of d.c. quantities?
a. Inductors
b. Resistors
c. Capacitors
d. All of the above
ANSWER: C
114. What would be the value of power factor for series RLC circuit under
the resonance phenomenon?
a. 0
b. 0.5
c. 1
d. Infinity
ANSWER: C
115. Which among the following get/s cancelled under the resonance
condition in a.c. circuits, if inductive and capacitive reactances are in
parallel?
a. Reactance
b. Susceptance
c. Resistance
d. All of the above
ANSWER: B
116. Which among the following condition is true at the resonance?
a. Xc > XL
b. Xc = XL
c. Xc < XL
d. None of the above
ANSWER: B
117. If a differential equation is said to be homogeneous, what would be
the value of a forcing function?
a. 0
b. 1
c. ∞
d. -1
ANSWER:A
118. Which notation of instant implies that the unchanged condition of
network is about to change?
a. t(0)+
b. t(0)–
c. t*
d. tˆ
ANSWER: B
119. Reactance curve is basically a graph of individual reactances verses
__________
a. Frequency
b. Phase
c. Amplitude
d. Time period
ANSWER: A
120. Which type of impedance in asymmetrical network is estimated at a
single pair of network terminals especially in the chain of infinite
networks?
a. Image impedance
b. Iterative impedance
c. Characteristic impedance
d. All of the above
ANSWER B
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