116.
A
synchronous machine
has its field winding
on the stator and armature winding on the rotor. Under steady running condition,
the air gap field
(a) rotates at synchronous speed w.r.t. rotor
(b) rotates at synchronous speed in the direction ofrotation of the rotor
(c) remains stationary
w.r.t. stator (cl) remains stationary w.r.t. rotor.
117.
In a pure LC parallel circuit under
resonance condition, current drawn from the supply mains is
(a) very large
(c) V/./LC,
(b) vJLC
(d) Zero.
118.
In a circuit
the voltage and current are
given by V = (10 + j5) and i = (6 + j4). The circuit
IS
(a) inductive
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(b) capacitive
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(c) resistive
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(d) it could
be any of the above.
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119.
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The power
in the circuit
of problem 118 is
(a) 60 watt
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(b) 20 watt
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(c) 80 watt
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(d) 70
watt.
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120.
The reactive power in the circuit of problem 1 18 is
(a) 70 V Ars (b) 60 V Ars
(c) 10 V Ars (d) - 10 V Ars.
121.
The current at a given point in a certain circuit
may be given a function
of time as
i(t)
= - 3 + t
The total charge passing the point between
t = 99 sec and t = 102 sec is
(a) 112
C (b) 242.5 C
(c) 292.5 C (d) 345.6 C.
122.
An alternator
has a phase sequence
of RYB for its phase voltages. In case the field
current is reversed, the phase sequence will become
(a) RBY
(c) YRB
(b) RYB
(d) None of the ahove.
123.
An alternator
has a phase sequence
of RYB for its phase voltage. In case the direction
of rotation of alternator
is reversed, the phase sequence will become
(a)
RBY
(c) YRB
(b) RYB
(d) None of the above.
124.
Modern high speed synchronous
generator used in thermal plants have
Modern high speed synchronous
generator used in thermal plants have
(a)
salient pole rotors (b) cylindrical rotor
(c) either salient or cylindrical (d) spherical
rotor.
125.
In a split phase 1-phase induction motor the wire of the main winding as compared to auxiliary winding
is
(a) thinner (b) thicker
(c) same size (d) could be either way.
126.
The rotor of a 1-phase induction
motor is
(a)
a
cage or wound rotor
(c) always a wound rotor
(b) always
a cage rotor
(d) a double cage rotor.
127.
In a capacitor start motor, the capacitor
is connected
(a)
in series with the main winding
(c) in parallel with the auxiliary
winding
128.
A ceiling fan uses
(a)
split phase motor
(c) capacitor
start motor
129.
A
two-phase servo-motor has
(a)
wound rotor
(c) wound
or cage rotor
130.
The motor used in electric
toys is
(a)
split phase motor
(c) shaded
pole motor
(b) in series with the auxiliary winding
(d) in series with both the windings.
(b) capacitor start capacitor run
motor
(d) universal
motor.
(b) cage rotor
(d) double cage rotor.
(b) permanent capacitor motor
(d) capacitor start motor.
131.
The voltage fed to the two windings of a two-phase
servo motor must be
(a)
in phase with each other (b) goo apart
with each other
(c) 180° apart with each other
(d) more than goo but less than 180° apart with each other.
132.
A stepper
motor is a
(a)
de motor
(c) two-phase motor
(b) single
phase ac motor
(d) multi-phase motor.
133.
Phantom loading heat run test on transformers is performed by means of
Phantom loading heat run test on transformers is performed by means of
(a)
S.C. Test (b) O.C. Test
(c) Half time on S.C. and halftime
on D.C. test
(d) Sumpner's
Test.
3
134.
A power transformer has its maximum efficiency at 4 th full load. Its iron loss and full
load copper loss Pc are related as
16
(a)
P/Pc = g
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135.
In case of a transformer
the low voltage winding is placed near the core because
(a) it reduces
insulation requirement (b) it reduces hysteresis
loss
(c) it is convenient (d) it reduces
eddy current loss.
136.
Conservator on a transformer is provided to
(i) prevent
oil from coming in contact
with the atmosphere
(ii)
allow breathing and to increase the oil surface exposed to atmosphere
(iii)
allow breathing and also to reduce the oil surface
exposed to atmosphere.
Tick out the correct answer
(a) only (i) is
true (b) only (ii) is correct
(c) only (iii) is correct (d) (i) (ii) (iii) all are correct.
137.
Two transformers connected in parallel share loads in the ratio of their KVA ratings pro vided their impedances
are
(a)
in inverse ratio oftheir ratings
(c) equal
(b) in direct ratio of their ratings
(d) none of the above is necessary.
138.
A transformer is operating
under no load condition
at rated voltage.
A small air gap is now cut across the yoke of its core. The maximum flux density and magnetising current respectively.
(a)
decrease and decrease (b) decrease and increase
(c) increase and increase (d) remain
same and increase.
139.
A 440/220 V transformer has per unit impedance of 0. 1 In order to circulate full load current during shot circuit
the voltage impressed on high voltage side is
(a)
22 V
(c) 44 volt
(b) 10 v
(d) 20 volt.
140.
For fixed primary
voltage and secondary load current if the p.f. of the load is changed from
0.6 lead to 0.8 lead, the secondary voltage
(a) increases (b) decreases
(c) first decreases and then increases (d) does not change.
141.
A transformer has maximum
efficiency at full load. Its all day efficiency
will be maximum when it is operated
(a)
full load all the time
3
(b)
full load half the time and 4th load half time
(c)
full load and halfload
each half the time
(d) full load half time and no load half the time
142.
Inter poles help commutation in a de machine by
(a)
aiding the main poles
(b)
causing dynamically induced e.m.f. in the coils undergoing commutation
(c)
causing
statically induced e.m.f. in the coils undergoing commutation
(d) cancelling the armature reaction m.m.f.
143.
If the armature current
if a.d.c. motor is increased keeping the field flux constant,
the torque developed
(a)
increases proportionally
increases proportionally
(c) increases proportional to F
(b) decreases in inverse
ratio
(d) remains
constant.
144.
The critical field resistance
of a.d.c. shunt generator is
(a)
the value of field
circuit resistance above which the generator would fail to excited
(b)
the value of field circuit resistance below which this generator
would fail to excite
(c)
the resistance of the field
winding (d) none of the above.
145.
For a.d.c. shunt generator, the critical resistances are for
(a)
load circuit
only (b) field circuit only
(c) load and field circuits (d) none of the two circuits.
146.
In Hopkinson's test on two identical d.c. machines the power input
to the armature circuit consists of
(a) rated
power of the two machines
(b)
copper loss + no load iron loss + windage and friction
loss + stray load loss
(c)
armature copper loss + no load iron loss + stray load loss
(d)
armature copper loss + no load iron loss + windage
and friction
loss
147.
Two coupled d.c. series motors with constant
torque load are changed
over from series to parallel connection
across a fixed voltage
supply. The speed of the combined set as com pared to original speed becomes
(a) Twice (b) Half
(c) -J2 times (d) no change.
148.
A d.c. machine
has maximum efficiency when
(a)
iron losses equal copper losses (b) constant losses equal variable
losses
(c)
windage and friction
losses equal copper losses
(d)
(a) and (b).
149.
The d.c. generator used for voltage boost is
(a) shunt (b) series
(c) separately excited (d) compound.
150.
In a level compound
generator the terminal voltage at half load as compared to no load is
(a)
more (b) less
(c) same (d) none ofthe above is necessary.
Answers:
l16. (c)
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l1 7. (d)
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l18. (b)
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l19. (c)
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120. (d)
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121.
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(c)
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122. (b)
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123. (a)
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124. (b)
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125. (b)
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126. (b)
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127.
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(b)
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128. (c)
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129. (b)
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130. (c)
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131. (b)
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132. (d).
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133.
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(d)
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134. (d)
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135. (a)
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136. (c)
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137. (a)
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138. (d)
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139.
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(c)
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140. (b)
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141. (a)
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142. (b)
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143. (a)
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144. (a)
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145.
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(c)
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146. (b)
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147. (a)
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148. (b)
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149. (b)
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150. (a)
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