Multiple Choice Questions Topic Outline
- MCQs in Cells and Batteries
- MCQs in Electric Generator
- MCQs in Electronic Power Supply
- MCQs in Voltage Regulation
- MCQs in Photovoltaic/Thermoelectric Generator
- MCQs in Distribution Transformer
- MCQs in Uninterrupted Power Supply (UPS)
- MCQs in Float-Battery System
- MCQs in Converters
- MCQs in Inverters
The Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part 3 of the Series
101. The synchronous reactance of an alternator _______ as the iron is saturated
- A. decreases
- B. remains the same
- C. increases
- D. becomes doubled
102. A 4 pole dc machine has magnetic circuits
- A. 2
- B. 4
- C. 8
- D. 6
103. The current in armature conductors of a dc machine is
- A. pure dc
- B. ac
- C. pulsating dc
- D. pure dc plus pulsating dc
104. The ac armature winding of an alternator operates at ______ the field of winding
- A. the same voltage as
- B. much higher voltage than
- C. much lesser voltage than
- D. half the voltage than
105. Why are the field poles and the armature of a dc machine laminated?
- A. to reduce the weight of the machine
- B. to reduce eddy current
- C. to decrease the speed
- D. to reduce armature reaction
106. The back emf or counter emf in a dc motor
- A. opposes the applied voltage
- B. aids the armature current
- C. aids the supplied voltage
- D. opposes the armature current
107. The synchronous reactance of an alternator is due to
- A. leakage flux
- B. armature reaction
- C. dc field excitation
- D. hysteresis loss
108. Back emf in a dc motor is maximum at
- A. no load
- B. half full load
- C. full load
- D. three fourth full load
109. The mechanical power developed in a dc motor is maximum when back emf is equal to _____ the applied voltage
- A. twice
- B. one third
- C. one half
- D. one fourth
110. The core type transformer is generally suitable for
- A. high voltage and small output
- B. low voltage and high output
- C. high voltage and high output
- D. low voltage and low output
111. The transformer that should never have the secondary open circuited when primary is energized is
- A. power transformer
- B. auto transformer
- C. voltage transformer
- D. current transformer
112. The field winding of an armature is _______ excited
- A. dc
- B. ac
- C. both ac and dc
- D. battery
113. The salient pole construction for field structure of an alternator is generally used for _____ machine
- A. 2 pole
- B. 8 pole
- C. 4 pole
- D. 6 pole
114. When the speed of a dc motor increases, its armature current
- A. increases
- B. remains the same
- C. decreases
- D. becomes infinite
115. The frequency of emf generated in an 8 pole alternator at 900 rpm is
- A. 50 hz
- B. 120 hz
- C. 60 hz
- D. 240 hz
116. In case if a 4 pole machine, 1 mechanical degree corresponds to _____ electrical degree
- A. 2
- B. 8
- C. 4
- D. 6
117. The torque developed by a dc motor is directly proportional to
- A. flux per pole x armature current
- B. armature resistance x applied voltage
- C. armature resistance x armature current
- D. flux per pole x applied voltage
118. AC machine in which the torque is produced by the interaction of currents in the stator and currents induced in the motor by transformer action
- A. squirrel cage motor
- B. stepper motor
- C. synchronous motor
- D. induction motor
119. Machine in which torque is produced by the interaction of ac current in the stator and dc currents in the rotor turning synchronism
- A. synchronous motor
- B. induction motor
- C. squirrel cage motor
- D. stepper motor
120. The main drawback of a dc shunt generator is that
- A. terminal voltage drops considerably with load
- B. shunt field circuit has high resistance
- C. generated voltage is small
- D. it is expensive
121. DC machines which are subjected to abrupt changes of load are provided with
- A. interpole windings
- B. compensating winding
- C. equalizers
- D. copper brushes
122. The shaft torque in a dc motor is less than total armature torque because of _____ in the motor
- A. copper losses
- B. iron and friction losses
- C. field losses
- D. hysteresis loss
123. Armature reaction in a dc motor is increased
- A. When the armature current increases
- B. when the armature current decreases
- C. when the field current increases
- D. by interpole
124. An ideal transformer is one which
- A. has no losses and leakage reactance
- B. does not work
- C. has the same number of primary and secondary turns
- D. has the same primary and secondary voltage
125. If a power transformer is operated at very high frequencies then
- A. primary reactance is too much increased
- B. primary will draw large power
- C. core losses will be excessive
- D. core loss is negligible
126. With respect to the direction of rotation, interpoles on a dc motor must have the same polarity as the main poles
- A. ahead of them
- B. in parallel with them
- C. behind them
- D. beside them
127. The open circuit test on a transformer is always made on
- A. low voltage winding
- B. high voltage winding
- C. either low or high voltage
- D. neither low or high voltage
128. In the short circuit test in a transformer, _____ winding is generally short circuited
- A. high voltage
- B. low voltage
- C. either low or high voltage
- D. neither low nor high voltage
129. In a dc motor, the brushes are shifted from the mechanical neutral panel in a direction opposite to the rotation to
- A. decreased speed
- B. reduced sparking
- C. increase speed
- D. produce flat characteristics
130. The number of cycles generated in a 6 pole alternator in one revolution is
- A. 3
- B. 5
- C. 6
- D. 2
131. If the lagging load power factor of an alternator is decreased, the demagnetizing effect of the armature reaction
- A. remains the same
- B. is increased
- C. is decreased
- D. becomes infinite
132. In a very large dc motor with severe heavy duty, armature reaction effects are corrected by
- A. using interpole only
- B. using compensatory windings in addition to interpoles
- C. shifting the brush position
- D. fixing the brush position
133. The amount of copper in the primary is ______ that of the secondary
- A. about the same as
- B. smaller than
- C. greater than
- D. twice
134. The open circuit test on a transformer gives
- A. copper losses
- B. iron losses
- C. friction losses
- D. total losses
135. The speed of a _______ motor is practically constant
- A. commutatively compounded
- B. differentially compounded
- C. series
- D. shunt
136. The running speed of a dc series motor is basically determined by
- A. field excitation
- B. armature resistance
- C. load
- D. applied voltage
137. If the excitation of an alternator operating in parallel with other alternators is decreased, its
- A. power factor becomes more leading
- B. output kW will change
- C. power factor becomes more lagging
- D. power factor becomes unity
138. The distribution of load between two alternators operating in parallel can be changed by changing
- A. phase sequence
- B. field excitation of alternators
- C. driving torques of prime movers
- D. current direction
139. After a shunt motor is up to speed the speed may be increased considerably by
- A. increasing field circuit resistance
- B. decreasing field circuit resistance
- C. increasing the armature circuit resistance
- D. reducing the load
140. When the secondary of a transformer is short circuited, the primary inductance
- A. is decreased
- B. remains the same
- C. is increased
- D. becomes zero
141. For the same rating ______ motor has the least starting torque
- A. commulatively compounded
- B. shunt
- C. series
- D. differentially compounded
142. The deciding factor in the selection of a dc motor for a particular application is its _____ characteristics
- A. speed torque
- B. torque armature current
- C. speed armature current
- D. speed
143. The rotor of a turbo alternator is made cylindrical in order to reduce
- A. eddy current loss
- B. wind age loss
- C. hysteresis loss
- D. copper loss
144. The disadvantage of a short pitched coil is that
- A. harmonics are introduced
- B. waveform becomes non-sinusoidal
- C. voltage round the coil is reduced
- D. voltage round coil is increases
145. The demand for a large increase in torque of a dc shunt motor is met by a
- A. large decreased in speed
- B. large increased in current
- C. large increased in speed
- D. small increased in current
146. For 20% increase in current, the motor that will give the greatest increase in torque is ______ motor
- A. shunt
- B. series
- C. differentially compounded
- D. commulatively compounded
147. What cell is used to detect infrared radiation, either its generated voltage or its change of résistance may be used as a measure of the intensity of the radiation?
- A. lead sulfide cell
- B. Faure storage cell
- C. infrared cell
- D. Leclanche cell
148. A galvanic cell resulting from difference in potential between adjacent on the surface of a metal immersed in an electrolyte
- A. NiCd cell
- B. lead acid cell
- C. local cell
- D. lithium cell
149. Which motor is used to start heavy loads?
- A. series
- B. differentially compounded
- C. shunt
- D. commulatively compounded
150. When load is removed, the motor that will run at the highest speed is the _____ motor
- A. shunt
- B. commulatively compounded
- C. series
- D. differentially compounded
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