MCQ in Power Generators (Cells and Batteries) Part 3 | ECE Board Exam

(Last Updated On: May 3, 2019)

This is the Multiples Choice Questions Part 3 of the Series in Power Generators, Sources, Principles and Applications as one of the Electronics Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electronics Engineering field, Electronics Books, Journals and other Electronics References.

MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Cells and Batteries
• MCQ in Electric Generator
• MCQ in Electronic Power Supply
• MCQ in Voltage Regulation
• MCQ in Photovoltaic/Thermoelectric Generator
• MCQ in Distribution Transformer
• MCQ in Uninterrupted Power Supply (UPS)
• MCQ in Float-Battery System
• MCQ in Converters
• MCQ in Inverters

Continue Practice Exam Test Questions Part 3 of the Series

Choose the letter of the best answer in each questions.

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

Questions and Answers in Power Generators, Sources, Principles, Applications

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Complete List of MCQ in Electronics Engineering per topic