Top 200 Electrical Engineers Objective Questions and Answers

In this article, we published the top 200 electrical engineers objective questions and answers for electrical and electronics engineers.

Electrical Engineers Objective Questions

Top 200 Electrical Engineers Objective Questions and Answers

The below list provides all the multiple-choice questions (MCQ) related to electrical engineers.

Answers are available at the bottom of the article.

1. Carbon brushes are used in a dc machine because

A)carbon is cheap
B)carbon lubricates and polishes the commutator
C)contact resistance is decreased
D)carbon is abundant

2. A type of secondary cell that can be recharged but with an electrolyte that cannot be refilled

A)Sealed secondary cell
B)Sealed rechargeable cell
C)Alkaline cell
D)Lealanche cell

3. A stand alone solar power system

A)need a full wave rectifier
B)requires the use of dry cells
C)relies on the electric utility at night
D)uses solar panels and batteries

4. The alternators driven by _____ do not have a tendency to hunt

A)diesel engines
B)prime movers
C)steam engines
D)water turbines

5. Which motor is used to start heavy loads?

A)series
B)shunt
C)differentially compounded
D)commulatively compounded

6. Galvanic cell is the other name of

A)secondary cell
B)primary cell
C)voltaic cell
D)solar cell

7. In a wave winding, the commutator pitch is approximately equal to

A)half the pole pitch
B)pole pitch
C)twice the pole pitch
D)thrice the pole pitch

8. The armature of a dc machine is laminated in order to reduce

A)Copper loss
B)Frictional loss
C)Hysteresis loss
D)Eddy current loss

9. The stator of an alternator is identical to that of a

A)1 phase induction motor
B)dc generator
C)3 phase induction motor
D)Rosenberg generator

10. The salient pole construction for field structure of an alternator is generally used for ______ machine

A)4 pole
B)6 pole
C)2 pole
D)8 pole

11. A transformer operates poorly at very low frequencies because

A)primary reactance is too much
B)permeability core is reduced
C)magnetizing current is abnormally high
D)permeability of core is increased

12. A dc compound generator having full load terminal voltage equal to the no-load generator voltage is called ______ generator

A)under compounded
B)flat compounded
C)un compounded
D)over compounded

13. The demand for a large increase in torque of a dc series motor is met by a

A)large decrease in speed
B)large increase in speed
C)large decrease in current
D)small decrease in speed

14. The open circuit test on a transformer is always made on

A)low voltage winding
B)neither low or high voltage
C)either low or high voltage
D)high voltage winding

15. The greatest percentage of the heat loss in a dc machine is due to

A)eddy current loss
B)hysteresis loss
C)copper loss
D)frictional loss

16. Intermittent sparking at the brushes of dc motor may be caused due to

A)an open armature coil
B)incorrect voltage
C)loose coupling
D)intermittent load

17. In a dc generator armature reaction _______ pole tip

A)weakens the flux at the leading
B)strengthens the flux at the leading
C)strengthens the flux at the trailing
D)weakens the flux at the trailing

18. The size of a dc generator can be reduced by using

A)iron commutator
B)magnetic material of high permeability
C)high resistance winding material
D)lap winding

19. For the same rating, a dc machine has _______ an ac machine

A)the same weight as
B)less weight than
C)half the weight than
D)more weight than

20. In a simplex wave winding, the number of parallel paths is equal to

A)2
B)1
C)number of pair poles
D)number of poles in the machine

21. A _______ is a group of cells that generates electric energy from their internal chemical reaction

A)power supply
B)battery
C)regulator
D)solar energy

22. Which motor never use belt connected loads?

A)Shunt
B)Series
C)Commulatively compounded
D)Differentially compounded

23. A commutatively compounded motor does not run at dangerous speed at light loads because of the presence of

A)series
B)interpoles
C)shunt winding
D)compensating windings

24. The transformer that should never have the secondary open-circuited when the primary is energized is

A)power transformer
B)auto transformer
C)voltage transformer
D)current transformer

25. A transformer will have zero efficiency at

A)no load
B)half full load
C)full load
D)twice the load

26. The effect of armature reaction is to

A)make the flux constant
B)decreased the total flux
C)make the air gap flux uniform
D)increase the total flux

27. The nature of armature winding of a dc machine is decided by

A)number of coils
B)front pitch
C)commutator path
D)back pitch

28. Four carbon zinc cell in series will provide about

A)8Vdc
B)2Vdc
C)9Vdc
D)6Vdc

29. The mechanical power developed in a dc motor is maximum when back emf is equal to ______ the applied voltage

A)one half
B)twice
C)one fourth
D)one third

30. To increase current capacity, cells are connected in

A)parallel
B)series- parallel
C)series
D)parallel- series

31. Silver cadmium is secondary cell with a nominal open circuit voltage of

A)1.1V
B)1.2V
C)1.35V
D)1.5V

32. A 12v battery is rated at 48 ah.

If it must deliver an average of 2.0 a, how long will the battery take before it needs recharging

A)24hrs
B)48hrs
C)96hrs
D)4hrs

33. For the same rating _______ motor has the least starting torque

A)shunt
B)differentially compounded
C)commulatively compounded
D)series

34. With respect to the direction of rotation, interpoles on a dc motor must have the same polarity as the main poles

A)in parallel with them
B)behind them
C)ahead of them
D)beside them

35. If the lagging load power factor of an alternator is decreased, the demagnetizing effect of the armature reaction

A)becomes infinite
B)is decreased
C)remains the same
D)is increased

36. The ac armature winding of an alternator operates at _______ the field of winding

A)much higher voltage than
B)the same voltage as
C)much lesser voltage than
D)half the voltage than

37. What can be found in a transformer with the open-circuit test?

A)Total equivalent resistance
B)Turns ratio
C)Total equivalent leakage resistance
D)Copper losses

38. What gives the relative activity in forming ion charges for some of the chemical elements?

A)Electromotive series
B)Both Electrochemical series & Electromotive series
C)Electrochemical series
D)Electrical series

39. The brush voltage drop in a dc machine is about

A)10V
B)20V
C)0.1V
D)2V

40. What is the nominal output of an automotive battery having six lead-acid cells in series?

A)12V
B)3V
C)24V
D)6V

41. The field structure of a dc machine uses

A)Salient pole arrangement
B)Non salient pole arrangement
C)Silicon steel
D)Cast steel

42. The real working Part of a dc machine is the

A)commutator
B)field winding
C)stator
D)armature winding

43. For given number of poles (2) and armature conductors, a lap winding will carry ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a wave winding

A)more current than
B)less current than
C)half the current than
D)same current as

44. A separately excited dc generator is not used because

A)it is costly
B)a separate dc source is required for field circuit
C)it is bulky
D)voltage drops considerably with load

45. The efficiency of a transformer will be at maximum when

A)copper loss is zero
B)copper loss is equal to constant loss
C)resistance of the two windings are equal
D)leakage reactance of the two windings are equal

46. A 4 pole dc machine has magnetic circuits

A)2
B)8
C)4
D)6

47. The speed at which a 6 pole alternator should be drive to generate 50 cycles per second is

A)1200 rpm
B)500 rpm
C)1000 rpm
D)1500 rpm

48. The terminal voltage of a ________ generator vary widely with changes in load current

A)shunt
B)over compounded
C)series
D)flat compounded

49. An ideal transformer is one which

A)has the same number of primary and secondary turns
B)has the same primary and secondary voltage
C)has no losses and leakage reactance
D)does not work

50. The maximum flux produced in the core of a transformer is

A)inversely proportional to primary voltage
B)inversely proportional to supply frequency
C)inversely proportional to secondary voltage
D)directly proportional to supply frequency

51. When load is removed, the motor that will run at the highest speed is the ​______ motor

A)shunt
B)differentially compounded
C)series
D)commulatively compounded

52. The rotor of a turbo alternator is made cylindrical in order to reduce

A)wind age loss
B)eddy current loss
C)copper loss
D)hysteresis loss

53. The voltage regulation of an alternator with a power factor of 0.8 lagging is ______ at unity power factor

A)greater than
B)D. 100%
C)the same as
D)smaller than

54. 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

55. the load on an alternator is increased, the terminal voltage increases if the load power factor is

A)lagging
B)leading
C)unity
D)zero

56. The most commonly used method of speed control of a dc motor is by varying

A)voltage applied to the motor
B)armature circuit resistance
C)felids strength
D)effective number of conductors in series

57. The greatest eddy current loss occurs in the ______ of a dc machine

A)field poles
B)armature
C)yoke
D)commutating process

58. A dc motor is still used in industrial applications because it

A)provides fine speed control
B)is cheap
C)has no replacement
D)is simple in construction

59. The air gap in an alternator is ______ in an induction machine

A)much longer than
B)about the same as
C)much shorter than
D)one-half than

60. DC series motors are used in those applications where ______​ required

A)variable speed
B)constant speed
C)low no load speed
D)high starting torque

61. Which of the following is not a secondary cell?

A)Silver-oxide
B)Silver-zinc
C)Lead-acid
D)Nickel-iron

62. A storage battery in which the electrodes are grids of lead containing lead oxides that changes in composition during charging and discharging and the electrolyte is dilute sulfuric acid

A)Leclanche battery
B)Faure storage battery
C)Nickel cadmium battery
D)Lead and battery

63. When the speed of a dc motor increases, its armature current

A)increases
B)remains the same
C)becomes infinite
D)decreases

64. The core type transformer is generally suitable for

A)low voltage and high output
B)low voltage and low output
C)high voltage and high output
D)high voltage and small output

65. Majority of alternators in use have

A)revolving field type construction
B)stationary field type construction
C)revolving ac armature winding
D)stationary ac armature winding

66. For the same rating ​_____ motor has the highest staring torque

A)series
B)differentially compounded
C)shunt
D)commutatively compound

67. The ac armature winding of an alternator is

A)pi connected
B)star delta connected
C)generally delta connected
D)always star connected

68. Cumulatively compounded motors are used in applications where ______ is required

A)sudden heavy loads for a short duration
B)constant speed
C)poor speed regulation
D)variable speed

69. When the secondary of a transformer is short-circuited, the primary inductance

A)is increased
B)remains the same
C)is decreased
D)becomes zero

70. Armature reaction in a dc motor is increased

A)when the armature current decreases
B)when the field current increases
C)by interpole
D)When the armature current increases

71. Which of the following is not a primary cell?

A)Mercuric oxide
B)Edison call
C)Carbon-zinc
D)Zinc-chloride

72. The rating of an alternator is expressed in

A)KVAR
B)kVA
C)kW
D)HP

73. What is the approximate efficiency of large transformer?

A)95%
B)65%
C)80%
D)50%

74. The core type transformer provides

A)much longer magnetic pattern
B)lesser average length per turn
C)longer magnetic path
D)shorter magnetic path

75. Volt is a unit of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

A)magneto motive force
B)energy
C)electromotive force
D)force

76. DC machines which are subjected to abrupt changes of load are provided with

A)interpole windings
B)copper brushes
C)equalizers
D)compensating winding

77. In a very large dc motor with severe heavy duty, armature reaction effects are corrected by

A)fixing the brush position
B)shifting the brush position
C)using compensatory windings in addition to interpoles
D)using interpole only

78. The shaft torque in a dc motor is less than total armature torque because of ______ in the motor

A)iron and friction losses
B)hysteresis loss
C)field losses
D)copper losses

79. A transformer will work on

A)dc only
B)pulsating dc
C)ac only
D)ac as well as dc

80. The voltage of the bus bar to which several alternators are paralleled may be raised by simultaneously _______ of all alternators

A)decreasing field excitation
B)increasing input to prime movers
C)decreasing input to prime movers
D)increasing field excitation

81. the primary leakage flux links

A)secondary winding only
B)primary winding only
C)neither primary nor secondary windings
D)both primary and secondary windings

82. An 8 pole duplex lap winding will have ______​ parallel paths

A)8
B)32
C)16
D)4

83. If the excitation of an alternator operating in parallel with other alternators is decreased, its

A)power factor becomes more leading
B)power factor becomes unity
C)output kW will change
D)power factor becomes more lagging

84. The armature winding of a dc Machine is ______ winding

A)a closed circuit
B)partly open circuit and partly closed circuit
C)an open circuit
D)lap

85. A graphical relation between the generated emf and the field current of a machine

A)voltage generation curve
B)voltage current curve
C)magnetization curve
D)current generation curve

86. In a lap winding, the number of the brushes required is equal to

A)number of coils
B)number of poles
C)commutator pitch
D)number of pairs of poles

87. In an auto transformer, the primary and secondary are ​_______​ coupled

A)only electrically
B)only magnetically
C)directly
D)magnetically as well as electrically

88. considered as the main types of battery

A)Voltaic cell and lithium cell
B)Lithium cell and alkaline
C)Leclanche cell and carbon zinc
D)Carbon-zinc dry cell and lead sulphuric wet cell

89. The common dry cell, which is a primary cell having a carbon positive electrode and a zinc negative electrode in an electrolyte of sal ammoniac and a depolarizer

A)Lithium cell
B)Lead acid cell
C)Faure storage cell
D)Leclanche cell

90. An example of rechargeable dc source is an/a

A)optoisolator
B)photovoltaic cell
C)lithium battery
D)lead acid battery

91. The armature winding of a dc machine is placed on the rotor to

A)reduce losses
B)save iron
C)facilitate commutation
D)reduce armature reaction

92. Which is the most suitable for punch presses?

A)differentially compounded motor
B)commutatively compounded motor
C)series motor
D)shunt motor

93. low speed alternators are driven by

A)hydraulic turbines
B)steam engines
C)diesel engines
D)steam turbines

94. Damper windings are used in alternators to

A)reduce eddy current loss
B)reduce wind age losses
C)prevent hunting
D)achieve synchronism

95. The effect of leakage flux in a transformer is to

A)increase copper losses
B)decrease copper losses
C)reduce eddy current losses
D)cause voltage drop in the windings

96. If the excitation of an alternator operating in parallel with other alternators is increased above the normal value excitation of excitation its

A)output current decreases
B)power factor becomes more leading
C)output kw decreases
D)power factor becomes more lagging

97. A dc series motor is most suitable for

A)lathes
B)cranes
C)pump
D)punch presses

98. In a practical transformer, copper losses account for how many percent of the total losses?

A)75%
B)95%
C)85%
D)25%

99. A triplex wave winding will have ______ parallel paths

A)8
B)4
C)6
D)2

100. What is the output of a lead acid cell?

A)1.5V
B)1.35V
C)2.1V
D)1.25V

101. The winding of the transformer with greater number of turns will be

A)high voltage winding
B)either high or low voltage winding
C)high power
D)low voltage winding

102. Excessive sparking at the brushes may caused due to

A)dirt on the commutator
B)misalignment of machine
C)loose coupling
D)worn bearings

103. The demand for a large increase in torque of a dc shunt motor is met by a

A)large increased in speed
B)small increased in current
C)large decreased in speed
D)large increased in current

104. In the short circuit test in a transformer, ​_______​ winding is generally short circuited

A)low voltage
B)either low or high voltage
C)high voltage
D)neither low nor high voltage

105. The voltage per turn of the primary of a transformer is ​ ​_______ the voltage per turn of the secondary

A)more than
B)the same as
C)less than
D)twice

106. The number of cycles generated in a 6 pole alternator in one revolution is

A)2
B)5
C)3
D)6

107. The iron losses in a dc motor depend upon

A)both flux and speed
B)flux only
C)speed only
D)temperature

108. To produce an output of 7.5v, how many carbon zinc cells are connected in series?

A)4
B)6
C)5
D)3

109. Which of the following is the main function of a dc motor?

A)to change mechanical energy to electrical energy
B)to generate power
C)to change electrical energy to mechanical energy
D)to change chemical energy to mechanical energy

110. Hot bearings of a dc motor may be caused by

A)incorrect voltage
B)poor ventilation
C)lack of dirty lubricant
D)loose coupling

111. A machine with field excitation by both shunt and series windings

A)complex machine
B)universal machine
C)shunt/ series machine
D)compound machine

112. For a given dc generator, the generated voltage depends upon

A)both speed and flux
B)armature rotation
C)speed only
D)flux only

113. For the same rating, the size of low speed alternator is ______ that of high speed alternator

A)about the same as
B)more than
C)twice
D)less than

114. Three cells connected in series from a

A)voltage divider
B)voltage multiplier
C)hybrid
D)battery

115. The friction and wind age losses in a dc motor depends upon

A)flux
B)field and armature resistance
C)speed
D)armature current

116. The frequency of emf generated in an 8 pole alternator at 900 rpm is

A)120hz
B)60hz
C)50hz
D)240hz

117. The voltage output of a cell depends on

A)electrochemical series
B)electromotive series
C)its elements
D)its electrodes

118. What refers to a method in which the charger and the battery are always connected to each other for supplying current to the load

A)Continuous charging
B)Infinite charging
C)On line charging
D)Float charging

119. Excessive motor vibration is caused by

A)too much brush tension
B)bent shaft
C)open armature coil
D)worn bearings

120. In a dc machine, the number of commutator segments is equal to

A)number of conductors
B)twice the number of coils
C)twice the number of poles
D)number of coils

121. Combination of ac motor, dc generator, and exciter to provide adjustable voltage dc power to a dc motor.

A)Universal motor
B)Ward-Leonard system
C)Compound motor
D)Half wave SCR adjustable voltage supply

122. The torque developed by a dc motor is directly proportional to

A)flux per pole x applied voltage
B)flux per pole x armature current
C)armature resistance x armature current
D)armature resistance x applied voltage

123. The armature of a dc machine is made of

A)silicon steel
B)cast steel
C)soft iron
D)wrought iron

124. In a chemical cell current is the movement of

A)positive ions only
B)negative ions only
C)positive and negative ions
D)positive charges

125. The speed of a dc motor is

A)inversely proportional to armature current
B)inversely proportional to flux per pole
C)inversely proportional to applied voltage
D)directly proportional to flux per pole

126. A motor takes a large current at starting because

A)back emf is high
B)shunt field is producing weak field
C)back emf is low
D)the armature resistance is high

127. The amount of copper in the primary is ______ that of the secondary

A)about the same as
B)twice
C)smaller than
D)greater than

128. Which is a variable speed motor?

A)differentially compounded
B)series
C)commutatively compounded
D)shunt

129. High speed alternators are driven by

A)hydraulic turbines
B)diesel engine
C)steam turbines
D)diesel engine

130. The greatest percentage of power loss in a dc motor is due to

A)friction loss
B)wind age loss
C)core loss
D)copper loss

131. The common 9v flat battery for transistor radio has ______ cells connected ins series

A)12
B)9
C)3
D)6

132. A storage battery in which the plates consist if lead antimony supporting grids covered with a lead oxide paste immersed in weak sulfuric acid

A)Leclanche cell
B)primary battery
C)secondary battery
D)Faure storage battery

133. The stator of n alternator is wound for ​______ on the rotor

A)twice the number of poles
B)the same number of poles as
C)less number of poles than
D)a more number of poles than

134. Small Dc machines generally have ______ poles

A)6
B)4
C)8
D)2

135. As the load increases a, ​______ motor will speed uo

A)differentially compounded
B)shunt
C)series
D)commutatively compounded

136. 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)Faure storage cell
B)Leclanche cell
C)lead sulfide cell
D)infrared cell

137. The efficiency of the turbo-alternator ______ with increase in speed

A)becomes 100%
B)decreases
C)increases
D)remains the same

138. The deciding factor in the selection of a dc motor for a particular application is its ​ ​ ​ ​ ​ ​ ​ ​ ​ characteristics

A)speed armature current
B)speed torque
C)speed
D)torque armature current

139. This synchronous reactance of an alternator is generally ______​ armature resistance

A)10 times smaller than
B)10 – 100 times greater than
C)5 times smaller than
D)5 times greater than

140. For 20% increase in current, the motor that will give the greatest increase in torque is ______ motor

A)shunt
B)series
C)commulatively compounded
D)differentially compounded

141. The field winding of an armature is _____ excited

A)dc
B)battery
C)ac
D)both ac and dc

142. To increase the voltage output, cells are connected in

A)parallel
B)series-parallel
C)series
D)parallel-series

143. The current in armature conductors of a dc machine is

A)pure dc plus pulsating dc
B)pure dc
C)pulsating dc
D)ac

144. In a dc motor, the brushes are shifted from the mechanical neutral plane in a direction opposite to the rotation to

A)produce flat characteristics
B)reduced sparking
C)decreased speed
D)increase speed

145. The flux in the core o a single phase transformer is

A)partly alternating and partly rotating
B)constant
C)purely alternating one
D)purely rotating one

146. The amount of back emf of shunt motor will increase when

A)the field is weakened
B)the load is decreased
C)the load is increased
D)the field is strengthen

147. A galvanic cell resulting from difference in potential between adjacent on the surface of a metal immersed in an electrolyte

A)local cell
B)lithium cell
C)NiCd cell
D)lead acid cell

148. The running speed of a dc series motor is basically determined by

A)field excitation
B)armature resistance
C)applied voltage
D)load

149. The distribution of load between two alternators operating in parallel can be changed by changing

A)phase sequence
B)driving torques of prime movers
C)current direction
D)field excitation of alternators

150. Two things which are same for primary and secondary of transformer are

A)ampere turns and voltage per turn
B)number of turns and power
C)current and inducted voltage
D)resistance and leakage reactance

151. Leclanche cell is the other name of

A)carbon zinc cell
B)lead acid cell
C)zinc chloride
D)mercuric cell

152. The back emf or counter emf in a dc motor

A)opposes the applied voltage
B)opposes the armature current
C)aids the supplied voltage
D)aids the armature current

153. If a power transformer is operated at very high frequencies then

A)core losses will be excessive
B)core loss is negligible
C)primary reactance is too much increased
D)primary will draw large power

154. A transformer is an efficient device because it

A)uses electric coupling
B)is a static device
C)uses capacitive coupling
D)uses inductive coupling

155. The yoke of a dc machine carries ​______ poke flux

A)one fourth of
B)one third of
C)two times of
D)one half of

156. The open circuit test on a transformer gives

A)friction losses
B)copper losses
C)total losses
D)iron losses

157. Nickel-iron cells is a secondary cell with a nominal open- circuit voltage output of 1.2 and is otherwise known as

A)Galvanic cell
B)Voltaic cell
C)Leclanche cell
D)Edison cell

158. The disadvantage of a short pitched coil is that

A)voltage round coil is increases
B)waveform becomes non-sinusoidal
C)voltage round the coil is reduced
D)harmonics are introduced

159. A method of converting chemical energy into electric energy by dissolving two different conducting materials in an electrolyte

A)Battery
B)Cell
C)Charging
D)Voltaic cell

160. Which of the following is the main function of a battery?

A)To provide a source of variable dc voltage of variable polarity
B)To provide a source of steady DC voltage to fixed polarity
C)To provide a source of variable dc voltage of fixed polarity
D)To provide a source of steady dc voltage of variable polarity

161. Why are the field poles and the armature of a dc machine laminated?

A)to reduce armature reaction
B)to decrease the speed
C)to reduce eddy current
D)to reduce the weight of the machine

162. A series motor will over speed when

A)load is removed
B)the load is increased
C)the field id opened
D)the armature circuit is open

163. In a vacuum cleaner, _____ motor is generally used

A)series
B)commutatively compounded
C)shunt
D)differentially compounded

164. DC shunt motors are used in those applications where ______​ is required

A)practically constant speed
B)variable speed
C)high starting torque
D)high no load speed

165. Transformers having ratings less than 5kva are generally

A)self cooled
B)oil cooled
C)water cooled
D)natural air cooled

166. If a transformer core has air gaps then

A)hysteresis loss is decreased
B)magnetizing current is greatly increased
C)reluctance of magnetic path is decreased
D)eddy current is increased

167. The speed of a _______ motor is practically constant

A)commutatively compounded
B)series
C)shunt
D)differentially compounded

168. The commutator pitch for a simplex lap winding is equal to

A)poles pairs
B)1
C)number of poles of the machines
D)2

169. Back emf in a dc motor is maximum at

A)half full load
B)full load
C)no load
D)three fourth full load

170. The voltage regulation of an alternator is larger than of a dc generator because of

A)large leakage reactance
B)complex effects of armature reaction
C)large armature resistance
D)small armature resistance

171. In an alternator, the effect of armature reaction is minimum at power factor of

A)0.866 leading
B)0.866 lagging
C)0.5 lagging
D)Unity

172. High voltage dc machines use what winding?

A)open circuit
B)Lap
C)either lap or wave
D)wave

173. The coupling field between electrical and the mechanical systems of a dc machine is

A)electromagnetic field
B)electric field
C)magnetic field
D)both electric and magnetic fields

174. The yoke of a dc machine is made of

A)silicon steel
B)aluminium
C)cast steel
D)soft iron

175. The main drawback of a dc shunt generator is that

A)terminal voltage drops considerably with load
B)it is expensive
C)generated voltage is small
D)shunt field circuit has high resistance

176. Which DC machines are the most common?

A)8 pole
B)2 pole
C)6 pole
D)4 pole

177. Which of the following is a dry storage cell?

A)Edison cell
B)Nickel cadmium cell
C)Mercury cell
D)Leclanche cell

178. The number of parallel paths in a simplex lap winding is equal to

A)1
B)number of poles
C)2
D)number of pair poles

179. In case if a 4 pole machine, 1 mechanical degree corresponds to ​______​ electrical degree

A)4
B)6
C)2
D)8

180. The synchronous reactance of an alternator ______ as the iron is saturated

A)becomes doubled
B)remains the same
C)increases
D)decreases

181. A small 9V battery might be used to provide power to

A)a radio transmitter
B)an electric stove
C)an electronic calculator
D)a personal computer

182. When the load on a transformer is increased, the eddy current loss

A)remains the same
B)is increased
C)is decreased
D)becomes zero

183. A series motor designed to operate on dc or ac

A)Compound motor
B)Series motor
C)Shunt motor
D)Universal motor

184. By laminating the core of a transformer, ​_______ decreases

A)copper loss
B)eddy current loss
C)hysteresis loss
D)leakage reactance

185. 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)induction motor
B)synchronous motor
C)stepper motor
D)squirrel cage motor

186. Connecting batteries of equal voltage in parallel

A)increases the internal resistance
B)multiplies the voltage available
C)multiplies the current available
D)reduces the power available

187. Which of the most suitable motor for elevator

A)Commutatively compounded
B)Differentially compounded
C)Series
D)Shunt

188. Overheating of a dc motor is often due to

A)insufficient end play
B)overloads
C)loose parts
D)rough commutator

189. The field winding of a dc shunt machine usually carries _____​ of the rated current of the machine

A)15% to 20%
B)less than 0.5%
C)2% to 5%
D)more than 20%

190. After a shunt motor is up to speed the speed may ne increased considerably by

A)reducing the load
B)decreasing field circuit resistance
C)increasing field circuit resistance
D)increasing the armature circuit resistance

191. Which motor has the best speed regulation?

A)Series
B)Shunt
C)Differentially compounded
D)Commutatively compounded

192. The frequency of the system with which several alternators are parallel can be increased by simultaneously ______ of all generators

A)decreasing the speed of prime movers
B)increasing the speed of prime movers
C)decreasing the field excitation
D)increasing the field excitation

193. a constant voltage source has

A)High internal resistance
B)low internal resistance
C)minimum efficiency
D)minimum current capacity

194. The synchronous reactance of an alternator is due to

A)leakage flux
B)armature reaction
C)dc field excitation
D)hysteresis loss

195. Difference between the speed of a rotating magnetic field and the associated rotor

A)slip
B)salient pole
C)pull out torque
D)split

196. Why are carbon brushes preferable compared to copper brushes

A)they reduce sparking
B)they have lower resistance
C)they have longer life
D)they are cheaper

197. A transformer is so designed that primary and secondary windings have

A)loose magnetic coupling
B)tight magnetic coupling
C)good electric coupling
D)critical magnetic coupling

198. When the primary of a transformer is connected to a dc supply

A)core losses are increased
B)a primary draw small current
C)primary may burned out
D)primary leakage reactance is increased

199. The temperature rise of a transformer is directly proportional to

A)leakage reactance
B)apparent power
C)reactive power
D)true power

200. One of the following is a false statement

A)primary cell is not rechargeable
B)storage cell has a reversible chemical reaction
C)lead acid cell is rechargeable
D)carbon zinc cell has unlimited shelf life

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