MCQOPTIONS
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MCQOPTIONS
This section includes 252 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
can give uniform speed variation |
| A. | in both directions |
| B. | in one direction |
| C. | below normal speed only |
| D. | above normal speed only. |
| Answer» B. in one direction | |
| 102. |
To get the speed of DC motor below the normal speed without wastage of electrical energy we use |
| A. | ward leonard control |
| B. | rheostatic control |
| C. | any of the ward leonard or rheostatic method can be used |
| D. | not possible |
| Answer» B. rheostatic control | |
| 103. |
Starting gear used in Ward Leonard method |
| A. | is of small size |
| B. | is of large size |
| C. | size depends on application |
| D. | is absent |
| Answer» E. | |
| 104. |
Ward Leonard method is an ideal choice for motor which undergoes frequent starting, stopping, speed reversal. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 105. |
Efficiency of Ward Leonard method is |
| A. | higher than rheostatic control method but lower than shunted field control method |
| B. | lower than rheostatic control method |
| C. | higher than rheostatic control method and shunted field control method |
| D. | depends on load |
| Answer» D. depends on load | |
| 106. |
Speed-power characteristic for Ward Leonard speed control method |
| A. | will start from origin |
| B. | will start from some positive value on power axis |
| C. | will start from some positive value on speed axis |
| D. | depends on other parameters |
| Answer» B. will start from some positive value on power axis | |
| 107. |
Reducing the field current will give us |
| A. | constant torque and variable power speed control |
| B. | constant torque speed control |
| C. | variable power speed control |
| D. | constant power speed control |
| Answer» C. variable power speed control | |
| 108. |
b) DC generator |
| A. | reduce armature voltage |
| B. | increase armature voltage |
| C. | increase field current |
| D. | decrease field current |
| Answer» E. | |
| 109. |
Reducing the armature voltage will give us |
| A. | variable torque speed control |
| B. | constant torque speed control |
| C. | variable and constant both can be achieved |
| D. | cannot comment on torque |
| Answer» C. variable and constant both can be achieved | |
| 110. |
Ward Leonard method is |
| A. | armature control method |
| B. | field control method |
| C. | combination of armature control method and field control method |
| D. | totally different from armature and field control method |
| Answer» D. totally different from armature and field control method | |
| 111. |
with the remaining brushes, voltage and power that could be obtained from the machine are |
| A. | e, p |
| B. | e, 2p/3 |
| C. | e/p, 2p/3 |
| D. | e, p/3 |
| Answer» B. e, 2p/3 | |
| 112. |
While doing regular checks on the dc machine with the lap connected winding, it is reported to have ammeter fluctuations, this can be due to |
| A. | different air gaps under poles |
| B. | variable reluctances in the core |
| C. | irregular design deformations |
| D. | all of the mentioned |
| Answer» E. | |
| 113. |
unused component in the machine, then we must |
| A. | s/p/2 should not be an integer |
| B. | s/p/2 should be integer |
| C. | s/p should be integer |
| D. | s/p should not be an integer |
| Answer» B. s/p/2 should be integer | |
| 114. |
For an electrical machine with C number of coils and P poles, the distance between the coils connected by an equalizer ring is? |
| A. | c/p |
| B. | c/2 |
| C. | 2c/p |
| D. | c/2p |
| Answer» D. c/2p | |
| 115. |
With a P-pole DC machine with armature current Ia, the current per brush arm for a lap connected windings is? |
| A. | ia/p |
| B. | ia/2p |
| C. | 2ia/p |
| D. | ia/4p |
| Answer» D. ia/4p | |
| 116. |
In AC machines we should prefer double layer winding over single layer windings because |
| A. | it requires identical coils |
| B. | it is economical to use |
| C. | it offers lower leakage reactance |
| D. | all of the mentioned |
| Answer» B. it is economical to use | |
| 117. |
We can employ dummy coils in a DC machine to |
| A. | compensate reactance voltage |
| B. | reduce armature reaction |
| C. | provide mechanical balance to the armature |
| D. | improve the waveforms generated inside the commutator |
| Answer» B. reduce armature reaction | |
| 118. |
Commutator segments in a DC shunt machine is equal to the number of |
| A. | coil sides |
| B. | turns |
| C. | coils |
| D. | slots |
| Answer» B. turns | |
| 119. |
A 200V dc machine has 4 poles and 40 coils, having simplex lap winding. The number of commutator segments which required in the given machine will be? |
| A. | 40 |
| B. | 20 |
| C. | 80 |
| D. | 26 |
| Answer» B. 20 | |
| 120. |
The simplex lap winding has the range of winding pitch of |
| A. | (-2,2) |
| B. | (-1,1) |
| C. | more than 2 |
| D. | less than 1 |
| Answer» B. (-1,1) | |
| 121. |
We can place closed windings in |
| A. | ac commutator machine |
| B. | stepper motor |
| C. | ac machine |
| D. | dc machine |
| Answer» B. stepper motor | |
| 122. |
Concentrated winding differ from distributed winding with the concern of |
| A. | identical magnetic axis |
| B. | two magnetic axis |
| C. | no magnetic axis |
| D. | physical spacing |
| Answer» B. two magnetic axis | |
| 123. |
Which of the following machines can be used to place open slot winding? |
| A. | ac machine |
| B. | ac commutator machine, ac machine |
| C. | dc machines |
| D. | all of the mentioned |
| Answer» B. ac commutator machine, ac machine | |
| 124. |
fast when under-loaded? |
| A. | due to weak field |
| B. | due to high line voltage |
| C. | due to brush-shifted to neutral |
| D. | all of the mentioned |
| Answer» B. due to high line voltage | |
| 125. |
avoided by using |
| A. | a turn or two of cumulative compounding |
| B. | compensating winding |
| C. | stablizer winding |
| D. | all of the mentioned |
| Answer» C. stablizer winding | |
| 126. |
A laboratory group was working with a set of 3-hp shunt DC motor. But there was a mistake that it was fused with a 0.3A fuse instead 3A fuse. Then it was started |
| A. | a flash occurred instantly |
| B. | it ran for 3s and fuse was blown |
| C. | it ran normal |
| D. | none of the mentioned |
| Answer» C. it ran normal | |
| 127. |
The torque limit of speed for a shunt motor |
| A. | remains constant till base speed |
| B. | remains constant after base speed |
| C. | varies linearly after base speed |
| D. | varies inversely till base speed |
| Answer» B. remains constant after base speed | |
| 128. |
works well for speed |
| A. | below, above |
| B. | above, below |
| C. | base speed. |
| Answer» B. above, below | |
| 129. |
must be ensured that |
| A. | it is used on separately excited machine |
| B. | it is used on shunt machine |
| C. | it is used on series machine |
| D. | any of the mentioned machine |
| Answer» B. it is used on shunt machine | |
| 130. |
by |
| A. | armature voltage control |
| B. | field resistance control |
| C. | any of the methods |
| D. | none of the mentioned |
| Answer» B. field resistance control | |
| 131. |
resistance will |
| A. | decrease the speed of motor |
| B. | increase the speed of motor |
| C. | not have signicant effect on speed |
| D. | no effect |
| Answer» B. increase the speed of motor | |
| 132. |
Mark the wrong option. Which of the following cause and effect behaviour in speed control is correct when field resistance is increased. |
| A. | decrease in flux |
| B. | increase in armature current |
| C. | increase in emf |
| D. | decrease in speed |
| Answer» D. decrease in speed | |
| 133. |
Ward-Leonard system of system of speed control is not recommended for |
| A. | constant speed operation |
| B. | wide speed |
| C. | frequent-motor reversed |
| D. | very slow speed |
| Answer» B. wide speed | |
| 134. |
(II) If a large 3–phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged. |
| A. | i is true, ii is false |
| B. | i is true and ii is also true |
| C. | i is false, ii is true |
| D. | i and ii are false |
| Answer» B. i is true and ii is also true | |
| 135. |
The rotor of 3-phase slip ring induction motor is fed from a 3-phase supply with its stator winding short circuited having rotor rotating clockwise at a speed of Nr, then the |
| A. | speed of air gap field w.r.t. stator is ns-nr anticlockwise |
| B. | speed of air gap field w.r.t. stator is ns-nr clockwise |
| C. | speed of airgap field w.r.t rotor is ns clockwise |
| D. | speed of airgap field w.r.t. stator is ns-nr clockwise |
| Answer» B. speed of air gap field w.r.t. stator is ns-nr clockwise | |
| 136. |
The PWM control of DC motor varies |
| A. | linearly with speed |
| B. | inversely with speed |
| C. | parabolically with speed |
| D. | exponentially with speed |
| Answer» B. inversely with speed | |
| 137. |
An induction motor when started on load, it does not accelerate up to full speed but runs at 1/7th of the rated speed. The motor is said to be |
| A. | locking |
| B. | plumming |
| C. | crawling |
| D. | cogging |
| Answer» D. cogging | |
| 138. |
The great advantage of the double squirrel-cage induction motor over single cage rotor is that its |
| A. | efficiency is higher |
| B. | power factor is higher |
| C. | slip is larger |
| D. | starting current is lower |
| Answer» E. | |
| 139. |
The low no load power factor |
| A. | reduces full load operating pf |
| B. | increases full load operating pf |
| C. | reduces full load excitation voltage |
| D. | increases full load excitation voltage |
| Answer» B. increases full load operating pf | |
| 140. |
Mechanically air gaps in induction motor are kept very low to avoid |
| A. | lower power factor |
| B. | lagging nature |
| C. | magnetizing current |
| D. | all of the mentioned |
| Answer» E. | |
| 141. |
At no load induction motor has possible power factor as |
| A. | 0.2 |
| B. | 0.5 |
| C. | 0.65 |
| Answer» B. 0.5 | |
| 142. |
The no load current of the induction motor is high due to |
| A. | long and high reluctance path between stator and rotor |
| B. | mutual flux having moderate reluctance path between stator and rotor |
| C. | leakage flux having low reluctance iron core |
| D. | leakage flux having high reluctance iron core |
| Answer» B. mutual flux having moderate reluctance path between stator and rotor | |
| 143. |
The no load current of the transformer is very less due to |
| A. | mutual flux having low reluctance iron core |
| B. | mutual flux having high reluctance iron core |
| C. | leakage flux having low reluctance iron core |
| D. | leakage flux having high reluctance iron core |
| Answer» B. mutual flux having high reluctance iron core | |
| 144. |
no load estimated current for the machine? |
| A. | 12 a |
| B. | 20 a |
| C. | 30 a |
| D. | 5 a |
| Answer» B. 20 a | |
| 145. |
No load current in induction motor is 10- 20% of full load current and the no load current of transformer is 2-6%. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 146. |
A 3-phase induction motor with its rotor blocked behaves similar to a |
| A. | transformer under short circuit of secondary terminals |
| B. | transformer under open circuit of secondary |
| C. | synchronous motor under slip test |
| D. | synchronous motor under open circuit |
| Answer» B. transformer under open circuit of secondary | |
| 147. |
An induction motor can be said analogous to |
| A. | transformer |
| B. | synchronous motor |
| C. | universal motor |
| D. | stepper motor |
| Answer» B. synchronous motor | |
| 148. |
For a dc machine, its commutator has a diameter of 50 c rotating at 1000 rpm. For a brush width of 1 cm, the time commutation taken by the machine will be |
| A. | 0.382 ms |
| B. | 0.456 ms |
| C. | 0.573 ms |
| D. | 0.312 ms |
| Answer» B. 0.456 ms | |
| 149. |
A dc machine is run at rated speed in forward direction and then in backward direction. It is observed that, speeds of the rotation are different, then it leads to the conclusion of |
| A. | incorrect brush placement |
| B. | incorrect pole and core alignment |
| C. | incorrect field supply |
| D. | all of the mentioned |
| Answer» B. incorrect pole and core alignment | |
| 150. |
If the students give a forward shift of 10° to the dc generator, then it |
| A. | reduces flux per pole |
| B. | improves flux per pole |
| C. | increases the flux density in core |
| D. | none of the mentioned |
| Answer» B. improves flux per pole | |