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MCQOPTIONS
This section includes 378 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
A DC shunt generator delivers 480 A at 200 V. Its armature and field winding resistance are 0.02 Ω and 40 Ω respectively. What will be the value of generated emf? |
| A. | 200.7V |
| B. | 209.7V |
| C. | 220.7V |
| D. | 215.7V |
| Answer» C. 220.7V | |
| 152. |
A 4-pole wave wound armature has 720 conductors and is rotated at 1000 rpm. If the useful flux is 20 mWb, calculate the generated voltage. |
| A. | 480 V |
| B. | 960 V |
| C. | 360 V |
| D. | 240 V |
| Answer» B. 960 V | |
| 153. |
For single phase rotary converters, when the power factor is unity, the ac to dc current ratio will be |
| A. | 1.0 |
| B. | 0.707 |
| C. | 1.4 |
| D. | 0.5 |
| Answer» C. 1.4 | |
| 154. |
An 8 pole lap wound DC shunt generator is supplying 295A to a load. The field current of the generator is 5A. The current per parallel path is: |
| A. | 300 A |
| B. | 200 A |
| C. | 150 A |
| D. | 37.5 A |
| Answer» E. | |
| 155. |
If the field of a d.c. shunt motor gets opened: |
| A. | It will continue to run at the rated speed |
| B. | Its speed will become very high |
| C. | The motor will stop |
| D. | Its speed will reduce |
| Answer» C. The motor will stop | |
| 156. |
For an identical DC generator, what should be the number of poles such that the emf generated in case of lap winding and wave winding configuration will be the same? |
| A. | 8 |
| B. | 6 |
| C. | 2 |
| D. | 4 |
| Answer» D. 4 | |
| 157. |
A DC shunt generator, having a terminal voltage of 250 V, is delivering 195 A to load. Its armature and field winding resistance are 0.02 Ω and 50 Ω respectively. What will be the value of generated emf? |
| A. | 256 V |
| B. | 270 V |
| C. | 282 V |
| D. | 254 V |
| Answer» E. | |
| 158. |
A 6 pole dc armature has simplex lap connected 720 conductors, 3 turns per coil and 4 coil sides per slot. Determine the number of slots in the armature and state whether equalizers can be employed or not? |
| A. | 60 slots and not possible |
| B. | 30 slots and possible |
| C. | 60 slots and possible |
| D. | 30 slots and not possible |
| Answer» D. 30 slots and not possible | |
| 159. |
In case of DC generators, lap winding is suitable for: |
| A. | High current and low voltage ratings |
| B. | Low current and low voltage ratings |
| C. | High current and high voltage ratings |
| D. | Low current and high voltage ratings |
| Answer» B. Low current and low voltage ratings | |
| 160. |
D.C. generator works on the principle of |
| A. | Electromagnetic Induction |
| B. | Ohm’s Law |
| C. | Lenz’s Law |
| D. | Kirchhoff’s Law |
| Answer» B. Ohm’s Law | |
| 161. |
DC generators are installed near the load centres to reduce |
| A. | Iron losses |
| B. | Line losses |
| C. | Sparking |
| D. | Corona losses |
| Answer» C. Sparking | |
| 162. |
Equalizer rings in D.C. generator with lap windings are used for |
| A. | Equal distribution of current at brush for sparkles commutation |
| B. | Prevention of harmonics |
| C. | Reduction of noise and vibration |
| D. | Avoiding overhang |
| Answer» B. Prevention of harmonics | |
| 163. |
If a D.C. generator fails to build up the probable cause could not be |
| A. | Imperfect brush contact |
| B. | Field resistance less than the critical resistance |
| C. | No residual magnetism in the generator |
| D. | Faulty shunt connections tending to reduce the residual magnetism |
| Answer» C. No residual magnetism in the generator | |
| 164. |
In a separately excited generator supplying rated load the armature reaction: |
| A. | Is always present |
| B. | Is always absent |
| C. | May be sometimes present |
| D. | None of the above |
| Answer» B. Is always absent | |
| 165. |
Flashing the field of D.C. generator means |
| A. | Neutralizing residual magnetism |
| B. | Creating residual magnetism by a D.C. source |
| C. | Making the magnetic losses of forces parallel |
| D. | Increasing flux density by adding extra turns of windings on poles |
| Answer» C. Making the magnetic losses of forces parallel | |
| 166. |
If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by |
| A. | Blv |
| B. | Blv² |
| C. | Bl²v |
| D. | Bl²v² |
| Answer» B. Blv² | |
| 167. |
A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be |
| A. | Zero |
| B. | About 2 V |
| C. | About 50 V |
| D. | 220 V |
| Answer» C. About 50 V | |
| 168. |
The e.m.f. generated in a D.C. generator is directly proportional to |
| A. | Flux/pole |
| B. | Speed of armature |
| C. | Number of poles |
| D. | All of the above |
| Answer» E. | |
| 169. |
A shunt generator can self-excite |
| A. | Only if the resistance of the field circuit is less than critical value |
| B. | Only if the resistance of the field circuit is greater than critical value |
| C. | Irrespective of the value of the resistance in the field circuit |
| D. | None of the above |
| Answer» B. Only if the resistance of the field circuit is greater than critical value | |
| 170. |
Armature reaction of an unsaturated D.C. machine is |
| A. | Cross-magnetizing |
| B. | Demagnetizing |
| C. | Magnetizing |
| D. | None of above |
| Answer» B. Demagnetizing | |
| 171. |
Satisfactory commutation of D.C. machines requires |
| A. | Brushes should be of proper grade and size |
| B. | Brushes should smoothly run in the holders |
| C. | Smooth, concentric commutator properly undercut |
| D. | All of the above |
| Answer» E. | |
| 172. |
Armature coil is short circuited by brushes when it lies |
| A. | Along neutral axis |
| B. | Along field axis |
| C. | In any of the above positions |
| D. | In none of the above positions |
| Answer» B. Along field axis | |
| 173. |
The material for commutator brushes is generally |
| A. | Mica |
| B. | Copper |
| C. | Cast iron |
| D. | Carbon |
| Answer» E. | |
| 174. |
Copper brushes in D.C. machine are used |
| A. | Where low voltage and high currents are involved |
| B. | Where high voltage and small currents are involved |
| C. | In both of the above cases |
| D. | In none of the above cases |
| Answer» B. Where high voltage and small currents are involved | |
| 175. |
In D.C. generators, lap winding is used for |
| A. | High voltage, high current |
| B. | Low voltage, high current |
| C. | High voltage, low current |
| D. | Low voltage, low current |
| Answer» C. High voltage, low current | |
| 176. |
Which generator would you prefer for feeding long D.C. transmission lines? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Over compound generator |
| D. | Flat compound generator |
| Answer» D. Flat compound generator | |
| 177. |
In over compounded generator, full load terminal voltage is |
| A. | Almost zero |
| B. | Less than no load terminal voltage |
| C. | More than no load terminal voltage |
| D. | Equal to no-load terminal voltage |
| Answer» D. Equal to no-load terminal voltage | |
| 178. |
To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them |
| A. | just ahead of magnetic neutral axis |
| B. | in magnetic neutral axis |
| C. | just behind the magnetic neutral axis |
| D. | |
| Answer» B. in magnetic neutral axis | |
| 179. |
Which of the following generator will have negligible terminal voltage while running on no-load? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Compound generator |
| D. | Separately excited generator |
| Answer» B. Shunt generator | |
| 180. |
In case of D.C. machines, mechanical losses are primary function of |
| A. | Current |
| B. | Voltage |
| C. | Speed |
| D. | None of above |
| Answer» D. None of above | |
| 181. |
In a D.C. generator in case the resistance of the field winding is increased, then output voltage will |
| A. | Increase |
| B. | Decrease |
| C. | Remain unaffected |
| D. | Fluctuate heavily |
| Answer» C. Remain unaffected | |
| 182. |
A D.C. generator works on the principle of |
| A. | Lenz's law |
| B. | Ohm's law |
| C. | Faraday's law of electromagnetic induction |
| D. | None of the above |
| Answer» D. None of the above | |
| 183. |
Number of tapings for each equalizer ring is equal to |
| A. | Number of pole pairs |
| B. | Number of poles |
| C. | Number of parallel paths |
| D. | Number of commutator segments |
| Answer» B. Number of poles | |
| 184. |
In a D.C. machine stray loss is the sum of |
| A. | Total copper loss and mechanical loss |
| B. | Armature copper loss and iron loss |
| C. | Shunt field copper loss and mechanical loss |
| D. | Iron loss and mechanical loss |
| Answer» E. | |
| 185. |
The voltage drop for which of the following types of brush can be expected to be least? |
| A. | Graphite brushes |
| B. | Carbon brushes |
| C. | Metal graphite brushes |
| D. | None of the above |
| Answer» D. None of the above | |
| 186. |
In a four-pole D.C. machine |
| A. | All the four poles are north poles |
| B. | Alternate poles are north and south |
| C. | All the four poles are south poles |
| D. | Two north poles follow two south poles |
| Answer» C. All the four poles are south poles | |
| 187. |
The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» C. 6 | |
| 188. |
Inter-pole flux should be sufficient to |
| A. | Neutralize the commutating self induced e.m.f. |
| B. | Neutralize the armature reaction flux |
| C. | Neutralize both the armature reaction flux as well as commutating e.m.f. induced in the coil |
| D. | Perform none of the above functions |
| Answer» D. Perform none of the above functions | |
| 189. |
In D.C. generators the polarity of the interpoles |
| A. | Is the same as that of the main pole ahead |
| B. | Is the same as that of the immediately preceding pole |
| C. | Is opposite to that of the main pole ahead |
| D. | Is neutral as these poles do not play part in generating e.m.f. |
| Answer» B. Is the same as that of the immediately preceding pole | |
| 190. |
An exciter for a turbo generator is a |
| A. | Separately excited generator |
| B. | Shunt generator |
| C. | Series generator |
| D. | Compound generator |
| Answer» C. Series generator | |
| 191. |
In a D.C. generator the critical resistance refers to the resistance of |
| A. | Brushes |
| B. | Field |
| C. | Armature |
| D. | Load |
| Answer» C. Armature | |
| 192. |
While applying Fleming's right-hand rule to and the direction of induced e.m.f., the thumb points towards |
| A. | Direction of induced e.m.f. |
| B. | Direction of flux |
| C. | Direction of motion of the conductor if forefinger points in the direction of generated e.m.f. |
| D. | Direction of motion of conductor, if forefinger points along the lines of flux |
| Answer» E. | |
| 193. |
The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage |
| A. | Will be less than 250 V |
| B. | Will always be 250 V |
| C. | May be greater or less than 250 V |
| D. | None of the above |
| Answer» D. None of the above | |
| 194. |
If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to |
| A. | reverse the field connections |
| B. | increase the field resistance |
| C. | increase the speed of primemover |
| D. | check armature insulation resistance |
| Answer» B. increase the field resistance | |
| 195. |
The bearings used to support the rotor shafts are generally |
| A. | Ball bearings |
| B. | Bush bearings |
| C. | Magnetic bearings |
| D. | Needle bearings |
| Answer» B. Bush bearings | |
| 196. |
The insulating material used between the commutator segments is normally |
| A. | Graphite |
| B. | Paper |
| C. | Mica |
| D. | Insulating varnish |
| Answer» D. Insulating varnish | |
| 197. |
In case of D.C. machine winding, number of commutator segments is equal to |
| A. | Number of armature coils |
| B. | Number of armature coil sides |
| C. | Number of armature conductors |
| D. | Number of armature turns |
| Answer» B. Number of armature coil sides | |
| 198. |
Which of the following could be lamina proximately the thickness of laminations of a D.C. machine? |
| A. | 0.005 mm |
| B. | 0.05 mm |
| C. | 0.5 m |
| D. | 5 m |
| Answer» D. 5 m | |
| 199. |
The essential condition for parallel operation of two D.C. generators is that they have |
| A. | Same kW rating |
| B. | The same operation r.p.m. |
| C. | The same drooping voltage characteristics |
| D. | Same percentage regulation |
| Answer» D. Same percentage regulation | |
| 200. |
A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave |
| A. | will be zero |
| B. | will be of 5 Hz |
| C. | will be of 5 xiVHz |
| D. | will be of v Hz 5 |
| Answer» C. will be of 5 xiVHz | |