MCQOPTIONS
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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.
| 301. |
_ Two generators A and B have 6 poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be$? |
| A. | 2 : 3 |
| B. | 3 : 1 |
| C. | 3 : 2 |
| D. | 1 : 3 |
| Answer» C. 3 : 2 | |
| 302. |
_ In D.C. generators, lap winding is used for$? |
| 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 | |
| 303. |
_ The essential condition for parallel operation of two D.C. generators is that they have$? |
| A. | same kW rating |
| B. | the same operation r.p.m. |
| C. | the same drooping voltage characteristics |
| D. | same percentage regulation |
| Answer» D. same percentage regulation | |
| 304. |
_The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be$? |
| A. | 640 V |
| B. | 620 V |
| C. | 600 V |
| D. | 580 V |
| Answer» E. | |
| 305. |
_In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilized is called$? |
| A. | Rotor |
| B. | Stator |
| C. | Field |
| D. | Armature |
| Answer» E. | |
| 306. |
_The series field of a short-shunt D.C. generator is excited by$? |
| A. | external current |
| B. | armature current |
| C. | shunt current |
| D. | load current |
| Answer» E. | |
| 307. |
_The function of pole shoes in the case of D.C. machine is$? |
| A. | To reduce the reluctance of the magnetic path |
| B. | To spread out the flux to achieve uniform flux density |
| C. | To support the field coil |
| D. | To discharge all the above functions |
| Answer» E. | |
| 308. |
_Armature reaction in a generator results in$? |
| A. | Demagnetization of leading pole tip and magnetization of trailing pole tip |
| B. | Demagnetization of trailing pole tip and magnetization of leading pole tip |
| C. | Demagnetizing the center of all poles |
| D. | Magnetizing the center of all poles |
| Answer» B. Demagnetization of trailing pole tip and magnetization of leading pole tip | |
| 309. |
_In D.C. generators, the cause of rapid brush wear may be$? |
| A. | Severe sparking |
| B. | Rough commutator surface |
| C. | Imperfect contact |
| D. | Any of the above |
| Answer» E. | |
| 310. |
_In lap winding, the number of brushes is always$? |
| A. | Double the number of poles |
| B. | Same as the number of poles |
| C. | Half the number of poles |
| D. | Two |
| Answer» C. Half the number of poles | |
| 311. |
_The main factor which leads to unstable parallel operation of flat and over compounded generators is$? |
| A. | their rising voltage characteristics |
| B. | unequal number of turns in their series field windings |
| C. | unequal speed regulation of their primemovers |
| D. | unequal series field resistances |
| Answer» B. unequal number of turns in their series field windings | |
| 312. |
_The armature core of a D.C. generator is usually made of$? |
| A. | Silicon steel |
| B. | Copper |
| C. | Nonferrous material |
| D. | Cast-iron |
| Answer» B. Copper | |
| 313. |
_A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave$? |
| A. | will be zero |
| B. | will be of 5 Hz |
| C. | will be of 5 xiVHz |
| D. | will be of v Hz 5 |
| Answer» C. will be of 5 xiVHz | |
| 314. |
_In D.C. generators the polarity of the interpoles$? |
| 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 | |
| 315. |
_The voltage drop for which of the following types of brush can be expected to be least?$? |
| A. | Graphite brushes |
| B. | Carbon brushes |
| C. | Metal graphite brushes |
| D. | None of the above |
| Answer» D. None of the above | |
| 316. |
_In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when$? |
| A. | There is no load on the generator |
| B. | The generator runs on full load |
| C. | The generator runs on overload |
| D. | The generator runs on designed speed |
| Answer» B. The generator runs on full load | |
| 317. |
_Lap winding is composed of$? |
| A. | Any even number of conductors |
| B. | Any odd number of conductors |
| C. | That even number which is exact multiple of poles + 2 |
| D. | That even number which is exact multiple of poles |
| Answer» B. Any odd number of conductors | |
| 318. |
_The insulating material used between the commutator segments is normally$? |
| A. | Graphite |
| B. | Paper |
| C. | Mica |
| D. | Insulating varnish |
| Answer» D. Insulating varnish | |
| 319. |
_The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage$? |
| A. | Will be less than 250 V |
| B. | Will always be 250 V |
| C. | May be greater or less than 250 V |
| D. | None of the above |
| Answer» D. None of the above | |
| 320. |
_If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be$? |
| A. | Demagnetization only |
| B. | Cross magnetization as well as magnetization |
| C. | Cross-magnetization as well as demagnetizing |
| D. | Cross magnetization only |
| Answer» D. Cross magnetization only | |
| 321. |
Eddy currents are induced in the pole shoes of a D.C. machine due to$? |
| A. | Oscillating magnetic field |
| B. | Pulsating magnetic flux |
| C. | Relative rotation between field and armature |
| D. | All above |
| Answer» D. All above | |
| 322. |
Flashing the field of D.C. generator means$? |
| 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 | |
| 323. |
The e.m.f. generated in a D.C. generator is directly proportional to$? |
| A. | Flux/pole |
| B. | Speed of armature |
| C. | Number of poles |
| D. | All of the above |
| Answer» C. Number of poles | |
| 324. |
The material for commutator brushes is generally$? |
| A. | Mica |
| B. | Copper |
| C. | Cast iron |
| D. | Carbon |
| Answer» E. | |
| 325. |
Armature reaction of an unsaturated D.C. machine is$? |
| A. | Cross-magnetizing |
| B. | Demagnetizing |
| C. | Magnetizing |
| D. | None of above |
| Answer» B. Demagnetizing | |
| 326. |
Which generator would you prefer for feeding long D.C. transmission lines?$? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Over compound generator |
| D. | Flat compound generator |
| Answer» D. Flat compound generator | |
| 327. |
Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.$? |
| A. | Series field |
| B. | Compensating field |
| C. | Inter pole field |
| D. | Shunt field |
| Answer» E. | |
| 328. |
An exciter for a turbo generator is a$? |
| A. | Separately excited generator |
| B. | Shunt generator |
| C. | Series generator |
| D. | Compound generator |
| Answer» C. Series generator | |
| 329. |
In a four-pole D.C. machine$? |
| A. | All the four poles are north poles |
| B. | Alternate poles are north and south |
| C. | All the four poles are south poles |
| D. | Two north poles follow two south poles |
| Answer» C. All the four poles are south poles | |
| 330. |
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be$? |
| A. | 150 V |
| B. | Less than 150 V |
| C. | Greater than 150 V |
| D. | None of the above |
| Answer» D. None of the above | |
| 331. |
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be? |
| A. | 150 V |
| B. | Less than 150 V |
| C. | Greater than 150 V |
| D. | None of the above |
| Answer» D. None of the above | |
| 332. |
In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called? |
| A. | rotor |
| B. | stator |
| C. | field |
| D. | armature |
| Answer» E. | |
| 333. |
In a shunt generator the voltage build up is generally restricted by? |
| A. | speed limitation |
| B. | armature heating |
| C. | insulation restrictions |
| D. | saturation of iron |
| Answer» E. | |
| 334. |
Two generators are running in parallel. One of the generators may run as motor for which of the following reasons?? |
| A. | The direction of that generator is reversed |
| B. | The speed of that generator is increased |
| C. | The field of that generator is weakened |
| D. | That generator takes large share of loads |
| Answer» E. | |
| 335. |
In the case of lap winding resultant pitch is? |
| A. | Multiplication of front and back pitches |
| B. | Division of front pitch by back pitch |
| C. | Sum of front and back pitches |
| D. | Difference of front and back pitches |
| Answer» E. | |
| 336. |
In a D.C. generator the actual flux distribution depends upon? |
| A. | size of air gap |
| B. | shape of the pole shoe |
| C. | clearance between tips of the adjacent pole shoes |
| D. | all of the above |
| Answer» E. | |
| 337. |
Open circuited armature coil of a D.C. machine is? |
| A. | Identified by the scarring of the commutator segment to which open circuited coil is connected |
| B. | Indicated by a spark completely around the commutator |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» D. None of the above | |
| 338. |
To avoid formation of grooves in the commutator of a D.C. machine? |
| A. | The brushes of opposite polarity should track each other |
| B. | The brushes of same polarity should track each other |
| C. | Brush position has no effect on the commutator grooving |
| D. | All of the above |
| Answer» B. The brushes of same polarity should track each other | |
| 339. |
When two D.C. generators are running in parallel an equalizer bar is used? |
| A. | To increase the series flux |
| B. | To increase the generated e.m.f. |
| C. | To reduce the combined effect of armature reaction of both the machines |
| D. | So that the two identical machines will pass approximately equal currents to the load |
| Answer» E. | |
| 340. |
In D.C. generators on no-load, the air gap flux distribution in space is? |
| A. | Sinusoidal |
| B. | Triangular |
| C. | Pulsating |
| D. | Flat topped |
| Answer» E. | |
| 341. |
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 | |
| 342. |
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 | |
| 343. |
In D.C. generators, the brushes on commutator remain in contact with conductors which? |
| A. | Lie under South Pole |
| B. | Lie under North Pole |
| C. | Lie under interpolar region |
| D. | Are farthest from the poles |
| Answer» D. Are farthest from the poles | |
| 344. |
Brushes of D.C. machines are made of? |
| A. | Carbon |
| B. | Soft copper |
| C. | Hard copper |
| D. | All of above |
| Answer» B. Soft copper | |
| 345. |
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 | |
| 346. |
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralized by all of the following except? |
| A. | Interpoles |
| B. | Dummy coils |
| C. | Compensating winding |
| D. | Shifting of axis of brushes |
| Answer» C. Compensating winding | |
| 347. |
A cumulatively compounded long shunt generator when operating as a motor would be |
| A. | Cumulatively compounded long shunt |
| B. | Differentially compounded long shunt |
| C. | Cumulatively compounded short shunt |
| D. | Differentially compounded short shunt |
| Answer» C. Cumulatively compounded short shunt | |
| 348. |
In a D.C. machine, short-circuited field coil will result in |
| A. | odour of barning insulation |
| B. | unbalanced magnetic pull producing vibrations |
| C. | reduction of generated voltage for which excitation has to be increased to maintain the voltage |
| D. | all above |
| Answer» E. | |
| 349. |
Compensating windings are used in D.C. generators |
| A. | Mainly to reduce the eddy currents by providing local short-circuits |
| B. | To provide path for the circulation of cooling air |
| C. | To neutralize the cross-magnetizing effect of the armature reaction |
| D. | None of the above |
| Answer» D. None of the above | |
| 350. |
In case of a flat compounded generator |
| A. | Voltage generated is less than the rated voltage |
| B. | Generated voltage is proportional to the load on the generator |
| C. | Voltage remains constant irrespective of the load |
| D. | Speed varies in proportion to the load on the generator |
| Answer» D. Speed varies in proportion to the load on the generator | |