MCQOPTIONS
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MCQOPTIONS
This section includes 312 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
The deciding factor in the selection of a dc motor for a particular application is its ____ characteristics |
| A. | speed-torque |
| B. | speed-armature current |
| C. | torque-armature current |
| D. | none of the above |
| Answer» B. speed-armature current | |
| 252. |
The most commonly used method of speed control of a DC motor is by varying ____. |
| A. | voltage applied to a motor |
| B. | field control |
| C. | effective number of conductors in series |
| D. | armature circuit resistance |
| Answer» C. effective number of conductors in series | |
| 253. |
The speed of a ____ motor is practically constant |
| A. | cumulative compound |
| B. | series |
| C. | differential compound |
| D. | shunt motor |
| Answer» E. | |
| 254. |
The torque developed by a dc motor is directly propotional to--- |
| A. | flux per pole x armature current |
| B. | armature resistance x applied voltage |
| C. | armature resistancex armature current |
| D. | none of the above |
| Answer» B. armature resistance x applied voltage | |
| 255. |
The speed of a dc motor is |
| A. | directly propotional to flux per pole |
| B. | inversely propotional to flux per pole |
| C. | inversely propotional to applied voltage |
| D. | none of the above |
| Answer» C. inversely propotional to applied voltage | |
| 256. |
The amount of back emf of a shunt motor will increase when |
| A. | the load is increased |
| B. | the field is weakened |
| C. | the field is strengthened |
| D. | none of the above |
| Answer» D. none of the above | |
| 257. |
When the speed of dc motor increases , its armature current ---- |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | none of the above |
| Answer» C. remains constant | |
| 258. |
The mechanical power developed in a dc motor is maximum when back emf (Eb) is equal to ------the applied voltage (V) |
| A. | twice |
| B. | half |
| C. | one third |
| D. | none of the above |
| Answer» C. one third | |
| 259. |
The value of back EMF in a DC motor is maximum at ____. |
| A. | no load |
| B. | full load |
| C. | half of full load |
| D. | none of the above |
| Answer» B. full load | |
| 260. |
The field poles and armature of a D.C. machine are laminated to___. |
| A. | reduce the weight of the machine |
| B. | decrease the speed |
| C. | reduce eddy currents |
| D. | reduce armature reaction |
| Answer» D. reduce armature reaction | |
| 261. |
A D.C. motor is still used in industrial applications because it____. |
| A. | is cheap |
| B. | is simple in construction |
| C. | provides fine speed control |
| D. | none of the above |
| Answer» D. none of the above | |
| 262. |
Wave wound genrators provide |
| A. | less current but more voltage |
| B. | more current but less voltage |
| C. | more current but less voltage |
| D. | none of the above |
| Answer» B. more current but less voltage | |
| 263. |
A 30W, 300V D.C. shunt genrator has armature and field resistances of 0.05Ω and 100Ω respectively. What is generated e.m.f.? |
| A. | 295.25v |
| B. | 311.25v |
| C. | 305.15v |
| D. | none of the above |
| Answer» D. none of the above | |
| 264. |
____ together are called stray losses |
| A. | copper and iron losses |
| B. | iron and mechnical losses |
| C. | field copper and iron losses |
| D. | frictional and copper losses |
| Answer» C. field copper and iron losses | |
| 265. |
The field structure of a dc machine uses ____. |
| A. | salient pole arrangement |
| B. | non-salient pole arrangement |
| C. | both a and b |
| D. | none of the above |
| Answer» B. non-salient pole arrangement | |
| 266. |
A 4-pole dc machine has ____ magnetic circuits. |
| A. | 2 |
| B. | 8 |
| C. | 4 |
| D. | none of above |
| Answer» D. none of above | |
| 267. |
The yoke of a dc machine carries ____pole flux. |
| A. | the |
| B. | one-half of |
| C. | two times the |
| D. | none of the above |
| Answer» C. two times the | |
| 268. |
____ dc machine are most common. |
| A. | 2-pole |
| B. | 4-pole |
| C. | 6-pole |
| D. | 8-pole |
| Answer» C. 6-pole | |
| 269. |
. The coupling field electrical and mechanical systems of dc machine is____. |
| A. | electric field |
| B. | magnetic field |
| C. | both electric and magnetic fields |
| D. | mechanical field |
| Answer» C. both electric and magnetic fields | |
| 270. |
The real working part of a dc machine is the ___. |
| A. | commutator |
| B. | field winding |
| C. | armature winding |
| D. | none of the above |
| Answer» D. none of the above | |
| 271. |
. The armature of a dc machine is made of____. |
| A. | silicon steel |
| B. | wrought iron |
| C. | cast steel |
| D. | soft iron |
| Answer» B. wrought iron | |
| 272. |
In Fleming's right-hand rule, the thumb point towards |
| A. | direction of flux |
| B. | direction of induced e.m.f. |
| C. | direction of motion of conductor, if fore finger points along the lines of flux |
| D. | direction of motion of the conductor\ if fore finger point in the direction of generated e.m.f. |
| Answer» D. direction of motion of the conductor\ if fore finger point in the direction of generated e.m.f. | |
| 273. |
The yoke of a d.c. machine is made of ____. |
| A. | silicon steel |
| B. | soft iron |
| C. | aluminum |
| D. | cast steel |
| Answer» E. | |
| 274. |
When load is removed, .......motor will run at the highest speed. |
| A. | shunt |
| B. | cumulative - compound |
| C. | differential compound |
| D. | series |
| Answer» E. | |
| 275. |
The Ta/Ia graph of a dc series motor is a |
| A. | parabola from no load to overload |
| B. | straight line throughout |
| C. | parabola throughout |
| D. | parabola upto full load and a straight line at overloads |
| Answer» E. | |
| 276. |
The induced emf in the armature conductors of a dc motor is |
| A. | sinusoidal |
| B. | trapezoidal |
| C. | rectangular |
| D. | alternating |
| Answer» B. trapezoidal | |
| 277. |
The Eb/V ratio of a dc motor is an indication of its |
| A. | efficiency |
| B. | speed regulation |
| C. | starting torque |
| D. | running torque |
| Answer» B. speed regulation | |
| 278. |
The counter emf of dc motor |
| A. | often exceeds the supply voltage |
| B. | aids the applied voltage |
| C. | helps in energy conversion |
| D. | regulates its armature voltage |
| Answer» D. regulates its armature voltage | |
| 279. |
In a DC motor, unidirectional torque is produced with the help of |
| A. | brushes |
| B. | commutator |
| C. | end-plates |
| D. | both a and b |
| Answer» E. | |
| 280. |
In a d.c. machine, the armature mmf is |
| A. | stationary w.r.t. armature. |
| B. | rotating w.r.t. field. |
| C. | stationary w.r.t. field. |
| D. | rotating w.r.t. brushes. |
| Answer» D. rotating w.r.t. brushes. | |
| 281. |
In 8 - pole wave connected motor armature, the number of parallel paths are |
| A. | 8 |
| B. | 4 |
| C. | 2 |
| D. | 1 |
| Answer» D. 1 | |
| 282. |
The speed of a dc motor can be controlled by varying |
| A. | its flux per pole |
| B. | resistance of armature circuit |
| C. | applied voltage |
| D. | all of the above |
| Answer» E. | |
| 283. |
The DC motor, which can provide zero speed regulation at full load without any controller is |
| A. | series |
| B. | shunt |
| C. | cumulative compound |
| D. | differential compound |
| Answer» C. cumulative compound | |
| 284. |
In a DC series motor increasing the load current will |
| A. | decrease the speed |
| B. | increase the speed |
| C. | better commutation |
| D. | increase the back emf |
| Answer» B. increase the speed | |
| 285. |
A DC series motor is best for driving |
| A. | lathes |
| B. | cranes and hoists |
| C. | shears and punches |
| D. | machine tools |
| Answer» C. shears and punches | |
| 286. |
which of the following motor has the constant speed? |
| A. | series motor |
| B. | shunt motor |
| C. | cumulatively compound motor |
| D. | all of the above |
| Answer» C. cumulatively compound motor | |
| 287. |
Voltage equation of a dc motor is |
| A. | v = eb + iara |
| B. | eb = v + iara |
| C. | v = eb/iara |
| D. | v = eb + ia2ra |
| Answer» B. eb = v + iara | |
| 288. |
In DC machine, lap winding is used in |
| A. | high current and low voltage applications |
| B. | high voltage and low current applications |
| C. | where constant speed is required |
| D. | where greater load is connected |
| Answer» B. high voltage and low current applications | |
| 289. |
What type of connection is made in between the interpole & the field winding? |
| A. | series |
| B. | parallel |
| C. | compound |
| D. | none of the options |
| Answer» C. compound | |
| 290. |
What is the effect of armature reaction? |
| A. | armature flux weakens the main field flux |
| B. | armature flux distorts the main field flux |
| C. | both option b & a |
| D. | none of the options |
| Answer» D. none of the options | |
| 291. |
What is the actual arrangement of series wound generator? |
| A. | armature and field both are parallel |
| B. | armature and field both are connected |
| C. | increase the speed of shaft rotation |
| D. | armature and field both are in series with the load |
| Answer» E. | |
| 292. |
In DC machine, brushes are always placed along |
| A. | magnetic neutral axis |
| B. | geometrical neutral axis |
| C. | armature axis |
| D. | load axis |
| Answer» B. geometrical neutral axis | |
| 293. |
In a DC generator the emf generated by the armature is maximum when |
| A. | rate of change of flux is maximum |
| B. | rate of change of flux is minimum |
| C. | induced voltage is high |
| D. | shaft rotation is high |
| Answer» B. rate of change of flux is minimum | |
| 294. |
Magnetic field of a DC generator is produced by what? |
| A. | permanent magnets |
| B. | electromagnets |
| C. | both option b & c |
| D. | none of the options |
| Answer» C. both option b & c | |
| 295. |
A 4 pole DC generator rotates at 1500 rpm. How many times in a second, will the emf induced in each armature conductor changes its direction? |
| A. | 750 |
| B. | 100 |
| C. | 500 |
| D. | 200 |
| Answer» C. 500 | |
| 296. |
The material used for commutator brushes is mostly |
| A. | copper |
| B. | carbon |
| C. | mica |
| D. | cast iron |
| Answer» C. mica | |
| 297. |
The output voltage of a DC generator is |
| A. | e = v + iara |
| B. | e = v – iara |
| C. | e = v + ia |
| D. | e = v + ra |
| Answer» B. e = v – iara | |
| 298. |
A flywheel is employed with a dc compound motor to reduce the peak demand, the compound motor should be: |
| A. | level compound |
| B. | differential compound |
| C. | cumulative compound |
| D. | none of the above |
| Answer» D. none of the above | |
| 299. |
When the direction of power flow in a differential compounded motor reverses, it will operate as a: |
| A. | cumulative compound generator |
| B. | differential compound generator |
| C. | series motor |
| D. | shunt motor |
| Answer» B. differential compound generator | |
| 300. |
Which of the following dc motor has maximum self relieving property: |
| A. | shunt |
| B. | series |
| C. | cumulative compound |
| D. | differential compound |
| Answer» C. cumulative compound | |