MCQOPTIONS
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MCQOPTIONS
This section includes 244 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?? |
| A. | Low cost |
| B. | Wide speed range |
| C. | Stability |
| D. | High starting torque |
| Answer» B. Wide speed range | |
| 202. |
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?? |
| A. | The motor will stop |
| B. | The motor will continue to run |
| C. | The armature may burn |
| D. | The motor will run noisy |
| Answer» D. The motor will run noisy | |
| 203. |
Which of the following loss in a D.C. generator varies significantly with the load current?? |
| A. | Field copper loss |
| B. | Windage loss |
| C. | Armature copper loss |
| D. | None of the above |
| Answer» D. None of the above | |
| 204. |
Which one of the following is not the function of pole shoes in a D.C. machine?? |
| A. | To reduce eddy current loss |
| B. | To support the field coils |
| C. | To spread out flux for better uniformity |
| D. | To reduce the reluctance of the magnetic path |
| Answer» B. To support the field coils | |
| 205. |
In variable speed motor? |
| A. | A stronger commutating field is needed at low speed than at high speed |
| B. | A weaker commutating field is needed at low speed than at high speed |
| C. | Same commutating field is needed at low speed than at high speed |
| D. | None of the above is correct |
| Answer» C. Same commutating field is needed at low speed than at high speed | |
| 206. |
In D.C. machines the residual magnetism is of the order of? |
| A. | 2 to 3 percent |
| B. | 10 to 15 percent |
| C. | 20 to 25 percent |
| D. | 50 to 75 percent |
| Answer» B. 10 to 15 percent | |
| 207. |
If a D.C. motor is connected across the A.C. supply it will |
| A. | Run at normal speed |
| B. | Not run |
| C. | Run at lower speed |
| D. | Burn due to heat produced in the field winding by eddy currents |
| Answer» E. | |
| 208. |
A D.C. series motor is that which |
| A. | Has its field winding consisting of thick wire and less turns |
| B. | Has a poor torque |
| C. | Can be started easily without load |
| D. | Has almost constant speed |
| Answer» B. Has a poor torque | |
| 209. |
In Ward-Leonard control the lower limit of speed is imposed by |
| A. | Residual magnetism of the generator |
| B. | Core losses of motor |
| C. | Mechanical losses of motor and generator together |
| D. | All of the above |
| Answer» B. Core losses of motor | |
| 210. |
If a D.C. motor is to be selected for conveyors, which rioter would be preferred? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Differentially compound motor |
| D. | Cumulative compound motor |
| Answer» B. Shunt motor | |
| 211. |
The total losses in a well designed D.C. generator of 10 kW will be nearly |
| A. | 100 W |
| B. | 500 W |
| C. | 1000 W |
| D. | 1500 W |
| Answer» C. 1000 W | |
| 212. |
Which of the following load normally needs starting torque more than the rated torque? |
| A. | Blowers |
| B. | Conveyors |
| C. | Air compressors |
| D. | Centrifugal pumps |
| Answer» C. Air compressors | |
| 213. |
The speed of a D.C. motor can be varied by varying |
| A. | Field current |
| B. | Applied voltage |
| C. | Resistance in series with armature |
| D. | Any of the above |
| Answer» E. | |
| 214. |
The speed of a D.C. series motor is |
| A. | Proportional to the armature current |
| B. | Proportional to the square of the armature current |
| C. | Proportional to field current |
| D. | Inversely proportional to the armature current |
| Answer» E. | |
| 215. |
If the field of a D.C. shunt motor gets opened while motor is running |
| A. | The speed of motor will be reduced % |
| B. | The armature current will reduce |
| C. | The motor will attain dangerously high speed 1 |
| D. | The motor will continue to run at constant speed |
| Answer» D. The motor will continue to run at constant speed | |
| 216. |
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of |
| A. | D.C. series motor |
| B. | D.C. shunt motor |
| C. | Induction motor |
| D. | All of above motors |
| Answer» B. D.C. shunt motor | |
| 217. |
In a differentially compounded D.C. motor, if shunt field suddenly opens |
| A. | The motor will first stop and then run in opposite direction as series motor |
| B. | The motor will work as series motor and run at slow speed in the same direction |
| C. | The motor will work as series motor and run at high speed in the same direction |
| D. | The motor will not work and come to stop |
| Answer» B. The motor will work as series motor and run at slow speed in the same direction | |
| 218. |
Which of the following motors is usually used in household refrigerators? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Single phase induction motor (split phase start or induction run motor) |
| D. | Reluctance motor |
| Answer» D. Reluctance motor | |
| 219. |
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because |
| A. | Back e.m.f. is equal to armature drop |
| B. | Armature drop is negligible |
| C. | Flux is proportional to armature current |
| D. | Flux is practically constant in D.C. shunt motors |
| Answer» E. | |
| 220. |
Regenerative method of braking is based on that |
| A. | Back e.m.f. is less than the applied voltage |
| B. | Back e.m.f. is equal to the applied voltage |
| C. | Back e.m.f. of rotor is more than the applied voltage |
| D. | None of the above |
| Answer» C. Back e.m.f. of rotor is more than the applied voltage | |
| 221. |
In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to |
| A. | 100% of the previous value |
| B. | 50% of the previous value |
| C. | 25% of the previous value |
| D. | 10% of the previous value |
| Answer» D. 10% of the previous value | |
| 222. |
One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven |
| A. | Runs as a generator |
| B. | Does not run as a generator |
| C. | Also runs as a motor comes to stop after sometime |
| D. | None of these |
| Answer» B. Does not run as a generator | |
| 223. |
If the supply voltage for a D.C. motor is increased, which of the following will decrease? |
| A. | Starting torque |
| B. | Operating speed |
| C. | Full-load current |
| D. | All of the above |
| Answer» D. All of the above | |
| 224. |
Which of the following losses are significantly reduced by laminating the core of a D.C. generator? |
| A. | Hysteresis losses |
| B. | Eddy current losses |
| C. | Copper losses |
| D. | Windage losses |
| Answer» C. Copper losses | |
| 225. |
D.C. series motors are used |
| A. | Where load is constant |
| B. | Where load changes frequently |
| C. | Where constant operating speed is needed |
| D. | In none of the above situations |
| Answer» E. | |
| 226. |
The armature torque of the D.C. shunt motor is proportional to |
| A. | field flux only |
| B. | armature current only |
| C. | both (A) and (B) |
| D. | none of the above |
| Answer» C. both (A) and (B) | |
| 227. |
Which of the following motor has the poorest speed regulation? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» C. Differential compound motor | |
| 228. |
Usually wide and sensitive speed control is desired in case of |
| A. | Centrifugal pumps |
| B. | Elevators |
| C. | Steel rolling mills |
| D. | Colliery winders |
| Answer» E. | |
| 229. |
In D.C. motor which of the following can sustain the maximum temperature rise? |
| A. | Slip rings |
| B. | Commutator |
| C. | Field winding |
| D. | Armature winding |
| Answer» D. Armature winding | |
| 230. |
Which D.C. motor has got maximum self loading property? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» E. | |
| 231. |
The condition for maximum efficiency for a D.C. generator is |
| A. | Eddy current losses = stray losses |
| B. | Hysteresis losses = eddy current losses |
| C. | Copper losses = 0 |
| D. | Variable losses = constant losses |
| Answer» E. | |
| 232. |
Which of the following method of speed control of D.C. machine will offer minimum efficiency? |
| A. | Voltage control method |
| B. | Field control method |
| C. | Armature control method |
| D. | All above methods |
| Answer» D. All above methods | |
| 233. |
In a manual shunt motor starter |
| A. | Over load relay is connected in series and no volt relay in parallel with the load |
| B. | Over load relay is connected in parallel and no volt relay in series with the load |
| C. | Over load relay and no volt relay are both connected in series with the load |
| D. | Over load relay and no volt relay are both connected in parallel with the load |
| Answer» B. Over load relay is connected in parallel and no volt relay in series with the load | |
| 234. |
In case of conductively compensated D.C. series motors, the compensating winding is provided |
| A. | As separately wound unit |
| B. | In parallel with armature winding |
| C. | In series with armature winding |
| D. | In parallel with field winding |
| Answer» D. In parallel with field winding | |
| 235. |
As the load is increased the speed of D.C. shunt motor will |
| A. | Reduce slightly |
| B. | Increase slightly |
| C. | Increase proportionately |
| D. | Remains unchanged |
| Answer» B. Increase slightly | |
| 236. |
The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator? |
| A. | Hysteresis loss |
| B. | Field copper loss |
| C. | Armature copper loss |
| D. | Eddy current loss |
| Answer» D. Eddy current loss | |
| 237. |
Which of the following law/rule can he used to determine the direction of rotation of D.C. motor? |
| A. | Lenz |
| B. | Faraday |
| C. | Coulomb’s law |
| D. | Fleming |
| Answer» E. | |
| 238. |
Which D.C. motor will be preferred for machine tools? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulative compound motor |
| D. | Differential compound motor |
| Answer» C. Cumulative compound motor | |
| 239. |
Which of the following application requires high starting torque? |
| A. | Lathe machine |
| B. | Centrifugal pump |
| C. | Locomotive |
| D. | Air blower |
| Answer» D. Air blower | |
| 240. |
The type of D.C. motor used for shears and punches is |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential computed D.C. motor |
| D. | Cumulative compound D.C. motor |
| Answer» E. | |
| 241. |
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | Become zero |
| Answer» B. Decrease | |
| 242. |
In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will |
| A. | Remain unchanged |
| B. | Reduce to one-fourth value |
| C. | Increase four folds |
| D. | Be doubled |
| Answer» B. Reduce to one-fourth value | |
| 243. |
If I2 be the armature current, then speed of a D.C. shunt motor is |
| A. | Independent of Ia |
| B. | Proportional to Ia |
| C. | Varies as Ia |
| D. | None of these |
| Answer» B. Proportional to Ia | |
| 244. |
Hopkinson's test on D.C. machines is conducted at |
| A. | No load |
| B. | Part load |
| C. | Full load |
| D. | Overload |
| Answer» D. Overload | |