McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
Chapters
| 151. |
In a D.C. shunt motor, speed is |
| A. | independent of armature current |
| B. | directly proportional to the armature current |
| C. | proportional to the square of the current |
| D. | inversely proportional to the armature current |
| Answer» A. independent of armature current | |
| 152. |
A direct on line starter is used: for starting motors |
| A. | iip to 5 H.P. |
| B. | up to 10 H.P. |
| C. | up to 15 H.P. |
| D. | up to 20 H.P. |
| Answer» A. iip to 5 H.P. | |
| 153. |
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» C. The armature may burn | |
| 154. |
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. shuntmotors |
| Answer» D. flux is practically constant in D:C. shuntmotors | |
| 155. |
In a D.C. shunt motor, under the conditions of maximum power, the current inthe armature will be |
| A. | almost negligible |
| B. | rated full-load current |
| C. | less than full-load current |
| D. | more than full-load current |
| Answer» D. more than full-load current | |
| 156. |
These days D.C. motors are widely used in |
| A. | pumping sets |
| B. | air compressors |
| C. | electric traction |
| D. | machine shops |
| Answer» C. electric traction | |
| 157. |
By looking at which part of the motor, it can be easily confirmedthat a particular motor is D.C. motor? |
| A. | Frame |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» C. Commutator | |
| 158. |
In which of the following applications D.C. series motor is invariably tried? |
| A. | Starter for a car |
| B. | Drive for a water pump |
| C. | Fan motor |
| D. | Motor operation in A.C. or D.C. |
| Answer» A. Starter for a car | |
| 159. |
In D.C. machines fractional pitch winding is used |
| A. | to improve cooling |
| B. | to reduce copper losses |
| C. | to increase the generated e.m.f. |
| D. | to reduce the sparking |
| Answer» D. to reduce the sparking | |
| 160. |
A three point starter is considered suitable for |
| A. | shunt motors |
| B. | shunt as well as compound motors |
| C. | shunt, compound and series motors |
| D. | all D.C. motors |
| Answer» B. shunt as well as compound motors | |
| 161. |
In case-the conditions for maximum power for a D.C. motor are established,the efficiency of the motor will be |
| A. | 100% |
| B. | around 90% |
| C. | anywhere between 75% and 90% |
| D. | less than 50% |
| Answer» D. less than 50% | |
| 162. |
The ratio of starting torque to full-load torque is least in case of |
| A. | series motors |
| B. | shunt motors |
| C. | compound motors |
| D. | none of the above |
| Answer» B. shunt motors | |
| 163. |
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» C. Field winding | |
| 164. |
Which of the following law/rule can he used to determine the direction of rotationof D.C. motor ? |
| A. | Lenz's law |
| B. | Faraday's law |
| C. | Coloumb'slaw |
| D. | Fleming's left-hand rule |
| Answer» D. Fleming's left-hand rule | |
| 165. |
Which of the following load normally needs starting torque more than therated torque? |
| A. | Blowers |
| B. | Conveyors |
| C. | Air compressors |
| D. | Centrifugal pumps |
| Answer» B. Conveyors | |
| 166. |
The starting resistance of a D.C. motor is generally |
| A. | low |
| B. | around 500 Q |
| C. | 1000 Q |
| D. | infinitely large |
| Answer» A. low | |
| 167. |
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» D. inversely proportional to the armature current | |
| 168. |
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» C. 25% of the previous value | |
| 169. |
The current drawn by the armature of D.C. motor is directly proportional to |
| A. | the torque required |
| B. | the speed of the motor |
| C. | the voltage across the terminals |
| D. | none of the above |
| Answer» A. the torque required | |
| 170. |
The power mentioned on the name plate of an electric motor indicates |
| A. | the power drawn in kW |
| B. | the power drawn in kVA |
| C. | the gross power |
| D. | the output power available at the shaft |
| Answer» D. the output power available at the shaft | |
| 171. |
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» D. Differentially compounded motor | |
| 172. |
Which D.C. motor will be suitable alongwith flywheel for intermittent light andheavy loads? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» C. Cumulatively compounded motor | |
| 173. |
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens |
| A. | nothing will happen to th£ motor |
| B. | this will make armature to take heavy current, possibly burning it |
| C. | this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| D. | motor will run at very slow speed |
| Answer» C. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses | |
| 174. |
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» D. in none of the above situations. | |
| 175. |
For the same H.P. rating and full load speed, following motor has poor starting torque |
| A. | shunt |
| B. | series |
| C. | differentially compounded |
| D. | cumulativelyc'ompounded |
| Answer» C. differentially compounded | |
| 176. |
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» C. in series with armature winding | |
| 177. |
Sparking at the commutator of a D.C. motor may result in |
| A. | damage to commutator segments |
| B. | damage to commutator insulation |
| C. | increased power consumption |
| D. | all of the above |
| Answer» D. all of the above | |
| 178. |
Which of the following motor is preferred for operation in highly explosive atmosphere ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» C. Air motor | |
| 179. |
If the supply voltage for a D.C. motor is increased, which of the following willdecrease ? |
| A. | Starting torque |
| B. | Operating speed |
| C. | Full-load current |
| D. | All of the above |
| Answer» C. Full-load current | |
| 180. |
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 unifor-mity |
| D. | To reduce the reluctance of the mag-netic path |
| Answer» A. To reduce eddy current loss | |
| 181. |
The mechanical power developed by a shunt motor will be maximum when theratio of back e.m.f. to applied voltage is |
| A. | 4.0 |
| B. | 2.0 |
| C. | 1.0 |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 182. |
For which of the following applications a D.C. motor is preferred over an A.C. motor? |
| A. | Low speed operation |
| B. | High speed operation |
| C. | Variable speed operation |
| D. | Fixed speed operation |
| Answer» C. Variable speed operation | |
| 183. |
In D.C. machines the residual magnetism is of the order of |
| A. | 2 to 3 per cent |
| B. | 10 to 15 per cent |
| C. | 20 to 25 per cent |
| D. | 50 to 75 per cent |
| Answer» A. 2 to 3 per cent | |
| 184. |
Which D.C. motor is generally preferred for cranes and hoists ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» A. Series motor | |
| 185. |
Three point starter can be used for |
| A. | series motor only |
| B. | shunt motor only |
| C. | compound motor only |
| D. | both shunt and compound motor |
| Answer» D. both shunt and compound motor | |
| 186. |
Sparking, is discouraged in a D.C. motor because |
| A. | it increases the input power con-sumption |
| B. | commutator gets damaged |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» B. commutator gets damaged | |
| 187. |
Speed control by Ward Leonard method gives uniform speed variation |
| A. | in one direction |
| B. | in both directions |
| C. | below normal speed only |
| D. | above normal speed only. |
| Answer» B. in both directions | |
| 188. |
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be |
| A. | level compounded |
| B. | under compounded |
| C. | cumulatively compounded |
| D. | differentially compounded |
| Answer» C. cumulatively compounded | |
| 189. |
Following motor is used where high starting torque and wide speed range control is required. |
| A. | Single phase capacitor start |
| B. | Induction motor |
| C. | Synchronous motor |
| D. | D.C. motor |
| Answer» D. D.C. motor | |
| 190. |
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 samedirection |
| D. | the motor will not work and come to stop |
| Answer» A. the motor will first stop and then run in opposite direction as series motor | |
| 191. |
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» B. Series motor | |
| 192. |
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» A. D.C. series motor | |
| 193. |
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» A. reduce slightly | |
| 194. |
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» B. armature current only | |
| 195. |
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» C. Armature control method | |
| 196. |
Usually wide and sensitive speed control is desired in case of |
| A. | centrifugal pumps |
| B. | elevators |
| C. | steel rolling mills |
| D. | colliery winders |
| Answer» D. colliery winders | |
| 197. |
The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load.The speed regulation of the motor is |
| A. | 2.36% |
| B. | 4.76% |
| C. | 6.77% |
| D. | 8.84% |
| Answer» B. 4.76% | |
| 198. |
The armature voltage control of D.C. motor provides |
| A. | constant torque drive |
| B. | constant voltage drive |
| C. | constant current drive |
| D. | none of the above |
| Answer» A. constant torque drive | |
| 199. |
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit |
| A. | a resistance is connected in series with armature |
| B. | a resistance is connected parallel to the armature |
| C. | armature is temporarily open circuited |
| D. | a high value resistor is connected across the fieldwinding |
| Answer» A. a resistance is connected in series with armature | |
| 200. |
The speed of a D.C. shunt motor can be increased by |
| A. | increasing the resistance in armature circuit |
| B. | increasing the resistance in field circuit |
| C. | reducing the resistance in the field circuit |
| D. | reducing the resistance in the armature circuit |
| Answer» B. increasing the resistance in field circuit | |
Done Studing? Take A Test.
Great job completing your study session! Now it's time to put your knowledge to the test. Challenge yourself, see how much you've learned, and identify areas for improvement. Don’t worry, this is all part of the journey to mastery. Ready for the next step? Take a quiz to solidify what you've just studied.