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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.
| 151. |
_ The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by$? |
| A. | Reducing the field current |
| B. | Decreasing the armature current |
| C. | Increasing the armature current |
| D. | Increasing the excitation current |
| Answer» B. Decreasing the armature current | |
| 152. |
_ The starting resistance of a D.C. motor is generally$? |
| A. | Low |
| B. | Around 500 Q |
| C. | 1000 Q |
| D. | Infinitely large |
| Answer» B. Around 500 Q | |
| 153. |
_ Why are the D.C. motors preferred for traction applications?$? |
| A. | Torque and speed are inversely proportional to armature current |
| B. | Torque is proportional to armature current |
| C. | Torque is proportional to square root of armature current |
| D. | The speed is inversely proportional to the torque and the torque is proportional to square of armature current |
| Answer» E. | |
| 154. |
_ D.C. shunt motors are used for driving$? |
| A. | Trains |
| B. | Cranes |
| C. | Hoists |
| D. | Machine tools |
| Answer» E. | |
| 155. |
_ The current drawn by the armature of D.C. motor is directly proportional to$? |
| A. | The torque required |
| B. | The speed of the motor |
| C. | The voltage across the terminals |
| D. | None of the above |
| Answer» B. The speed of the motor | |
| 156. |
_ When two D.C. series motors are connected in parallel, the resultant speed is$? |
| A. | More than the normal speed |
| B. | Loss than the normal speed |
| C. | Normal speed |
| D. | Zero |
| Answer» D. Zero | |
| 157. |
_ Which of the following loss in a D.C. generator is dissipated in the form of heat?$? |
| A. | Mechanical loss |
| B. | Core loss |
| C. | Copper loss |
| D. | All of the above |
| Answer» E. | |
| 158. |
_ In a D.C. shunt motor, speed is$? |
| 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» B. Directly proportional to the armature current | |
| 159. |
_ For which types of D.C. motor, dynamic braking is generally used?$? |
| A. | Shunt motors |
| B. | Series motors |
| C. | Compound motors |
| D. | All of the above |
| Answer» E. | |
| 160. |
_ During rheostat braking of D.C. series motors$? |
| A. | Motor is run as a generator |
| B. | Motor is reversed in direction |
| C. | Motor is run at reduced speed |
| D. | None of these |
| Answer» B. Motor is reversed in direction | |
| 161. |
_ The ratio of starting torque to full-load torque is least in case of$? |
| A. | Series motors |
| B. | Shunt motors |
| C. | Compound motors |
| D. | None of the above |
| Answer» C. Compound motors | |
| 162. |
_ In which of the following applications D.C. series motor is invariably tried?$? |
| A. | Starter for a car |
| B. | Drive for a water pump |
| C. | Fan motor |
| D. | Motor operation in A.C. or D.C. |
| Answer» B. Drive for a water pump | |
| 163. |
__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» E. | |
| 164. |
__Ward-Leonard control is basically a__ |
| A. | Voltage control method |
| B. | Field diverter method |
| C. | Field control method |
| D. | Armature resistance control method |
| Answer» B. Field diverter method | |
| 165. |
__At the instant of starting when a D.C. motor is put on supply, it behaves like__ |
| A. | A highly resistive circuit |
| B. | A low resistance circuit |
| C. | A capacitive circuit |
| D. | None of the above |
| Answer» C. A capacitive circuit | |
| 166. |
__The direction of rotation of a D.C. series motor can be changed by__ |
| A. | Interchanging supply terminals |
| B. | Interchanging field terminals |
| C. | Either of (A) and (B) above |
| D. | None of the above |
| Answer» C. Either of (A) and (B) above | |
| 167. |
__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» E. | |
| 168. |
__If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens__ |
| A. | This will make armature to take heavy current, possibly burning it |
| B. | This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| C. | Nothing will happen to motor |
| D. | Motor will come to stop |
| Answer» B. This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses | |
| 169. |
__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 field winding |
| Answer» B. A resistance is connected parallel to the armature | |
| 170. |
__Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity?__ |
| A. | Swinburne's test |
| B. | Hopkinson's test |
| C. | Field test |
| D. | Brake test |
| Answer» D. Brake test | |
| 171. |
_If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking$? |
| A. | Regenerative |
| B. | Plugging |
| C. | Dynamic braking |
| D. | None of the above |
| Answer» C. Dynamic braking | |
| 172. |
_In a D.C. generator, the iron losses mainly take place in$? |
| A. | Yoke |
| B. | Commutator |
| C. | Armature conductors |
| D. | Armature rotor |
| Answer» E. | |
| 173. |
The speed of a D.C. shunt motor can be increased by$? |
| A. | Increasing the resistance in armature circuit |
| B. | Increasing the resistance in field circuit |
| C. | Reducing the resistance in the field circuit |
| D. | Reducing the resistance in the armature circuit |
| Answer» C. Reducing the resistance in the field circuit | |
| 174. |
Sparking at the commutator of a D.C. motor may result in$? |
| A. | Damage to commutator segments |
| B. | Damage to commutator insulation |
| C. | Increased power consumption |
| D. | All of the above |
| Answer» E. | |
| 175. |
Which motor should not be started on no-load?$? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 176. |
Torque developed by a D.C. motor depends upon$? |
| A. | Magnetic field |
| B. | Active length of the conductor |
| C. | Current flow through the conductors |
| D. | All above factors |
| Answer» E. | |
| 177. |
Sparking, is discouraged in a D.C. motor because$? |
| A. | It increases the input power consumption |
| B. | Commutator gets damaged |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» C. Both (A) and (B) | |
| 178. |
Which of the following motors is most suitable for signaling devices and many kinds of timers?$? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Induction motor |
| D. | Reluctance motor |
| Answer» E. | |
| 179. |
Following motor is used where high starting torque and wide speed range control is required.$? |
| A. | Single phase capacitor start |
| B. | Induction motor |
| C. | Synchronous motor |
| D. | D.C. motor |
| Answer» E. | |
| 180. |
The plugging gives the$? |
| A. | Zero torque braking |
| B. | Smallest torque braking |
| C. | Highest torque braking |
| D. | None of the above |
| Answer» D. None of the above | |
| 181. |
Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?$? |
| A. | Providing laminations in armature core |
| B. | Providing laminations in stator |
| C. | Using nonmagnetic material for frame |
| D. | Using material of low hysteresis coefficient for armature core material |
| Answer» E. | |
| 182. |
The purpose of retardation test on D.C. shunt machines is to find out$? |
| A. | Stray losses |
| B. | Eddy current losses |
| C. | Field copper losses |
| D. | Windage losses |
| Answer» B. Eddy current losses | |
| 183. |
Speed control by Ward Leonard method gives uniform speed variation$? |
| A. | In one direction |
| B. | In both directions |
| C. | Below normal speed only |
| D. | Above normal speed only |
| Answer» C. Below normal speed only | |
| 184. |
Which D.C. motor is preferred for elevators?$? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» E. | |
| 185. |
A direct on line starter is used: for starting motors$? |
| A. | Up to 5 H.P. |
| B. | Up to 10 H.P. |
| C. | Up to 15 H.P. |
| D. | Up to 20 H.P. |
| Answer» B. Up to 10 H.P. | |
| 186. |
In the D.C. motor the iron losses occur in$? |
| A. | The field |
| B. | The armature |
| C. | The brushes |
| D. | The commutator |
| Answer» C. The brushes | |
| 187. |
In D.C. machines the residual magnetism is of the order of$? |
| A. | 2 to 3 percent |
| B. | 10 to 15 percent |
| C. | 20 to 25 percent |
| D. | 50 to 75 percent |
| Answer» B. 10 to 15 percent | |
| 188. |
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?$? |
| A. | Low cost |
| B. | Wide speed range |
| C. | Stability |
| D. | High starting torque |
| Answer» B. Wide speed range | |
| 189. |
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?$? |
| A. | The motor will stop |
| B. | The motor will continue to run |
| C. | The armature may burn |
| D. | The motor will run noisy |
| Answer» D. The motor will run noisy | |
| 190. |
Differentially compound D.C. motors can find applications requiring$? |
| A. | High starting torque |
| B. | Low starting torque |
| C. | Variable speed |
| D. | Frequent on-off cycles |
| Answer» C. Variable speed | |
| 191. |
In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be$? |
| A. | 100% |
| B. | Around 90% |
| C. | Anywhere between 75% and 90% |
| D. | Less than 50% |
| Answer» E. | |
| 192. |
Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control$? |
| A. | Drum type controller is used |
| B. | Three point starter is used |
| C. | Four point starter is used |
| D. | All above can be used |
| Answer» B. Three point starter is used | |
| 193. |
In variable speed motor$? |
| A. | A stronger commutating field is needed at low speed than at high speed |
| B. | A weaker commutating field is needed at low speed than at high speed |
| C. | Same commutating field is needed at low speed than at high speed |
| D. | None of the above is correct |
| Answer» C. Same commutating field is needed at low speed than at high speed | |
| 194. |
No-load speed of which of the following motor will be highest?$? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differentiate compound motor |
| Answer» C. Cumulative compound motor | |
| 195. |
Which of the following loss in a D.C. generator varies significantly with the load current?$? |
| A. | Field copper loss |
| B. | Windage loss |
| C. | Armature copper loss |
| D. | None of the above |
| Answer» D. None of the above | |
| 196. |
Which one of the following is not the function of pole shoes in a D.C. machine?$? |
| 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 | |
| 197. |
No-load speed of which of the following motor will be highest?? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differentiate compound motor |
| Answer» C. Cumulative compound motor | |
| 198. |
Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control? |
| A. | Drum type controller is used |
| B. | Three point starter is used |
| C. | Four point starter is used |
| D. | All above can be used |
| Answer» B. Three point starter is used | |
| 199. |
Differentially compound D.C. motors can find applications requiring? |
| A. | High starting torque |
| B. | Low starting torque |
| C. | Variable speed |
| D. | Frequent on-off cycles |
| Answer» C. Variable speed | |
| 200. |
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» E. | |