MCQOPTIONS
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MCQOPTIONS
This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Dc Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
WHICH_OF_THE_FOLLOWING_QUANTITY_WILL_DECREASE_IF_SUPPLY_VOLTAGE_IS_INCREASED??$ |
| A. | Starting torque |
| B. | Operating speed |
| C. | Full-load current |
| D. | Cannot be determined |
| Answer» D. Cannot be determined | |
| 2. |
Sometimes motor has to be de-rated.$ |
| A. | True |
| B. | False |
| Answer» B. False | |
| 3. |
In which of the following case we will get maximum power?$ |
| A. | E<sub>a</sub> = 2 x supply voltage |
| B. | E<sub>a</sub> = supply voltage |
| C. | Supply voltage = 2 x E<sub>a</sub> |
| D. | supply voltage = 4 x E<sub>a</sub> |
| Answer» D. supply voltage = 4 x E<sub>a</sub> | |
| 4. |
Sparking is discouraged in a DC motor. |
| A. | True |
| B. | False |
| Answer» C. | |
| 5. |
In DC machines the residual magnetism is present. The order of residual magnetism is ___________ |
| 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» B. 10 to 15 per cent | |
| 6. |
The armature shaft of a DC motor must be able to withstand ______________ |
| A. | Bending moment due to weight of the armature. |
| B. | Any unbalanced magnetic pull on the armature core. |
| C. | Twisting stains due to transmission of torque. |
| D. | Bending moment, unbalanced magnetic pull and twisting stains |
| Answer» E. | |
| 7. |
An electric motor is having constant output power. So, motor will have a torque speed characteristic ______________________? |
| A. | Circle about the origin. |
| B. | Straight line parallel to the speed axis. |
| C. | Straight line through the origin. |
| D. | Rectangular hyperbola |
| Answer» E. | |
| 8. |
Which power is mentioned on a name plate of a motor? |
| A. | Gross power |
| B. | Power drawn in kVA |
| C. | Power drawn in kW |
| D. | Output power available at the shaft |
| Answer» E. | |
| 9. |
The current drawn by the armature of DC motor is directly proportional to ________________ |
| A. | Torque |
| B. | Speed |
| C. | The voltage across the terminals |
| D. | Cannot be determined |
| Answer» B. Speed | |
| 10. |
Direction of rotation of motor is determined by ____________ |
| A. | Faraday’s law |
| B. | Lenz’s law |
| C. | Coulomb’s law |
| D. | Fleming’s left-hand rule |
| Answer» E. | |
| 11. |
In DC motor, which of the following part can sustain the maximum temperature rise? |
| A. | Field winding |
| B. | Commutator |
| C. | Slip rings |
| D. | Armature winding |
| Answer» B. Commutator | |
| 12. |
Which part will surely tell that given motor is DC motor and not an AC type? |
| A. | Winding |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» D. Stator | |
| 13. |
What will happen, with the increase in speed of a DC motor? |
| A. | Back emf increase but line current falls. |
| B. | Back emf falls and line current increase. |
| C. | Both back emf as well as line current increase. |
| D. | Both back emf as well as line current fall. |
| Answer» B. Back emf falls and line current increase. | |
| 14. |
What will happen if the back emf of a DC 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 | |
| 15. |
What will happen if DC shunt motor is connected across AC supply? |
| A. | Will run at normal speed |
| B. | Will not run |
| C. | Will Run at lower speed |
| D. | Burn due to heat produced in the field winding |
| Answer» E. | |