MCQOPTIONS
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MCQOPTIONS
This section includes 43 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
By low voltage application, we can start a: |
| A. | Schrage motor |
| B. | Synchronous motor |
| C. | Slip ring induction motor |
| D. | DC compound motor |
| Answer» B. Synchronous motor | |
| 2. |
At what angle difference are the main winding and the start winding separated in a split-phase capacitor start induction motor? |
| A. | 30° mechanical |
| B. | 90° electrical |
| C. | 45° electrical |
| D. | 45° mechanical |
| Answer» C. 45° electrical | |
| 3. |
In case of split phase motors, the phase shift between two currents is usually limited to |
| A. | 30 degrees |
| B. | 60 degrees |
| C. | 90 degrees |
| D. | 150 degrees |
| Answer» B. 60 degrees | |
| 4. |
A shaded pole motor is basically a __________ motor. |
| A. | single-phase induction |
| B. | shunt |
| C. | synchronous |
| D. | series |
| Answer» B. shunt | |
| 5. |
A universal motor is preferred for which application? |
| A. | High speed and high torque |
| B. | Low speed |
| C. | Low torque and high speed |
| D. | Low torque |
| Answer» B. Low speed | |
| 6. |
In a split phase motor, the running winding should have ________. |
| A. | High resistance and low inductance |
| B. | Low resistance and high inductance |
| C. | High resistance as well as high inductance |
| D. | Low resistance as well as low inductance |
| Answer» C. High resistance as well as high inductance | |
| 7. |
Preferred motor in electric shaver is: |
| A. | Shaded pole motor |
| B. | Hysteresis motor |
| C. | Reluctance motor |
| D. | Universal motor |
| Answer» E. | |
| 8. |
Electric shavers generally use |
| A. | Shaded pole motor |
| B. | Universal motor |
| C. | Reluctance motor |
| D. | Hysteresis motor |
| Answer» C. Reluctance motor | |
| 9. |
Both main winding and auxiliary winding of a single phase induction motor is placed on the ________ . |
| A. | both stator and rotor |
| B. | neither stator nor rotor |
| C. | stator |
| D. | rotor |
| Answer» D. rotor | |
| 10. |
In a single-phase capacitor start-and-run motor, the minimum number of capacitors to be used in it is: |
| A. | 4 |
| B. | 1 |
| C. | 3 |
| D. | 2 |
| Answer» E. | |
| 11. |
A split induction motor, if the centrifugal switch of a single-phase resistance does not open after the starting of the motor, then the motor: |
| A. | will run at the speed that is equal to synchronous speed |
| B. | will run at the speed that is more than the normal speed |
| C. | will draw very less current |
| D. | will draw high current and get over heated |
| Answer» E. | |
| 12. |
Locked rotor current of a shaded pole motor with respect to full load current is: |
| A. | Equal |
| B. | Less |
| C. | Slightly more |
| D. | Several times more |
| Answer» D. Several times more | |
| 13. |
As per double field revolving theory, a sinusoidally alternating flux can be looked upon as the combination of two revolving fluxes: |
| A. | equal in magnitude to that of the alternating flux, rotating at synchronous speed in the same direction |
| B. | of half the magnitude to that of the alternating flux, rotating at synchronous speed in the same direction |
| C. | equal in magnitude to that of the alternating flux, rotating at synchronous speed in the opposite direction |
| D. | of half the magnitude to that of the alternating flux, rotating at synchronous speed in the opposite direction |
| Answer» E. | |
| 14. |
A domestic mixer uses the following motor |
| A. | Induction motor |
| B. | Reluctance motor |
| C. | Universal motor |
| D. | Permanent magnet synchronous motor |
| Answer» D. Permanent magnet synchronous motor | |
| 15. |
In a capacitor start single phase induction motor the current in the: |
| A. | starting winding lags the voltage |
| B. | starting winding leads the voltage |
| C. | supply lines leads the voltage |
| D. | main winding leads the voltage |
| Answer» C. supply lines leads the voltage | |
| 16. |
If an application needs high speed and high starting torque, then which of the following motor will be preferred? |
| A. | Universal motor |
| B. | Shaded pole type motor |
| C. | Capacitor start motor |
| D. | Capacitor start and run motor |
| Answer» B. Shaded pole type motor | |
| 17. |
In double-field revolving theory, slip with respect to forward flux and backward flux are: |
| A. | sf = 1 – s, and sb = s |
| B. | sf = 2 – s, and sb = 1 - s |
| C. | sf = s, and sb = 2 - s |
| D. | sf = 1 – s, and sb = 2 - s |
| Answer» D. sf = 1 – s, and sb = 2 - s | |
| 18. |
A capacitor start, capacitor run single phase induction motor is basically a: |
| A. | ac series motor |
| B. | dc series motor |
| C. | 2 phase induction motor |
| D. | 3 phase induction motor |
| Answer» D. 3 phase induction motor | |
| 19. |
A scharge motor can run on |
| A. | Zero slip |
| B. | Negative slip |
| C. | Positive slip |
| D. | All of the above |
| Answer» E. | |
| 20. |
A universal motor is said to be inductively compensated when compensating winding: |
| A. | is short circuited on itself |
| B. | is not used |
| C. | has large reactance |
| D. | is kept open |
| Answer» B. is not used | |
| 21. |
For maximum torque which motor is not suitable? |
| A. | D.C. Series motor |
| B. | D.C. Compound motor |
| C. | Slip-Ring I.M. |
| D. | Resistance Split phase motor |
| Answer» E. | |
| 22. |
In a fan, air pressure increases up to about |
| A. | 20% |
| B. | 30% |
| C. | 10% |
| D. | 5% |
| Answer» D. 5% | |
| 23. |
___________ motor is referred to as a universal motor? |
| A. | Synchronous |
| B. | Series |
| C. | Shunt |
| D. | Single-phase induction |
| Answer» C. Shunt | |
| 24. |
In which of the following respects, the servomotors differ in application capabilities from large industrial motors?1. They produce high torque at all speeds including zero speed.2. They are capable of holding a static position.3. They do not overheat at standstill or lower speeds.4. Due to low-inertia they are not able to reverse direction quickly. |
| A. | 1, 2, 3 and 4 |
| B. | 1, 2 and 3 only |
| C. | 1, 2 and 4 only |
| D. | 3 and 4 only |
| Answer» C. 1, 2 and 4 only | |
| 25. |
If running winding of a single-phase induction motor is short-circuited |
| A. | run slower |
| B. | spark at light loads |
| C. | draw excessive current and overheat |
| D. | None of these |
| Answer» D. None of these | |
| 26. |
Choose the INCORRECT statement with respect to the single-phase hysteresis motor. |
| A. | The rotor is a smooth solid cylinder of hard steel and does not carry any winding. |
| B. | The stator is wound with only one winding without capacitor. |
| C. | The hysteresis motor has a low noise figure compared to the single-phase induction motor. |
| D. | The phenomenon of hysteresis causes the rotor magnetisation to lag behind the stator-created MMF wave. |
| Answer» C. The hysteresis motor has a low noise figure compared to the single-phase induction motor. | |
| 27. |
An alternating current series motor run on: |
| A. | Alternating current only |
| B. | Direct current only |
| C. | AC and DC both |
| D. | Pulsating DC |
| Answer» D. Pulsating DC | |
| 28. |
In the shaded pole squirrel cage induction motor the flux in the shaded part always |
| A. | leads the flux in the un-shaded pole segment |
| B. | lags the flux in the un-shaded pole segment |
| C. | is in out of phase with the flux in the un-shaded pole segment |
| D. | is in phase with the flux in the un-shaded pole segment |
| Answer» C. is in out of phase with the flux in the un-shaded pole segment | |
| 29. |
In designing AC servo motors, what is the ideal X/R ratio for stable operation? |
| A. | Low |
| B. | High |
| C. | Medium |
| D. | No particular ratio |
| Answer» B. High | |
| 30. |
A single-stack, 8-phase multipolar, stepper motor has 6 rotor teeth. The phases are excited one at a time. Find the step size. |
| A. | 25° |
| B. | 5° |
| C. | 15° |
| D. | 10° |
| Answer» D. 10° | |
| 31. |
Lower efficiency, lower power factor, are the features of which of the following motors? |
| A. | Single-phase induction motor |
| B. | DC shunt motor |
| C. | Three-phase induction motor |
| D. | Three-phase synchronous motor |
| Answer» B. DC shunt motor | |
| 32. |
In AC series motor, armature coils are usually connected to commutator through |
| A. | Resistance |
| B. | Inductors |
| C. | Capacitors |
| D. | Solid contact |
| Answer» B. Inductors | |
| 33. |
In a capacitor-start-and-run motor, the function of the running capacitor in series with the auxiliary winding is to_______. |
| A. | Improve power factor |
| B. | Increase overload capacity |
| C. | Reduce fluctuations in torque |
| D. | To improve torque |
| Answer» B. Increase overload capacity | |
| 34. |
A single-phase motor is made self-starting by the addition of a/an ________. |
| A. | running winding |
| B. | starting winding |
| C. | electric starter |
| D. | autotransformer |
| Answer» C. electric starter | |
| 35. |
Following figure is a characteristic curve of |
| A. | DC series motor |
| B. | AC series motor |
| C. | Shunt motor |
| D. | Capacitor start and run single phase motor |
| Answer» C. Shunt motor | |
| 36. |
Before a capacitor-start motor can reverse its direction of rotation, the ________. |
| A. | centrifugal switch must be opened |
| B. | running winding must be opened |
| C. | starting winding must be connected to the line |
| D. | capacitor connections must be changed |
| Answer» D. capacitor connections must be changed | |
| 37. |
A stepper motor has a step angle of 2.5°. If the shaft is to make 25 revolutions, the number of steps required will be |
| A. | 1800 |
| B. | 2200 |
| C. | 2800 |
| D. | 3600 |
| Answer» E. | |
| 38. |
Hybrid stepper motor has 40 stator teeth and 50 rotor teeth. Find the step angle. |
| A. | 3.6° |
| B. | 5.4° |
| C. | 1.8° |
| D. | 7.2° |
| Answer» D. 7.2° | |
| 39. |
As compared to a split phase motor, a capacitor start motor has _____. |
| A. | Higher starting torque |
| B. | Lowe starting torque |
| C. | Higher running torque |
| D. | None of these |
| Answer» B. Lowe starting torque | |
| 40. |
Compensating winding is used in an AC series motor in order to: |
| A. | decrease starting current |
| B. | reduce effect of armature reaction |
| C. | reduce sparking at brushes |
| D. | increase torque |
| Answer» D. increase torque | |
| 41. |
A single-phase induction motor with single stator winding inherently has _________ starting torque. |
| A. | zero |
| B. | finite but moderate |
| C. | finite but large |
| D. | infinite |
| Answer» B. finite but moderate | |
| 42. |
In a split phase capacitor start induction motor, a time phase difference between currents in the main and auxiliary winding is achieved by: |
| A. | Placing the two windings at angle 90° electrical in the stator slots |
| B. | Applying two phase supply across the two windings |
| C. | Connecting the two windings in series across a single-phase supply |
| D. | Introducing capacitive reactance in the auxiliary winding circuit |
| Answer» E. | |
| 43. |
Among the following types of single phase induction motor which one has the highest power factor at full load? |
| A. | Shaded pole type |
| B. | Split-phase type |
| C. | Capacitor-start type |
| D. | Capacitor-run type |
| Answer» E. | |