MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 80 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A synchronous machine is called as doubly excited machine because |
| A. | .It can be over excited |
| B. | It has two sets of rotor poles |
| C. | Both its rotor and stator are excited |
| D. | It needs twice the normal exciting current |
| Answer» D. It needs twice the normal exciting current | |
| 52. |
Synchronous capacitor is |
| A. | An ordinary static capacitor bank |
| B. | An over excited synchronous motor driving mechanical load |
| C. | An over excited synchronous motor running without mechanical load |
| D. | None of the above |
| Answer» D. None of the above | |
| 53. |
In a synchronous motor, damper winding is provided to |
| A. | Stabilize rotor motion |
| B. | Suppress rotor oscillations |
| C. | Develop necessary starting torque |
| D. | Both B and C |
| Answer» E. | |
| 54. |
[10]A 3-phase squirrel cage induction motor supplied from a balanced 3-phase source drives a mechanical load. The torque-speed characteristics of the motor (solid curve) and of the load (dotted curve) are shown. Of the two equilibrium points A and B, which of the following options correctly describes the stability of A and B? [GATE 2009] |
| A. | A is stable B is unstable |
| B. | A is unstable B is stable |
| C. | Both are stable |
| D. | Both are unstable |
| Answer» C. Both are stable | |
| 55. |
The thrust developed by a linear induction motor depends on |
| A. | Synchronous speed |
| B. | Rotor input |
| C. | Number of poles |
| D. | both A and B |
| Answer» E. | |
| 56. |
The starting torque of a 1-phase induction motor is |
| A. | High |
| B. | Medium |
| C. | Low |
| D. | Zero |
| Answer» E. | |
| 57. |
Star- delta starter of an induction motor |
| A. | Inserts resistance in rotor circuit |
| B. | Inserts resistance in stator circuit |
| C. | Applies reduced voltage to rotor |
| D. | Applies reduced voltage to stator |
| Answer» E. | |
| 58. |
The stator core of the induction motor is made of |
| A. | Laminated cast iron |
| B. | Mild steel |
| C. | Silicon steel stampings |
| D. | Soft wood |
| Answer» D. Soft wood | |
| 59. |
Rotating magnetic field is produced in A.... |
| A. | single - phase induction motor |
| B. | three phase induction motor |
| C. | dc series motor |
| D. | ac series motor |
| Answer» C. dc series motor | |
| 60. |
the difference between the synchronous speed and the actual speed of an induction motor is known as |
| A. | Regulation |
| B. | back lash |
| C. | slip |
| D. | lag |
| Answer» D. lag | |
| 61. |
The effect of increasing the length of the air gap in an induction motor will increase |
| A. | power factor |
| B. | speed |
| C. | magnetising current |
| D. | air-gap flux |
| Answer» D. air-gap flux | |
| 62. |
The speed of an induction motor |
| A. | decreases too much with the increase of load |
| B. | increase with the increase of load |
| C. | decreases slightly with the increase of load |
| D. | remains constant with the increase of load |
| Answer» D. remains constant with the increase of load | |
| 63. |
The crawling in an induction motor is caused by |
| A. | improper design of the machine |
| B. | low voltage supply |
| C. | high loads |
| D. | harmonics developed in the motor |
| Answer» E. | |
| 64. |
Which generator has poorest voltage regulation |
| A. | series |
| B. | shunt |
| C. | compound |
| D. | high |
| Answer» B. shunt | |
| 65. |
An ideal dc generator has .......... voltage regulation. |
| A. | low |
| B. | . zero |
| C. | positive |
| D. | negative |
| Answer» C. positive | |
| 66. |
The commutation process in a dc generator basically involves |
| A. | passage of current from moving armature to a stationary load |
| B. | reversal of current in an armature coil as it crosses MNA |
| C. | conversion of ac to dc |
| D. | suppression of reactance voltage |
| Answer» C. conversion of ac to dc | |
| 67. |
In a dc generator, the generator, the generated emf is directly proportional to the |
| A. | field current |
| B. | pole flux |
| C. | number of armature parallel paths |
| D. | number of dummy coils |
| Answer» C. number of armature parallel paths | |
| 68. |
The critical resistance of the dc generator is the resistance of |
| A. | armature |
| B. | field |
| C. | load |
| D. | brushes |
| Answer» C. load | |
| 69. |
In small DC machines, armature slots are sometimes not made axial but are skewed, results in |
| A. | quieter operation |
| B. | slight decrease in losses |
| C. | saving of copper |
| D. | both a and b |
| Answer» E. | |
| 70. |
The sole purpose of a commutator in a dc generator is to |
| A. | increase output voltage |
| B. | reduce sparking at brushes |
| C. | provide smoother output |
| D. | convert the induced ac into dc |
| Answer» E. | |
| 71. |
The basic requirement of a dc armature winding is that it must be |
| A. | a closed one |
| B. | a lap winding |
| C. | a wave winding |
| D. | either b or c |
| Answer» B. a lap winding | |
| 72. |
The most economical method of finding no losses of a large dc shunt motor is |
| A. | Hopkinsons test |
| B. | Swinburns test |
| C. | Retardation test |
| D. | Fields test |
| Answer» C. Retardation test | |
| 73. |
the main disadvantage of hopkinson's test for finding efficiency of shunt dc motors is that it |
| A. | Requires full load power |
| B. | Ignores any change in iron loss |
| C. | Needs one motor and one generator |
| D. | Requires two identical shunt machines |
| Answer» E. | |
| 74. |
One of the main advantage of the swinburn's test is |
| A. | It is applicable both shunt and compound motors |
| B. | It needs one running test |
| C. | It is very economical and convenient |
| D. | It ignores any charge in iron loss |
| Answer» D. It ignores any charge in iron loss | |
| 75. |
In a DC series motor increasing the load current will |
| A. | Decrease the speed |
| B. | Increase the speed |
| C. | Better commutation |
| D. | Increase the back emf |
| Answer» B. Increase the speed | |
| 76. |
A DC series motor is best for driving |
| A. | Lathes |
| B. | Cranes and hoists |
| C. | Shears and punches |
| D. | Machine tools |
| Answer» C. Shears and punches | |
| 77. |
The usual test to find the efficiency of the traction motor is |
| A. | Fields test |
| B. | Retardation test |
| C. | Hopkinsons test |
| D. | Swinburns test |
| Answer» B. Retardation test | |
| 78. |
which of the following motor has the constant speed? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compound motor |
| D. | All of the above |
| Answer» C. Cumulatively compound motor | |
| 79. |
Both Hopkinson's test and Field test |
| A. | Require two electrically coupled series motors |
| B. | Need two similar mechanically coupled motors |
| C. | Use negligible power |
| D. | Are regenerative tests |
| Answer» C. Use negligible power | |
| 80. |
Voltage equation of a dc motor is |
| A. | V = Eb + IaRa |
| B. | Eb = V + IaRa |
| C. | V = Eb/IaRa |
| D. | V = Eb + Ia2Ra |
| Answer» B. Eb = V + IaRa | |