300 Important DC Generator MCQ Question and Answer | PDF Free Download
1.The equalizer rings are used in a lap wound dc generator to
- ANeutralize the armature reaction effect
- BAvoid short circuiting
- CAvoid unequal distribution of currents at brushes for sparkles commutation
- DAndroid harmonics generated in the emf provide mechanical balancing
2.In a lap wound dc generator having P poles and Z conductors, the maximum number of equalizer rings will be
- AZ/P
- B2Z/P
- CZ/2P
- DZ/4P
3.In a DC machine, the number of tapings to each equalizer ring is equal to number of
- APoles
- BPole pairs
- CParallel paths
- DCommutator segments
4.A frog leg winding is used in a dc machine to eliminate
- AThe use of equalizers in lap winding
- BThe use of compensating winding
- CThe use of compensating winding
- DReactance voltage produced due to commutation
5.A 250 V dc generator is run at rated speed with no excitation. The open circuit voltage will be
- AZero
- BVery small, say about 2 or 3 V
- CAbout 100 V
- D250 V
6.At a certain speed and flux, the voltage generated by dc generator is 230 volts. If the speed is increased by 20% and the flux is simultaneously reduced by 10%, the voltage will be
- AIncrease by 10 %
- BReduced by 20 %
- CIncreased by 8 %
- DDecreased by 8 %
7.The field coils of a dynamo have an inductance of 8 H and have a resistance of 60 ohm and are connected to 120 V dc source. The steady state current in the filed coil is
- A15 A
- B2 A
- CZero A
- DNone of the above
8.A 4-pole lap wound dc generator has a developed power of P watts and voltage of E volts. The adjacent brushes of the machine are removed as they are worn out. If the machine operates with the remaining brushes, the developed voltage and power that can be obtained from the machine are
- AE,P
- BE/2, P/2
- CE, P/4
- DE, P/2
9.The armature resistance of a 6-pole lap wound dc machine is 0.05 ohm. If the armature is rewound as a wave winding, what is the armature resistance?
- A0.45 ohm
- B0.30 ohm
- C0.15 ohm
- D0.10 ohm
10.In DC Generators, the air gap flux distribution in space at no load is
- ASinusoidal
- BTriangular
- CFlat topped
- DPulsating
11.The armature MMF waveform of a dc machine is
- APulsating
- BRectangular
- CTriangular
- DSinusoidal
12.The armature mmf of a dc machine has
- ATriangular space distribution and rotates at the speed of armature
- BTrapezoidal space distribution and is stationary in space
- CStepped distribution and rotates the speed of armature
- DTriangular space distribution and is stationary in space
13.In a dc machine, the actual flux distribution depends upon
- ASize of air gap
- BShape of pole shoes
- CClearance between tips of the adjacent pole shoes
- DAll of the above
14.In a dc machine, the space waveform of the air gap flux distribution affects
- ATorque only
- BVoltage only
- CBoth the torque and voltage
- DNeither the torque nor the voltage
15.In a dc machine the armature mmf is
- AStationary with respect to the field poles but rotating with respect to the armature
- BRotating with respect to field poles as well as armature
- CRotating with respect to field poles
- DStationary with respect to armature
16.Armature reaction in dc shunt generator, running at full load with the brushed not shifted form the geometrical neutral plane and saturation neglected is
- AAbsent
- BCross magnetizing
- CDemagnetizing
- DMagnetizing
17.In a dc machine without any brush shift, the shift of the magnetic neutral axis owing to armature reaction is
- AIn the direction of rotation for both the generator and the motor
- BAgainst the direction rotation for both the generator and the motor
- CIn the direction of rotation for the generator and against the direction of rotation for the motor
- DAgainst the direction of rotation for the generator and in the direction of rotation of motor
18. In a dc machine, on no load the magnetic neutral axis
- AMoves from geometrical neutral axis in the direction of rotation
- BMoves from geometrical neutral axis in the opposite direction of rotation
- CCoincides with the geometrical neutral axis
- DNone of the above
19.Due to magnetic saturation, the flux per pole in a dc machine without brush shift
- AIncreases in both the generators and the motors with load
- BIncreases in both the generators and the motors with load
- CIncreases in generators but decrease in motors with loads
- DDecreases generators and increases in motors with load
20.If the brushes are given a small amount of forward shift in case of a dc generator, the armature reaction effect will be
- ATotally demagnetizing
- BTotally cross-magnetizing
- CPartially demagnetizing and partially cross-magnetizing
- DTotally magnetizing