MCQs 1: The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________?
MCQs 2: In a D.C. generator the critical resistance refers to the resistance of_____________?
MCQs 3: A D.C. welding generator has____________?
MCQs 4: To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them?
just ahead of magnetic neutral axis
in magnetic neutral axis
just behind the magnetic neutral axis
none
MCQs 5: Which of the following statement about D.C. generators is false ?
Compensating winding in a D.C. machine helps in commutation
In a D. C. generator interpoles winding is connected in series with the armature winding
Back pitch and front pitch are both odd and approximately equal to the pole pitch
Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators
MCQs 6: Armature coil is short circuited by brushes when it lies_____________?
MCQs 7: A cumulatively compounded long shunt generator when operating as a motor would be____________?
cumulatively compounded long shunt
deferentially compounded long shunt
cumulatively compounded short shunt
differentially compounded short shunt
MCQs 8: The demagnetising component of armature reaction in a D.C. generator___________?
reduces generator e.m.f.
increases armature speed
reduces interpoles flux density
results in sparking trouble
MCQs 9: To avoid formation of grooves in the commutator of a D.C. machine?
the brushes of opposite polarity should track each other
the brushes of same polarity should track each other
brush position has no effect on the commutator grooving
None
MCQs 10: Magnetic field in a D.C. generator is produced by_______________?
MCQs 11: The number of brushes in a commutator depends on______________?
MCQs 12: The following constitute short-circuit in the armature winding.
Insulation failure between two commutator bars
Insulation failure between two turns of a coil
Two of more turns of the same coil getting grounded
All of the above
MCQs 13: Compensating windings are used in D.C. generators______________?
mainly to reduce the eddy currents by providing local short-circuits
to provide path for the circulation of cooling air
to neutralise the cross-magnetising effect of the armature reaction
none of the above
MCQs 14: Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
MCQs 15: The rapid wear of brushes takes place due to____________?
abrasion from dust
excessive spring pressure
rough commutator bars
high mica insulation between com-mutation bars
all of the above factors
MCQs 16: In a D.C. generator the ripples in the direct e.m.f. generated are reduced by_____________?
using conductor of annealed copper
using commutator with large number of segments
using carbon brushes of superior quality
using equiliser rings
MCQs 17: In D.C. generators, lap winding is used for______________?
high voltage, high current
low voltage, high current
high voltage, low current
low voltage, low current
MCQs 18: Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be_______________?
MCQs 19: Number of tappings for each equalizer ring is equal to_____________?
MCQs 20: The voltage drop for which of the following types of brush can be expected to be least ?
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