DC Generators MCQ Practice Test - Set 01 - ObjectiveBooks

# Practice Test: Question Set - 01

1. In D.C. generators, the cause of rapid brush wear may be
(A) Severe sparking
(B) Rough commutator surface
(C) Imperfect contact
(D) Any of the above

2. The insulating material used between the commutator segments is normally
(A) Graphite
(B) Paper
(C) Mica
(D) Insulating varnish

3. Eddy currents are induced in the pole shoes of a D.C. machine due to
(A) Oscillating magnetic field
(B) Pulsating magnetic flux
(C) Relative rotation between field and armature
(D) All above

4. Which of the following statement about D.C. generators is false?
(A) Compensating winding in a D.C. machine helps in commutation
(B) In a D. C. generator interpoles winding is connected in series with the armature winding
(C) Back pitch and front pitch are both odd and approximately equal to the pole pitch
(D) Equalizing bus bars are used with parallel running of D.C. shunt generators

5. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by
(A) Using conductor of annealed copper
(B) Using commutator with large number of segments
(C) Using carbon brushes of superior quality
(D) Using equalizer rings

6. Satisfactory commutation of D.C. machines requires
(A) Brushes should be of proper grade and size
(B) Brushes should smoothly run in the holders
(C) Smooth, concentric commutator properly undercut
(D) All of the above

7. In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when
(A) r.p.m. is more than 300
(B) r.p.m. is less than 300
(C) Number of poles is 4
(D) Number of poles is 2

8. In D.C. generators on no-load, the air gap flux distribution in space is
(A) Sinusoidal
(B) Triangular
(C) Pulsating
(D) Flat topped

9. Flashing the field of D.C. generator means
(A) Neutralizing residual magnetism
(B) Creating residual magnetism by a D.C. source
(C) Making the magnetic losses of forces parallel
(D) Increasing flux density by adding extra turns of windings on poles

10. The following constitute short-circuit in the armature winding.
(A) Insulation failure between two commutator bars
(B) Insulation failure between two turns of a coil
(C) Two of more turns of the same coil getting grounded
(D) All of the above

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