DC Generator Multiple Choice Questions and Answers

21. If brushes of a D.C. generator are moved in order to bring these brushes in magneticneutral axis, there will be

1. demagnetisation only
2. cross magnetisation as well as magnetisation
3. crossmagnetisation as well as demagnetising
4. cross magnetisation only

22. While applying Flemings right-hand rule to And the direction of induced e.m.f., the thumb points towards

1. direction of induced e.m.f.
2. direction of flux
3. direction of motion of the conductor if forefinger points in the direction of generatede.m.f.
4. direction of motion of conductor, if forefinger points along the lines of flux

23. In lap winding, the number of brushes is always

1. double the number of poles
2. same as the number of poles
3. half the number of poles
4. two

24. Which of the following components of a D.C, generator plays vital role for providingdirect current of a D.C. generator ?

1. Dummy coils
2. Commutator
3. Eye bolt
4. Equilizer rings

25. The e.m.f. generated by a shunt wound D.C. generator is E. Now while pole flux remainsconstant, if the speed of the generator is doubled, the e.m.f. generated will be

1. E/2
2. 2E
3. slightly less than E
4. E

26. The series field of a short-shunt D.C. generator is excited by

1. external current
2. armature current
3. shunt current
4. load current

27. In a D.C. generator

1. external resistance = internal char-acteristic - armature reaction
2. internal characteristic = magnetisation characteristic - ohmic drop
3. external characteristic = magnetisation characteristic - ohmic drop - armature reaction
4. magnetisation characteristic = external characteristic

28. The critical resistance of the D.C. generator is the resistance of

1. field
2. brushes
3. armature
4. load

29. Permeance is the reciprocal of

1. flux density
2. reluctance
3. ampere-turns
4. resistance

30. A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speedincreases to 1200 r.p.m., the generated e.m.f. will be nearly

1. 150 V
2. 175 V
3. 240 V
4. 290 V