A. external resistance = internal char-acteristic – armature reaction
B. internal characteristic = magnetisation characteristic – ohmic drop
C. external characteristic = magnetisation characteristic – ohmic drop – armature reaction
D. magnetisation characteristic = external characteristic
D.C. Generators
Fleming’s right-hand rule regarding direction of induced e.m.f., correlates__________?
A. magnetic flux, direction of current flow and resultant force
B. magnetic flux, direction of motion and the direction of e.m.f. induced
C. magnetic field strength, induced voltage and current
D. magnetic flux, direction of force and direction of motion of conductor
In D.C. generators, current to the external circuit from armature is given through_____________?
A. commutator
B. solid connection
C. slip rings
D. none of above
In D.C. generators, lap winding is used for______________?
A. high voltage, high current
B. low voltage, high current
C. high voltage, low current
D. low voltage, low current
The material for commutator brushes is generally_______________?
A. mica
B. copper
C. cast iron
D. carbon
The field coils of D.C. generator are usually made of_____________?
A. mica
B. copper
C. cast iron
D. carbon
Magnetic field in a D.C. generator is produced by_______________?
A. electromagnets
B. permanent magnets
C. both A. and B.
D. none of the above
While applying Fleming’s right-hand rule to And the direction of induced e.m.f., the thumb points towards___________?
A. direction of induced e.m.f.
B. direction of flux
C. direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
D. direction of motion of conductor, if forefinger points along the lines of flux
The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be_______________?
A. E/2
B. 2E
C. slightly less than E
D. E
Equilizer rings are required in case armature is_______________?
A. wave wound
B. lap wound
C. delta wound
D. duplex wound
