A. is amenable to better voltage control
B. is more stable
C. has exciting current independent of load current
D. has all above features
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In a four-pole D.C. machine____________?
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In lap winding, the number of brushes is always_____________?
A. all the four poles are north poles
B. alternate poles are north and south
C. all the four poles are south poles
D. two north poles follow two south poles
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The bearings used to support the rotor shafts are generally______________?
A. double the number of poles
B. same as the number of poles
C. half the number of poles
D. two
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In D.C. generators, the cause of rapid brush wear may be___________?
A. ball bearings
B. bush bearings
C. magnetic bearmgs
D. needle bearings
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For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f___________ ?
A. severe sparking
B. rough commutator surface
C. imperfect contact
D. any of the above
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Copper brushes in D.C. machine are used_____________?
A. Lap winding
B. Wave winding
C. Either of A. and B. above
D. Depends on other features of design
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In case of D.C. machines, mechanical losses are primary function of____________?
A. where low voltage and high currents are involved
B. where high voltage and small cur-rents are involved
C. in both of the above cases
D. in none of the above cases
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Fleming’s right-hand rule regarding direction of induced e.m.f., correlates__________?
A. current
B. voltage
C. speed
D. none of above
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In D.C. generators the pole shoes are fastened to the pole core by_____________?
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