Top 350+ Solved Electrical Machine 1 MCQ Questions Answer
Q. Interpole flux should be sufficient to
a. neutralise the commutating self induced e.m.f.
b. neutralise the armature reaction flux
c. neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil
d. perform none of the above functions
Q. D.C. generator generally preferred for charging automobile batteries is
a. series generator
b. shunt generator
c. long shunt compound generator
d. any of'the above
Q. In a D.C. generator the number of mechanical degrees and electrical degreeswill 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
Q. In D.C. generators the polarity of the interpoles
a. is the same as that of the main pole ahead
b. is the same as that of the immediately preceding pole
c. is opposite to that of the main pole ahead
d. is neutral as these poles do not play part in generating e.m.f.
Q. The e.m.f. generated in a D.C. generator is directly proportional to
a. flux/pole
b. speed of armature
c. number of poles
d. all of the above
Q. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except
a. interpoles
b. dummy coils
c. compensating winding
d. shifting of axis of brushes
Q. In D.C. generators on no-load, the air gap flux distribution in space is
a. sinusoidal
b. triangular
c. pulsating
d. flat topped
Q. The purpose of providing dummy coils in a generator is
a. to reduce eddy current losses
b. to enhance flux density
c. to amplify voltage
d. to provide mechanical balance for the rotor
Q. If a D.C. generator fails to build up the probable cause could not be
a. imperfect brush contact
b. field resistance less than the critical resistance
c. no residual magnetism in the generator
d. faulty shunt connections tending to reduce the residual magnetism
Q. Flashing the field of D.C. generator means
a. neutralising 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
Q. In a D.C. generator the critical resistance refers to the resistance of
a. brushes
b. field
c. armature
d. load
Q. To achieve sparkless commutation brushes of a D.C. generator are rockedmahead soas to bring them
a. just ahead of magnetic neutral axis
b. in magnetic neutral axis
c. just behind the magnetic neutral axis
d. none