Hi readers, this post is on dc generator multiple choice questions check out and comment if you have any doubts....
1) The reactance voltage is
A) directly proportional to armature current and commutation period
B) directly proportional to commutation period and inversely proportional to armature current
C) directly proportional to armature current and inversely proportional to commutation period
D) none of the above
Ans:C
2) If the armature current is increased to double its previous value and the time of commutation is halved, how will the reactance voltage vary?
A) It will be halved
B) It will remain same
C) It will be doubled
D) It will become four times
Ans:D
3) In a dc machine, the sparking between brushes and commutator surface may be due to
A) under commutation
B) over commutation
C) too rapid reversal of current
D) any of the above
Ans:D
4) Air gap at the pole tips of a dc machine is kept more than that at the centre of the pole mainly to reduce
A) reactance voltage
B) effect of armature reaction
C) losses of armature core
D) noise of machine
Ans:B
5) Commutation in a dc machine may be explained as a process
A) in which magnetic field is set up
B) by virtue of which emf is induced in the armature conductors
C) by which current in a coil is reversed during the period it is short-circuited by the brush
D) how armature flux affects the main field flux
Ans:C
6) Current in a coil under going commutation is not able to get reversed completely by the end of commutation period. It is due to
A) reactance voltage induced in the coil
B) coil resistance
C) armature emf
D) none of the above
Ans:A
7) In a dc shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will
A) improve but terminal voltage will fall
B) worsen and terminal voltage will fall
C) improve and terminal voltage will rise
D) worsen and terminal volatge will rise
Ans:A
8) At a certain speed and flux, the voltage generated by a dc generator is 230 volts. If the speed is increased by 20% and the flux is simultaneously reduced by 10%, the voltage will be
A) increased by 10%
B) reduced by 20%
C) increased by 8%
D) decreased by 8%
Ans:C
9) In order to ascertain whether a dc machine is lap wound or wave wound on the basis of visual observations of the armature, one should observe the
A) connections to the brushes
B) connections to the commutator
C) connections to the field winding
D) direction of end connections.
Ans:D
10) The field coils of a dynamo have an inductance of 8H and have a resistance of 60 ohms and are connected to 120 V dc source. The steady state current in the field coil is
A) 15 A
B) 2 A
C) zero A
D) none of the above
Ans:B
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1) The reactance voltage is
A) directly proportional to armature current and commutation period
B) directly proportional to commutation period and inversely proportional to armature current
C) directly proportional to armature current and inversely proportional to commutation period
D) none of the above
Ans:C
2) If the armature current is increased to double its previous value and the time of commutation is halved, how will the reactance voltage vary?
A) It will be halved
B) It will remain same
C) It will be doubled
D) It will become four times
Ans:D
3) In a dc machine, the sparking between brushes and commutator surface may be due to
A) under commutation
B) over commutation
C) too rapid reversal of current
D) any of the above
Ans:D
4) Air gap at the pole tips of a dc machine is kept more than that at the centre of the pole mainly to reduce
A) reactance voltage
B) effect of armature reaction
C) losses of armature core
D) noise of machine
Ans:B
5) Commutation in a dc machine may be explained as a process
A) in which magnetic field is set up
B) by virtue of which emf is induced in the armature conductors
C) by which current in a coil is reversed during the period it is short-circuited by the brush
D) how armature flux affects the main field flux
Ans:C
6) Current in a coil under going commutation is not able to get reversed completely by the end of commutation period. It is due to
A) reactance voltage induced in the coil
B) coil resistance
C) armature emf
D) none of the above
Ans:A
7) In a dc shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will
A) improve but terminal voltage will fall
B) worsen and terminal voltage will fall
C) improve and terminal voltage will rise
D) worsen and terminal volatge will rise
Ans:A
8) At a certain speed and flux, the voltage generated by a dc generator is 230 volts. If the speed is increased by 20% and the flux is simultaneously reduced by 10%, the voltage will be
A) increased by 10%
B) reduced by 20%
C) increased by 8%
D) decreased by 8%
Ans:C
9) In order to ascertain whether a dc machine is lap wound or wave wound on the basis of visual observations of the armature, one should observe the
A) connections to the brushes
B) connections to the commutator
C) connections to the field winding
D) direction of end connections.
Ans:D
10) The field coils of a dynamo have an inductance of 8H and have a resistance of 60 ohms and are connected to 120 V dc source. The steady state current in the field coil is
A) 15 A
B) 2 A
C) zero A
D) none of the above
Ans:B
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