Hi readers,this is post on dc generator with multiple choice questions check out and comment if you have any doubts...
1) In a dc machine, the armature is always on the rotor unlike an ac machine where it could be either on the stator or rotor, because
A) commutation action would otherwise not be possible
B) armature reaction demagnetising action would otherwise be more
C) otherwise it would not be possible to place compensating winding in pole shoes.
D) self-starting of dc motor would not be possible otherwise.
Ans:A
2) A duplex lap winding with equalizers and even number of pairs of poles is
A) doubly re-entrant and number of coils per pair of poles is an odd integer.
B) doubly re-entrant and number of coils per pair of poles is an even integer.
C) singly re-entrant and number of coils per pair of poles is an even integer.
D) singly re-entrant and number of coils per pair of poles is an odd integer.
Ans:A
3) The function of pole shoes in a dc machine is to
A) support the field coils.
B) reduce the reluctance of the magnetic path.
C) spread out the flux to achieve uniform flux distribution in the air gap.
D) all the above
Ans:D
4) In an electromechanical energy conversion device, the developed torque depends upon
A) stator field strength and torque angle
B) stator field and rotor field strengths
C) stator field and rotor field strengths and the torque angle
D) stator field strength only.
Ans:C
5) If a current carrying coil is placed in a uniform magnetic field direction of magnetic induction, then
A) the net force and torque on the coil are both zero
B) the net force is zero but torque is finite
C) the net force is finite but torque is zero
D) the net force and torque are both finite
Ans:A
6) A conductor is rotating within a magnetic field. At which of the positions do the peak voltage occur?
A) At right angles to the axis of magnetic field
B) along the axis of the magnetic field
C) At 45 angles to the axis of magnetic field
D) any where
Ans:B
7) EMF induced in a coil rotating in a uniform magnetic field will be maximum when the
A) flux linking with the coil is maximum
B) rate of change of flux linkage is minimum
C) rate of change of flux linkage is maximum
D) rate of cutting flux by the coil sides is minimum.
Ans:C
8) Reluctance torque in rotating machines is present, when
A) air gap is not uniform
B) reluctance seen by stator mmf varies
C) reluctance seen by rotor mmf varies
D) reluctance seen by the working mmf varies
Ans:D
9) An 8-pole, dc generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 wb. The machine is running at 250rpm. The induced armature voltage is
A) 96 V
B) 192 V
C) 384 V
D) 768 V
Ans:C
10) A 4-pole dynamo with wave wound armature has 51 slots containing 20 conductors in each slot. The induced emf is 357 V and the speed is 8500 rpm. The flux per pole will be
A) 3.5 mWb
B) 1.2 mWb
C) 14 mWb
D) 21 mWb
Ans:B
if you like my post please share it with your friends and subscribe to news letter....
1) In a dc machine, the armature is always on the rotor unlike an ac machine where it could be either on the stator or rotor, because
A) commutation action would otherwise not be possible
B) armature reaction demagnetising action would otherwise be more
C) otherwise it would not be possible to place compensating winding in pole shoes.
D) self-starting of dc motor would not be possible otherwise.
Ans:A
2) A duplex lap winding with equalizers and even number of pairs of poles is
A) doubly re-entrant and number of coils per pair of poles is an odd integer.
B) doubly re-entrant and number of coils per pair of poles is an even integer.
C) singly re-entrant and number of coils per pair of poles is an even integer.
D) singly re-entrant and number of coils per pair of poles is an odd integer.
Ans:A
3) The function of pole shoes in a dc machine is to
A) support the field coils.
B) reduce the reluctance of the magnetic path.
C) spread out the flux to achieve uniform flux distribution in the air gap.
D) all the above
Ans:D
4) In an electromechanical energy conversion device, the developed torque depends upon
A) stator field strength and torque angle
B) stator field and rotor field strengths
C) stator field and rotor field strengths and the torque angle
D) stator field strength only.
Ans:C
5) If a current carrying coil is placed in a uniform magnetic field direction of magnetic induction, then
A) the net force and torque on the coil are both zero
B) the net force is zero but torque is finite
C) the net force is finite but torque is zero
D) the net force and torque are both finite
Ans:A
6) A conductor is rotating within a magnetic field. At which of the positions do the peak voltage occur?
A) At right angles to the axis of magnetic field
B) along the axis of the magnetic field
C) At 45 angles to the axis of magnetic field
D) any where
Ans:B
7) EMF induced in a coil rotating in a uniform magnetic field will be maximum when the
A) flux linking with the coil is maximum
B) rate of change of flux linkage is minimum
C) rate of change of flux linkage is maximum
D) rate of cutting flux by the coil sides is minimum.
Ans:C
8) Reluctance torque in rotating machines is present, when
A) air gap is not uniform
B) reluctance seen by stator mmf varies
C) reluctance seen by rotor mmf varies
D) reluctance seen by the working mmf varies
Ans:D
9) An 8-pole, dc generator has a simplex wave-wound armature containing 32 coils of 6 turns each. Its flux per pole is 0.06 wb. The machine is running at 250rpm. The induced armature voltage is
A) 96 V
B) 192 V
C) 384 V
D) 768 V
Ans:C
10) A 4-pole dynamo with wave wound armature has 51 slots containing 20 conductors in each slot. The induced emf is 357 V and the speed is 8500 rpm. The flux per pole will be
A) 3.5 mWb
B) 1.2 mWb
C) 14 mWb
D) 21 mWb
Ans:B
if you like my post please share it with your friends and subscribe to news letter....
EmoticonEmoticon