1. The armature winding of DC machine is placed on the rotor to
(a) reduce losses
(b) escalate commutation
(c) reduce armature reaction
(d) reduce weight
Answer
2. The yoke of a DC machine is generally made of
(a) carbon
(b) soft iron
(c) cast steel
(d) silicon steel
Answer
3. Number of magnetic circuits in a four pole DC machine are
(a) one
(b) two
(c) four
(d) eight
Answer
4. The armature of DC machine is laminated in order to reduce
(a) copper losses
(b) hysteresis losses
(c) eddy current losses
(d) friction frictional losses
Answer
5. In a DC Machine, the current flow in a armature circuit is
(a) AC
(b) pulsating DC
(c) pure DC
(d) none of the above
Answer
6. The number of commutator segments in a DC machine is equal to
(a) number of poles
(b) number of conductors
(c) number of coils
(d) number of turns
Answer
7. As the armature reaction effect increases, the main flux of DC machine is
(a) decreases
(b) increases
(c) remain same
(d) none of the above
Answer
8. The space wave form of the air gap flux distribution of an DC machine will results change in
(a) current
(b) voltage
(c) torque
(d) none of the above
Answer
9. In DC machines, slot wedges are generally made of
(a) silicon steel
(b) fibre
(c) impregnated paper
(d) cotton
Answer
10. The number of brushes used in a lap wound DC machine is always equal to
(a) number of conductors
(b) number of poles
(c) number of coils
(d) number of pole pairs
Answer
11. In which part of DC machine the eddy current loss is maximum
(a) yoke
(b) field pole
(c) air gap
(d) armature
Answer
12. In order to reduce the size of DC generator, the magnetic material must have
(a) high permeability
(b) low permeability
(c) high resistance
(d) high reluctance
Answer
13. In DC machine, the air gap flux distribution in space at no old is
(a) sinusoidal
(b) DC
(c) flat topped
(d) pulsuating
Answer
14. In DC machine, the teeth in the armature are sometime skewed in order to reduce
(a) copper losses
(b) iron losses
(c) magnetic locking
(d) vibration
Answer
15. In DC machines if the resistance of carbon brushes increases, the sparking at the brushes
(a) increases
(b) decreases
(c) remains same
(d) none of the above