Thursday, September 22, 2016

DC machine Questions



Q1:- A simple method of increasing the voltage of and dc generator is
1.       To decrease the air gap flux density
2.       To increase the speed of rotation
3.       To decrease the speed of rotation
4.       To increase the length of the armature

ANSWER:-2


Q2:- An external resistance is added in the series with the field of a dc shunt motor .When the motor runs the effect of resistance is

1.       To reduce the speed of the motor
2.       To increase the speed of the motor
3.       To reduce the armature current drawn by the motor
4.       To reduce the losses

ANSWER:-2



Q3:- If the speed of dc generator is increased the generated emf

1.       Increases
2.       Decreases
3.       Remains constant
4.       First decreases and then increases

ANSWER:-1



Q4:- If the speed of a shunt motor increases the back emf

1.       Increases
2.       Decreases
3.       Remains constant
4.       First decreases and the increases

ANSWER:-1



Q5:- The function of a commutator in dc generator is

1.       To collect current from conductor
2.       To change dc to ac
3.       To conductor the current to the brushes
4.       To change ac to dc

ANSWER:-4


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