Quiz on dc generator

 

1. A simple method of increasing the voltage of a DC generator is

A) to decrease the air gap flux density
B) to decrease the speed of rotation
C) to increase the length of armature
D) to increase speed of rotation

ANSWER= (D) to increase the speed of rotation
Explain:- emf proportion to speed

 

2. Dummy coil in a DC generator is used to reduce

A) Hysteresis losses
B) Mechanical unbalance
C) Armature reaction
D) to reduce emf

ANSWER= (B) Mechanical unbalance
Explain:- some slots without armature winding that is caused unbalance

 

3. In dc generator, the critical resistance is equal to resistance of the

A) Load
B) brush
C) filed
D) armature
ANSWER= (C) field
Explain:- if field resistance is high then field current is not produce flux so no Generate residual magnesium for build up voltage in case of dc shunt generator


 

4. Armature reaction At Full load of a large DC machine can be tested by

A) swinburne test
B) Brake test
C) shot circuit test
D) hopkinson test

ANSWER= (D) hopkinson test
Explain:- also know as back to back test used to find out Armature reaction , temperature rises in larger machine


 

5. The number of brushes in a commutator depends on

A) Amount of current to be collected
B) winding
C) speed
D) voltage

ANSWER= (A) Amount of current to be collected
Explain:-