EM-1 QUIZ

To improve commutation, one can use:

• Interpoles

• Laminated core

• AC supply

• Stepper winding

EMF in a DC generator is induced due to

• Electrostatic effect

• Mechanical friction

• Chemical reaction

• Electromagnetic induction

The purpose of a commutator in a DC generator is to:

• Reduce losses

• Increase EMF

• Reduce speed

• Reverse the direction of current in coils

If armature reaction is not compensated in a DC generator

• Sparking occurs at the brushes

• Terminal voltage becomes perfectly constant

• No effect

• Efficiency increases

Self-excited DC generators require .............. to build up voltage.

• Permanent magnet

• External DC supply

• Commutator

• Residual magnetism

Armature reaction in a DC generator causes:

• Increase in efficiency

• Increase in speed

• Distortion of flux

• Reduced torque

The main function of a DC generator is to

• Store energy

• Convert mechanical energy into electrical energy

• Convert electrical energy into mechanical energy

• Reduce voltage

Increasing armature speed in a DC generator:

• Decreases EMF

• Increases EMF

• Reduces efficiency

• No effect

Separately excited DC generators have:

• External DC supply for field

• Only series field

• No field winding

• Only shunt field

What is the purpose of the brushes in a DC generator?

• To collect the current from commutator

• To reduce friction

• To increase efficiency

• To regulate voltage