Electrical Machines
Which of the following is/are the advantages of carbon brush over the copper brush?

All of these
 In case of any sparking they will be less damaged than copper brushes
 They are self lubricating in nature
 They are not hard as copper brush

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Interpoles in a DC motor must be

 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.

ANSWER DOWNLOAD EXAMIANS APP