Question

Which conductors are in point of contact with brushes?

(a) Lie under south pole

(b) Lie under north pole

(c) Lie in inter polar region

(d) Are farthest from the poles

The question was posed to me by my college director while I was bunking the class.

The origin of the question is Brushes and Commutator Assembly topic in chapter DC Machines of DC Machines

Answer 1

The correct answer is (c) Lie in inter polar region

To elaborate: Because of the diamond shape of coils, the brushes which are physically opposite the pole centres are electrically connected to coil-sides lying close to the interpolar region. Thus, electrically the brushes are displaced 90° elect. From the axes of the main poles.