Question

What is the use of brushes in DC machines?

(a) to connect the parts of the machine to the external circuit

(b) to conduct current between moving parts

(c) to conduct current between stationary wires and moving parts

(d) used for smooth conduction of current

I had been asked this question during a job interview.

I need to ask this question from Design of Commutator and Brushes topic in portion Thermal Design Aspects of Electrical Machines & D.C of Design of Electrical Machines

Answer 1

Right choice is (c) to conduct current between stationary wires and moving parts

To explain: Brushes are another important part in the construction of DC machine. They are connected in the lower end of the machine to allow the current flow between the moving parts and stationary wires.