The material for commutator brushes is generally

The field coils of D.C. generator are usually made of

A. Mica

B. Copper

C. Cast iron

D. Carbon

A cumulatively compounded long shunt generator when operating as a motor would be

A. Cumulatively compounded long shunt

B. Differentially compounded long shunt

C. Cumulatively compounded short shunt

D. Differentially compounded short shunt

If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be

A. Demagnetization only

B. Cross magnetization as well as magnetization

C. Cross-magnetization as well as demagnetizing

D. Cross magnetization only

Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be

A. 270 V

B. 267.5 V

C. 265 V

D. 257.5 V