1.In a D.C. machine, the value of peripheral speed should not, normally, exceed

2.In a D.C. machine the current per brush arm should not be more than

3.In a D.C. machine the number of brush arms is _____ the number of poles.

4.In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made

5.______ brushes are fragile and cause excessive wear of commutator,