DC Generators
To avoid formation of grooves in the commutator of a D.C. machine

The brushes of same polarity should track each other
All of these
The brushes of opposite polarity should track each other
Brush position has no effect on the commutator grooving

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DC Generators
When two D.C. generators are running in parallel an equalizer bar is used

So that the two identical machines will pass approximately equal currents to the load
To increase the generated e.m.f.
To reduce the combined effect of armature reaction of both the machines
To increase the series flux

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DC Generators
In a dc generator, the eddy current power loss is

Inversely proprtional to thickness of each lamination
Directly proportional to thickness of each lamination
Directly proportional to sqaure of thickness of each lamination
None of the listed here

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