DC Generators
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralized by all of the following except

Shifting of axis of brushes
Compensating winding
Interpoles
Dummy coils

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DC Generators
In a D.C. generator

Internal characteristic = magnetization characteristic ohmic drop
External characteristic = magnetization characteristic ohmic drop armature reaction
External resistance = internal characteristic armature reaction
Magnetization characteristic = external characteristic

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