DC Generators
In a D.C. generator

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

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

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

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