Electrical Machines
The synchronous reactance( Xs) is the

 reactance due to leakage flux
 reactance either due to armature reaction or leakage flux
 reactance due to armature reaction of the machine
 combined reactance due to armature reaction and leakage flux

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Electrical Machines
With the increase in speed of a DC motor

 back emf falls and line current increases.
 back emf increases but line current falls.
 both back emf as well as line current fall.
 both back emf as well as line current increase.

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