Electrical Machines
What is the mechanical power developed by a DC series motor is maximum?

 Back emf is equal to half the applied voltage.
 Back emf is equal to zero.
 None of above.
 Back emf is equal to applied voltage.

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Electrical Machines
A DC shunt generator builds up to a voltage of 220 V at no load while running at its rated speed. If the speed of the generator is raised by 25% kepping the circuit conditions unaltered, then the Voltage to which the machine would build up will

 increase to a value greater than 1.25 times 220 V
 increase to 1.25 times 220 V
 increase to value lying between 220 V and 1.25 times 220 V
 not change and remain at 220 V

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Electrical Machines
With the increase in speed of a DC motor

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

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