Electrical Machines
Mechanical energy is supplied to DC generator at the rate of 4200 J / s. The generator delivers 32.2 Amp at 120 V. What is the percentage efficiency of the generator?

 212 V.
 205 V.
 210 V.
  201.02 V.

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Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

 changes to three times the original value
 changes to 0.5 times the original value
 remain the same as the original
 changes to 1.5 times the original value

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Electrical Machines
The speed of a DC series motor is

 Inversely proportional to the armature current.
 Proportional to field current.
 Proportional to the square of the armature current.
 Proportional to the armature current.

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