Electrical Machines
A single-phase transformer has its maximum efficiency at 60 percent of full load. At full load copper loss will be

  more than core loss.
 less than core loss.
 zero.
 equal to core loss.

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Electrical Machines
With the increase in speed of DC motor

 Both back emf as well as line current fall.
 Both back emf as well as line current increase.
  Back emf increase but line current falls.
 Back emf falls and line current increase.

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Electrical Machines
The armature mmf of a DC machine has

  triangular space distribution and is stationary in space.
  triangular space distribution and rotates at the speed of armature.
  trapezoidal space distribution and is stationary in space.
 stepped distribution and rotates at the speed of armature.

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Electrical Machines
Flashing of DC generator means

 neutralization of residual magnetism.
  creation of residual magnetism by a DC source.
None of these
  increasing flux density by providing extra ampere-turns in field.

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Electrical Machines
When the supply terminal of a DC shunt motor are interchanged

 The direction of rotation will reverse.
 The motor will stop.
  The motor will run at its normal speed in the same direction as before.
 The motor will run much faster in the same direction.

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