Electrical Machines
Consider the following statements regarding the magnetization characteristics of a dc generator : 1. It represents the variation of field flux with field current. 2. Variation of open-circuit terminal voltage with field current is independent of speed 3. It is non-linear from zero to rated field current 4. It helps to determine the critical field resistance at a given speed 5. It always starts from the origin Which of these statements are correct ?

 3 and 5
 1, 2 and 5
 2, 3 and 4
 1 and 4

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Electrical Machines
The residual magnetism of a self-excited dc generator is lost. To build up its emf again

 the armature connection must be reversed
 the field winding must be replaced
 the field winding connection must be reversed
 field winding must be excited by low voltage dc supply

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

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