Electrical Machines
A shunt generator has a critical field resistance of 300 Ω at a speed of 800 rpm if the speed is raised to 1000 rpm the critical field resistance is

 150 Ω.
  375 Ω.
 225 Ω.
 145 Ω.

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Electrical Machines
Cogging of induction motor occurs at

 low voltage and when stator and rotor poles are not equal.
 high voltage and when stator and rotor poles are equal.
 high voltage and when stator and rotor poles are not equal.
 low voltage and when stator and rotor poles are equal.

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