Electrical Machines
DC motors are stopped by opening line switches and not by forcing the handle of the motor starter back to OFF position. This is due to occurance of

 Heavy sparking at the first stud of starting resistance steps.
 Heavy sparking at brushes.
 None of these.
 Both of above.

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Electrical Machines
An inverted V curve of synchronous motor shows variation of

 power factor and supply voltage during hunting.
 supply voltage and field current at constant excitation.
 supply voltage and excitation current at constant load.
  power factor and DC excitation at constant load.

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Electrical Machines
In synchronous generator, inverted V curve is drawn between

 field current on X-axis and power factor on Y-axis
 field current on X-axis and armature current on Y-axis
 field current on Y-axis and power factor on X-axis
 field current on Y-axis and armature current on X-axis

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Electrical Machines
In speed control of DC Series motor, speed lower than the rated speed can be obtained by

 Any of the above.
 Connecting an additional resistance in stator circuit.
 Connecting an additional resistance in the field circuit.
 Connecting an additional resistance in the armature circuit.

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Electrical Machines
In a step down transformer which one of the following statements is true?

  Number of secondary turns is less than primary turns.
 Secondary power is less than primary power.
 Secondary current is less than primary current.
 Number of secondary turns is more than that of primary.

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