Electrical Machines
A separately-excited dc motor has an armature resistance of 0.5 Ω. It runs off a 250 V dc supply Drawing an armature current of 20 A at 1500 rpm. The torque developed for an armature current Of 10 A, for the same field current, will be

 15.6 Nm
 16.55 Nm
 15.92 Nm
 15.28 Nm

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Electrical Machines
Short circuit test is performed on a transformer with a certain impressed voltage at rated frequency. If the short circuit test is now performed with the same magnitude of impressed voltage, but at frequency higher than the rated frequency then

 The magnetude of current will increase, but power factor will decrease.
 The magnitude will both increase.
 The magnitude of circuit as well as the power factor will decrease.
 The magnitude of current will decrease but the power factor will increase.

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Electrical Machines
For a single phase capacitor start induction motor which of the following is valid?

 Direction of rotation cannot be changed.
 Rotation can be changed by interchanging supply terminals.
 None of these.
  Rotation can be changed by reversing main winding terminals.

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