71. The synchronous watt is
- the torque which under synchronous speed would develop a power of I watt or power input to rotor in watts
- shaft output in watts
- input power to stator
- the unit of ratings of synchronous machines
72. The no-load current in an induction motor is _______ in comparison to that of a power transformer
- much lower
- much higher
- slightly less
- slightly more
73. In the three-phase induction motor, the variable mechanical load is represented electrically by a variable ________ only
- inductance
- capacitance
- resistance
- any of these
74. If the load of an induction motor is increased from no load to full load, its slip and the power factor will, respectively
- decrease, decrease
- decrease, increase
- increase, decrease
- increase, increase
75. The power factor of an induction motor operating at no load will have a value around
- 0.9 lag
- 0.2 lead
- 0.2 lag
- 0.9 lead
76. The power factor of the three-phase induction motor is likely to be maximum when it will operate at
- full load
- no load
- maximum slip
- maximum torque
77. In a three-phase induction motor when the load is increased from the light load
- rotor pf increases but stator pf decreases
- stator pf increases but the rotor pf decreases
- both stator and rotor p increases
- both stator and rotor pf decreases
78. An induction motor always operates on lagging power factor. This is due to
- stator reactance
- rotor leakage reactance
- the large reactive lagging magnetizing current essential to produce the magnetic flux
- all of the above
79. Open circuit is usually conducted on
- slip-ring motor
- wound rotor motors
- either a and b
- none of these
80. Blocked rotor test of an induction motor corresponds, in case of a transformer, to
- full load
- half-full load
- no load
- short-circuit operation