41. what is the frequency of rotor current of a 50 Hz induction motor operating at 2% slip?
- 1 Hz
- 100 Hz
- 2 Hz
- 50 Hz
42. A voltmeter gives 120 oscillations per minute when connected to the rotor of an induction motor. The frequency is 50 Hz. The slip of the motor is
- 2 %
- 4 %
- 5 %
- 25 %
43. In the slip-ring induction motor, the frequency of rotor currents can be measured with a
- Galvanometer
- Wattmeter
- DC moving coil millivoltmeter
- None of the above
44. A center zero ammeter connected in the rotor circuit of a 6-pole, 50 Hz induction motor makes 30 oscillations in one minute. The rotor speed is
- 970 rpm
- 990 rpm
- 1010 rpm
- 1030 rpm
45. In a 3-phase 50 Hz induction motor the voltage between the slip-rings at standstill is 50 V. At full load, the slip is 0.04. the voltage between slip rings at full load is
- 50 V
- 2 V
- 20 V
- 5 V
46. The direction of rotor current produced in an induction motor can be determined by
- Lenz’s law
- Induction law
- Fleming’s right hand rule
- Fleming’s left hand rule
47. In case of an induction motor the leakage flux is more in comparison to that of a transformer. This is due to
- revolving rotor
- air gap between rotor and stator
- higher flux densities in induction motor
- none of the above
48. In an induction motor, the phase reactance is _______ in comparison to phase resistance.
- quite high
- very small
- slightly high
- almost same
49. In an induction motor under the running condition, the rotor reactance per phase is ________ its standstill phase reactance.
- s times
- equal to
- 1/s times
- (1-s) times
50. Insertion of resistance in the rotor circuit of an induction motor to develop a given torque causes ________ in rotor current.
- almost no change
- increase
- decrease
- none of these