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MCQs 1: A series wound motor is also called as universal motor because

It will run equally well using either an ac or a dc voltage source It will run well below and above rated speed It can be used in all kinds of applications None of these
Answer Explanation

MCQs 2: In the flux control method for controlling the speed of d.c. shunt motor, the speed control is not possible

Below normal rated speed Above normal rated speed Both (a) and (b) None of these
Answer Explanation

MCQs 3: In armature voltage control method or rheostatic control method for speed control in d.c. shunt motor, a variable resistance is

Added in series with the armature Added in series with the field Connected across armature Both in series with armature and field
Answer Explanation

MCQs 4: Which method is suitable for the speed control, below and above the normal rated speed of d.c. shunt motor?

Flux control method Rheostatic control method Voltage control method All of these
Answer Explanation

MCQs 5: If a resistance is added in series with the field winding of d.c. shunt motor, then its

Both speed and torque decreases Both speed and torque increases Speed decreases, torque increases Speed increases, torque decreases
Answer Explanation

MCQs 6: Ward-Leonard system is used for

Wide range of speed control Very sensitive speed control Both (a) & (b) None of these
Answer Explanation

MCQs 7: For frequent starting, stopping and reversals, which motor is commonly used?

Permanent d.c. motor Ward-Leonard system Brushless d.c. motor All of these
Answer Explanation

MCQs 8: The basic difference between three point starter and four point starter is

No volt coil is connected in series with the field winding in three point starter while connected independently across the supply in four point starte No volt coil is connected across supply in three point starter while in series with field winding in four point starter. No volt coil is connected across field winding in three point starter while connected across supply in four point starter. None of these
Answer Explanation

MCQs 9: Which starter does not provide high speed protection to the d.c. shunt motor?

Three point starter Four point starter Two point starter None of these
Answer Explanation

MCQs 10: For the protection of d.c. series motor, which starter is commonly used?

Two point starter Three point starter Four point starter None of these
Answer Explanation

MCQs 11: The speed of permanent magnet d.c. motor cannot be controlled by

Flux control method Rheostatic control method Electronic circuits None of these
Answer Explanation

MCQs 12: The number of windings on the field of permanent magnet d.c. motor is

More compared to shunt motor Less compared to shunt motor Absent None of these
Answer Explanation

MCQs 13: Permanent magnet d.c. motors are extensively used in

Automobiles Heaters Air conditioners All of these
Answer Explanation

MCQs 14: In the biomedical instruments like artificial heart pumps, the commonly used motor is

Permanent magnet d.c. motor Brushless d.c. motor Ward-Leonard system Series motor
Answer Explanation

MCQs 15: A machine operating as motor may go into regenerative braking mode if its speed becomes

Sufficiently high to make back emf greater than supply voltage Sufficiently low to make back emf greater than supply voltage Sufficiently high to make back emf half of the supply voltage Sufficiently low to make back emf half of the supply voltage
Answer Explanation

MCQs 16: In a three phase induction motor, the resultant of three alternating fluxes, separated from each other by 120 degree has constant amplitude

Equal to the maximum amplitude of an individual flux Twice of the maximum amplitude of an individual flux 1.5 times of the maximum amplitude of an individual flux All of these
Answer Explanation

MCQs 17: If the frequency of a three phase induction motor is doubled and number of poles is halved, then its synchronous speed is given by

Remains same Becomes double of the original synchronous speed Becomes four times of the original synchronous speed Becomes half of the original synchronous speed
Answer Explanation

MCQs 18: A three phase 4 pole, induction motor is supplied from 50 Hz supply. Then its synchronous speed will be

1000 rpm 1500 rpm 1600 rpm 2000 rpm
Answer Explanation

MCQs 19: In a three phase induction motor, the direction of rotation of rotating magnetic field can be reversed by

Interchanging any two terminals of three phase winding while connecting it to ac supply by reversing the direction of rotating magnetic field Cannot be changed None of these
Answer Explanation

MCQs 20: For connecting the rotating member of machine to the external stationary circuit,

Slip rings and brush assembly is used Only slip ring is used Only brushes are used Directly connected to the external stationary circuit
Answer Explanation

MCQs 21: If the air gap of the induction motor increases then its power factor

Increase Decreases Remains same Either increases or decreases
Answer Explanation

MCQs 22: When the air gap is smaller in induction motor then its

magnetizing current reduces starting torque increases both a and b neither a nor b
Answer Explanation

MCQs 23: In squirrel cage rotor, bars are usually brazed to the end rings. The end rings are used to

Prevent rotor leakage current Give reduced starting torque Provide good mechanical strength All of these
Answer Explanation

MCQs 24: Slots of squirrel cage rotor are generally skewed to

Reduce magnetic hum Reduce magnetic locking Make motor operation smooth All of these
Answer Explanation

MCQs 25: The wound rotor induction motor gives

high stating torque moderate starting torque reduced starting torque all of these
Answer Explanation

MCQs 26: The slip ring or wound rotor induction motor find its applications in

lifts, cranes lathes drilling machines printing machines
Answer Explanation

MCQs 27: For the speed control of squirrel cage induction motor, the most suitable method is

Rotor resistance control Rotor reactance control Stator resistance control Stator reactance control
Answer Explanation

MCQs 28: “The direction of induced current in the rotor is so as to oppose the cause producing it”. This is given by

Faraday’s law Lenz’s law Electromagnetic law Ampere’s law
Answer Explanation

MCQs 29: If the rotor of the machine catches the speed of the rotating magnetic field, then the motor will

Rotate at the speed of rotating magnetic field Rotate at double the speed of the rotating magnetic field Eventually stop None of these
Answer Explanation

MCQs 30: At start, the slip of the induction motor is

1 0 0.5 None of these
Answer Explanation

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