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This set of Electrical and Electronics Engineering Multiple Choice Questions & Answers (MCQs) focuses on Electrical And Electronics Engineering Set 7
Q1 | Air ducts are provided in armature core to
- increase the core area
- cool the armature
- to accommodate the windins
- none of these
Q2 | Due to which of the following reasons, copper brushes in D.C. machine are used?
- when high voltage and small currents are involved
- when low voltage and high currents are involved
- in both of the above cases
- in none of the above cases
Q3 | The magnitude of induced emf in a dc generator is given by
- blv
- bil
- bv/l
- bi/l
Q4 | In a dc generator, the eddy current power loss is
- directly proportional to thickness of each lamination
- inversely proportional to thickness of each lamination
- directly proportional to square of thickness of each lamination
- none of the above
Q5 | In a 240v dc motor, back emf is 220v and Ra= 0.5Ω then its armature current is
- 20a
- 10a
- 80a
- 40a
Q6 | ----- is the power equation of dc motor
- via = ebia + ia2 ra
- via = ebia + ia ra2
- vn = eb n + nia ra
- via = eb2ia + ia2 ra
Q7 | A 4 pole 1500 rpm,dc generator has a lap wound armature having 24 slots with 10 conductors/slot.If flux/pole is 0.04Wb then emf generator in armature is -----V
- 480v
- 240v
- 960v
- 120v
Q8 | A 8 pole dc generator has a lap wound armature having 400 armature turns. If flux/pole is 10mWb and emf generated in armature is 200v then speed is -----rpm
- 2000 rpm
- 1500 rpm
- 500 rpm
- 1000rpm
Q9 | A 4 pole 1200 rpm, dc generator has lap wound armature producing 240v emf in the armature with flux/pole as 0.02Wb,then total number of armature conductors are
- 2400
- 1000
- 600
- 1200
Q10 | The stator of I.M. motor is made up off---------- laminations.
- cast iron
- cast steel
- silicon steel
- steel
Q11 | Stator part of I.M. has slots to hold -------
- rotor winding
- stator winding
- shaft
- brush
Q12 | Stator windings are insulated from core with the help of
- slot insulator
- epoxy coating
- a or b
- none
Q13 | 3 phase I.M. are classified as --- and---- based on rotor construction.
- slip ring & squirrel cage
- split phase &squirrel cage
- capacitor start motor& slip ring
- shaded pole& capacitor start
Q14 | When a induction motor is switched on a rotor frequency is
- 60
- same as supply frequency
- same as slip frequency
- zero
Q15 | when the rotor of induction motor is standstill the value of slip is
- zero
- 1
- 100
- infinite
Q16 | Squirrel cage I.M.motor has skewed rotor bar to help to produce constant --- .
- voltage
- torque
- frequency
- magnetic field
Q17 | The effect of increasing the length of the air gap in an induction motor will increase
- power factor
- speed
- magnetizing current
- air-gap flux
Q18 | the difference between the synchronous speed and the actual speed of an induction motor is known as
- regulation
- back lash
- slip
- lag
Q19 | Rotating magnetic field is produced in a....
- single - phase induction motor
- three phase induction motor
- dc series motor
- ac series motor
Q20 | Star- delta starter of an induction motor
- inserts resistance in rotor circuit
- inserts resistance in stator circuit
- applies reduced voltage to rotor
- applies reduced voltage to stator
Q21 | Star- delta starter of an induction motor
- applies voltage of √3 times of rated voltage to stator
- applies reduced voltage of 1/√3 times of rated voltage to stator
- applies reduced voltage of 1/√3 times of rated voltage to rotor
- applies voltage of √3 times of rated voltage to rotor
Q22 | The speed of an induction motor
- decreases too much with the increase of load
- increase with the increase of load
- decreases slightly with the increase of load
- remains constant with the increase of load
Q23 | The stator of I.M produces ---- magnetic field.
- steady
- rotating
- alternating
- pulsating
Q24 | If the frequency of 3-phase supply to stator of 3-phase I.M. is increased,then synchronous speed----
- is decreased
- is increased
- remains unchanged
- none
Q25 | An I.M. moror is preferred to a D.C. motor because of its-----
- high starting torque
- fine speed control
- simple and rugged construction
- none