Quiz  /  Electrical Machines Gate & PSU MCQ Questions With Answers

  • 1. 
    How will you find the magnetic flux density?

  • B=ϕ÷AB=\phi\div AB=ϕ÷A
  • E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ​
  • H=MMFLH=\frac{MMF}{L}H=LMMF​
  • MMM=NIMMM=NIMMM=NI

  • 2. 
    What two power losses occur in a transformer when operating on no-load?

  • Mechanical losses, core losses
  • Frictional losses, heat losses
  • Rotational losses, copper losses
  • Copper losses, core losses

  • 3. 
    In DC Series motor the field flux becomes independent of the armature current after it reaches a saturation point

  • True
  • False

  • 4. 
    Which property of a transformer is measured by the change in output voltage from no-load to full-load conditions?

  • voltage ratio
  • transformer efficiency
  • voltage regulation
  • power transfer

  • 5. 
    Write the formula for finding mmf?

  • B=ϕ÷AB=\phi\div AB=ϕ÷A
  • E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ​
  • H=MMFLH=\frac{MMF}{L}H=LMMF​
  • mmf=NImmf=NImmf=NI

  • 6. 
    What is the shape of the laminations used in the magnetic circuit of a single phase shell-type transformer?

  • LL
  • TT
  • LE
  • EI

  • 7. 
    What is the danger of opening the secondary circuit of an energized current transformer?

  • High voltage appears across the secondary.
  • Large current flows in the primary.
  • High voltage appears across the primary.
  • Large current flows in the secondary.

  • 8. 
    What conditions must be satisfied before connecting two transformers in parallel to share a common load?

  • Same inductance, same kVA rating
  • Same polarity, same phase sequence
  • Same polarity resistance, same current ratio
  • Same number of polarity turns, same voltage regulation

  • 9. 
    What is the essential property of the oil used in transformer tanks to facilitate cooling?

  • High viscosity.
  • Low hydrogen content
  • High carbon content
  • Low viscosity

  • 10. 
    In DC motor speeds above the rated speed are usually increased by changing which of the following winding current:

  • field winding
  • armature winding
  • either field or armature winding
  • none of these

  • 11. 
    The direction of the induced emf in generators is found out using:

  • Fleming's right hand rule
  • Fleming's left hand rule
  • Faraday's left hand rule
  • Right hand thumb rule

  • 12. 
    What is the ideal electrical angle of separation of the start and run windings to create a rotating magnetic field in a split phase induction motor?

  • 30
  • 60
  • 90
  • 120

  • 13. 
    What type of transformer is used for interconnecting high voltage transmission systems operating at different voltage levels?

  • Current transformer
  • wound transformer
  • Voltage transformer
  • Autotransformer

  • 14. 
    How can we select the thickness of fuse wire?

  • based on load current
  • based on voltage
  • both
  • none

  • 15. 
    ____ is followed to determine the direction of coil movement for electric motors

  • Fleming's left hand rule
  • Faraday's left hand rule
  • Faraday's right hand rule
  • Fleming's right hand rule

  • 16. 
    Speed of the induction motor reduces with the load applied

  • True
  • False

  • 17. 
    Which symbol is used to represent electrical flux?

  • ϕ\phiϕ
  • H
  • B
  • A

  • 18. 
    During open circuit test of a transformer

  • primary is supplied rated voltage
  • primary is supplied full-load current
  • primary is supplied current at reduced voltage
  • primary is supplied rated kVA

  • 19. 
    A d.c. generator whose field magnet winding is supplied from an independent external d.c. source:

  • Self Excited DC generator
  • Separately excited DC generator

  • 20. 
    Which motor has high starting torque

  • DC Series Motor
  • DC Shunt Motor

  • 21. 
    Why are power transformers operated in parallel?

  • To increase the current rating of the supply.
  • To maximize power supply flexibly.
  • To improve voltage regulation.
  • To reduce heat loss.

  • 22. 
    What does the thumb indicate in Fleming's left hand rule

  • Force
  • Current
  • Magnetic field
  • Voltage
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