Generated EMF MCQ

Test your knowledge with important Generated EMF MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more Generated EMF MCQs at Bissoy

• The DC machines are designed with flat topped flux density waves because _______________
  ক

  average value of brush voltage is more for a flat topped B-wave

  খ

  average value of brush voltage is less for a flat topped B-wave

  গ

  losses for flat topped B-wave are less

  ঘ

  none of the mentioned
• A 6 pole machine is rotating at a speed of 1200rpm. This speed in mechanical rad/sec and electrical radians per second is respectively?
  ক

  40π, 40π/3

  খ

  120π, 40π

  গ

  20π, 60π

  ঘ

  40π, 120π
• If the dimensions of all the parts of a synchronous generator and the number of field and armature turns are doubled, then the generated voltage will change by a factor of ________
  ক

  1

  খ

  2

  গ

  4

  ঘ

  8
• In an alternator, frequency per revolution is equal to ___________
  ক

  number of poles

  খ

  twice the number of poles

  গ

  speed in rps

  ঘ

  number of pole-pairs
• If the rotor of an induction motor is made to revolve in a direction opposite to the rotating flux wave, then RMS value of EMF induced in one phase of rotor E is proportional to ____________
  ক

  2-s

  খ

  s

  গ

  1-s

  ঘ

  2+s
• The equation for slip speed is ____________
  ক

  (ω-ωr)/ω

  খ

  ω-ωr

  গ

  (ωr-ω)/ω

  ঘ

  ωr
• A polyphase induction motor of the slip ring or wound rotor type can be used ____________
  ক

  for high start-up torque applications

  খ

  as a frequency converter

  গ

  any of the mentioned

  ঘ

  none of the mentioned
• In an AC machine, the effect of distributing the turns in different slots, results in a further reduction of generated EMF by the factor kd. This factor is called ____________
  ক

  distribution/speed factor

  খ

  coil pitch factor

  গ

  winding factor

  ঘ

  all of the mentioned
• The effect of short pitched coil on the generated EMF is _____________
  ক

  increasing

  খ

  decreasing

  গ

  either increasing or decreasing

  ঘ

  none of the mentioned
• Which of the following equations represents the RMS value of the generated EMF in a short-pitched N-turn armature coil of an AC machine ____________
  ক

  E = √2πkpfrNΦ

  খ

  E = 2πkpfrNΦ

  গ

  E = NΦωrkpsinωrt

  ঘ

  None of the mentioned
• In a short pitched coil, the coil pitch factor kp, is given by ____________
  ক

  kp = cosε

  খ

  kp = cosε/2

  গ

  kp = √2πfrNΦcosε

  ঘ

  kp = cosε/2cosωrt
• In AC rotating machines, the generated or speed EMF ___________
  ক

  leads Φ by 90°

  খ

  lags Φ by 90°

  গ

  is in phase with working flux

  ঘ

  lags Φ by 180°
• In the equation for RMS value of the generated EMF in a full pitched coil of an AC machine, E = Emax/√2 = √2πfrNΦ, fr depends on ____________
  ক

  rotating speed of the armature coil

  খ

  rotating speed of the flux density wave

  গ

  relative velocity between the flux density wave and armature coil

  ঘ

  all of the mentioned
• The EMF equation e = NωrΦsinωrt is applicable to ____________
  ক

  AC systems with time variant field flux

  খ

  DC systems with time variant field flux

  গ

  Both AC and DC systems with time invariant field flux

  ঘ

  Both AC and DC systems with time variant field flux
• Which of the following statements is/are correct regarding the generation of EMF in rotating electrical machines in the armature winding? EMF is generated ____________
  ক

  by rotating armature windings through a magnetic field

  খ

  by rotating magnetic field with respect to the armature windings

  গ

  by designing the magnetic circuit to have variable reluctance with rotor rotation

  ঘ

  all of the mentioned