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Electrical Machines (GATE)

Comprehensive quiz covering transformers, DC machines, AC machines, and induction motors for GATE preparation

15 Questions Published
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Questions

Question 1 Multiple Choice (Single Answer)

Is there any change in loss in a power transformer if in place of sinusoidal wave, a peaked wave voltage is fed to the primary?

  1. Copper loss will be less.
  2. Noise level will be reduced.
  3. Iron losses will be more.
  4. Iron losses will be less.
  5. None of these
Question 2 Multiple Choice (Single Answer)

The constant power loss of a transformer is given by

  1. copper loss
  2. copper and eddy current losses
  3. eddy current and hysteresis losses
  4. copper loss, eddy current loss and hysteresis loss
  5. None of these
Question 3 Multiple Choice (Single Answer)

Can a 50 Hz transformer be used for 25 Hz if the input voltage is maintained at the rated voltage corresponding to 50 Hz?

  1. Yes
  2. No
  3. No, resistance has to be decreased
  4. Yes, at constant voltage
  5. None of these
Question 4 Multiple Choice (Single Answer)

_______ is the dominant harmonic flux.

  1. First harmonic flux
  2. Second harmonic flux
  3. Third harmonic flux
  4. Fourth harmonic flux
  5. Fifth harmonic flux
Question 5 Multiple Choice (Single Answer)

An 8-pole duplex winding has ____ parallel paths.

  1. 2
  2. 4
  3. 8
  4. 16
  5. 20
Question 6 Multiple Choice (Single Answer)

The natue of armature winding of an ac machine is decided by

  1. back pitch
  2. commutator pitch
  3. pole pitch
  4. front pitch
  5. None of these
Question 7 Multiple Choice (Single Answer)

Which of the following is a single excited magnetic field system?

  1. Relay
  2. DC shunt motor
  3. DC series motor
  4. DC shunt generator
  5. Synchronous motor
Question 8 Multiple Choice (Single Answer)

Heat loss that occurs in a dc machine is due to

  1. eddy current loss
  2. hysteresis loss
  3. copper loss
  4. friction loss
  5. brushes
Question 9 Multiple Choice (Single Answer)

If a 220/440V, 50 Hz single phase transformer operates on 220V, 40 Hz supply with secondary winding, then

  1. eddy current and hysteresis loss of the transformer decreases
  2. eddy current and hysteresis increases
  3. hysteresis loss increases, while eddy current remains the same
  4. hysteresis loss remains the same, whereas eddy current decreases
  5. None of these
Question 10 Multiple Choice (Single Answer)

Which of the following statements is/are true in case of series generator?

  1. Induced voltage is proportional to speed and armature current.
  2. Torque is proportional to square of armature current.
  3. Armature current is inversely proportional to speed for a constant Ea.
  4. Only 1 and 2
  5. 1, 2 and 3
Question 11 Multiple Choice (Single Answer)

Which of the following statements is/are true for open circuit test?

  1. OC test gives magnetic current and core loss at rated voltage.
  2. OC test gives sum of hysteresis and eddy current losses.
  3. OC test is performed with rated transformer voltage.
  4. All of the above
  5. None of these
Question 12 Multiple Choice (Single Answer)

Which method is economical while starting a single phase motor?

  1. Resistance start
  2. Inductance start
  3. Capacitance start
  4. Split phase motor
  5. Electrolyte capacitor
Question 13 Multiple Choice (Single Answer)

Which of the following is/are true with respect to induction motors?

  1. Simple and rugged construction
  2. Good power factor
  3. High efficiency
  4. Absence of commutator
  5. All of the above
Question 14 Multiple Choice (Single Answer)

Arc resistance may be increased by

  1. arc lightening
  2. arc cooling
  3. arc splitting
  4. Only 1 and 2
  5. 1, 2 and 3
Question 15 Multiple Choice (Single Answer)

Which of the following materials is used in high frequency transformer?

  1. Silicon
  2. Ferrite core
  3. CRGOS
  4. Aluminium
  5. None of these
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