DC Motor MCQ Ex: Speed Control, Characteristics - Electronic Engineering


DC motors and generators, their characteristics, speed control, and starting of DC Motors. Method of braking motor, Losses, and efficiency of DC Machines.


    Question 1: Which of the following losses are significantly reduced by laminating the core of a DC generator?

  • Hysteresis losses
  • Copper losses
  • Eddy current losses
  • Windage losses
  • Answers: Eddy current losses

    Question 2: Which loss in a DC generator does not vary with load as well as flux density?

  • Windage loss
  • Copper loss
  • Eddy current loss
  • Hysteresis loss
  • Answers: Windage loss

    Question 3: As there is no back EMF at the instant of starting a DC motor, in order to prevent a heavy current from flowing though the armature circuit?

  • armature is temporarily open circuited
  • a resistance is connected parallel to the armature
  • a high value resistor is connected across the field winding
  • a resistance is connected in series with armature
  • Answers: a resistance is connected in series with armature

    Question 4: Which of the following law/rule can' he used to determine. the direction of rotation of DC motor?

  • Faraday's law
  • Fleming's left-hand rule
  • Coloumb's law
  • Lenz's law
  • Answers: Fleming's left-hand rule

    Question 5: When two DC series motors are connected in parallel, the resultant speed is?

  • zero
  • loss than the normal speed
  • normal speed
  • more than the normal speed
  • Answers: normal speed

    Question 6: In case of a shunt motor if the supply voltage is increased by 10%, which of the following will decrease?

  • none of the above
  • starting torque
  • full load speed
  • full load current
  • Answers: full load current

    Question 7: Which of the following methods of braking is used in rolling mills?

  • Dynamic braking
  • Plugging
  • Regenerative braking
  • Mechanical brakes
  • Answers: Plugging

    Question 8: For which application a DC motor is preferred over an AC motor?

  • Low speed operation
  • High speed operation
  • Variable speed operation
  • Fixed speed operation
  • Answers: Variable speed operation

    Question 9: Which motor should not be started on no-load?

  • Series motor
  • Differentially compounded motor
  • Cumulatively compounded motor
  • Shunt motor
  • Answers: Series motor

    Question 10: Which of the following can be used for controlling the speed of a DC motor?

  • Transistor
  • Thermistor
  • Thyratron
  • Thyristor
  • Answers: Thyristor

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