DC Motor MCQ Ex: Speed Control, Characteristics - Electronic Engineering
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DC motors and generators, their characteristics, speed control, and starting of DC Motors. Method of braking motor, Losses, and efficiency of DC Machines.
- Hysteresis losses
- Copper losses
- Eddy current losses
- Windage losses
Question 1: Which of the following losses are significantly reduced by laminating the core of a DC generator?
Answers: Eddy current losses
- Windage loss
- Copper loss
- Eddy current loss
- Hysteresis loss
Question 2: Which loss in a DC generator does not vary with load as well as flux density?
Answers: Windage loss
- 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
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?
Answers: a resistance is connected in series with armature
- Faraday's law
- Fleming's left-hand rule
- Coloumb's law
- Lenz's law
Question 4: Which of the following law/rule can' he used to determine. the direction of rotation of DC motor?
Answers: Fleming's left-hand rule
- zero
- loss than the normal speed
- normal speed
- more than the normal speed
Question 5: When two DC series motors are connected in parallel, the resultant speed is?
Answers: normal speed
- none of the above
- starting torque
- full load speed
- full load current
Question 6: In case of a shunt motor if the supply voltage is increased by 10%, which of the following will decrease?
Answers: full load current
- Dynamic braking
- Plugging
- Regenerative braking
- Mechanical brakes
Question 7: Which of the following methods of braking is used in rolling mills?
Answers: Plugging
- Low speed operation
- High speed operation
- Variable speed operation
- Fixed speed operation
Question 8: For which application a DC motor is preferred over an AC motor?
Answers: Variable speed operation
- Series motor
- Differentially compounded motor
- Cumulatively compounded motor
- Shunt motor
Question 9: Which motor should not be started on no-load?
Answers: Series motor
- Transistor
- Thermistor
- Thyratron
- Thyristor
Question 10: Which of the following can be used for controlling the speed of a DC motor?
Answers: Thyristor
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