DC Motor MCQs with Answers:Following Multiple Choice Questions (MCQs) are based on “DC Motor”. These are related with subject Electrical Machines or Basic Electrical Engineering. This topic is mostly beneficial in the field of Electronics, Electrical and Mechanical Engineering.
Topics: Speed control and Braking of DC motors
These MCQs will be useful in various competitive examinations, entrance examinations, oral examination (Viva voce), certifications and interviews.
MCQ on DC Motor
Que.1The speed of the DC motor can be varied by changing
- Flux
- resistance of the armature
- applied voltage
- All of the above
✔ View Answer
Option 4: All of the above
Explanation:Resistance in armature circuit: When a resistance is inserted in the armature circuit, the speed drop (Dw) increases and the motor speed decreases.
Terminal voltage (armature voltage): Reducing the armature voltage of the motor reduces the motor speed.
Field flux (or field voltage): Reducing the field voltage reduces the flux. The motor speed then increases.
Que.2 When the speed of the d.c. motor increases its armature current __________.
- increases
- remains constant
- decreases
- any of the above
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Option 3: decreases
Que.3Which of the following speed control method is not used in DC series motor.
- Flux control method
- Variable resistance in series with motor
- Ward Leonard system of speed control
- Series parallel control
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Option 3: Ward Leonard system of speed control
Explanation: Ward Leonard system of speed control is only used for shunt motors.Que.4 Consider the following statements for Series parallel control of DC motors
i. For high speed, motors are connected in series
ii. For low speed, motors are connected in parallel
- Only statement i is correct
- Only statement ii is correct
- Both statements are wrong
- Both statements are correct
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Option 3: Both statements are wrong
Explanation:For low speed, connected in series
For High speed, connected in Parallel
When in series, two motors have same current passing through them, although voltage across each is V/2.
When in parallel, two motors have same voltage across them, although current through each is I/2.
Que.5 The advantages of flux control method are
i. It provides relatively smooth and easy control
ii. Speed control above rated speed is possible
- Only statement (i) is correct
- Only statement (ii) is correct
- Both statements are wrong
- Both (i) and (ii) are correct
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Option 4: Both (i) and (ii) are correct
Que.6 Identify the correct statement/s.
i. In braking of DC shunt motor, reverse current braking is also known as plugging.
ii. In braking of DC shunt motor, Rheostatic braking is also known as Static braking.
- Both statements are correct.
- Both statements are wrong.
- Only statement 2 is correct.
- Only statement 1 is correct.
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Option 4: Only statement 1 is correct.
Explanation:In braking of DC shunt motor, Rheostatic braking is also known as Static braking.Que.7A 25kW, 250V DC shunt generator has armature and filed resistances of 0.06 and 100Ω respectively. Determine the total armature power developed when working as motor taking 25kW input.
- 21.9 kW
- 26.25 kW
- 28.5 kW
- 23.8 kW
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Option 4: 23.8 kW
Que.8A 500 V shunt motor runs at its normal speed of 250 rpm when the armature current is 200A. The resistance of armature is 0.12 ohm. Calculate the speed when a resistance is inserted in the field reducing the shunt field to 80% of normal value and the armature current is 100A.
- 290 rpm.
- 570 rpm.
- 320 rpm.
- 150 rpm.
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Option 3: 320 rpm.
Que.9 Following diagram represents
- Rheostatic braking
- Reverse current braking
- Regenerative braking
- Static braking
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Option 2: Reverse current braking
Que.10Following figure represents the internal wiring of ____________ .
- Four-point starter
- Three-point starter
- Ten-point starter
- Drum controller starter
✔ View Answer
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