DC Motor MCQs with Answers Page-2

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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: Types of DC motorsand their applications.

These MCQs will be useful in various competitive examinations, entrance examinations, oral examination (Viva voce), certifications and interviews.

MCQ on DC Motor

Que.1 Which of the following d.c. motor has highest speed at no-load condition?
  1. Cumulative compound motor
  2. Shunt motor
  3. Differentially compound motor
  4. series motor

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Option 4: series motor

Explanation:At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.
Que.2If the pole flux of a d.c. motor approaches zero. its speed will
  1. not change
  2. approach zero
  3. approach infinity
  4. approach a stable value somewhere between zero and infinity.

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Option 3: approach infinity

Que.3When the speed of the DC motor increases its armature current __________.
  1. increases
  2. remains constant
  3. decreases
  4. any of the above

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Option 3: decreases

Que.4A d.c. shunt motor is found suitable to drive fans because they require
  1. small torque at start up
  2. large torque at high speeds
  3. practically constant voltage
  4. both (1) and (2)

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Option 4: both (1) and (2)

Que.5 A 230 V, d.c. shunt motor takes a line current of 10 A. The resistance of shunt field winding is 200Ω and resistance of the armature is 0.3 Ω. Find the back e.m.f. (approximate).
  1. 110 V
  2. 227 V
  3. 243 V
  4. 221 V

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Option 2: 227V into d.c.

Que.6 Following diagram represents
DC Motor MCQs with Answers Page-2
  1. Long shunt compound wound motor
  2. Short shunt compound wound motor
  3. Series wound d.c. motor
  4. Shunt wound d.c. motor

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Option 3: Series wound d.c. motor generator

Explanation:The armature and field are connected in series hence it is a d.c. series motor.
Que.7 Following diagram represents the equivalent circuit of
DC Motor MCQs with Answers Page-2
  1. Long shunt compound wound motor
  2. Short shunt compound wound motor
  3. Separately excited d.c. motor
  4. Shunt wound d.c. motor

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Option 3: Separately excited d.c. motor

Explanation:A separate power supply is provided to field in separately excited d.c. motor.
Que.8 When the speed of the DC motor increases its armature current __________.
  1. increases
  2. remains constant
  3. decreases
  4. any of the above

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Option 3: decreases

Que.9______ d.c. motor would be suitable for drives requiring high starting torque but only fairly constant speed such as crushers.
  1. Compound
  2. Series
  3. Shunt
  4. Permanent magnet

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Option 1: Compound

Que.10Which motor develops least torque between no-load and full-load?
  1. Cumulative compound
  2. Differential compound
  3. Shunt
  4. Series

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Option 4: Series

Que.11As the load is increased, the speed of a d.c. shunt motor _________.
  1. increases slightly
  2. increases proportionately
  3. remains constant
  4. reduces slightly

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Option 4: reduces slightly

Que.12 Which of the following will decrease when the supply voltage of a d.c. motor is increased?
  1. Operating speed
  2. Full-Load Current
  3. Starting Torque
  4. No load current

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Option 2: Full-Load Current

Que.13 Torque of a d.c. motor depends on
  1. magnetic field
  2. Length of the conductor
  3. current flow through the conductor
  4. All of the above

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Option 4: All of the above

Que.14 DC shunt motors are used to drive
  1. machine tools
  2. elevator
  3. trains
  4. cranes

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Option 1: machine tools

Que.15Which of the following would be most suitable application of a d.c. compound motor?
  1. reciprocating pump
  2. centrifugal pump
  3. electric locomotive
  4. fan

✔ View Answer

Option 1: reciprocating pump

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