# DC Motor MCQs with Answers Page-2

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

#### 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.

#### 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

#### 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)

1. 110 V
2. 227 V
3. 243 V
4. 221 V

#### Option 2: 227V into d.c.

##### Que.6 Following diagram represents
1. Long shunt compound wound motor
2. Short shunt compound wound motor
3. Series wound d.c. motor
4. Shunt wound d.c. motor

#### 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
1. Long shunt compound wound motor
2. Short shunt compound wound motor
3. Separately excited d.c. motor
4. Shunt wound d.c. motor

#### 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

#### 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

#### Option 1: Compound

1. Cumulative compound
2. Differential compound
3. Shunt
4. Series

#### 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

#### 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
3. Starting Torque

##### 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

#### Option 4: All of the above

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

#### 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