# DC Motor MCQs with Answers Page-3

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
1. Flux
2. resistance of the armature
3. applied voltage
4. All of the above

#### 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 __________.
1. increases
2. remains constant
3. decreases
4. any of the above

#### Option 3: decreases

##### Que.3Which of the following speed control method is not used in DC series motor.
1. Flux control method
2. Variable resistance in series with motor
3. Ward Leonard system of speed control
4. Series parallel control

#### Option 3: Ward Leonard system of speed control

Explanation: Ward Leonard system of speed control is only used for shunt motors.
##### ii. For low speed, motors are connected in parallel
1. Only statement i is correct
2. Only statement ii is correct
3. Both statements are wrong
4. Both statements are correct

#### 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.
##### ii. Speed control above rated speed is possible
1. Only statement (i) is correct
2. Only statement (ii) is correct
3. Both statements are wrong
4. Both (i) and (ii) are correct

#### Option 4: Both (i) and (ii) are correct

##### ii. In braking of DC shunt motor, Rheostatic braking is also known as Static braking.
1. Both statements are correct.
2. Both statements are wrong.
3. Only statement 2 is correct.
4. Only statement 1 is correct.

#### Option 4: Only statement 1 is correct.

Explanation:In braking of DC shunt motor, Rheostatic braking is also known as Static braking.
1. 21.9 kW
2. 26.25 kW
3. 28.5 kW
4. 23.8 kW

1. 290 rpm.
2. 570 rpm.
3. 320 rpm.
4. 150 rpm.

#### Option 3: 320 rpm.

##### Que.9 Following diagram represents
1. Rheostatic braking
2. Reverse current braking
3. Regenerative braking
4. Static braking

#### Option 2: Reverse current braking

##### Que.10Following figure represents the internal wiring of ____________ .
1. Four-point starter
2. Three-point starter
3. Ten-point starter
4. Drum controller starter