# MCQs on Electrical Actuating Systems – Electrical Motors

1 - Question

Who discovered the magnetic effect of electric current?
a) Grueblerowen
b) Joseph Henry
c) Oersted
d) Robert Abalakov
Explanation: Oersted discovered the magnetic effect of electric current. He accidentally discovered this phenomenon in the year 1820. He proved this phenomenon with the deflecting needle of magnetic compass.

2 - Question

What is the working principle of DC motor?
a) Fleming’s right hand rule
b) Fleming’s left hand rule
c) Maxwell’s second law
d) Maxwell’s third law
Explanation: The working principle of motor Fleming’s left hand rule. It states that, when a current carrying conductor is place in a magnetic field then it experiences a force. The direction of force can be determined by Fleming’s left hand rule.

3 - Question

What is the full form of CPR with respect to motor movement?
a) Clocks per rotation
b) Counts per revolution
c) Counts per rotation
d) Clocks per revolution
Explanation: CPR stands for Counts per revolution with respect to motor movement. 2 square pulses are generated at a time by a typical motor encoder, CPR (Counts per revolution) is the is the number of quadrature decode states that exists between these two square pulses. advertisement

4 - Question

How many leads does a 2 phase bipolar stepper motor have?
a) 1
b) 3
c) 4
d) 5
Explanation: A bipolar stepper motor has 4 leads. Bipolar stepper motors have two windings; one winding per stator phase. Each coil or winding has 2 leads. Therefore total 2 windings (coils) will have 4 leads.

5 - Question

Speed of an induction motor remains same even if we increase the rotor resistance.
a) True
b) False
Explanation: Speed of an induction motor does not remain same; it varies when we increase the rotor resistance. This method is called as rotor resistance speed control of induction motor. The motor speed decreases when we increase the rotor resistance. This method is not applicable for cage rotor type induction motor.

6 - Question

Speed control of an ac motor can be achieved by varying the input frequency.
a) True
b) False
Explanation: Speed control of an ac motor can be achieved by varying the input frequency. Usually AC motors run on a constant speed; this because of the constant voltage and constant frequency. Speed of an ac motor can be varied by changing the input voltage or frequency.

7 - Question

Which finger denotes the direction of current in Fleming’s left hand rule?
a) Middle finger
b) First finger
c) Thumb
d) Little finger
Explanation: Middle finger denotes the direction of current in Fleming’s left hand rule. Fleming’s left hand rule states that, when a current carrying conductor is place in a magnetic field then it experiences a force. The direction of force can be determined by Fleming’s left hand rule. Where First finger denotes the direction of magnetic field and thumb denotes the direction of force.

8 - Question

Which type of motor is not an encoder motor?
a) Stepper motor
b) Servo motor
c) BO motor
d) BLDC Drone motor
Explanation: BO motor is not an encoder motor. It does not require special types of encoders or motor drivers for running it. It can be simple be used by connecting the positive and negative terminal of the battery.

9 - Question

Who invented Induction motor?
a) Nicola Tesla
c) Philip Vaughan
d) Mark Henry
Explanation: Nicola Tesla invented Induction motor. He was a Serbian-American inventor born on 10 July 1856. He is very famous for his contribution towards modern alternating current supply systems. He is also well known for his contribution towards wireless power supply.

10 - Question

Which finger denotes the direction of magnetic field in Fleming’s left hand rule?
a) Middle finger
b) First finger
c) Thumb
d) Little finger
Explanation: First finger denotes the direction of magnetic field in Fleming’s left hand rule. Fleming’s left hand rule states that, when a current carrying conductor is place in a magnetic field then it experiences a force. The direction of force can be determined by Fleming’s left hand rule. Where middle finger denotes the direction of current and thumb denotes the direction of force.

11 - Question

Which is an example of motor driver?
a) KSD9700
b) XMPA06B2131
c) L298N
d) 792XDXM4L-24A
Explanation: L298N is an example of motor driver. It is a dual H-Bridge type motor driver. 792XDXM4L-24A is an example of relay. XMPA06B2131 is an example of pressure switch. KSD9700 is an example of temperature switch.

12 - Question

Which is an example of single H-bridge type motor driver?
a) DRV8829
b) XMPA06B2131
c) L298N
d) 792XDXM4L-24A
Explanation: DRV8829 is an example of single H-bridge type motor driver. It is manufactured by “TEXAS INSTRUMENTS”. L298N is an example of dual H-Bridge type motor driver. 792XDXM4L-24A is an example of relay. XMPA06B2131 is an example of pressure switch.

13 - Question

AC motors do not have brushes.
a) True
b) False
Explanation: AC motors do not have brushes. Due to the absence of brush mechanism AC motors have longer life expectancy. DC motors comes in two forms, Brushed and Brushless motors. DC motors without brushes are termed as BLDC (Brushless DC) motors.

14 - Question

How many windings does a 2 phase bipolar stepper motor have?
a) 2
b) 3
c) 4
d) 5
Explanation: A 2 phase bipolar stepper motor has 2 windings. One winding is present for each phase. So, in total two windings are present for 2 phases. Each coil or winding has 2 leads. Therefore total 2 windings (coils) will have 4 leads.

15 - Question

Which finger denotes the direction of force in fleming’s left hand rule?
a) Middle finger
b) First finger
c) Thumb
d) Little finger