250+ TOP MCQs on AVR Interfacing with Motors and Answers

AVR Microcontroller Questions on “Interfacing with Motors”.

1. Why are relays used for driving the motors?
a) they can be used as switch as well as they provide isolation
b) they increase the current capability required by the motors
c) they are used to reduce the back emf from the motors
d) all of the mentioned

Answer: a
Clarification: Relay is the electrically controlled switch and it allows isolation of two separate sections of the system. It has three main components: the coil, the common pole and the contacts. When an electric field is applied to the coil; it gets energized and generates a magnetic field which will force the common pole to change contact from Normally Closed to Normally Open.

2. Why are ULN2803 normally used between the microcontrollers and the relays?
a) for switching purposes
b) for increasing the current capability required by a relay
c) for increasing the voltage capability required by a relay
d) all of the mentioned

Answer: b
Clarification: More current is desired for driving a motor with the help of a relay, so a ULN2803 is used for increasing the current as per the requirement of the relay.

3. Why are opto isolators normally used between the microcontrollers and the ULN2803?
a) to optimize the current
b) to reduce the back emf
c) to increase the current
d) to increase the voltage

Answer: b
Clarification: Opto isolators are used between the microcontrollers and the ULN2803 chips in order to decrease the back emf from the ULN2803 and to save the microcontrollers for a long time.

4. Which of the following is a type of an electromagnetic relay?
a) SPST
b) SPDT
c) DPDT
d) All of the mentioned

Answer: d
Clarification: There are normally three kinds of electromagnetic relays. They are SPST(single pole single throw), SPDT(single pole double throw) and the DPDT(double pole double throw) relays.

5. Reed switches show connectivity whenever they are in the presence of an electrical field?
a) true
b) false
c) can’t say
d) depends on the conditions

Answer: b
Clarification: Reed switches are the devices that show connectivity whenever they are in the presence of some magnetic field.

6. Which of the following is an application of stepper motors?
a) in printers
b) in robots
c) in vehicles
d) all of the mentioned

Answer: d
Clarification: Stepper motors are used wherever there is a need of a movement at an angle, maybe it in printers, in motors or in vehicles stepper motors are used everywhere.

7. What are normal 4 step sequence of a stepper motor if we start to move in clockwise direction with 0110 value?
a) 1100,1001,0011,0110
b) 0011,1001,1100,0110
c) 1001,1100,0110,0011
d) 0101,1010,0101,1010

Answer: b
Clarification: For a normal 4 step sequence of a stepper motor, if we start to move in a clockwise direction then we rotate towards right direction with every rotation.

8. What is the meaning of a step angle?
a) angle which a stepper motor has
b) angle between the two windings of the stator in a stepper motor
c) minimum degree of rotation associated with a single step
d) angle between the stator and the rotor

Answer: c
Clarification: Step angle is the minimum degree of rotation associated with a single step.

9. For a normal 4 step sequence, what are the number of teeth required to accomplish a 2 degree step angle?
a) 180
b) 90
c) 360
d) 45

Answer: d
Clarification: For a 2 degree step angle there will be 180 step per rotation, so the total number of rotor teeth are (180/4=45).

10. Ounch-inch is a unit of a torque.
a) true
b) false
c) can’t say
d) depends on the situation

Answer: a
Clarification: Torque is a quantity which is obtained by multiplying the amount of force that is applied at a particular angle. It is measured in terms of ounch-inch.