Lesson T4.4.1

T4.4.1 Sensors and actuators Quiz: KS3 Design & Technology, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T4.4.1, Sensors and actuators: 20 multiple choice questions for the KS3 Design & Technology (National Curriculum), Unit 4: Technical knowledge, written with Revision Ninja.

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The 20 questions

  1. What is a sensor?

    • A device that converts electrical energy into movement, light or sound in the product
    • A device that controls the speed of a motor by changing the voltage across it
    • A device that stores energy for later release in a sudden burst of power
    • A device that detects a physical change and converts it into an electrical signal

  2. What is an actuator?

    • A device that converts an electrical signal into a physical action, such as movement
    • A device that changes an analogue signal into a digital form for the program to use
    • A device that measures the temperature or light level of the surroundings continuously
    • A device that holds a fixed amount of electrical charge until it is required

  3. What does a servo motor do in a robot arm?

    • Keeps turning continuously at the same speed regardless of the signal it receives
    • Senses the distance to an object by bouncing sound off it and timing the echo
    • Stores energy in a spring so that the arm can be released in a sudden movement
    • Turns to a specific angle when it receives a control signal

  4. Which of these is an input device?

    • A DC motor, which turns a shaft when a current is supplied through its coil
    • A heating element, which becomes hot when a current flows through its wire
    • A buzzer, which produces a sound when a current flows through its element
    • A push switch, which detects when a user presses it

  5. Which sensor measures distance by sending sound pulses and timing the echo?

    • A tilt switch, which closes when the device is tilted to one side
    • An ultrasonic sensor, which sends pulses and times how long the echo takes to return
    • An LDR, which changes resistance as the light falling on it changes
    • A thermistor, which changes resistance as the temperature around it changes

  6. What does an analogue sensor reading produce for a microcontroller?

    • Readings that are only ever on or off, so they need no conversion at all
    • Readings that always give the same value, so no conversion is ever needed
    • A continuous range of values that an analogue-to-digital converter turns into numbers
    • Readings that are sent directly to a motor without any processing by the program

  7. Why would a designer use a potentiometer as an input?

    • It stores a set amount of charge so that a timer can count the seconds
    • It switches a large current on and off without needing a separate control circuit
    • It lets the user set a value, such as a volume level, by turning a knob
    • It produces light whose brightness depends on the current flowing through it

  8. A robot must avoid walls. Which sensor combination is most suitable?

    • A solenoid for distance and an LED for physical contact with the wall
    • An ultrasonic sensor for distance and a bump switch for physical contact
    • A DC motor for distance and a capacitor for physical contact with the wall
    • A buzzer for distance and a thermistor for physical contact with the wall

  9. A designer wants a motor to rotate a door latch to an exact angle. Which actuator is best?

    • An LDR, which changes its resistance when light falls on its surface
    • A servo motor, which can be set to turn to an exact angle
    • A piezo buzzer, which makes a sound when it is switched on by the controller
    • A thermistor, which changes its resistance when it is heated by the sun

  10. What is the role of a control program in a sensor and actuator system?

    • To connect the sensors directly to the actuators without making any decisions
    • To read the inputs, make a decision and send signals to the outputs
    • To store energy from the battery so that the system runs for a longer period
    • To convert light into sound so that the user can hear the result of the action

  11. What does an analogue output mean in a control system?

    • An output produced by a switch when a user presses it on the product casing
    • An output that is only ever high or low at any single moment in time
    • An output that is sent only to the input pins of the same microcontroller
    • An output that can take any value within a range, such as a gradually changing voltage

  12. What is a digital input signal?

    • A signal that changes smoothly through every value in a continuous range of voltages
    • A signal that always plays a fixed sound pitch through a connected buzzer
    • A signal that is either high or low, representing two states such as on or off
    • A signal that is stored as a music file so that it can be replayed later on request

  13. A microcontroller reads a value from 0 to 1023 from a sensor. What does this show?

    • The sensor has produced a 1023 V signal, which the program reads directly from the pin
    • An analogue-to-digital converter has turned the sensor voltage into a 10-bit number
    • The sensor has produced a single tone at 1023 hertz that the microcontroller can hear
    • The sensor has switched on and off 1023 times in one second of operation

  14. Which sensor could detect whether a box lid is open or closed?

    • A DC motor, which turns when the lid is lifted up by the user of the box
    • A thermistor, which changes resistance as the box warms up or cools down
    • A magnetic reed switch, which closes when a magnet passes close to it
    • A buzzer, which sounds when the box is opened by the user of the product

  15. A sensor reading is compared with a threshold. What is a threshold?

    • The maximum voltage that the sensor is designed to withstand without being damaged
    • The number of readings that the microcontroller can store in its memory at once
    • The smallest change in reading that the sensor is able to detect at all times
    • The value at which the program takes a particular action, such as switching a lamp on

  16. Why might a designer choose a stepper motor for a product?

    • To convert sound into an electrical signal for use by a microphone in the product
    • To produce heat in a small space so that a food container can be warmed
    • To move to exact positions in small steps under the control of signals
    • To run at very high speed continuously with no need for any control of position

  17. What is a feedback sensor in a control system?

    • A sensor that sends sound to the user through a speaker fitted to the product casing
    • A sensor that stops all outputs whenever the user presses a button on the product
    • A sensor that is only connected to the power supply to measure the voltage available
    • A sensor that measures the output so that the system can correct its own behaviour

  18. Why is a pull-down resistor often used with a push switch on a microcontroller input?

    • To convert the switch's signal into a digital number that the program can store
    • To hold the input at a low level when the switch is open, so the reading is reliable
    • To store charge so that the switch stays on after it has been released by the user
    • To increase the current through the switch so that the input is powered more brightly

  19. A fan switches on when the room temperature passes a set value. Which is the output?

    • The fan motor switching on, driven by the control signal from the controller
    • The room temperature rising above the set value, which the sensor measures
    • The microcontroller's clock speed, which is used to run the program code
    • The thermistor's resistance value, which is stored in the controller's memory

  20. Why must an actuator with a high current be driven through a transistor from a microcontroller?

    • A transistor stores the program so that the actuator can run without the microcontroller
    • A transistor raises the microcontroller's voltage to the full value of the mains supply
    • A microcontroller cannot send any signal at all unless it is connected to a transistor first
    • A microcontroller pin can supply only a small current, so a transistor switches the larger current needed

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