Questions: Sensors Basics

Question 1

What does a sensor do in a circuit?

• A. It stores energy like a battery
• B. It detects something in the environment and converts it into an electrical signal
• C. It makes the circuit faster
• D. It controls the voltage of the battery

Answer: (B)

A sensor is an input device. It detects a physical quantity — light, heat, motion, sound, pressure — and converts that detection into an electrical change (more or less current, higher or lower voltage) that the rest of the circuit can respond to.

Question 2

A sensor detects something in the environment AND decides what to do about it.

• T. True
• F. False

Answer: False

A sensor only detects — it is an input device. It reports what it senses as an electrical signal. The decision about what to do with that information is made by the rest of the circuit (or a computer). A temperature sensor reports that it is cold; the thermostat circuit decides to turn on the heater.

Question 3

Name an everyday device that uses a sensor, and explain what the sensor detects.

Model answer: An automatic door at a store uses a motion sensor that detects when a person approaches. When it senses motion, the circuit activates the motor that opens the door.

Other examples: a phone screen that dims in bright light (light sensor), a thermostat that turns on heat when it is cold (temperature sensor), a car backup alarm that beeps when close to an object (distance sensor), a smoke detector (particle sensor). In each case, the sensor detects a change, and the circuit responds.