Sensors

What is the definition of a sensor?

• A sensor is a device that detects or measures a physical property (like temperature or light) and converts it into an electrical signal.

• A sensor is a device that stores electrical energy for later use.

• A sensor is a machine that produces mechanical energy from electrical energy.

• A sensor is a tool used to amplify sound signals.

Answer explanation

The correct choice defines a sensor accurately as a device that detects or measures physical properties and converts them into electrical signals, distinguishing it from other options that describe different types of devices.

What is the purpose of sensors?

• Sensors collect analogue data from the environment, which computers can process after conversion using an ADC (Analogue-to-Digital Converter).

• Sensors are used to display information on screens.

• Sensors are devices that store digital data for long-term use.

• Sensors are used to increase the speed of computer processors.

Answer explanation

The correct choice explains that sensors collect analogue data from the environment, which is then converted to digital form by an ADC for computer processing. This highlights the primary function of sensors.

What does a Temperature sensor (thermistor) detect?

• Heat / temperature

• Sound

• Light

• Pressure

Answer explanation

A thermistor is a type of temperature sensor that detects heat or temperature changes. It measures the resistance change in response to temperature variations, making 'Heat / temperature' the correct choice.

Which of the following is an example use of a Temperature sensor (thermistor)?

• Parking sensors

• Air conditioning systems

• Compass apps

• Voice recognition systems

Answer explanation

A thermistor is commonly used in air conditioning systems to monitor and regulate temperature, ensuring optimal performance. The other options do not primarily rely on temperature sensing.

What does a Light sensor (LDR – Light Dependent Resistor) detect?

• Light intensity

• Sound waves

• Magnetic field

• Temperature

Answer explanation

A Light Dependent Resistor (LDR) detects light intensity. It changes its resistance based on the amount of light falling on it, making it ideal for measuring light levels.

Which of the following is an example use of a Light sensor (LDR – Light Dependent Resistor)?

• Automatic street lights

• Car tire pressure monitoring

• Greenhouses

• Chemical plants

Answer explanation

Automatic street lights use LDRs to detect ambient light levels, turning on at dusk and off at dawn. This makes them a prime example of LDR application, unlike the other options which do not utilize light sensors.

What does a Pressure sensor detect?

• Force or pressure

• Temperature

• Light intensity

• Sound

Answer explanation

A pressure sensor is specifically designed to detect force or pressure applied to it. It measures the mechanical force exerted by fluids or gases, making 'Force or pressure' the correct choice.

What does a Sound sensor (microphone) detect?

• Sound levels

• Light intensity

• Temperature

• Humidity

Answer explanation

A sound sensor, or microphone, detects sound levels by converting sound waves into electrical signals. It does not measure light intensity, temperature, or humidity, making 'Sound levels' the correct choice.

What does a Moisture / humidity sensor detect?

• Water vapour / moisture level

• Air pressure

• Light intensity

• Sound waves

Answer explanation

A moisture/humidity sensor specifically detects water vapour or moisture levels in the air, making 'Water vapour / moisture level' the correct choice. The other options do not relate to moisture detection.

What does an Infrared (IR) sensor detect?

• Infrared radiation (motion)

• Sound waves

• Visible light

• Magnetic fields

Answer explanation

An Infrared (IR) sensor detects infrared radiation, which is often associated with heat and motion. This makes 'Infrared radiation (motion)' the correct choice, as it specifically relates to what IR sensors are designed to sense.