What is a light-controlled variable resistor?

A light-controlled variable resistor is commonly known as a photoresistor, or LDR (light-dependent resistor). This type of component alters its resistance based on the amount of light it is exposed to; as light intensity increases, the resistance decreases. It operates on the principle of photoconductivity, where certain materials become more conductive when they absorb photons.

Photoresistors are widely used in various applications, such as light sensing, automatic lighting systems, and alarm systems, due to their ability to respond to light levels dynamically. This makes them suitable for triggering events based on ambient light conditions, such as turning on street lights at dusk.

While photocells, photodiodes, and phototransistors are related devices used in light detection and control, they operate under different principles or serve different functions. For instance, a photocell is a more general term that can refer to any device that detects light, which can include photoresistors. Photodiodes and phototransistors are semiconductor devices that convert light into an electrical signal but have distinct operation methods and are used in more sophisticated applications compared to photoresistors.