What is a photocell?

A photocell, also known as a photoresistor or light-dependent resistor (LDR), is a type of resistor that changes its resistance based on the amount of light it is exposed to. It is made from a semiconductor material that exhibits a decrease in resistance when exposed to light.

Photocells are commonly used in electronic circuits as sensors to detect light levels, such as in streetlights, solar panels, and camera exposure meters. They are also used in automatic lighting systems and security alarms to switch lights on or trigger an alarm when it gets dark.

The resistance of a photocell can range from a few hundred ohms in bright light to several megaohms in darkness. This variability in resistance allows for the measurement of light intensity and can be used to control devices based on ambient light levels.

Overall, photocells are inexpensive, lightweight, and easy to use, making them a popular choice for light sensing applications in various industries.