What is the primary function of a photo cell in a lighting system?

The primary function of a photo cell, also known as a photocell or light sensor, in a lighting system is to control light levels based on the amount of ambient light detected. When the natural light falls below a certain threshold, the photo cell activates the lighting system, turning the lights on. Conversely, when there is sufficient natural light, the photo cell can turn off the lights, helping to conserve energy and ensuring that lighting levels are appropriate for visibility and safety. This automatic adjustment enhances efficiency in lighting use and contributes to energy savings, reducing costs for the user.

The other options do not accurately describe the purpose of a photo cell. For instance, measuring voltage does not relate to light detection but rather to electrical monitoring in circuits. Detecting motion is typically associated with motion sensors, which activate lights based on movement rather than ambient light levels. Emitting light refers to a source of illumination, like LED bulbs or incandescent lights, rather than a sensor that manages light based on environmental conditions.