Photoelectric cell devices are used in which type of detection?

• A. Smoke detectors
• B. Photoelectric cell devices
• C. Inconel loop
• D. Optical detectors

Answer: (A)

Photoelectric sensing uses light and a detector to sense particles in a medium. In smoke detection, a light source and a photodetector are arranged so that, in clean air, little or no light reaches the sensor. When smoke enters the chamber, the smoke particles scatter light toward the detector, producing a signal that triggers the alarm. This makes photoelectric cells particularly well-suited for detecting smoke, especially from smoldering fires that produce a lot of smoke.

Other options describe different concepts not based on this light-scattering principle. An Inconel loop relates to a different type of flame/temperature sensing, not photoelectric smoke detection, and “optical detectors” is a broad category that doesn’t specify the smoke-detection application.