Which heat detector uses two metals, one which expands faster than the other when heated to break a circuit and send a signal to the alarm control panel?

The bimetallic detector operates based on the principle of differential thermal expansion. It consists of two different metals that are bonded together. When the temperature rises, one of the metals expands at a faster rate than the other, causing the bimetallic strip to bend. This bending action can break the electrical circuit within the detector, triggering a signal to the alarm control panel.

This design leverages the physical properties of metals and their rates of expansion, making bimetallic detectors reliable for detecting heat. They are commonly used in environments where fire hazards exist, as they can respond quickly to increases in temperature. This characteristic sets them apart from other types of detectors, such as ionization and photoelectric detectors, which primarily focus on smoke detection rather than direct heat measurement. Additionally, rate of rise detectors specifically monitor changes in temperature over time but do not utilize the two-metal mechanism that characterizes bimetallic detectors.