Final answer:
A bimetallic strip thermostat uses the different thermal expansion coefficients of brass and steel to turn on heating or cooling devices by bending and activating an electrical switch when temperature rises.
Step-by-step explanation:
In a bimetallic strip used as a thermostat, the brass and steel metals respond differently to temperature changes due to their different thermal expansion coefficients. Brass expands more than steel for the same rise in temperature, causing the strip to bend. This bending motion can actuate a mechanical switch, which in this case, would be part of a circuit in a thermostat system. As the temperature increases, the brass side expands more, bending the strip and activating the switch. These switches are typically used to turn on heating or cooling devices depending on the desired set temperature.
The basic properties of thermal expansion are critical to the functioning of bimetallic strips. The differential expansion of two attached metals results in a predictable bending motion, which can be utilized to open or close electrical contacts within a circuit. This applies not only in thermostats but also in other devices where temperature-dependent switching is required.
In the context of a thermostat, when a bimetallic strip made of brass and steel becomes hot, the brass side's greater expansion causes the strip to bend and turn on components such as heaters or fans that are designed to regulate temperature. Upon cooling, the strip straightens and can lead to the turning off of these components, maintaining a stable temperature environment.