Thermal expansion devices are instruments that utilize the principle of thermal expansion, where materials expand when heated and contract when cooled. These devices are commonly used in various applications, such as in thermostats and bridges, to accommodate changes in temperature and prevent structural damage. One common type of thermal expansion device is the bimetallic strip, which consists of two different metals bonded together. As temperatures change, the metals expand at different rates, causing the strip to bend. This bending motion can be used to activate switches or control mechanisms in various systems, ensuring proper operation under varying thermal conditions.