What is the device that consists of two unlike metal strips that are attached and have different rate of expamsion and contraction?

Answer 1

This is called a 'Bi-metal' strip.

The different rates of expansion cause it to bend, when the temperature is altered.

Many uses as a rudimentary temperature sensor.

Used electrically, where the movement operates a switch and mechanically where it will operate a trip lever.

Still used, in toasters, electric kettles and room thermostats, but increasingly replaced by electronic sensors, such as thermistors.

Answer 2

The device you are referring to is called a bimetallic strip. It is made by joining two different metals with different coefficients of thermal expansion, causing the strip to bend when exposed to temperature changes. This is commonly used in thermostats and temperature-controlled devices.