What Are Bimetallic Strip And Bimetallic Thermometer?

A strip made by firmly attaching two different metals side by side, which when heated bends, and on cooling returns o original shape is called bimetallic strip for example iron brass strip. This bending is due to the difference in values of co-efficient of linear expansion of two metals that is one metal expands more than the other over the same rise of temperature.  Bimetallic strip is used in making circuit breakers in electrical heating circuit devices.

Bimetallic thermometer is a device which works on the principle of thermal expansion in which bimetallic strip is used to determine the temperature of the body. A bimetal strip can be used to make a simple thermometer, which is easy to read.

In such type of thermometer, is used in shape of a coil. One end of a coil is fixed and a pointer is attached to the free end. When the temperature rises, the bimetallic strip coils itself into an even tighter spiral due to different expansion rates of the two metals, which form the bimetal strip, and the pointer moved across the temperature scale. The bending of bimetallic spiral type strip changes with temperature and the pointer indicates the reading on the scale

A bi-metallic strip is a thin strip of two metals bonded together back-to-back (usually rectangular in shape) that has one metal coating one side and another metal coating the other side. As the temperature changes, the expansion of the two metals being different causes the metal strip to bend toward the side of the metal with less expansive reaction to the heat. A bi-metallic thermometer uses this expansion to indicate temperature on a gage or scale (a mechanical action).