A Discuss the role of linear thermal expansion in the operat

(A) Discuss the role of linear thermal expansion in the operation of a days gone by home thermostat. Specifically, discuss the use of bi-metallic strips.

(B) Using the 2nd Law of Thermodynamics, explain how an air conditioner is able to deliver cold air when it is hot outside. Include a brief explanation of the refrigeration cycle.

Solution

A)

The coffiencients of linear expansion of metals are different. The bi metallic strips consists of two different metal strips. The expansion of these strips is different for same temperature difference across them as they are made of different metals. On heating the bi metallic strip bends towards the metal strip having low coffiecient of linear expansion whereas when temperature decreases, the strip bends towards the metal strip which has high coffiencient of linear expansion. Thus it is used to change the change in temperature into mechanical displacement.