Bimetallic Strip

A bimetallic strip consists of two different metals with different coefficients of thermal expansion bonded together along their lengths. When this strip is heated or cooled, the two metals expand or contract at different rates, causing the strip to bend or curve.

Extension Mechanism:

When the strip is heated:

• The metal with the higher coefficient of thermal expansion (expands more) elongates more than the other.

• Since the two metals are joined, they cannot slide over each other. The strip bends towards the side of the metal that expands less, and the metal that expands more moves to the outside of the curve.

• This bending is often referred to as thermal extension deformation.

Key Concepts:

• Unequal expansion causes curvature, not just linear extension.

• The amount of bending depends on:

  • The difference in thermal expansion coefficients.

  • The temperature change.

  • The thickness and length of the strip.

Applications:

• Thermostats (mechanical temperature sensors)

• Thermal switches

• Circuit breakers

• Temperature compensation devices