Question

A bimetallic strip consists of metals $X$ and $Y$. It is mounted rigidly at the base as shown in the figure. The metal $X$ has a higher coefficient of expansion than metal $Y$. When the bimetallic strip is placed in a cold bath,

• A. It will bend towards right.
• B. It will bend towards left.
• C. It will not bend but shrink.
• D. It will neither bend nor shrink

Answer 1

The correct option is B It will bend towards left.

Given:
Coefficient of expansion of $X$
$\left({\alpha }_X\right)$ is greater than coefficient of expansion of $Y$ $\left({\alpha }_Y\right)$

This means with per degree fall in temperature, $X$ strip will contract more than $Y$ strip.
And we know that for arc having some width, outer circumference is greater than inner circumference, therefore $X$ will be inward and $Y$ outward in the arc formed. So, bimetallic strip will bend towards left.
Before cooling -


After cooling -