Chapter 21, Problem 46A

Would a bimetallic strip function if the two different metals happened to have the same rates of expansion? Is it important that they expand at different rates? Explain.

To determine

If both the metals of bimetallic strip possess the same expansion rate, then such a strip will work or not.

Explanation of Solution

Introduction:

Bimetallic strip is a strip that consists of bi (means two) metallic strips placed over each other. It is generally used in thermostats, bimetallic strip thermometers. Its main function is to break the open circuit.

In bimetallic strip, there are two metals having different rates of expansion. These two metal strips are placed one over the other.

When heat is applied to the bimetallic strip, one of the metals having comparatively more rate of expansion starts expanding more as compared to the other metal and it bends forming a curve. Both metals expand but out of the two metals, whose rate of expansion is more bends more than other metal.

Both metals should have different rate of expansion. If rate of expansion of both metals are same then both will bend in opposite direction and it won’t perform its function.

Figure shown below exactly tells how before and after expansion bimetallic strip looks like.

When heat is provided, the metal having more rate of expansion is outside and metal having less rate of expansion will bend inside.

Conclusion:

Both metals should have different coefficient of expansion.