Question

If a bimetallic strip of iron and copper is heated, then it will
A. not bend
B. bend with copper strip at convex side
C. bend with iron strip at convex side
D. get twisted

Answer 1

Hint: In the given question, the concept of linear thermal expansion is used. The strip of the material with a more significant linear expansion coefficient will expand more than the strip with a lower linear expansion coefficient.

Complete step by step answer:
According to the question, the strips of copper and iron are fused to form a bimetallic strip. The metals of each strip still retain its individual properties.The copper has a higher thermal expansion coefficient value (), while iron has a thermal expansion coefficient () that is lower than that of copper. This implies that for an equal rise in the temperature of both the
materials, the copper strip will expand more than that of the iron strip.So, for an equal rise in temperature, there will be unequal linear expansion. On the contrary, as the strips are joined together, they cannot expand independently. This will create stress at the boundary, which will tend to bend the faster-expanding metal outwards while bending the slower expanding metal inwards.Therefore, the bimetallic strip will bend with the copper strip at the convex side, while the iron strip tends to turn at the concave side, and option (B) is correct.

Note: The following bimetallic strips are used as a mechanical tool to measure the temperature change. An alloy would not be working as the substitute as in an alloy; the individual properties of the metals are lost. In contrast, in the bimetallic strip, the metals exhibit their unique properties independent of each other. Thus, the bending effect appears on the strip.