# Bimetals

Classical Mechanics Level 2

Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bimetallic objects consist of layers of different metals. The above left diagram [A] shows a bimetal consisting of two metals $$X$$ and $$Y$$ being heated up. The above right diagram [B] shows a bimetal consisting of two metals $$Z$$ and $$W$$ being cooled down. Now, the linear expansion coefficients of iron, copper and aluminium are $$12 \times 10^{-6} \text{ /K}$$, $$16 \times 10^{-6} \text{ /K}$$ and $$23 \times 10^{-6} \text{ /K}$$, respectively. Which of the following combinations will bend the bimetals upwards (resulting in the right ends lifted up as in the diagram)?

a) X=iron, Y=copper in the bimetal [A].

b) X=aluminium, Y=iron in the bimetal [A].

c) Z=aluminium, W=copper in the bimetal [B].

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