A copper and a steel wire of the same diameter are connected end to end. A deforming force $F$ is applied to this composite wire which causes a total elongation of 1 cm. The two wires will have

Consider the diagram where a deforming force $F$ is applied to the combination

For steel wire, $Y_{steel}=\frac{\mathrm{Stress}}{\mathrm{Strain}}=\frac{F/A}{\mathrm{Strain}}$

where, $F$ is tension in each wire and $A$ is cross-section area of each wires.

As $F$ and $A$ are same for both the wires, hence stress will be same for both the wires.

                 ${\left(\mathrm{Strain}\right)}_{\mathrm{steel}}=\frac{\mathrm{Stress}}{Y_{\mathrm{steel}}}, {\left(\mathrm{Strain}\right)}_{\mathrm{copper}}=\frac{\mathrm{Stress}}{Y_{\mathrm{copper}}}$

As,         $Y_{\mathrm{steel}}\ne Y_{\mathrm{copper}}$

Hence, the two wires will have different strains.