For an axial member, normal strain is defined as the change in member length $\mathrm{\delta }$ divided by the initial member length $\mathrm{L}$:

$\mathrm{\epsilon }=\frac{\mathrm{\delta }}{\mathrm{L}}$

Using this definition, the normal strain can be computed for wire $\left(1\right)$:

$$\begin{gathered} {\mathrm{\epsilon }}_1=\frac{{\mathrm{\delta }}_1}{{\mathrm{L}}_1}=\frac{0.84 \mathrm{mm}}{600 \mathrm{mm}} \\ =0.0014 \mathrm{mm}/\mathrm{mm}=\mathbf{1}\mathbf{,}\mathbf{400}\mathbf{ }\mathbf{\mu \epsilon } \end{gathered}$$