Define the Young modulus of a material.
State an expression, using some or all of $L$, $A$, $E$ and $\rho$, for the resistance $R_0$ of the wire.
Show that the spring constant $k_0$ of the wire is given by $k_0 = \dfrac{EA}{L}$.
The wire is stretched, within the limit of proportionality, by a tensile force $F$. Assume that any changes in the cross-sectional area of the wire are negligible. On Fig. 3.1, sketch the variation with $F$ of the resistance $R$ of the wire.
On Fig. 3.2, sketch the variation with $F$ of the spring constant $k$ of the wire.
Copper has a resistivity of $1.8 \times 10^{-8}\,\Omega\,\text{m}$ and a Young modulus of $1.3 \times 10^{11}\,\text{Pa}$. A copper wire of diameter $1.6\,\text{mm}$ has a resistance of $0.034\,\Omega$. Show that the length of the wire is $3.8\,\text{m}$.
Use the equation in (b)(ii) to determine the spring constant of the wire.