\(I-V\) characteristic of a copper wire of length \(L\) and area of cross-section \(A\) is shown in figure. The slope of the curve becomes

\(I-V\) characteristics of copper wire of length \(L\) and area of cross-section \(A\) is shown in the figure.

Since, \(I-V\) characteristic is a straight line, hence it obeys \(\mathrm{Ohm}^{\prime}\) s law. According to which resistance of copper wire,
\(R =\frac{V}{I}=\cot \theta \)
\(\Rightarrow R =\cot \theta \)
\(\Rightarrow \rho \cdot \frac{l}{A} =\cot \theta\)
or \(\quad \tan \theta \propto\left(\frac{A}{\rho l}\right)\)
Hence, slope \((\tan \theta)\) of the curve becomes
(i) less if the length of the wire is increased.
(ii) more if the area of the wire is increased.
(iii) less if a wire of steel of same dimensions is used as \(\rho_{\text {steel }}>\rho_{\text {copper }}\).
(iv) less if experiment is performed at higher temperature.