A student investigates the resistivity of a wire using a circuit containing a cell of e.m.f. $\epsilon$ and internal resistance $r$, connected to an ammeter and a wire of length $L$, diameter $d$, and resistivity $\rho$. The relationship between the reciprocal of the current $1/I$ and the length of the wire $L$ is given by: \

\\frac{1}{I} = \\left(\\frac{4\rho}{\pi \varepsilon d^2}\\right) L + \\frac{r}{\varepsilon}{\char"24}$ The student measures the cell's e.m.f. as $\varepsilon = 2.00 \pm 0.10\text{ V}$ and determines the wire's diameter to be $d = 0.320 \pm 0.008\text{ mm}$. From a plot of $\frac{1}{I}$ against $L$, the student determines the following parameters: * Gradient of the line of best fit = $6.20\text{ A}^{-1}\text{ m}^{-1}$ * $y$-intercept of the line of best fit = $0.50\text{ A}^{-1}$ * Maximum $y$-intercept from the line of worst fit = $0.85\text{ A}^{-1}$