Read the voltmeter scale, then enter the p.d. $V$ in Table 1.1 on page 4.
Calculate $\frac{1}{V}$ and write the result in Table 1.1 on page 4, using the correct number of significant figures.
She carries out the procedure again in (a) with $l = 30.0\,\text{cm}$, $40.0\,\text{cm}$, $60.0\,\text{cm}$ and $80.0\,\text{cm}$. Her findings are given in Table 1.1. Suggest why the student opens the switch between readings.
On the grid in Fig. 1.3 on page 5, plot $\frac{1}{V}$ on the $y$-axis against $l$ on the $x$-axis. Begin both axes at the origin $(0,0)$, then draw the best-fit straight line.
Calculate the gradient $m$ of your line. Show your working in full and mark on the graph the values you used.
Extend the line until it crosses the $y$-axis, then measure the intercept $c$ where the line meets the $y$-axis.
Calculate the electromotive force (e.m.f.) $E$ of the cell by using $E = \frac{k}{c}$, where $k = 1.0\,\text{V}$.
Suggest one practical reason why, even though the experiment was carried out carefully, the student’s value for $E$ may not be the true value.
The values in Table 1.1 show that as the length $l$ of resistance wire increases, the potential difference $V$ falls. State how the results show that $l$ is not inversely proportional to $V$.