Write down the voltmeter reading $V_0$ shown in Fig. 3.2.
Write down the ammeter reading $I$ shown in Fig. 3.3.
Fill in the heading for each column in Table 3.1, and also add the value of $I$ from (b).
Plot $V$ against $I$ with $V$ on the $y$-axis and $I$ on the $x$-axis, starting both axes at $(0,0)$, then draw the best-fit straight line.
Find the gradient $m$ of your line, noting that $m$ is numerically equal to the resistance $r$ of the power supply.
Continue your best-fit line until it reaches the $y$-axis and record the value of the electromotive force $V_0$.
Compare $V_0$ from (a) with the value obtained from the graph in (e)(ii). State whether the two values match to within $10\%$ and support your answer with a calculation.
Give one practical reason why values of $d$ below $20.0\,\text{cm}$ should not be used.
Complete the circuit diagram to show the connection of a variable resistor.