On Fig. 2.1, draw a voltmeter so that it measures the potential difference (p.d.) across terminals X and Y.
On Fig. 2.2, draw an arrow (↔) to show exactly between which two points she should measure $l=80.0$ cm for wire A.
Read the values of V and I shown on the meters in Fig. 2.3 and Fig. 2.4, and enter them in the first line of Table 2.1.
Calculate, and enter in Table 2.1, the resistance R of each wire combination. Use the equation: $R=\frac{V}{I}$.
Write down a resistance $R_A$. $R_A$ is the value of R from Circuit A. Calculate a resistance $R_B$. Use the value of R from Circuit B and the equation $R_B=R\times2$. Calculate a resistance $R_C$. Use the value of R from Circuit C and the equation $R_C=R\times3$.
A student suggests that the values of $R_A$, $R_B$ and $R_C$ ought to be equal. State whether your results support this suggestion. Use values from your results to justify your answer.
Briefly explain why resistor $R_P$, shown in Fig. 2.1, must stay in the circuit throughout the experiment.
One possible difficulty in this type of experiment is that the resistance wires heat up. Suggest what should be done to reduce this.