What is meant by electric potential difference across a component?
A circuit is made up of four resistors and a battery with electromotive force (e.m.f.) $8.0\,\text{V}$ and negligible internal resistance. With the variable resistor set to resistance $R$, the currents in the circuit are $0.030\,\text{A}$, $I_1$ and $I_2$, as displayed in Fig. 6.1.
Find the charge that flows through the battery in $4.0\,\text{minutes}$.
Calculate $I_1$.
Calculate $I_2$.
Determine $R$.
In part (b), the variable resistor has a scale so that its resistance can be read accurately. The $240\,\Omega$ resistor is now swapped for a new resistor $X$ with unknown resistance. A galvanometer is connected as shown in Fig. 6.2. Using resistance ratios, explain how this circuit can be used to find the resistance of $X$.