Define the electromotive force (e.m.f.) of a battery.
A battery with e.m.f. $6.0\,\text{V}$ and internal resistance $0.50\,\Omega$ is joined in series with two resistors $X$ and $Y$, as illustrated in Fig. 6.1. The resistance of $X$ is $4.0\,\Omega$ and the resistance of $Y$ is $12\,\Omega$. Calculate the current in the circuit.
Calculate the terminal potential difference (p.d.) at the battery terminals.
Calculate the resistance $R$ of the combination of resistors $Y$ and $Z$.
State and explain how the terminal p.d. across the battery is affected. No numerical value is needed.
For the circuits in (b) and (c), show that the ratio $$\frac{\text{power developed in the external circuit in Fig. 6.1}}{\text{power developed in the external circuit in Fig. 6.2}}$$ is approximately $0.8$.