Demonstrate that the combined resistance of the two resistors, each of resistance $X$, is four times larger in Fig. 5.1 than in Fig. 5.2.
Explain why $I_2$ is not four times as large as $I_1$.
Using Kirchhoff’s second law, state equations, in terms of e.m.f., current, $X$ and $r$, for the circuit of Fig. 5.1.
Using Kirchhoff’s second law, state equations, in terms of e.m.f., current, $X$ and $r$, for the circuit of Fig. 5.2.
Use the equations in (a)(iii) to calculate the resistance $X$.
Calculate the ratio $$\frac{\text{power dissipated in one resistor of resistance }X\text{ in Fig. 5.1}}{\text{power dissipated in one resistor of resistance }X\text{ in Fig. 5.2}}.$$
In Fig. 5.1 and Fig. 5.2 the resistors are replaced with identical $12\,\text{V}$ filament lamps. Explain why the resistance of each lamp when it is in series is not the same as the resistance of each lamp when it is in parallel.
Using Kirchhoff’s second law, state equations, in terms of e.m.f., current, $X$ and $r$, for 1. the circuit of Fig. 5.1, 2. the circuit of Fig. 5.2.