(a)[2]
State two roles that capacitors play in electrical circuits.
(b)
Three capacitors are connected in parallel to a power supply, as shown in Fig. 4.1. The capacitors have capacitances $C_1$, $C_2$ and $C_3$. The power supply provides a potential difference $V$.
(b(i))[1]
Explain why the charge on each capacitor’s positive plate is not the same.
(b(ii))[2]
Use your answer in (i) to demonstrate that the combined capacitance $C$ of the three capacitors is $C = C_1 + C_2 + C_3$.
(c)
A student has three capacitors, each with capacitance $12\,\mu\text{F}$. Draw one circuit diagram for each case to show how the student connects the three capacitors so that the combined capacitance is:
(c(i))[1]
An equivalent capacitance of $8\,\mu\text{F}$.
(c(ii))[1]
An equivalent capacitance of $18\,\mu\text{F}$.