Physics 9702 · AS & A Level · Capacitors and capacitance
Capacitors and capacitance — practice question
Two parallel-plate capacitors $C_1$ and $C_2$ are attached to a supply with potential difference (p.d.) $V_S$. They can be arranged either in series or in parallel. The supply delivers charge $Q_S$, while the plates of the two capacitors gain charges $Q_1$ and $Q_2$ respectively. The p.d.s across the capacitor plates are $V_1$ and $V_2$ respectively. Complete Table 6.1 to show the relationships between $Q_S$, $Q_1$ and $Q_2$, and between $V_S$, $V_1$ and $V_2$, for series and parallel connections of the capacitors to the supply.
(a)[4]
Fill in Table 6.1 to show the links between $Q_S$, $Q_1$ and $Q_2$, and also between $V_S$, $V_1$ and $V_2$, for capacitors connected in series and in parallel to the supply.
(b(i))[2]
An isolated capacitor with capacitance $470\,\mu\text{F}$ stores $19\,\text{mJ}$ of energy. Calculate the p.d. across the capacitor.
(b(ii))[2]
Calculate the charge on the capacitor.
(b(iii))[3]
The capacitor is then joined in parallel to a capacitor of capacitance $180\,\mu\text{F}$ that starts uncharged. Determine the total energy, in mJ, now stored in the two capacitors.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “charges in series: $Q_s = Q_1 = Q_2$” …