Physics 9702 · AS & A Level · Capacitors and capacitance

Capacitors and capacitance — practice question

(a(i))[1]

Define capacitance as the charge stored per unit potential difference.

(a(ii))[4]

A capacitor consists of two metal plates insulated from each other, as shown in Fig. 5.1. Explain why the capacitor is described as storing energy but not charge.

(b)

Three initially uncharged capacitors X, Y and Z, each with capacitance $12\,\mu\text{F}$, are connected as shown in Fig. 5.2. A potential difference of $9.0\,\text{V}$ is applied across points A and B.

(b(i))[2]

Three initially uncharged capacitors X, Y and Z, each with capacitance $12\,\mu\text{F}$, are connected as shown in Fig. 5.2. A potential difference of $9.0\,\text{V}$ is applied across points A and B. Calculate the equivalent capacitance of capacitors X, Y and Z.

(b(ii))[2]

Explain why applying a potential difference of $9.0\,\text{V}$ gives a charge of $72\,\mu\text{C}$ on one plate of capacitor X.

(b(iii)1)[1]

Determine the potential difference across capacitor X.

(b(iii)2)[2]

Determine the charge on one plate of capacitor Y.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Capacitance is the charge divided by the potential difference, $C=\frac{Q}{V}$

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