State what the capacitance of a parallel plate capacitor means.
A capacitor with capacitance $C$ is placed in the circuit shown in Fig. 7.1. When the two-way switch is set to A, the capacitor is charged until the potential difference across it is $V$. The switch is then moved to B and the capacitor completely discharges through the sensitive ammeter. The switch is alternated repeatedly between A and B so that the capacitor charges and discharges with frequency $f$. Show that the average current $I$ in the ammeter is given by the expression $I = fCV$.
A capacitor with capacitance $C$ is placed in the circuit shown in Fig. 7.1. When the two-way switch is set to A, the capacitor is charged until the potential difference across it is $V$. The switch is then moved to B and the capacitor completely discharges through the sensitive ammeter. The switch is alternated repeatedly between A and B so that the capacitor charges and discharges with frequency $f$.
When the potential difference $V$ is $150\,\text{V}$ and the frequency $f$ is $60\,\text{Hz}$, the average current in the ammeter is $4.8\,\mu\text{A}$. Calculate the capacitance, in pF, of the capacitor.
A second capacitor, with the same capacitance as the capacitor in (b), is joined to the circuit of Fig. 7.1. The two capacitors are in series. State and explain the new reading on the ammeter.