A switch S allows capacitor C to be completely charged by a cell and then completely discharged through an ammeter - AQA - A-Level Physics - Question 17 - 2022 - Paper 2

To find the average conventional current in the ammeter, we can use the formula for current:

$I = nQ$

where:

• $I$ is the average current,
• $n$ is the number of charge cycles per second, and
• $Q$ is the charge stored in the capacitor.

The charge $Q$ in a capacitor is given by:

$Q = C imes V$

In this case:

• The capacitance $C = 0.40 \mu F = 0.40 \times 10^{-6} F$,
• The voltage $V = 4.0 V$.

Calculating $Q$:

$Q = 0.40 \times 10^{-6} F \times 4.0 V = 1.6 \times 10^{-6} C$

Now substituting into the formula for current with $n = 8000$ cycles per second:

$I = 8000 \text{ cycles/s} \times 1.6 \times 10^{-6} C = 1.28 \times 10^{-2} A = 1.3 \times 10^{-2} A$