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 magnitude of the average conventional current, we can use the formula for current, which is given by:

$I = \frac{Q}{t}$

Where:

• Q is the charge,
• t is the time.

First, we calculate the charge (Q) stored in the capacitor:

$Q = C \times V$

Substituting the values we have:

• Capacitance (C) = 0.40 µF = $0.40 \times 10^{-6}$ F
• Voltage (V) = 4.0 V

Thus,

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

Next, the time for one charge-discharge cycle is:

$t = \frac{1}{4000} = 0.00025 ext{ s}$

Using the values in the current formula:

$I = \frac{1.6 \times 10^{-6}}{0.00025} = 6.4 \times 10^{-3} ext{ A} = 1.3 \times 10^{-2} ext{ A}$