7.4.1 Capacitance

Definition

Capacitance $( C )$ is a measure of a capacitor's ability to store electric charge. Specifically, it is defined as the amount of charge $( Q )$ that a capacitor can store per unit of potential difference $( V )$ across its plates. The relationship between charge, capacitance, and potential difference is given by the formula:

C = \frac{Q}{V}

Where:

$C$ is the capacitance measured in farads ( $F$ ),
$Q$ is the charge in coulombs ( $C$ ),
$V$ is the potential difference across the capacitor in volts ( $V$ ). Capacitance is essentially an indicator of how much electric charge a capacitor can hold at a given voltage. Capacitors are commonly used in circuits to store energy temporarily, filter signals, and manage power supply in electronic devices.

infoNote

Example Walkthrough:

Example 1: Suppose a capacitor stores a charge of $Q = :highlight[0.002]$ , $\text{C}$ when a potential difference of $V = :highlight[10]$ , $\text{V}$ is applied across it. Calculate the capacitance of the capacitor.

Identify known values:

Charge $Q = :highlight[0.002 \, \text{C}]$
Potential difference $V = :highlight[10 \, \text{V}]$

Use the formula:

C = \frac{Q}{V}

Substitute values:

C = \frac{0.002}{10} = :highlight[0.0002 \, \text{F}] = :highlight[200 \, \mu\text{F}]

So, the capacitance of the capacitor is $:highlight[200]$ microfarads $(\mu\text{F})$ .

Capacitance Simplified Revision Notes for A-Level AQA Physics

7.4.1 Capacitance

Definition

Example Walkthrough:

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