# Potential difference

The flowing through a component depends on:

• the of the
• the across the component
Potential difference is a measure of the amount of energy transferred between two points in a circuit.

### Measuring potential difference

Potential difference is also known as and is measured in volts (V). The potential difference across a component is measured using a placed with a component such as a lamp, as shown in this diagram:

## Energy, potential difference and charge

When a charge moves through a potential difference, electrical is done and energy transferred. The energy transferred can be calculated using the equation:

energy transferred = charge × potential difference

This is when:

• energy is measured in joules (J)
• charge is measured in coulombs (C)
• potential difference is measured in volts (V)
One volt is the potential difference when one coulomb of charge transfers one joule of energy.

### Example

2 C of charge transfers 4 J of energy. Calculate the potential difference needed.

Rearrange the equation:

energy transferred = charge × potential difference

potential difference = energy transferred ÷ charge

potential difference = 4 ÷ 2

= 2 V

Question

3 C of charge moves through a potential difference of 6 V. Calculate the energy transferred.

energy transferred = charge × potential difference

= 3 × 6

= 18 J