Potential difference

The current flowing through a component depends on:

curriculum-key-fact
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 voltage and is measured in volts (V). The potential difference across a component is measured using a voltmeter placed in parallel with a component such as a lamp, as shown in this diagram:

Circuit with a cell, switch and lamp. A voltmeter is connected in parallel with the lamp.

Energy, potential difference and charge

When a charge moves through a potential difference, electrical work 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)
curriculum-key-fact
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