Parallel Circuits (Oxford AQA IGCSE Combined Science Double Award)

Parallel Circuits

• For components connected in parallel:

  • The current from the supply splits in the branches

  • The potential difference across each branch is the same

  • The combined resistance is less than that of either component

Current in parallel

• A junction in a parallel circuit is where two or more wires meet

  • The current is always split at a circuit junction

• The current is conserved

  • This means the amount of current flowing into the junction is equal to the amount of current flowing out of it

  • This is because the charge is conserved

• Current does not always split equally – often there will be more current in some branches than in others

  • The current in each branch will only be identical if the resistance of the components along each branch is identical

• Current behaves in this way because it is the flow of electrons:

  • Electrons are physical matter – they cannot be created or destroyed

  • This means the total number of electrons (and hence current) going around a circuit must remain the same

  • When the electrons reach a junction, however, some of them will go one way and the rest will go the other

Current is split

Potential difference in parallel

• The potential difference across each branch is the same

Voltage is the same

Resistance in parallel

• The combined resistance is less than the resistance of any of the individual components

• If two resistors of equal resistance are connected in parallel, then the combined resistance will halve

  • Charge has more paths to travel along, so its flow is resisted less than if only one path existed

Resistance of two resistors