AQA GCSE Physics

Revision Notes

2.2.1 Series & Parallel Circuits

Series & Parallel Circuits

  • There are two ways of joining electrical components, in series and in parallel
    • Some circuits include both series and parallel parts
  • A series circuit consists of a string of two or more components, connected end to end:

    Series circuit, IGCSE & GCSE Physics revision notes

Diagram showing two bulbs connected in series

  • A parallel circuit consists of two or more components attached along separate branches of the circuit

Parallel circuit, IGCSE & GCSE Physics revision notes

Diagram showing two bulbs connected in parallel

Series Circuits

  • In a series circuit:
    • The current is the same at all points ie. through each component
    • The total potential difference of the power supply is shared between the components
    • The total resistance of two components is the sum of the resistance of each component

Lamps connected in a series circuit

  • In the above circuit:
    • The current from the power supply is the same as the current in both lamps I = I1 = I2
    • If the battery is marked 12 V, then the potential difference would be 12 ÷ 2 = 6 V across each lamp
    • If each lamp has a resistance of R, then the total resistance in the circuit is equal to R + R = 2R

Parallel Circuits

  • In a parallel circuit:
    • The total current through the whole circuit is the sum of the currents through the separate components
    • The potential difference across each component is the same
    • The total resistance of two resistors is less than the resistance of the smallest individual resistor

Lamps connected in a parallel circuit

  • In the above circuit:
    • Because the current splits up, the sum of currents in each branch will equal the current from the power supply I = I1 + I2
    • If the battery is marked 12 V, then the potential difference would be 12 V across each lamp
    • If each lamp has a resistance of R, then the total resistance in the circuit will be less than 2R

Exam Tip

  • Note that the 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 are 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

Junctions current splitting, IGCSE & GCSE Physics revision notes

Current is split at a junction into individual branches

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top