Comparing Series & Parallel Circuits (OCR GCSE Combined Science A (Gateway)): Revision Note

Katie M

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Katie M

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Comparing Series & Parallel Circuits

Current in Series & Parallel

  • In a series circuit, the current is the same at all points

  • In a parallel circuit, the current splits at junctions – some of it going one way and the rest going the other

current-series-parallel, IGCSE & GCSE Physics revision notes

Diagram showing the behaviour of current in series and parallel circuits

Potential Difference in Series & Parallel

  • In a series circuit, the voltage of the power supply is shared between the components

  • In a parallel circuit, the voltage across each component is the same

voltage-series-parallel, IGCSE & GCSE Physics revision notes

Diagram showing the behaviour of voltage in series and parallel circuits

Series and Parallel Circuit Summary Table

Series Parallel Circuits Summary Table, downloadable IGCSE & GCSE Physics revision notes

Worked Example

In the circuit below, ammeter A0 shows a reading of 10 A, and ammeter A1 shows a reading of 6 A.

WE Current Conservation Question image, downloadable IGCSE & GCSE Physics revision notes

What is the reading on ammeter A2?

Answer:

Step 1: Recall that at a junction, the current is conserved

  • This means that the total amount of current flowing into a junction is equal to the total amount flowing out

Step 2: Consider the first junction in the circuit where current splits

  • The diagram below shows the first junction in the circuit

WE Current Conservation Solution image, downloadable IGCSE & GCSE Physics revision notes

Step 3: Calculate the missing amount of current

  • Since 10 A flows in to the junction (the total current from the battery), 10 A must flow out of the junction

  • The question says that 6 A flows through ammeter A1 so the remaining current flowing through ammeter A2 must be:

10 A − 6 A = 4 A

  • Therefore, 4 A flows through ammeter A2

Examiner Tips and Tricks

The direction of current flow is super important when considering junctions in a circuit. You should remember that current flows from the positive terminal to the negative terminal of a cell/battery. This will help determine the direction current is flowing 'in' to a junction and which way the current then flows 'out'. 

Flow of charge, downloadable AS & A Level Physics revision notes
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Katie M

Author: Katie M

Expertise: Physics Content Creator

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.

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