Comparing Series & Parallel Circuits (OCR GCSE Physics A (Gateway)): Revision Note
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
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
Diagram showing the behaviour of voltage in series and parallel circuits
Series and Parallel Circuit Summary Table
Worked Example
In the circuit below, ammeter A0 shows a reading of 10 A, and ammeter A1 shows a reading of 6 A.
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
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'.
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