Current, resistance and potential difference — AQA GCSE Physics
Test yourself on Current, resistance and potential difference with AQA GCSE practice questions.
7 days Premium · Then free forever · No card, no charge
Current, resistance and potential difference explained
For a fixed potential difference, current and resistance work against each other: double the resistance and the current halves, because I = V ÷ R.
Read the full explanation
That single relationship explains most circuit questions. Close a switch that brings a second heating element into parallel and the total resistance of the circuit falls, so the current from the battery rises, and since the potential difference across the battery is unchanged the power output rises too, because P = I V. Add resistors in series instead and the total resistance increases, so the current falls. The same reasoning explains why a long thin wire passes a smaller current than a short thick one of the same material at the same potential difference.
Your focus
- Explain why a larger resistance gives a smaller current when the potential difference is fixed.
- Predict how closing a switch that adds a parallel branch changes the total resistance and the current.
- Link a change in current at constant potential difference to a change in power output.
Show all 4 objectives
- Compare the currents in two wires of different resistance connected to the same supply.
Current, resistance and potential difference exam tips
Marking Points
- one mark for stating that a greater resistance gives a smaller current at the same potential difference
- one mark for identifying whether the total resistance of the circuit rises or falls in the situation described
- one mark for deducing the resulting change in current
- one mark for linking that change to the power output using P = I V with the pd unchanged
Examiner Tips
- 💡Work through the chain in order: total resistance, then current, then power, each with its reason.
- 💡The second mark usually depends on the first, so an error about the resistance costs the rest.
- 💡State explicitly that the supply potential difference stays the same, because it is often the missing step.
Common Mistakes
- saying that adding a parallel branch increases the total resistance
- assuming the potential difference across the battery changes when a switch is closed
- reversing the relationship, so claiming more resistance means more current
- quoting P = I² R without any quantitative comparison, which the mark scheme ignores