GCSE Physics resources
AQA GCSE Electricity
Change one factor such as wire length, keep material and cross-sectional area constant, measure current and potential difference, and calculate resistance for each reading. The circuit should be switched off between readings to limit heating.
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Change one factor such as wire length, keep material and cross-sectional area constant, measure current and potential difference, and calculate resistance for each reading. The circuit should be switched off between readings to limit heating.
Before you revise
Choose an answer from memory. Your result tells you what to watch for in the guide.
Core revision guide
Resistance Required Practical questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.
Change one factor such as wire length, keep material and cross-sectional area constant, measure current and potential difference, and calculate resistance for each reading. The circuit should be switched off between readings to limit heating.
A resistance investigation needs pairs of voltage and current readings for each value of the independent variable. If wire temperature rises, its resistance can change for a reason other than the variable being tested. Switch off between readings and use a graph to expose the trend.
Resistance: R = V ÷ I (Ω, V, A). Choose each relationship from the physical change described, convert quantities into compatible units and keep the unit beside the final answer.
Misconception clinic
Read each belief, say what is wrong with it, then compare your correction.
Tempting idea: Changing wire length and thickness together.
Use instead: Change one factor such as wire length, keep material and cross-sectional area constant, measure current and potential difference, and calculate resistance for each reading. The circuit should be switched off between readings to limit heating.
Tempting idea: Using a hot wire without recognising the validity problem.
Use instead: A resistance investigation needs pairs of voltage and current readings for each value of the independent variable. If wire temperature rises, its resistance can change for a reason other than the variable being tested. Switch off between readings and use a graph to expose the trend.
Tempting idea: Recording V and I but never calculating resistance.
Use instead: Describe the circuit, independent/dependent/control variables, repeats, graph and how heating could affect validity.
Retrieval practice
Worked examples
These examples expose the difference between a secure measuring resistance fairly method and the common error “Changing wire length and thickness together.”.
R = 8.0 Ω.
Use the same wire at different lengths, measure p.d. and current for each, calculate R = V/I, repeat, and control material, diameter and heating.
The wire heats up and its resistance changes independently of length. Use low current and switch off between readings.
Exam precision
Do this: Describe the circuit, independent/dependent/control variables, repeats, graph and how heating could affect validity.
Independent practice
Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.
Marking guidance: Award one mark for the precise statement shown in the model answer.
Model answer: Length of wire.
Marking guidance: Award one mark for the precise statement shown in the model answer.
Model answer: Wire material and diameter; also keep temperature/current conditions controlled.
Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.
Model answer: R = 6.0 ÷ 0.25 = 24 Ω.
Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.
Model answer: It measures the current through the test wire.
Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.
Model answer: It measures the potential difference across that wire.
Marking guidance: Award one mark for the precise statement shown in the model answer.
Model answer: Repeat each length and calculate a mean, keeping the wire cool between readings.
Questions pupils ask
Change one factor such as wire length, keep material and cross-sectional area constant, measure current and potential difference, and calculate resistance for each reading. The circuit should be switched off between readings to limit heating.
Changing wire length and thickness together. A resistance investigation needs pairs of voltage and current readings for each value of the independent variable. If wire temperature rises, its resistance can change for a reason other than the variable being tested. Switch off between readings and use a graph to expose the trend.
Useful next steps