GCSE PHYSICS / CIRCUIT REASONING / INDEPENDENT SUPPLEMENT
YOUR STARTING POINT
Before V = IR,
ask what stays fixed.
GCSE physics method summary + 20 original tasks
For learners who can substitute into an equation but lose track of current, potential difference and
resistance when a circuit changes. Learn to name the quantity, trace the connections and state the
controlled condition before calculating.
One series path Separate parallel paths
The same current passes through each component. Each branch connects across the same two nodes. Branch
Component voltage drops add to the supply voltage. currents add to the supply current.
The key diagnostic
A larger resistance does not automatically create a larger voltage. With a fixed-voltage supply across a
single resistor, current falls. If current is deliberately held constant instead, a larger voltage is needed. The
equation is the same; the controlled condition is different.
A four-step working routine
1 / Trace: identify the whole circuit, each branch and the component asked about.
2 / Label: put each given I, V and R on the correct part.
3 / Fix: state what stays constant when something changes.
4 / Check: calculate with units, then check current at junctions or voltage around the series loop.
Route through the guide
Pages 2-5: meanings, three worked demonstrations, diagrams and meters. Pages 6-10: five practice sets.
Pages 11-14: separate explained solutions. Page 15: retry plan, scope and sources. Use extra paper for
working; attempt each set before opening its solutions.
Model used throughout
Steady direct-current circuits, ideal fixed-voltage sources unless otherwise stated, negligible wire resistance, and fixed ohmic
resistors at constant temperature. Diagrams are schematic; wire length on the page has no electrical meaning. No laboratory or
mains-wiring instructions.
Created with AI assistance; quantitative answers checked in code and pages visually reviewed. No independent expert review,
attendance, achieved grade or guaranteed result claimed. Independent of AQA; original practice, not an official paper.
Version 1.0 | September 2026 | Original method summary and practice 1
, GCSE PHYSICS / CIRCUIT REASONING / INDEPENDENT SUPPLEMENT
METHOD SUMMARY
Name the quantity.
Keep its units.
Quantity Meaning Measurement / unit
Current, I Rate of charge flow through a point Ammeter in series / ampere (A)
Potential difference, V Energy transferred per unit charge between two Voltmeter across two points / volt (V)
points
Resistance, R Ratio of potential difference to current for the R = V / I / ohm
stated conditions
One relation, three useful forms
V=IxR I=V/R R=V/I
Use V in volts and I in amperes to obtain R in ohms. Divide mA by 1000 to get A; multiply A by 1000 to get
mA. Do not divide by zero when rearranging. A zero-current reading alone does not determine resistance.
Do not treat potential difference as a force
Current describes charge passing a point, while potential difference compares energy per charge between
points. A resistor transfers energy; it does not use up charge. In a steady single loop, current before and
after a resistor is the same.
Worked demonstration A / two different changes
Case What stays fixed? Calculation
Start: 6 V across 12 ohms The starting condition I = = 0.50 A
Raise supply to 9 V R = 12 ohms I = = 0.75 A
Instead replace with 24 ohms at 6 V=6V I = = 0.25 A
V
The last two rows are separate changes from the starting case. Raising V at fixed R increases I. Raising R
at fixed V decreases I. Say which comparison you mean. For a fixed ohmic resistor at constant
temperature, current is proportional to its potential difference.
Condition check
If someone supplies only “R increases”, ask what happened to the source or current. There is not enough
information to determine both V and I. This is a reasoning issue, not a missing formula.
Version 1.0 | September 2026 | Original method summary and practice 2
YOUR STARTING POINT
Before V = IR,
ask what stays fixed.
GCSE physics method summary + 20 original tasks
For learners who can substitute into an equation but lose track of current, potential difference and
resistance when a circuit changes. Learn to name the quantity, trace the connections and state the
controlled condition before calculating.
One series path Separate parallel paths
The same current passes through each component. Each branch connects across the same two nodes. Branch
Component voltage drops add to the supply voltage. currents add to the supply current.
The key diagnostic
A larger resistance does not automatically create a larger voltage. With a fixed-voltage supply across a
single resistor, current falls. If current is deliberately held constant instead, a larger voltage is needed. The
equation is the same; the controlled condition is different.
A four-step working routine
1 / Trace: identify the whole circuit, each branch and the component asked about.
2 / Label: put each given I, V and R on the correct part.
3 / Fix: state what stays constant when something changes.
4 / Check: calculate with units, then check current at junctions or voltage around the series loop.
Route through the guide
Pages 2-5: meanings, three worked demonstrations, diagrams and meters. Pages 6-10: five practice sets.
Pages 11-14: separate explained solutions. Page 15: retry plan, scope and sources. Use extra paper for
working; attempt each set before opening its solutions.
Model used throughout
Steady direct-current circuits, ideal fixed-voltage sources unless otherwise stated, negligible wire resistance, and fixed ohmic
resistors at constant temperature. Diagrams are schematic; wire length on the page has no electrical meaning. No laboratory or
mains-wiring instructions.
Created with AI assistance; quantitative answers checked in code and pages visually reviewed. No independent expert review,
attendance, achieved grade or guaranteed result claimed. Independent of AQA; original practice, not an official paper.
Version 1.0 | September 2026 | Original method summary and practice 1
, GCSE PHYSICS / CIRCUIT REASONING / INDEPENDENT SUPPLEMENT
METHOD SUMMARY
Name the quantity.
Keep its units.
Quantity Meaning Measurement / unit
Current, I Rate of charge flow through a point Ammeter in series / ampere (A)
Potential difference, V Energy transferred per unit charge between two Voltmeter across two points / volt (V)
points
Resistance, R Ratio of potential difference to current for the R = V / I / ohm
stated conditions
One relation, three useful forms
V=IxR I=V/R R=V/I
Use V in volts and I in amperes to obtain R in ohms. Divide mA by 1000 to get A; multiply A by 1000 to get
mA. Do not divide by zero when rearranging. A zero-current reading alone does not determine resistance.
Do not treat potential difference as a force
Current describes charge passing a point, while potential difference compares energy per charge between
points. A resistor transfers energy; it does not use up charge. In a steady single loop, current before and
after a resistor is the same.
Worked demonstration A / two different changes
Case What stays fixed? Calculation
Start: 6 V across 12 ohms The starting condition I = = 0.50 A
Raise supply to 9 V R = 12 ohms I = = 0.75 A
Instead replace with 24 ohms at 6 V=6V I = = 0.25 A
V
The last two rows are separate changes from the starting case. Raising V at fixed R increases I. Raising R
at fixed V decreases I. Say which comparison you mean. For a fixed ohmic resistor at constant
temperature, current is proportional to its potential difference.
Condition check
If someone supplies only “R increases”, ask what happened to the source or current. There is not enough
information to determine both V and I. This is a reasoning issue, not a missing formula.
Version 1.0 | September 2026 | Original method summary and practice 2
