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Current resistance and potential difference - Teacher Slides.pptx
The lesson slides with the teacher's notes on each slide, and every question and mark scheme built in. Built from the lesson script on 30 September 2026.
AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Current, resistance and potential difference
Electricity
Lesson 2 of 10
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Warm-up
Electricity
Lesson 2 of 10
Answer each one, then check.
1
Write the unit of resistance.
2
What is the unit of potential difference?
3
Where is a voltmeter connected?
4
What does a longer wire do to resistance?
5
What is a current?
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Warm-up - Answers
Electricity
Lesson 2 of 10
1
Write the unit of resistance.
Ohm (Ω)
2
What is the unit of potential difference?
Volt (V)
3
Where is a voltmeter connected?
In parallel across the component
4
What does a longer wire do to resistance?
Increases it
5
What is a current?
A flow of charge
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Learning Objectives
Electricity
Lesson 2 of 10
1
Explain that current depends on resistance and potential difference.
2
Recall and apply V = IR.
3
Describe how to investigate the resistance of a wire and of combinations of resistors (Required Practical 3).
4
Interpret graphs of resistance against length.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Electricity
Lesson 2 of 10
V = IR
potential difference = current × resistance V = IR
The greater the resistance of a component, the smaller the current for a given potential difference across it. Questions use the term potential difference; voltage also gains credit.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Required Practical 3: Resistance of a Wire
Electricity
Lesson 2 of 10
Change only the length of wire between the clips.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Method: Resistance and Length of a Wire
Electricity
Lesson 2 of 10
Required Practical 3, part 1.
1
Set up
Connect the circuit with the ammeter in series and the voltmeter across the wire.
2
Set the length
Clip the crocodile clips at 0.20 m, and record the pd and current.
3
Switch off between readings
This keeps the wire at a constant temperature.
4
Repeat
Take readings at 0.40 m, 0.60 m, 0.80 m and 1.00 m.
5
Calculate
For each length R = V ÷ I.
6
Plot
Draw a graph of resistance against length: a straight line through the origin.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Method: Resistors in Series and Parallel
Electricity
Lesson 2 of 10
Required Practical 3, part 2.
1
Series
Connect known resistors in series, measure V and I, calculate R = V ÷ I.
2
Parallel
Repeat with the same resistors in parallel.
3
Compare
The series combination has a larger resistance than either resistor; the parallel combination has a smaller one.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Calculating Current
Electricity
Lesson 2 of 10
A 12 V battery is connected across a 4.0 Ω resistor. Calculate the current.
1
Rearrange
I = V ÷ R
2
Substitute
I = 12 ÷ 4.0
3
Answer
I = 3.0 A
ANSWER
3.0 A
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Calculating Potential Difference
Electricity
Lesson 2 of 10
A current of 0.50 A flows through a 20 Ω resistor. Calculate the potential difference across it.
1
Write the equation
V = IR
2
Substitute
V = 0.50 × 20
3
Answer
V = 10 V
ANSWER
10 V
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Calculating Resistance
Electricity
Lesson 2 of 10
A voltmeter reads 6.0 V and an ammeter reads 20 mA. Calculate the resistance.
1
Convert the current
20 mA = 0.020 A
2
Rearrange
R = V ÷ I
3
Substitute
R = 6.0 ÷ 0.020
4
Answer
R = 300 Ω
ANSWER
300 Ω
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Getting Good Results
Electricity
Lesson 2 of 10
Why we switch off between readings.
Heating
A current makes the wire hotter, and a hotter metal wire has a higher resistance.
Constant temperature
Use a low current and switch off between readings.
Zero errors
Check the meters read zero before starting.
Repeat
Repeat and average to reduce random errors.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Key Terms
Electricity
Lesson 2 of 10
Resistance
How much a component opposes the flow of current.
Ohm
The unit of resistance (Ω).
Potential difference
The energy transferred per coulomb; measured in volts.
Voltmeter
Measures pd; connected in parallel.
Constant temperature
Kept the same so the resistance does not change for other reasons.
Directly proportional
Doubling one quantity doubles the other.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Electricity
Lesson 2 of 10
YOUR TASK
Predict the Graph
10 minutes
A student measures the resistance of 20 cm, 40 cm, 60 cm, 80 cm and 100 cm of a wire. What does the graph of resistance against length look like? A 30 cm length has a resistance of 1.8 Ω; what is the resistance of 90 cm?
1
Sketch the axes.
2
Use the ratio of lengths.
WHAT A GOOD ANSWER SHOWS
A straight line through the origin: resistance is directly proportional to length. 90 cm is three times as long, so R = 5.4 Ω.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Can I...?
Electricity
Lesson 2 of 10
Recall V = IR.
Rearrange for I or R.
Convert mA to A.
Describe the resistance of wire method.
Explain why the wire is switched off between readings.
Draw a graph of R against length.
Say what happens to resistance in series and parallel.
Use the correct units.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Summary & Exam Focus
V = IR.
Ammeter in series, voltmeter in parallel.
Longer wire means greater resistance.
Switch off between readings to keep the temperature constant.
EXAM FOCUS
A potential difference of 9.0 V is applied across a resistor and the current is 0.30 A. Calculate the resistance. (2 marks)
State the equation, substitute and give the unit Ω.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Current, resistance and potential difference
Electricity
Lesson 2 of 10
Answer all questions. Use the mark allocation as a guide to how much to write. · 21 minutes
Question 1 · 2 marks · Calculate
The potential difference across a resistor is 9.0 V and the current through it is 0.30 A. Calculate the resistance of the resistor. Use the…
Question 2 · 2 marks · Calculate
A current of 0.15 A flows through a 40 Ω resistor. Calculate the potential difference across the resistor.
Question 3 · 4 marks · Use the graph
A student investigates how the resistance of a wire depends on its length. The graph shows the results. (a) Describe the relationship shown…
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Current, resistance and potential difference (cont.)
Electricity
Lesson 2 of 10
Question 4 · 6 marks · Describe
Describe an investigation to show how the resistance of a wire depends on its length. Your answer should include a circuit diagram…
Question 5 · 3 marks · Explain
Two identical resistors are connected first in series and then in parallel. Explain, without calculation, how the total resistance of each…
Question 6 · 3 marks · Calculate
A voltmeter reads 6.0 V and an ammeter reads 20 mA. Calculate the resistance of the component.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 1 · 2 marks · Calculate
Electricity
Lesson 2 of 10
“
The potential difference across a resistor is 9.0 V and the current through it is 0.30 A. Calculate the resistance of the resistor. Use the equation: potential difference = current × resistance
HOW TO ANSWER IT
Command word: Calculate. Worth 2 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 1 · mark scheme
Electricity
Lesson 2 of 10
2 marks available. Award a mark for each point made.
Correct substitution
1 mark
30 Ω
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 2 · 2 marks · Calculate
Electricity
Lesson 2 of 10
“
A current of 0.15 A flows through a 40 Ω resistor. Calculate the potential difference across the resistor.
HOW TO ANSWER IT
Command word: Calculate. Worth 2 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 2 · mark scheme
Electricity
Lesson 2 of 10
2 marks available. Award a mark for each point made.
Correct substitution
1 mark
6.0 V
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 3 · 4 marks · Use the graph
Electricity
Lesson 2 of 10
A student investigates how the resistance of a wire depends on its length. The graph shows the results. (a) Describe the relationship shown by the graph. (b) Use the graph to find the resistance of 70 cm of the wire. (c) Suggest why the student switched off the current between readings. (4 marks)
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 3 · mark scheme
Electricity
Lesson 2 of 10
4 marks available. Award a mark for each point made.
Straight line through the origin, or directly proportional
1 mark
4.2 Ω (accept 4.1 to 4.3)
1 mark
To keep the temperature constant or stop the wire heating
1 mark
Because temperature affects resistance
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 4 · 6 marks · Describe
Electricity
Lesson 2 of 10
“
Describe an investigation to show how the resistance of a wire depends on its length. Your answer should include a circuit diagram description, the measurements you would take, and how you would keep the test fair and safe.
HOW TO ANSWER IT
Command word: Describe. Worth 6 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 4 · mark scheme
Electricity
Lesson 2 of 10
6 marks available. Award a mark for each point made.
Level 3 (5 to 6 marks): a complete method with a correct circuit (ammeter in series, voltmeter across the wire), several lengths, calculation of R = V ÷ I for each, a graph, and control of temperature or safety
5 to 6 marks
Level 2 (3 to 4 marks): a method with most of the equipment and measurements, but with gaps in the detail or control
3 to 4 marks
Level 1 (1 to 2 marks): simple statements about measuring current and pd for wires
1 to 2 marks
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 5 · 3 marks · Explain
Electricity
Lesson 2 of 10
“
Two identical resistors are connected first in series and then in parallel. Explain, without calculation, how the total resistance of each arrangement compares with the resistance of one resistor.
HOW TO ANSWER IT
Command word: Explain. Worth 3 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 5 · mark scheme
Electricity
Lesson 2 of 10
3 marks available. Award a mark for each point made.
Series greater
1 mark
Parallel less
1 mark
A reason for either
1 mark
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 6 · 3 marks · Calculate
Electricity
Lesson 2 of 10
“
A voltmeter reads 6.0 V and an ammeter reads 20 mA. Calculate the resistance of the component.
HOW TO ANSWER IT
Command word: Calculate. Worth 3 marks, so plan before writing.
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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Question 6 · mark scheme
Electricity
Lesson 2 of 10
3 marks available. Award a mark for each point made.
Converts 20 mA to 0.020 A
1 mark
Correct substitution
1 mark
300 Ω
1 mark
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