Magnetism
This lesson builds electromagnetic induction and generators for GCSE Physics.
Use the core lesson first, then match the exam-board guidance to your school route. Many pupils meet this content through Combined Science as well as Separate Physics.
What you will learn
Exam-board fit
Exact paper labels and specification-point numbering vary by board and cohort, so match this lesson to your school route before using past-paper questions.
Induction scenarios supplied on this page
Use the moving magnet, coil and generator examples to practise induced potential difference explanations.
Clear explanation
Electromagnetic induction happens when a conductor cuts through magnetic field lines or when the magnetic field through a coil changes. This induces a potential difference.
A larger induced potential difference can be produced by moving faster, using a stronger magnet, using more turns on the coil or increasing coil area.
In a generator, mechanical work is transferred electrically as a coil or magnet rotates. This can produce alternating potential difference.
Key diagram
Worked examples
Increasing induced potential difference
A magnet is moved into a coil and a small reading appears.
Moving the magnet faster changes the magnetic field more quickly.
Adding more turns to the coil also increases the reading.
Quick checks
Choose an answer, then check your thinking.
1. What must change to induce a potential difference in a coil?
2. What energy transfer happens in a generator?
Practice questions
Question 1
Name two ways to increase induced potential difference in a coil.
Reveal answer and marking guidance
Answer: Move the magnet faster and add more turns to the coil.
Marking: Credit stronger magnet or larger coil area as alternatives.
Question 2
Why is no potential difference induced when the magnet and coil are both stationary?
Reveal answer and marking guidance
Answer: The magnetic field through the coil is not changing.
Marking: Credit no change in magnetic field linkage.
Question 3
What type of potential difference is produced by many simple rotating generators?
Reveal answer and marking guidance
Answer: Alternating potential difference.
Marking: Credit alternating because direction changes during rotation.
Question 4
State one difference between a motor and a generator.
Reveal answer and marking guidance
Answer: A motor uses electricity to produce movement; a generator uses movement to produce electricity.
Marking: Credit correct energy-transfer comparison.
Exam practice ladder
Answers and marking guidance
The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.
Common mistakes
- Saying induction needs a battery.
- Forgetting relative movement or changing field.
- Confusing generator effect with motor effect.
- Saying more turns reduce induced potential difference.
Exam-board guidance
All supported routes assess the core physics idea, but they may group topics, practicals and paper wording differently.
AQA GCSE Physics
AQA GCSE Physics: use this lesson for electromagnetic induction and generators, then check whether your class is taking Separate Physics or Combined Science.
OCR GCSE Physics
OCR GCSE Physics: the core physics idea is shared, but Gateway and Twenty First Century may organise questions differently.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: practise the concept, the equation use and the practical language because questions often connect them.
Eduqas GCSE Physics
Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.
WJEC Wales
WJEC Wales: check whether your class is using the current GCSE Physics route or a newer science route, then use this lesson for the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your unit and remember that practical skills are assessed directly.
Extension challenge
Explain how a bicycle dynamo can light a lamp only when the wheel is moving.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Next lesson
Next, continue with Transformers and the National Grid.