Magnetism
Lesson overview
This lesson introduces the core physics idea, the useful equipment and the calculation or data skills used on this page.
What you will learn
Induction scenarios supplied on this page
Use the moving magnet, coil and generator examples to practise induced potential difference explanations.
Generators and electromagnetic induction infographic
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.
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.
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.
Exam-board guidance
Short board notes only. Learn the core physics above first.
AQA GCSE Physics
AQA GCSE Physics: often rewards clear physics explanations, correct equations, units and practical evidence for electromagnetic induction and generators.
OCR GCSE Physics
OCR GCSE Physics: often values precise definitions, clear working, graph interpretation and links between models and evidence.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: often combines the concept with equation use, data handling and practical interpretation.
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: often expects accurate terms, units and evidence-based explanations using the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your current unit and use the same practical method language your class uses.
Next lesson
Next, continue with Transformers and the National Grid.