Link current to force
A current produces a magnetic field, and a current-carrying conductor in an external field can experience a force. Use field diagrams and Fleming’s left-hand rule carefully for Higher demand.
GCSE Physics resources
AQA GCSE Magnetism and electromagnetism
Magnetic Fields, Electromagnets and the Motor Effect
A current produces a magnetic field, and a current-carrying conductor in an external field can experience a force. Use field diagrams and Fleming’s left-hand rule carefully for Higher demand.
Start here
The quick revision snapshot
A current produces a magnetic field, and a current-carrying conductor in an external field can experience a force. Use field diagrams and Fleming’s left-hand rule carefully for Higher demand.
By the end, you should be able to…
- Explain link current to force using precise physics language.
- Apply the relevant equations, diagrams or practical method to an exam-style situation.
- Use the mini quizzes and practice answers to identify and correct a misconception.
Core learning content
Learn the idea before you practise it
Start with this short teaching sequence for Magnetic Fields, Electromagnets and the Motor Effect. Read the model, use the visual, then test your recall before moving into examples and exam practice.
Build the picture
A current creates concentric magnetic field lines around a straight wire. In a motor-effect question, distinguish field direction, current direction and force direction. Increasing current or field strength increases the force, while reversing either current or field reverses the force direction.
Use the right relationship
Choose a relationship because of the physical change in the question, not because it is familiar. Transformer ratio: Vₚ ÷ Vₛ = Nₚ ÷ Nₛ (V, turns). Power in an ideal transformer: VₚIₚ = VₛIₛ (W, V, A). Magnetic field strength idea: closer field lines = stronger field (qualitative). Keep the unit next to each value while you substitute.
What a strong answer does
Draw field direction, current direction and force direction as separate arrows, then state which variable would increase the force. Before writing, underline the command word and identify the information that matters. Keep a calculation as equation, substitution and answer with unit; keep an explanation as a linked chain using because, so or therefore. Finish by checking that the final sentence answers the exact context in the question and that the number, direction or conclusion agrees with the evidence given.
Retrieval practice
Quick checks
Answer without looking back first. The feedback explains the model, so a wrong answer still helps you learn.
Mini quiz 1
Check the core idea
Mini quiz 2
Apply the model
Mini quiz 3
Use exam precision
Try it
Magnetic field and motor model
How do current, field strength and conductor direction combine to produce a force?
What to notice: the readout and written explanation remain available if you do not use the controls.
Worked examples
See the method being built
Cover the answer, attempt the method and then compare your physics language as well as the number.
Example 1 · Field around wire
Describe the field around a straight current-carrying wire.
- State field shape.
- State effect of increasing current.
- Use concentric circles.
Show the answer
The field forms concentric circles around the wire; greater current produces a stronger field.
Example 2 · Electromagnet
Give two changes that strengthen an electromagnet.
- Change coil turns/current/core.
- State direction of change.
- Link to field strength.
Show the answer
Increase current or turns, and use a soft iron core to strengthen the electromagnet.
Example 3 · Motor force
A wire in a magnetic field has its current reversed. State force change.
- Keep field fixed.
- Reverse current.
- Use motor effect rule.
Show the answer
The force direction reverses.
Misconception clinic
Common wrong turns
Each of these is tempting because it sounds almost right. Replace it with the precise physics before you meet it in a question.
- Mixing field, current and force directions.
- Forgetting the motor-effect material is Higher Tier.
- Drawing field lines that cross.
Independent practice
Exam-style questions
Use the working space first. Reveal the guidance only after you have committed to an answer, then improve the exact part that would gain the next mark.
1. State the shape of a field around a bar magnet.
[1 mark]Show answer and marking guidance
Curved field lines from north to south outside the magnet.
2. State one way to strengthen an electromagnet.
[1 mark]Show answer and marking guidance
Increase current, add turns or use soft iron core.
3. State what happens to motor force if magnetic field direction reverses.
[1 mark]Show answer and marking guidance
Force direction reverses.
4. Name the rule used to find motor-force direction.
[1 mark]Show answer and marking guidance
Fleming’s left-hand rule.
5. Explain why an electric motor uses a split-ring commutator.
[3 marks]Show answer and marking guidance
It reverses current each half-turn so the turning force continues in the same rotational direction.
6. State one variable that increases force on a current-carrying wire.
[1 mark]Show answer and marking guidance
Current or magnetic field strength.
Questions pupils ask
GCSE Physics FAQs
What is the key idea in Magnetic Fields, Electromagnets and the Motor Effect?
Use field-line direction and the right-hand rule carefully. Electricity and magnetism are linked: current creates a magnetic field, and changing magnetic fields can induce a potential difference.
How should I practise Magnetic Fields, Electromagnets and the Motor Effect?
Read the snapshot, attempt the worked examples without looking, complete the mini quizzes and then use the practice questions to check your wording and method.
Next step
Keep your revision moving
Physics sticks when you move between explanation, retrieval and application.