Magnetism
This lesson builds motor effect and simple electric motors 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.
Motor diagrams supplied on this page
Use the wire-in-field and coil examples to practise force direction and motor explanations.
Clear explanation
The motor effect is the force on a current-carrying conductor in a magnetic field. The force is strongest when the wire is at right angles to the field.
The force can be increased by increasing current, using a stronger magnetic field or increasing the length of wire in the field.
In a simple DC motor, forces on opposite sides of the coil act in opposite directions, producing a turning effect. The split-ring commutator reverses current every half turn so the coil keeps rotating.
Key diagram
Worked examples
Increasing motor force
A wire carrying current is placed between magnet poles.
The force is too small.
The student increases current and uses stronger magnets.
Quick checks
Choose an answer, then check your thinking.
1. What experiences a force in the motor effect?
2. What part helps a simple DC motor keep rotating in the same direction?
Practice questions
Question 1
Name two ways to increase the force on a current-carrying wire in a magnetic field.
Reveal answer and marking guidance
Answer: Increase the current and use a stronger magnetic field.
Marking: Credit those or increasing wire length in the field.
Question 2
Why is there no motor effect if the current is switched off?
Reveal answer and marking guidance
Answer: There is no current in the conductor, so the magnetic interaction producing the force is absent.
Marking: Credit current is required.
Question 3
What does the split-ring commutator do?
Reveal answer and marking guidance
Answer: It reverses current in the coil every half turn.
Marking: Credit maintaining rotation in the same direction.
Question 4
When is the force on the wire greatest?
Reveal answer and marking guidance
Answer: When the wire is perpendicular to the magnetic field.
Marking: Credit right angle between current direction and field.
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
- Forgetting a current is required.
- Thinking a motor needs only one force on the coil.
- Confusing commutator with magnet.
- Saying stronger current reduces force.
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 motor effect and simple electric motors, 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
Annotate a simple motor diagram with current direction, magnetic field direction and force direction on each side of the coil.
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 Generators and Electromagnetic Induction.