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
Motor diagrams supplied on this page
Use the wire-in-field and coil examples to practise force direction and motor explanations.
Motors and the motor effect infographic
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.
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.
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.
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 motor effect and simple electric motors.
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 Generators and Electromagnetic Induction.