Describe how the strength and direction of a magnetic field around a bar magnet changes as you move from the poles to the middle of the magnet. Include in your answer what magnetic field lines tell us about both strength and direction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
The magnetic field is strongest at the poles of a bar magnet and becomes weaker as you move away from the poles towards the centre or the sides of the magnet.
Field lines are drawn closer together near the poles, showing a stronger field, and spread apart further away, indicating a weaker field.
Outside the magnet the field lines run from the north pole to the south pole.
The direction of a field line shows the direction a north pole would move if placed at that point, i.e. the direction the magnetic field acts.
Field lines are drawn closer together near the poles, showing a stronger field, and spread apart further away, indicating a weaker field.
Outside the magnet the field lines run from the north pole to the south pole.
The direction of a field line shows the direction a north pole would move if placed at that point, i.e. the direction the magnetic field acts.
Examiner tips
- Use the word ‘strongest’ for poles and ‘weaker’ for the centre; mention field lines being closer/further apart.
- State that lines run N→S outside the magnet and that the line direction shows the force on a north pole.
Common mistakes
- Confusing the direction of field lines with the direction of a south pole; they run N→S, not S→N.
- Forgetting to mention that field lines are closer together at the poles and farther apart away from them.
Mark scheme (5 marks)
- Magnetic field is strongest at the poles
- The field becomes weaker further from the poles / towards the centre/sides of the magnet
- Field lines closer together indicate a stronger field / field lines further apart indicate a weaker field
- Field lines run from north pole to south pole (outside the magnet)
- The direction of a magnetic field line shows the direction a north pole would move / the direction the field acts at that point
Key terms in this question
magnetic field · field lines · poles
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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