A compass needle is placed near a bar magnet. Describe what is meant by a magnetic field and explain how magnetic field lines are used to show both the direction and the strength of the magnetic field around the bar magnet.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A magnetic field is the region around a magnet where another magnet or magnetic material will experience a non‑contact force.
Magnetic field lines are drawn to run from the north pole to the south pole of the bar magnet. They show the direction that a north pole would be pushed or pulled if placed at that point.
Where the field lines are close together the field is stronger; where they are spread out the field is weaker.
The field is strongest at the poles because the lines are most concentrated there.
Magnetic field lines are drawn to run from the north pole to the south pole of the bar magnet. They show the direction that a north pole would be pushed or pulled if placed at that point.
Where the field lines are close together the field is stronger; where they are spread out the field is weaker.
The field is strongest at the poles because the lines are most concentrated there.
Examiner tips
- Use the phrase ‘region around a magnet’ for the definition.
- Show the direction of the field with the arrow from N to S.
- Explain that line density indicates field strength.
- Mention that the poles have the highest concentration of lines.
Common mistakes
- Confusing the direction of the field with the direction of the force on a south pole.
- Saying the field lines start at the south pole.
- Not linking line density to field strength.
Mark scheme (4 marks)
- A magnetic field is the region around a magnet where another magnet or magnetic material will experience a non-contact force.
- Magnetic field lines point from the north pole to the south pole of the magnet, showing the direction of the force on a north pole at that point.
- Where the field lines are closer together (more concentrated), the magnetic field is stronger.
- The field is strongest at the poles because the field lines are most concentrated there.
Key terms in this question
magnetic field · magnetic field lines
Related
- All Pearson Edexcel International GCSE Physics (4PH1) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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