Describe how you could use a plotting compass and a straight bar magnet to investigate the shape of the magnetic field around the magnet, and state what the direction of the compass needle tells you about the magnetic field.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student is investigating magnetic fields using simple equipment available in a school laboratory.
Model answer (4 marks)
Place the bar magnet on a flat surface and position the plotting compass near one end of the magnet.
Mark the position of the compass needle (e.g. mark a dot at the tip or tail of the needle) and move the compass to the next position.
Repeat this process to build up a series of points that can be joined to show the shape of the field lines or field pattern around the magnet.
The compass needle points in the direction of the magnetic field at that point, i.e. from the north pole to the south pole, indicating the direction of the field.
Mark the position of the compass needle (e.g. mark a dot at the tip or tail of the needle) and move the compass to the next position.
Repeat this process to build up a series of points that can be joined to show the shape of the field lines or field pattern around the magnet.
The compass needle points in the direction of the magnetic field at that point, i.e. from the north pole to the south pole, indicating the direction of the field.
Examiner tips
- Use the word ‘plot’ to show you are marking points; include the idea of joining them to form lines.
- Mention that the needle shows the field direction from north to south.
- Keep the answer concise – 4 marks, so one sentence per point.
- Use UK spelling (e.g. ‘magnet’).
Common mistakes
- Failing to mention that the needle shows the field direction from north to south.
- Writing a long paragraph instead of concise points.
- Using US spelling such as ‘color’ instead of ‘colour’.
Mark scheme (4 marks)
- Place the bar magnet on a flat surface and position the plotting compass near one end of the magnet
- Mark the position of the compass needle (e.g. mark a dot at the tip/tail of the needle) and move the compass to the next position
- Repeat to build up a series of points that can be joined to show the shape of the field lines / field pattern around the magnet
- The compass needle points in the direction of the magnetic field at that point / from north pole to south pole, showing the direction of the field
Key terms in this question
magnetic field · plotting compass
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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