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Magnetic Fields (CIE IGCSE Physics)
Revision Note
Magnetic fields
- A magnetic field is defined as:
A region in which a magnetic pole experiences a force
Magnetic field around a bar magnet
- The magnetic field is strongest at the poles
- Therefore, the magnetic field lines are closer together at the ends of the magnets
- The magnetic field becomes weaker as the distance from the magnet increases
- Therefore, the magnetic field lines get further apart
Magnetic field around a bar magnet
The magnetic field around a bar magnetMagnetic field lines
- Field lines always have an arrow indicating the direction of the field line
- The direction of the field line shows the direction that the magnetic force would act
- The field lines always go from a north pole to a south pole
Magnetic field strength
Extended tier only
- Magnetic forces are due to interactions between magnetic fields
- Two bar magnets can repel or attract
- This is shown by the magnetic field lines between the two magnets:
Attractive and repulsive magnetic fields
Magnetic field lines for attracting and repelling bar magnets
- The strength of the magnetic field is shown by the spacing of the magnetic field lines
- If the magnetic field lines are close together then the magnetic field will be strong
- If the magnetic field lines are far apart then the magnetic field will be weak
Exam Tip
If you are asked to draw the magnetic field around a bar magnet remember to indicate both the direction of the magnetic field and the strength of the magnetic field.You can do this by:
- Adding arrows pointing away from the north pole and towards the south pole
- Making sure the magnetic field lines are further apart as the distance from the magnet increases
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