Magnetic Fields (Cambridge (CIE) IGCSE Physics)
Revision Note
Written by: Ashika
Reviewed by: Caroline Carroll
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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 magnet
Magnetic 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
Examiner Tips and Tricks
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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