Magnetic Fields (Cambridge (CIE) IGCSE Physics)

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