Magnetic Fields (Oxford AQA IGCSE Physics)

Revision Note

Magnetic Fields

  • A magnetic field surrounds all magnets

  • A magnetic field is defined as:

The space around a magnet where a force acts on another magnet or a magnetic material (such as iron, steel, cobalt and nickel)

Magnetic field lines

  • Magnetic field lines represent:

    • The strength of the magnetic field

    • The direction of the magnetic field

  • The spacing of field lines shows the strength of the field

    • When the field lines are closer together, the field is stronger

    • When the field lines are further apart, the field is weaker

  • 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

Uniform magnetic field

  • A uniform magnetic field is where the field lines are equally spaced

    • All act in the same direction

    • Show the same strength at every point

  • A uniform magnetic field can be found between the opposite poles of two bar magnets or inside a solenoid

Uniform magnetic field

A north pole on the left side of the image has five equally spaced parallel arrows indicating the field pointing to the south pole
A uniform field is created when two opposite poles are held close together. Magnetic fields are always directed from North to South.

Magnetic field around one bar magnet

  • The magnetic field is strongest at the poles

    • Therefore, the magnetic field lines are closer together

  • 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

Lines leave the north pole of the magnet with arrows indicating the direction of the field and curve around to enter the south pole of the magnet. The lines are closer together closer to the magnet, for IGCSE & GCSE Physics revision notes
The magnetic field around a bar magnet

Magnetic field around two bar magnets

  • Two bar magnets can repel or attract, the field lines will look slightly different for each

  • Two attracting bar magnets placed end to end have:

    • A uniform field going from north to south between the nearby poles

    • Further away from the magnets, the field lines get further apart

  • Two repelling bar magnets placed end to end have:

    • Field lines going into the south poles or out of the north poles and not connecting at the nearest side

    • This creates a space between the magnets where there is no field present

Magnetic field around two bar magnets placed end to end

The magnetic field between two bar magnets placed end to end shows attraction between opposite poles and repulsion between like poles, for IGCSE & GCSE Physics revision notes
Magnetic field lines for two magnets placed end to end show magnetic field strength as well as the direction of the magnetic field
  • In a less common side-by-side configuration, the field lines still show attraction between opposite poles and repulsion between like poles

Magnetic field around two bar magnets placed side to side

The magnetic field between two bar magnets placed side to side shows attraction between opposite poles and repulsion between like poles, for IGCSE & GCSE Physics revision notes
The magnetic field between two bar magnets placed side to side

Examiner 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.

Do this by:

  • Adding arrows pointing away from the north pole towards the south pole

  • Make sure the magnetic field lines are further apart as the distance from the magnet increases

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