- Like with electric fields, field lines are used to represent the direction and magnitude of a magnetic field
- In a magnetic field, field lines are always directed from the north pole to the south pole
The magnetic field lines around a bar magnet show the field is strongest at the two poles
- The simplest representation of magnetic field lines can be seen around bar magnets
- These can be mapped using iron filings or plotting compasses
- The key aspects of drawing magnetic field lines are:
- Arrows point out of a north pole and into a south pole
- The direction of the field line shows the direction of the force that a free magnetic north pole would experience at that point
- The field lines are stronger the closer the lines are together
- The field lines are weaker the further apart the lines are
- Magnetic field lines never cross
Magnetic field between two bar magnets
- When two bar magnets are pushed together, they either attract or repel each other:
- Two like poles (north and north or south and south) repel each other
- Two opposite poles (north and south) attract each other
Two opposite poles attract each other and two like poles repel each other
Uniform magnetic fields
- In a uniform magnetic field, the strength of the magnetic field is the same at all points
- This is represented by equally spaced parallel lines, just like electric fields
A uniform magnetic field has equally spaced field lines and is created when two opposite poles are held close together
The Earth's magnetic field
- On Earth, in the absence of any magnet or magnetic materials, a magnetic compass will always point north
- This is because the north pole of the compass is attracted to the Earth's magnetic south pole (which is the geographic north pole)
The Earth's magnetic field acts in a similar way to a bar magnet. A compass points to the Earth's magnetic south pole which is the geographic north pole
