Magnetism – Revision Notes
1. Permanent Magnets and Their Behaviour
Permanent magnets have two poles: north and south.
Their interactions follow two rules:
Like poles repel each other (N–N or S–S).
Unlike poles attract each other (N–S).
These behaviours are explained by the magnetic field surrounding each magnet.
2. Magnetic Fields and Field Lines
A magnetic field is the region where magnetic forces act.
Field lines show:
Direction of the field (from north pole to south pole).
Strength of the field (closer lines = stronger field).
Field lines never cross because that would imply two different force directions at the same
point.
3. Induced Magnetism
Some materials (iron, steel, nickel, cobalt) can become temporary magnets.
How induction works:
These materials have tiny magnetic regions called domains.
Normally, domains point randomly.
When placed in a magnetic field, domains align, turning the object into an induced
magnet.
When the field is removed, domains lose alignment and the magnetism fades.
Example:
A paperclip sticks to a magnet because it becomes an induced magnet.
4. The Earth’s Magnetic Field and Compasses
1. Permanent Magnets and Their Behaviour
Permanent magnets have two poles: north and south.
Their interactions follow two rules:
Like poles repel each other (N–N or S–S).
Unlike poles attract each other (N–S).
These behaviours are explained by the magnetic field surrounding each magnet.
2. Magnetic Fields and Field Lines
A magnetic field is the region where magnetic forces act.
Field lines show:
Direction of the field (from north pole to south pole).
Strength of the field (closer lines = stronger field).
Field lines never cross because that would imply two different force directions at the same
point.
3. Induced Magnetism
Some materials (iron, steel, nickel, cobalt) can become temporary magnets.
How induction works:
These materials have tiny magnetic regions called domains.
Normally, domains point randomly.
When placed in a magnetic field, domains align, turning the object into an induced
magnet.
When the field is removed, domains lose alignment and the magnetism fades.
Example:
A paperclip sticks to a magnet because it becomes an induced magnet.
4. The Earth’s Magnetic Field and Compasses
