Electricity and magnetism

Simple phenomena of magnetism 

Magnets have these properties:
-has a magnetic field around it
-has 2 opposite poles (North or north-seeking pole and South or south-seeking pole) which exert forces on other magnets. Like poles repel and unlike poles attract.

Induced magnetism: magnets attract materials by inducing magnetism in them, in other words the material becomes a magnet as well. The side of the material facing the magnet will become the opposite pole as the magnet.

Ferrous material: magnetic – anything which contains iron, nickel, or cobalt can be magnetised
•Non-ferrous material: non-magnetic e.g. copper, grass, ketchup, butter, wood etc.

• magnetic forces are due to interactions between magnetic fields 
  

•Magnetisation methods:
-inducing magnetism produces a weak magnet. It can be magnetised strongly by stroking with one end of a magnet, in one direction.
-the most effective method is to place the metal in a long coil of wire (solenoid) and pass a large DC (direct current) through the coil.

Demagnetisation methods: 

SMASH IT WITH A HAMMER, dropping etc.
-heating to a high temperature
-solenoid method but with alternating current

Iron vs. steel: iron is a soft ferromagnetic material meaning it will magnetise and demagnetise easily. Steel is a hard ferromagnetic material meaning it is hard to magnetise and demagnetise. Soft ferromagnetic materials are used to create temporary magnets, for example the magnets which lift cars in a rubbish dump, or the magnet in a circuit breaker. Hard ferromagnetic materials are used to create permanent magnets like fridge magnets, horse-shoe magnets. 

The magnetic field lines go from north to south. The north pole of a magnet can be found by placing a compass near the magnet. The needle will point the direction of the magnetic field line.