Magnetism
Magnetism evolves with the discovery of Lodestone. Lodestone is used by Chinese about 900 years ago as a compass to navigate and explore on both the land and the sea. Lodestone, the "natural permanent magnet" has all the following magnetic properties...
- They attract magnetic materials
- They have 2 poles where magnetic properties are concentrated (N-S Poles)
- They always point in the N-S direction when suspended freely. N-Pole pointing to the North and S-Pole to the South.
- Like poles repel, unlike poles attract.
Magnetism - Magnetic and non-magnetic materials
Magnetic materials are materials that are easily attracted by a magnet. (Eg. iron, steel, nickle) In general, magnetic materials, if not magnetised, do not possess magnetic properties listed above. Remember, magnetic materials are not necessary magnet, unless magnetised.
As for non-magnetic materials, they are not attracted to by magnet and certainly cannot be magnetised. Such as wood, plastics, cloth and etc.
Magnetism - Magnetic Induction
When a magnetic material (unmagnetised) is placed near or touching a piece of permanent magnet, it will be magnetised and become a piece of magnet. In other words, the the material is said to have experienced a magnetic induction by the permanent magnet. However, this form of magnetism is only temporary.
Magnetism - Storage of Magnets
To prevent weakening of magnets, magnets can be stored with soft iron bar called "keepers" across the end of bar magnets as shown in the diagram below.
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