Properties of Magnetism
- Some substances are attracted by the magnet and they are called magnetic materials. Example: iron, steel etc
- Materials which are not attracted by magnets are called non-magnetic materials. Example: Aluminium, Copper etc
- The strength of a magnet (usually a bar magnet) is the most at the points near the ends which are called magnetic poles.
- A freely suspended magnet always points in the north-south direction. The end pointing North is called the North pole. And the end pointing South is called the South pole.
- Like poles repel and unlike poles attract.
- Magnetic poles always exists in pairs, a single magnetic pole never exists.
Theory of magnetism
In a ferromagnetic substance like iron there are tiny hypothetical called dipoles or domains. Each domain has its own North and South poles. In an unmagnetized iron bar, the domains are placed irregularly. And the magnetic field of the domains are cancelled out by one another. If the domains can be aligned, the iron bar will become a magnet.
When a magnet is brought close to in unmagnetized iron bar, an opposite magnetic pole is induced to the near side of the iron bar and a like pole is induced to the far side. Since unlike poles attracted, the iron bar attracted towards the magnet. Therefore we can say, before attraction magnetic induction takes place. Non-magnetic substances do not have any domains so no induction occurs and hence no attraction also occurs.