MAGNETISMHISTORY The term magnetism comes from the ancient Greek city of Magnesia, at which many natural magnets were found. We now refer to these natural magnets as lodestones (also spelled loadstone; lode means to lead or to attract) which contain magnetite, a natural magnetic material Fe3O4. These magnets were used by the ancient peoples as compasses to guide sailing vessels. Chinese as early as 121 AD knew that an iron rod which had been brought near one of these natural magnets would acquire and retain the magnetic property and that such a rod when suspended from a string would align itself in a north-south direction.

Use of magnets to aid in navigation can be traced back to at least the eleventh century.What is Magnetism?Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.ELECTRON THEORY OF MAGNETISM According to modern theory, a piece of ferromagnetic substance consists of a very large number of very small magnets which may consists of atoms or molecules. These magnets are arranged in random orientations When the body is magnetized in any manner, these magnets wheel around and align themselves along the direction of the magnetic field.

Atoms themselves have magnetic properties due to the spin of the atoms electrons. Groups of atoms join so that their magnetic fields are all going in the same direction These areas of atoms are called domains

What are magnetic domains?Magnetic substances like iron, cobalt, and nickel are composed of small areas where the groups of atoms are aligned like the poles of a magnet. All of the domains of a magnetic substance tend to align themselves in the same direction when placed in a magnetic field. These domains are typically composed of billions of atoms.

When an unmagnetized substance is placed in a magnetic field, the substance can become magnetized.This happens when the spinning electrons line up in the same direction.

How to break a magnet:1. Drop it2. Heat itThis causes the domains to become random again!

REMEMBER:For Every North, There is a SouthEvery magnet has at least one north pole and one south pole.If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole. No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole.

No Monopoles AllowedIt has not been shown to be possible to end up with a single North pole or a single South pole, which is a monopole ("mono" means one or single, thus one pole).The ends of a magnet are where the magnetic effect is the strongest. These are called poles. Each magnet has 2 poles 1 north, 1 south.

Magnetic Fields - The region where the magnetic forces act is called the magnetic fieldMagnetic Field LinesMagnetic field lines describe the structure of magnetic fields.Field lines converge where the magnetic force is strong, and spread out where it is weak. For instance, in a compact bar magnet or "dipole," field lines spread out from one pole and converge towards the other, and of course, the magnetic force is strongest near the poles where they come together.The Earth is a magnet:It exerts magnetic forces and is surrounded by a magnetic field that is strongest near the North and South magnetic poles

CLASSIFICATION OF MAGNETS1. NATURAL MAGNET - lodestone2. ARTIFICIAL MAGNET OR MANMADE MAGNET(A) temporary- ex. electromagnet(B) permanent- ex. bar magnet

MAGNETIC MATERIALS1. FERROMAGNETIC- strongly attracted by magnets and can be readily magnetized Ex. Iron, cobalt, nickel2. PARAMAGNETIC- slightly attracted by magnets Ex. Oxygen, platinum, aluminum 3. DIAMAGNETIC- nonmagnetic and slightly repelled by magnets Ex gold, mercury, silver, sodium chloride