# Magnetism

for Junior Science magnetism go here

Field lines about the Magnet by wally

Magnetics Field lines around a wire wally

Not all materials are magnetic, not even all metals can be attracted by magnets. We can make a magnetic field by passing an electric current through a wire wrapped about some metal core.

However somemetals can be magnetic without an electric current, read below

The magnetism comes from the filling of p shells in the 4th energy levels. usually these shells are filled in pairs, the electrons spin in opposite directions, which means there would be no magnetism on display. However if under a magnetic field some orbits are filled more easily this leads to samples of some metals, having all similiar orbits and in similiar directions filled, this leads to large loops, an extended orbit being filled.

## Diamagnetism

Diamagnetism is a very weak form of magnetic force. It can only be witnessed in strong external magnetic fields. Changes in the way the electrons orbit the nucleas cause a magnetic field to become induced, that is opposite to the direction of the field.

Diamagnetic materials include, glass, Au, Bi and H2O

Take a retort stand, from a long string suspend a small rod of glass, hold a neodymium magnet close by the suspended material.

Do not move the magnet! This will cause another force to come into play Electromagnetic Induction

Observe the effect, rearrange setup to find most effective range.

Repeat the experiment with a small roll of tinfoil (Al), about the same size as the glass!

Compare the results

The diamagnetic material is attracted to the weakest part of the external magnetic field

but what was happening the tinfoil?

## Paramagnetism

Paramagnetism is another form of magnetic force, like diamagnetism it requires an external magnetic force before the effects can be witnessed, you just did in the previous experiment, this time the effect was different, the material lined its self towards the magnet. The explanation for this is that the dipoles of the atoms* in the materials are affected by the magnetic field.

Paramagnetic materials include Al, W, Mg, Na, O, U.

(* atoms, in most of the paramagnetic materials the primary particle is actually the atom, this is due to the fact that most paramagnetic materials are metals. The dipoles are caused by the a (probabalistic) gathering of the electrons).

the continuing story of magnetism is continued when the 2 subjects of Electricity and Magnetism combine to make electromagnetism

Magnetic Levitation

• Electromagnets are used in particle accelerators.