PERMANENT MAGNETS Made from Fe, Co, Ni and some rare earth metals (ferromagnetic material)  In permanent magnets, electron spinning causes magnetic fields. Magnetic fields are caused by moving charges.  The atoms of permanent magnets are arranged in small structures called domains (~1 mm) where the electrons are spinning in the same direction  Each domain acts like a small magnet

Each magnets exists as a dipole: a north and south pole pair. Poles can’t exist on their own. Opposite poles attract; like poles repel

Some materials do not form magnetic fields, because the domains are random In some materials, the domains are organized so that the magnetic field of each domain add up to a larger magnetic field

Domains may be temporarily aligned by an external magnetic field The south poles of the domains point toward the north pole of the magnet

The domains of a magnet can be scrambled by heat, shock or other strong magnetic fields. Magnetic fields are measure in teslas (T)

The magnetic field is a vector. The direction is determined by the direction a north- pointing compass needle. Field lines leave the north pole and enter the south pole Field lines always form closed loops

The geographic north pole is actually the magnetic south pole

Computer Model of the earth’s magnetic field

Due to dynamic processes inside the earth, the magnetic poles are on the move

Earth’s magnetic field deflects high-speed charged particles called “solar wind” which are ejected from the sun.

Auroras are caused by solar wind particles when they excite air molecules. They occur near the poles because of the shape of the earth’s magnetic field.

 Magnetic flux is a measure of how many field lines pass through an area and is related to magnetic field strength