CHAPTER 18.1 NOTES Magnets and Magnetism

Magnets Permanent Magnets are any material that attracts iron or materials containing iron. Poles are the part of the magnet where the magnetic effects are the strongest. Poles are marked north and south because if a magnet is free to rotate it will point to the north

Magnetic Forces The force (push or pull) between two magnets is called the magnetic force. If the poles are the same, the force will push them apart (repel). If the poles are different, the force will pull them together (attract)

Magnetic Fields - are a lot like electrical fields The region around a magnet where the magnetic forces can push or pull materials, is called the magnetic field. Magnetic fields are strongest at the poles.

Magnetic Fields

What makes something magnetic? Moving electrons within the atoms produce magnetic fields that give the atom a north and south pole. Normally, these fields cancel each other out except in iron, cobalt and nickel where the atoms group together in domains. If the domains line up with most of the north poles and south poles in the same direction, the material becomes magnetic.

Domains Domains within most objects Domains within magnetized object.

Making or losing magnets. Magnets can be made out of objects made of iron, cobalt or nickel by aligning the domains. Simply rub the object along a magnet in one direction so that all the domains point in the same direction. You can lose alignment by dropping a magnet or hitting it too hard so the domains mix. If you heat up a magnet, the particles vibrate and move faster.

Cutting a magnet. If you cut a magnet in half, you end up with two separate magnets each with a north and south pole.

Types of magnets Temporary magnets are made from materials that are easy to magnetize but lose their magnetism easily. Permanent magnets are difficult to magnetize but stay magnetized for longer periods.

Earth as a Magnet The Earth rotates making the iron and nickel center build up magnetic charges. These charges move north and south creating a magnetic north and south pole which are close the geographic north and south poles.