The word "ferrous" usually refers to materials that have a lot of iron in them. It's common for these materials to be strongly magnetic, but not all of them are. Different types of iron and steel are more or less magnetic. High-chromium stainless steel is nearly non-magnetic, while pure iron tends to form magnets easily. Iron with impurities usually stays magnetic better than pure iron, however. As for "non-ferrous" materials, itís pretty hard to make any generalizations. Thatís a little like trying to describe non-elephants- the category is too broad. In case youíre wondering, there are plenty of non-ferrous magnetic materials. In fact, some of the strongest permanent magnets you can get are based on "rare-earth" elements, such as neodymium, rather than on iron.
Ok, hereís some uses of magnets:
If you want to tack a note on your refrigerator door without getting it gummy, you may use a permanent magnet to hold it up.
The electricity you get from a wall socket was generated by moving wires near permanent magnets (or vice-versa) at the generating plant.
A compass uses a small permanent magnet for its needle.
Electric motors use magnetic forces from electromagnets, and in some motors also permanent magnets.
Recycling facilities use electromagnets to separate steel cans out from other material.
If you ever need to have a magnetic resonance image taken for medical reasons, some or all of you will be shoved into a big superconducting electromagnet.
We could go on and on- magnetism is used all over the place.
(republished on 07/13/06)