People not familiar with magnetism often view it as a somewhat mysterious property of specially treated iron or steel.
A magnetized bar has its power concentrated at two ends, its poles; they are known as its north (N) and south (S) poles, because if the bar is hung by its middle from a string, its N end tends to point northwards and its S end southwards. The N end will repel the N end of another magnet, S will repel S, but N and S attract each other. The region where this is observed is loosely called a magnetic field; a more specific look at the concept of "field" is provided in a later section.
Either pole can also attract iron objects such as pins and paper clips. That is because under the influence of a nearby magnet, each pin or paper clip becomes itself a temporary magnet, with its poles arranged in a way appropriate to magnetic attraction.
But this property of iron is a very special type
of magnetism, almost an accident of nature!

Posted by Jay Roberts at 06:30 AM | Permalink