Chapter 8.1

The properties and interactions of magnets

 

 

 

●2000 years ago, the Greeks discovered magnetite in Magnesia

●Magnetic materials are surrounded by a Magnetic Field--it is strongest closest to the magnet

●The interaction between two magnetic materials is the Magnetic Force—it increases as they move closer together.

● Magnetic Poles—the regions of the magnet where the force is the strongest

·      All magnets have a north pole and a south pole

·     

S

Like poles repel; unlike poles attract (just like charges!)

·      Earth has magnetic poles (North and South)

·     

N

A compass needle is a small bar magnet that can rotate freely

·      It always points north

o    Why is the earth magnetic?

 

● Magnetic Materials—What makes materials magnetic?

·      Only some elements are—Iron, Nickel, and Cobalt

·      Their electrons have a special arrangement (ferromagnetic)

·      Each atom has a magnetic force, which exerts a force on nearby atoms—they align into magnetic domains

·      Magnetic Domains—groups of atoms with aligned magnetic poles

o    In a magnet, the domains point in the same direction

o    Permanent magnets are made by placing a magnetic material in a strong magnetic field, forcing the magnetic domains to line up