1. SPH3U/SPH4C

2.  Permanent  Temporary (materials that can be made magnetic but eventually lose their magnetic properties)

3.  Materials containing IRON, NICKEL, or COBALT can be magnetized when placed in/near a magnetic field.

4.  Ferromagnetic Materials: these materials include iron, nickel and cobalt (and alloys of these metals).  Two Types: Soft & Hard Ferromagnetic Ex. Pure iron – remains magnetic only in the presence of a magnetic field. TEMPORARY Magnet Ex. Steel (an alloy)– remains magnetic even after the magnetic field has been removed. SEMI-PERMANENT Magnet

5.  The magnetic field strength is a fundamental force called the: Electromagnetic Force  It is incredibly strong … it is the second strongest force of the 4 fundamental forces.  Much, much stronger than the gravitational force.

6.  What is the theory of magnets?  Magnets have a North and South pole (N & S)  All magnets are made of many smaller magnets called dipoles (2 poles)  Each dipole can interact with the other dipoles in the material, if the dipoles line up in a single direction, then small magnetic domains are created; these act like tiny bar magnets  In a strong magnetic field all of the small magnetic domains line up forming one large magnet with N and S poles  Breaking a magnetic in two; domains remain aligned and two new magnets are formed.  Disrupting the alignment of the domains so that the dipoles are randomly distributed in demagnetization.

7.  Magnetic Domains UNALIGNED  Result: Not Magnetic overall Regions or Domains Individual Dipoles in a domain

8.  Magnetic Domains ALIGNED  Result: Bar magnetic is formed Individual Dipoles in a domain Regions or Domains

9.  Demagnetization: when you disorder the alignment of the magnetic domains you will cause the material to not be magnetic overall. This can be done in 2 ways:  Physically disrupt the alignment by repeatedly striking the material  Disrupt the alignment by heating the material to a very high temperature.

10.  http://www.youtube.com/watch?v=9KOLu9MxFq8 Need more help understanding the domain theory of magnetism? Watch the video on YouTube using the link above.