1. Magnetism

2. Magnetism – The ability of certain metals to
attract iron, cobalt or nickel.
The Three Types of Magnets
1) Natural
2) Artificial
3) Electromagnets
The Laws of Magnetism
1) Every magnet has two poles
2) Like poles repel, unlike poles attract

3. The Nature of Magnetism
Weber’s Theory of Magnetism (why some items can
become magnetized )is based on the
following observations:
1) Breaking a magnet results in each fragment
becoming a whole magnet
2) Heating/hammering steel near a magnet
causes it to become magnetized
3) Stroking an iron bar with a magnet causes
the bar to become magnetized
4) Jarring steel filings near a magnet causes them
to become magnetized.

4. These observations and modern day atomic
theory suggest that:
1) Iron, nickel and cobalt consist of small discrete
magnets
2) Magnetic materials contain magnetic domains
(magnetic fields aligned in the same direction)
3) Magnetic domains consist of billions of
of dipoles (magnetic poles)
- In magnetized metals, the domains all
line up in the same direction.
- Nonmagnetized elements cannot be
magnetized, because they have equal
numbers of electrons spinning in each
direction.

5. Magnetic Fields
Magnets are surrounded by a magnetic field
(summation of domains) or flux
- The strength of a magnetic field is determined
by the number of lines of flux per square cm.

6. Characteristics of Magnetic Lines of Force
1) They leave the north pole and enter the south
pole of the magnet
2) Lines of force repel each other when traveling
in the same direction & attract when going
in the opposite direction

7. Characteristics of Magnetic Lines of Force
3) Lines of force are distorted by magnetic
materials, but not non-magnetic materials.

8. Magnetic Induction
When a magnetic material is brought near
a magnet, it becomes magnetized and assumes
a polarity opposite the polarity of that pole.
Magnetic Induction Depends on:
1) Permeability
2) Rententivity

9. Magnetic Classification of Matter
1) Ferromagnetic Materials
- Strong attraction to magnet
2) Paramagnetic Materials
- Feeble attraction to magnet
3) Non-Magnetic
- No attraction to magnet
4) Diamagnetic Materials
- Repelled by magnet