1. Inside a Magnet
Chapter 1, Section 2, p14-19

2. The Atom
Magnetic properties of materials depend on structure of its atoms
Matter: anything that has mass and takes up space
All matter is made of atoms
Atom: smallest particle of an element
Element: one of about 100 basic substances that make up all matter
Structure and composition of atoms that make up an element makes that element different from other elements

3. Structure of an Atom Nucleus: center region of an atom
Two kinds of particles are found inside nucleus:
Proton: particle that carries a positive charge
Neutron: particle that doesn’t carry any charge
The outer region is mostly empty space
Electron: particle that carries a negative charge
Move randomly through atom
Much smaller than neutrons & protons

4. Electron Spin
Each electron behaves like it is spinning, so it has a property called “electron spin”
A spinning electron produces a magnetic field that makes the electron behave like a tiny magnet in an atom
Most atoms have paired electrons spinning in opposite directions
Opposite spin = opposite magnetic fields = cancel out
Most atoms have weak magnetic properties
Some atoms have unpaired electrons = strong magnetic properties

5. Magnetic Domains
Magnetic fields of atoms in most materials point in random directions
Magnetic fields cancel one another
Weak magnetic force that you can’t detect
Magnetic fields of many atoms are aligned with each other in some materials
Magnetic domain: group of atoms that have their magnetic fields aligned
Domain acts like a bar magnet with north & south poles

6. Alignment of Domains
Direction domains point determines if the material is magnetized or not
Magnetic domains point in random directions
Cancel each other out = not magnetized
Magnetic domains pointing in the same direction
In magnetized material, all or most of the magnetic domains are arranged in same direction
Magnetic fields of domains are aligned

7. Magnetic Materials
Materials can be a strong magnet if it’s magnetic domains align
Ferromagnetic material: material that shows strong magnetic properties
Ferrum means “iron” (Fe)
Ferromagnetic material placed in a magnetic field acts like iron
Common ferromagnetic materials:
Iron, Nickel, Cobalt, Gadolinium
Rare elements: Samarium & Neodymium

8. Magnetic Materials Some magnets made from several different materials
Alloy: combination of several metals
Alnico:
Al uminum
N ickel
I ron
Co balt
Powerful magnets:
Platinum & Cobalt
Cobalt & Neodymium

9. Magnetic Materials
Ferrite – most commonly used material to make magnets today
Mixture of substances containing ferromagnetic elements
Brittle material that chips easily
Usually stronger & less expensive than metal magnets of same size

10. Making & Changing Magnets
Magnets can be made, destroyed or broken apart
Magnets can be made from ferromagnetic materials
No magnet can last forever

11. Making Magnets Magnets can be made by:
Placing unmagnetized ferromagnetic material in a strong magnetic field
Rubbing a ferromagnetic material with one pole of a magnet
Rub in one direction
Causes magnetic domains to line up in same direction
More domains lined up = more magnetic
Steel in paper clip / pure iron easy to magnetize

12. Making Magnets
Temporary magnet: magnet made from a material that easily loses its magnetism
Permanent magnet: magnet made from a material that keeps its magnetism for a long time

13. Destroying Magnets
Permanent magnets can also become unmagnetized just like temporary magnets
Drop it / strike it hard
Magnetic domains knocked out of alignment
Heat it
Particles vibrate faster and more randomly
Difficult for domains to stay lined up with movement
Every ferromagnetic material loses its magnetism a certain temperature
Temperature depends on material

14. Breaking Magnets What happens if you break a magnet in half?
You have two smaller magnets
Each smaller magnet has its own north & south poles
Figure 11
Magnet has many magnetic domains lined up in one direction
Many north and south poles are all facing each other
Produces strong magnetic force at poles (N) & (S)
The domains in two halves still line up when cut in half
Many north or south poles will still be at each end

15. Homework
Read Chapter 1, Section 2, p14-19
Answer ?s 1-3 p19