1. magnetism
Chapter 8

2. Magnetism Properties and interactions of magnets
2,000 years ago Greeks discovered a magnetic mineral; lodestone/magnetite

3. Magnetic… Force Field Poles 2 magnets exert force on each other
Strength of force increases as closer
Field
Surrounds a magnet
Exerts a force on other magnets and magnetic objects (iron, cobalt and nickel)
Poles
Regions where magnetic force is strongest
North and South poles
Like poles repel and opposite poles attract

4. Compasses & Earth
Compass needle is a small bar magnet which rotates because of force of magnetic field
Earth is a big magnet with a field
Earth’s magnetic poles: south magnetic pole is near its geographic north pole, so compass “points” north
Poles can swap over time; 150 times in 70myrs
Magnetic materials: iron, cobalt and nickel
Electrons have magnetic properties
Large groups of atoms align with poles = domains

6. If domains lined up = strong magnet
If domains random = no magnetism
Temporary magnet: can make items that have magnetic material in them magnetic by stroking it against a permanent magnet  line up domains but they can return to randomness!
Permanent magnet: maintains alignment
Can demagnetize by dropping or heating!!
If you break a magnet in half, get 2 smaller magnets!

7. Electric Current Moving charges produce magnetic fields
Electromagnets:
Temporary magnet made by wrapping a wire coil carrying a current around an iron core
As current flows, magnetic field inside loop is stronger than a straight wire
Solenoid; single wire wrapped into a cylinder
Electrical energy is converted into mechanical energy to do work

8. Electric Motor- changes electric energy into mechanical energy
Galvanometer- devices that use electromagnets to measure electric currents
Electric Motor- changes electric energy into mechanical energy
Generator- uses electromagnetic induction to change mechanical energy to electrical
Examples
Car alternator provides electric energy to operate lights, spark plugs, etc.
Home; electrical energy comes from power plant

9. Currents Direct Current (DC)- flows in one direction, batteries
Alternating Current (AC)- reverses direction of current in a regular pattern