1. 24-1 Magnets: permanent & temporary

2. General Properties
Hang the bar magnet from the thread, observe what happens…….
Positions itself in the N-S directions - magnet is polarized
Has two ends – North seeking and South seeking
A compass is a small magnet free to turn

3. General Properties
Observe what happens when another magnet is brought to the different sides of the magnet
The two N poles repel as the two S poles
N and S pole attract
All magnets have two singular poles or Monopoles
When magnet is broken in half, magnets orient themselves in a N & S direction

4. Simple Magnets
Touch a magnet to a piece of metal (iron nail) and try to pick up paper clips along the nail
Nail has become polarized (temporarily)
Either end of a magnet will attach to a metal

5. Permanent Magnets Made of ALNICO V
Aluminum – Nickel – Cobalt – and other rare earth elements

6. Magnetic Field Magnets are a long range force
Invisible “lines” surround the magnet showing the magnetic field
Number of magnetic lines is magnetic flux
# of lines is proportional to strength
Concentrated at the poles
Lines flow out of the N and into the S in closed loops

7. Electromagnetism
Electric currents through a wire create a magnetic field perpendicular to the current
First Right hand Rule
Direction of current  Thumb
Direction of magnetic field  Fingers coiled

8. Magnetic Field near a Coil
A wire looped several times to form a coil and a current is allowed to flow, the field around all the loops is always in the same direction
Solenoid
Long coil wire consisting of many loops

9. Magnetic Field near a Coil
When there is an electric current in a coil wire, the field acts like a permanent magnet
Electromagnet
Strength of the field is proportional to the current in the coil
Increasing the number of loops increases the strength

10. Electromagnet
Strength can also be increased by adding an iron rod inside the coil
Field will magnetize the rod
Second right hand rule
Direction of magnetic field produced by an electromagnet
Curl fingers around loops in the direction of the current
Thumb is the North pole of the magnet

11. Magnetic Domains
Each electron in an atom acts like a tiny electromagnet  generally in three magnetic elements
Iron, nickel, & cobalt
Groups of electrons are known as domains
Shown as arrows that are random in direction
Once a magnetic field is present, arrows aligned and become magnetized

12. Physics and Earth Science
Iron is found in the oceanic rocks as basalt
As ocean floor spreads, magma is released
Overtime, earth’s magnetic field has changed