1. How can we explain magnetism? Do Now: Why does a compass point north?

2. Magnets 2 poles: North and south SNSN Cannot isolate a pole SN S N

3. Like Poles ► 2 like poles experience a force of repulsion S NN S S N Donut magnet Demo

4. Unlike Poles ► 2 unlike signs experience a force of attraction N S

5. Compass ► Attracted to magnetic south pole S N Therefore this is magnetic north

6. Earth ► Earth is a huge magnet ► So why does the north pole of a compass point to the north pole of the Earth? Magnetic South Pole Magnetic North Pole Geographic

7. Ferromagnetic substances ► Substances that are naturally magnetic  Iron  Nickel  Cobalt

8. How do things become magnetized? Magnetism is caused by the spin of the unpaired electrons. When they spin in the same direction, they cause microscopic magnets called domains. If all the domains are aligned, a magnet is formed.

9. Temporary Magnet ► Created when a ferromagnetic substance is brought into close proximity to an easily magnetized substance (domains temporarily align) ► Occurs when the electrons spin in the same direction

10. Magnetic Field Lines If compasses are place around a magnet, we can visualize the field around the magnet. NS

11. Magnetic Fields ► Field lines are called lines of flux ► Defined as north to south ► Strongest where the lines of flux are closest

12. Magnetic Flux Magnetic flux describes the lines of a magnetic field around a magnetized object. Each magnetic flux line is equal to 1 Weber (Wb). The strength of the field, or magnetic flux density (B) is measured in Wb/m 2, or Tesla (T).

16. S S

18. If field lines point in the same direction, NS NS They repel. If field lines point in the opposite direction, NS NS They attract.

20. ► Magnetic fields are created by moving charges  Any time a charge moves (current) a magnetic field is created ► Outer Core of Earth is liquid iron and nickel  Ferromagnetic substances that have a charge and are moving So why is the Earth magnetic?

21. Magnetic Force Created when a moving charge passes through a magnetic fieldCreated when a moving charge passes through a magnetic field Reason: Charge has a magnetic field and it interacts with another magnetic fieldReason: Charge has a magnetic field and it interacts with another magnetic field Greatest force is when the charge passes perpendicular to the fieldGreatest force is when the charge passes perpendicular to the field

22. Sidenote: DeGaussing ► Planes, ships move through the Earth’s magnetic field. ► Just as moving a charge through a magnetic field creates a force, forcing an object to move through a magnetic field creates electricity ► This needs to be taken into account or else navigational equipment gets jacked up

23. Which produces the greatest force? e-e- B (magnetic lines of flux e-e- e-e-

24. Gamma Rays ► Moving charges through space ► Enter Earth’s magnetic field ► Magnetic force is created ► Gamma Rays get deflected ► The Earth is safe ► http://www.youtube.com/watch?v=0JYkR17 Ud5Q