1. Magnetism 3/28/14

2. Bellwork ► Where is the Earth’s north magnetic pole located? *Turn in the lab. ► Near the south geographic pole or Antarctica.

3. BW Aside: Compass History ► Invented around 200 B.C. in China ► Used loadstones to align with the Earth’s Magnetic field

4. Today’s Agenda ► Bellwork ► Magnetism Pre-Quiz ► Notes on Magnetism ► Homework: Magnetic Fields

5. Due Dates ► Tues. (4/1): Rough draft of the Science Fiction Story due ► Wed. (4/2): Magnetic Fields H.W. due ► Tues. (4/8): Final draft of the Science Fiction Story due

6. Pre-Quiz ► 1) Magnets can attract and repel certain materials. ► 2) Magnets repel non metals. ► 3) Magnets will attract / repel all metals. ► 4) Moving electrons are the source of magnetism. ► 5) The larger the magnet the stronger the magnetic force.

7. Pre-Quiz ► 6) Magnetic fields are three dimensional. ► 7) Only magnets have magnetic fields. ► 8) A magnet can have only one magnetic pole. ► 9) Magnetism will be blocked by materials that are insulators. ► 10) The magnetic north pole is located near the geographical North Pole.

8. Pre-Quiz Answers ► 1) Magnets can attract and repel certain materials. ► TRUE ► 2) Magnets repel non metals. ► FALSE ► 3) Magnets will attract / repel all metals. ► FALSE

9. Pre-Quiz Answers ► 4) Moving electrons are the source of magnetism. ► TRUE ► 5) The larger the magnet the stronger the magnetic force. ► FALSE ► 6) Magnetic fields are three dimensional. ► TRUE

10. Pre-Quiz Answers ► 7) Only magnets have magnetic fields. ► FALSE ► 8) A magnet can have only one magnetic pole. ► FALSE

11. Pre-Quiz Answers ► 9) Magnetism will be blocked by materials that are insulators. ► FALSE ► 10) The magnetic north pole is located near the geographical North Pole. ► FALSE

12. Gravity vs. Electromagnetic Force ► The Electromagnetic force is 10 20 time stronger then gravity!

13. Magnetism ► Opposite poles attract ► Like poles repel ► Magnetic poles ALWAYS come in pairs ► Magnetic fields are produced by the motion of an electric charge

14. Magnetic Fields

15. Magnetic Field Lines ► Start at the north pole and end on the south pole

16. Atomic Level of Magnetism (source of magnetism) ► Electrons spin about their axis ► Electrons orbit around the nucleus

18. Magnetic Materials ► Iron ► Nickel ► Cobalt - These are the only three elements that the electron’s spin and orbit align with each other - Other elements’ spins and orbits cancel out

19. Magnetic Domains ► Magnetic Domain: A microscopic cluster of atoms with their magnetic fields aligned ► Heating or dropping a magnet will weaken it (causing the domains to become unaligned)

21. Breaking a Magnet ► If you break a magnet in half you end up with two smaller magnets ► Even all the way down to the atomic level

23. Right Hand Rule ► Right-Hand Rule: determines the direction of the magnetic field around a current-carrying wire ► Right-Hand Rule: determines the direction of the magnetic field around a current-carrying wire

24. Right Hand Rule ► Point your thumb in the direction of the current (I) ► The curl of your fingers shows the direction of the magnetic field (B)

25. Right Hand Rule Symbols Vector arrows and loops A dot “●” means out of the page An ex “X” means into the page Label the symbols I = current B = magnetic field Dots “●” and exes “X” must be in pairs!