1. Magnetism Richard Wrangpetch

2. Warm up: Compass Activity What is the purpose of a compass? How does it work?

3. Magnetism Some objects can be magnetized Iron, placed near a permanent magnet, will become a magnet itself Remove the iron from the proximity of the magnet, or hammer it, it will lose its magnetism (soft magnet) Cobalt and nickel tend to retain magnetism (hard magnet) despite proximity to a permanent magnet or being struck

4. Magnetism On a magnet, each end is referred to as a pole. As you know, these poles attract opposite, and repel like. We call one end “north” and the other “south” The north pole of a magnet is a north (cardinal direction seeking pole, the south seeks cardinal south

5. Uncharged materials can become magnetized Once magnetized, an object exerts a magnetic field Magnetic fields are polar (North and South poles) Earth acts as one large magnet Birds use these field during Migration/ dogs while pooping

6. Groups of atoms with aligned electron spin are known as domains. Magnetism is induced by aligning areas called domains within a magnetic field.

7. Magnetic Domains Groups of atoms with aligned electron spin are known as domains. In the absence of a strong magnetic field, or after a previously magnetized object has been struck, domains are chaotic and disorganized. Soft magnets return to a random arrangement more quickly than do soft magnets Hard magnets retain domain alignment long after the removal of a magnetized source.

8. Induced Magnetism Some metals can be turned into temporary magnets by bringing them close to a magnet

9. A compass is a suspended magnet: its north pole is attracted to a magnetic south pole.

10. Magnetic field lines Activity MAGNETIC FIELD A magnetic field surrounds every magnet and is also produced by a charged particle in motion relative to some reference point.

11. Magnetic field lines Activity

12. Magnetism When an electric current runs through a wire a magnetic field is created If we run a wire with a strong current that is perpendicular (90 degree angle) to the plane, we can observe the magnetic field lines using iron filings

13. The magnetic field created around a wire has a direction. To determine this direction, we use the right hand rule. With hand wrapped around wire, thumb points in the direction of current. Fingers show the direction of the magnetic field. Conventional current (positive to negative) applies.

14. Magnetism The right hand rule also applies to a loop. Note that a loop’s magnetic field is similar to that of a bar magnet

15. Magnetism A solenoid is a long, helically wound coil of insulated wire. In essence, it is a series of loops that creates a powerful magnetic field.

16. Magnetism So why are some objects able to be magnetized (iron, cobalt, or nickel containing), while others are not (glass, plastic, organic)? Its all about the electron. Remember that electrons spin, like a top. In complex molecules, pairs of electrons spinning in opposite directions cancel each other out.

17. Magnetism In a metal, electrons have a great deal of freedom. In iron, nickel, and cobalt, electron spin does not cancel each other out. These substances are said to be ferromagnetic. In ferromagnetic materials, strong coupling occurs between neighboring atoms to form large groups of atoms whose net spins are aligned.

18. Ferrofluid https://www.youtube.com/watc h?v=PvtUt02zVAs