Magnetism What is it and why are “they” saying such nasty things about it? Daryl L Taylor DTFizzix.com Greenwich HS, CT 02/21/2012

Why are we here? We should learn – Where does magnetism come from? – How it relates to electricity? – What does it have to do with real life? – Watch floating fruit?

Electricity & Magnetism Related? So much so, you simply can’t have one without the other. – ‘+’ & ‘-’ relates to ‘N’ & ‘S’ A moving magnet will cause a motion of charges. [Induction DEMO!] (and verse visa…) Magnetic Fields are caused by moving electric charges. [Current-bearing wire DEMO!] [Electromagnet]

Recall Angular Momentum? (Before we get carried away with all this Magnetism nonsense…)

Spinning wheel/Hoberman/ShopVac DEMO thingee? – Why? ‘ L’ must be conserved. You feel a ‘tug’ in the opposing direction. You spin in the opposite direction Magnetic Moment is analogous!

Another vicious Right-Hand Rule…

Most atoms have single electrons or paired electrons that ‘spin’ in opposite directions. This ‘cancels’ any effective magnetic field.

Sorta like a wheel rotating in BOTH directions at once… Helicopter…

However, some – like iron, cobalt, nickel – have paired electrons that spin in the same direction. NOTE: LEFT HND e - … Thus, adding magnetic “strengths”.

Angular Momentum L=I  Magnetic Moment

Ferromagnetic Elements Strongly attracted in magnetic fields – Fe – Ni – Co – Gadolinium (#64) – Dysprosium (#66) – Holmium (#67; strongest of all…)

Paramagnetic Elements Weakly attracted in magnetic fields – Platinum – Al – O

Diamagnetic Elements Weakly repelled by BOTH poles – C – Cu – H 2 O (I know, not an element, but…)

Magnetic Field? Sorta the same as E Fields – Area around an electric charge where another charge feels a force. E=F/Q Mag Field – Area around a magnet where another magnet, paramagnet, or diamagnet feels a force. Math is weirder…

Mini-LAB Mapping a Field 3-D Field DEMO

Mag Field around a wire

Mag Field around a loop

Radius of charge in B Why? Lentz, that’s why!

E vs B Fields

Lorentz Force Law

Ugly RT Hand Rule

Current in B

Mass Spec

Misc Demos Lentz Law Spinny Thingee TV Destruction Lifter Magnet Magnetic Levitation – Biggee & Cutie

Misc Demos Plasma Globe – With Fluorescent Tube! DANGER! Plasma Disc Generator flashlights Incandescent Bulb w/magnet Conservation of L Disc – Volunteer!

MAFF…

Force on electric current in magnetic field… Ex 20-1 p512

MAFF… Force on moving charge in magnetic field… Ex 20-3 p514

MAFF… Example 20-4 p514

MAFF…

Aurora Thingee

Aurora e - levels

Ahh, But!!!! In reality…

N S

Earth’s Magnetic Field?? What science tells us? yrs

Earth’s Magnetic Field?? What science tells us? +10,000 yrs

Earth’s Magnetic Field?? What science tells us? +20,000 yrs

Magnetic File Cabinet DEMO ? Lodestone!

Core #’s Inner Radius = 1200 km Outer Radius = 3470 km T both = 24 hrs Mass inner = 0.02 M earth Mass outer = 0.31M earth – Find Ke rot of core!

5x10 32 J 5x10 32 J Analogies? About the amount of energy the entire Sun emits in 100 seconds. That's a whole lot of energy. five trillion one megaton bombs If it doesn't sound like much, let's convert it to megatons: it's the equivalent energy of five trillion one megaton bombs 5,000,000,000,000 MILLION TONS TNT! going off at once. That is comfortably more than the entire arsenal of the planet. – In fact, it's about 500 million times the explosive energy of every single nuclear weapon* on the Earth. *That we know of…

So, why were we here? We learned – Magnetism is created by moving charges Analogous to Angular Momentum – Conversely, a changing magnetic field creates a current. Electric generators – The earth is the largest magnet around? – Fruit and small animals can levitate?

So, why were we here? We learned – Not all magnetic fields are nice and pretty – Magnetic properties of an object are dictated by it’s domains. – Not everyone knows the $100 answers!