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Magnetism: What you SHOULD know. • What sticks (attracted) to magnets? – Plastic, liquids like water, metals? -Do all metals stick? – No Magnets are picky – iron containing materials (cobalt and nickel too) – But plastics and liquids with iron in them are magnetic too – And what are magnets or permanent magnets used to be iron containing but now exotic • Magnets interacting with other magnets – Can attract or repel! – They have POLES North and South -like poles repel, opposite poles attract – All magnets have a north and south pole, break a magnet and the pieces have north an south poles too! – Compass has magnet at the end of a needle and it is attracted to other magnets and the Earth is one BIG magnet. • Magnetic Patterns or Fields – Lines of Force (called field lines) trace out the direction a small magnet would point – Can use iron filings to show these Lines of Force (field lines) –they start and end on the magnet! – The Earth’s north pole is actually a magnetic South pole!! – Magnetism goes through (penetrates) non-magnetic material. • Electricity makes a magnetic field – Many loops (a coil) around a nail can make a strong electro-magnet – Information (music) can be stored using electricity to make permanent magnets on a tape • Magnets can make electricity – Move a magnet in a coil and current is generated – Generator motion makes electricity/ Motor electricity makes motion Magnetism: What you DON’T know. – fun with strong magnets • Actually magnets can effect more than just iron containing material! • Magnets with all metals – Eddy current – A moving magnet (1) makes a current in a stationary metal, but current makes a magnet (2)! And magnets interact! – Interaction acts to slow (damp) the magnet. • Magnets weakly attract nearly all non-iron containing materials – PARAmagnetism – Always attractive – Oxygen, O2, (even liquid oxygen) is paramagnetic. • Magnets very weakly repel a small number of materials – DIA-magnetism – Always repel and this can make levitation!! – Materials include graphite (aka pencil lead); water (frogs and strawberries too). – The effect is particularly strong in superconductors! – And this can be made to levitate a train!! • Other fun levitation schemes. – Active control – Mechanical constraint Magnetism: What you SHOULD know. (I) • What sticks (attracted) to • Dip the magnet into a magnets? bucket of different –Plastic, liquids like water, objects - What sticks? metals? -Do all metals stick? – Coins, plastic, wood, –No Magnets are picky – iron nails, water, etc. containing materials (cobalt • Show plastic magnets and and nickel too) ferrofluid. –But plastics and liquids with iron in them are magnetic too • Show neat magnets, balls, super strong, refrigerator –And what are magnets or etc. permanent magnets used to be iron containing but now exotic • Show repulsion • Magnets interacting with other attraction. magnets –Can attract or repel! – Break a magnet and –They have POLES North and show they always South -like poles repel, have a north and opposite poles attract south. –All magnets have a north and – Play with a compass. south pole, break a magnet and the pieces have north an south poles too! –Compass has magnet at the end of a needle and it is attracted to other magnets and the Earth is one BIG magnet. Magnetism: What you SHOULD know. (II) • Magnetic Patterns or Fields –Lines of Force trace out the direction a small magnet would point –Can use iron filings to show these Lines of Force –Earth’s north pole is actually a magnetic South pole!! –Magnetism goes through material. • Electricity makes a magnetic field –A coil around a nail can make a strong electromagnet –Music can be stored using electricity to make permanent magnets on a tape • Magnets can make electricity –Move a magnet in a coil and current is generated –Generator motion makes electricity/ Motor electricity makes motion. • Magnetic Patterns or Lines of Force or Fields – Use magnets – Use iron filings – Use 3D demo – Use magnerite • Electricity makes a magnetic field – Field pattern near wire or loop – Show electromagnet • Magnets can make electricity – Move magnet near wire or coil. – Show handcrank generator Magnetism: What you DON’T know. (I) – fun with strong magnets • Actually magnets can effect • Eddy Current more than just iron – Magnetic/ non magnetic ball containing material! bearing down a metal/plastic tube. – Move magnet over a copper plate. • Magnets with all metals – Eddy current –A moving magnet (1) makes a current in a stationary metal, but current makes a magnet (2)! And magnets interact! –Interaction acts to slow (damp) the magnet. • Magnets weakly attract nearly all non-iron containing materials – PARA-magnetism –Always attractive –Oxygen, O2, (even liquid oxygen) is paramagnetic. • Magnets weakly attract PARAmagnetism – Aluminum bar on a string with strong magnets on a turntable – Liquid O2 dripped on strong magnet. Magnetism: What you DON’T know. (I) – fun with strong magnets • Magnets very weakly repel a small number of materials – DIAmagnetism – Always repel and this can make levitation!! – Materials include graphite (aka pencil lead); water (frogs and strawberries too). – The effect is particularly strong in superconductors! – And this can be made to levitate a train!! • Other fun levitation schemes. – Active control – Mechanical constraint • Magnets very weakly DIA-magnetism – Always repel and can levitate – Materials include graphite (aka pencil lead); water (frogs and strawberries too). – The effect is particularly strong in superconductors! – And this can be made to levitate a train!! • Other fun levitation schemes. – Active control – Mechanical constraint Magnetism: What you DON’T know. (I) – fun with strong magnets • Magnets very weakly repel a small number of materials – DIA-magnetism –Always repel and this can make levitation!! –Materials include graphite (aka pencil lead); water (frogs and strawberries too). –The effect is particularly strong in superconductors! –And this can be made to levitate a train!! • Other fun levitation schemes. –Active control –Mechanical constraint • Magnets very weakly DIAmagnetism • Eddy Current – Magnetic/ non magnetic ball bearing down a metal/plastic tube. – Move magnet over a copper plate. • Magnets weakly attract PARAmagnetism – Aluminum bar on a string with strong magnets on a turntable – Liquid O2 dripped on strong magnet.