MagnetismBad Week …..Magnetism was known long ago.Lodestone (Mineral)New ConceptSlide 6Where is Magnetism Used??Magnet Demo – Compare to ElectrostaticsResults - MagnetsObservationsMagnetsConsider a Permanent MagnetIntroduce Another Permanent MagnetField of a Permanent MagnetSlide 15Convention For Magnetic FieldsTypical RepresentationExperiments with Magnets ShowCurrent Carrying WireSlide 20Compass and B FieldPlanet EarthInside it all.On the surface it looks like this..Inside: Warmer than FloriduhMuch Warmer than FloriduhFinallyIn BetweenSlide 29This planet is really screwed up!RepeatRowland’s ExperimentA Look at the PhysicsWHAT THE HECK IS THAT???The Lorentz ForceNicer PictureAnother PictureVECTOR CALCULATIONSPracticeUnitsteslas areThe Magnetic Force is Different From the Electric Force.WiresThe Wire in More DetailMagnetic LevitationMagLevSlide 47There was a crooked man who lived in a crooked house that was wired with crooked wiresCrooked Wire (in a plane) in a constant B fieldCase 1Case 2Current LoopThe Loop (From the top)An Application The GalvanometerThe other sidesA CoilDipole Moment DefinitionSlide 58Motion of a charged particle in a magnetic FieldTrajectory of Charged Particles in a Magnetic FieldSlide 61Review of Rotational MotionSlide 63Radius of a Charged Particle Orbit in a Magnetic FieldCyclotron FrequencyMore Circular Type Motion in a Magnetic FieldSlide 67Mass SpectrometerSlide 69An ExampleProblem ContinuedSlide 72Slide 73MagnetismMagnetism11MagnetismMagnetismA Whole New TopicA Whole New TopicMagnetismMagnetism22Bad Week …..Bad Week …..Examination #2 on FridayExamination #2 on FridayDon’t miss the WebAssign on RCDon’t miss the WebAssign on RC•RC will not be on the exam (you’re welcome!)RC will not be on the exam (you’re welcome!)Problem session on Wednesday Morning – Problem session on Wednesday Morning – 7:30 AM – Rm 306 – for 7:30 AM – Rm 306 – for BOTHBOTH sections. sections.Spring Break Cancelled.Spring Break Cancelled.Today we start on a new topic MAGNETISM.Today we start on a new topic MAGNETISM.Check the two files on the website Check the two files on the website concerning vector products. concerning vector products. •They may be helpful in this topic.They may be helpful in this topic.MagnetismMagnetism33Magnetism was known Magnetism was known long ago.long ago.Magnetism 4Lodestone (Mineral)•Lodestones attracted iron filings.•Lodestones seemed to attract each other.•Lodestone is a natural magnet.Magnetism 5New ConceptThe Magnetic Field–We give it the symbol B.–A compass will line up with it.–It has Magnitude and direction so it is a VECTOR.•There are some similarities with the Electric Field but also some significant differences.Magnetism 6Magnetism•Refrigerators are attracted to magnets!Magnetism 7Where is Magnetism Used??Where is Magnetism Used??•Motors•Navigation – Compass•Magnetic Tapes–Music, Data•Television–Beam deflection Coil•Magnetic Resonance Imaging•High Energy Physics ResearchMagnetism 8Magnet Demo – Compare to ElectrostaticsNSPivotMagnetWhat Happens??Magnetism 9Results - Magnets•Like Poles Repel•Opposite Poles Attract•Magnetic Poles are only found in pairs.–No magnetic monopoles have ever been observed.Shaded End is NORTH PoleShaded End of a compass pointsto the NORTH.S NMagnetism 10Observations•Bring a magnet to an electrically charged object and the observed attraction will be a result of charge induction or polarization.•Magnetic poles do not interact with stationary electric charges.•Bring a magnet near some metals (Co, Fe, Ni …) and it will be attracted to the magnet.–The metal will be attracted to both the N and S poles independently.–Some metals are not attracted at all. (Al, Cu, Ag, Au)–Wood is NOT attracted to a magnet.–Neither is water.•A magnet will force a compass needle to align with it. (No big Surprise.)Magnetism 11Magnets Cutting a bar magnet in half produces TWO bar magnets, each with N and S poles.Magnetic FieldMagnetism 12 Consider a Permanent MagnetN SBThe magnetic Field B goes from North to South.Magnetism 13Introduce Another Permanent MagnetN SBNSThe bar magnet (a magnetic dipole) wants to align with the B-field.pivotMagnetism 14The south pole of the small bar magnet is attracted towards the north pole of the big magnet. The North pole of the small magnet is repelled by the north pole of the large magnet. The South pole pf the large magnet creates a smaller force on the small magnet than does the North pole. DISTANCE effect.The field attracts and exerts a torque on the small magnet.Field of a Permanent MagnetN SBNSMagnetism 15Field of a Permanent MagnetN SBN SThe bar magnet (a magnetic dipole) wants to align with the B-field.Magnetism 16Convention For Magnetic Fields X Field INTO Paper Field OUT of Paper BMagnetism 17Typical RepresentationMagnetism 18Experiments with Magnets Show•Current carrying wire produces a circular magnetic field around it.•Force (actually torque) on a Compass Needle (or magnet) increases with current.Magnetism 19Current Carrying WireCurrent intothe page.BRight hand Rule-Thumb in direction of the currentFingers curl in the direction of BMagnetism 20Current Carrying WireCurrent Carrying Wire•B field is created at ALL POINTS in space surrounding the wire.•The B field has magnitude and direction.•Force on a magnet increases with the current.•Force is found to vary as ~(1/d) from the wire.Magnetism 21Compass and B Field•Observations–North Pole of magnets tend to move toward the direction of B while S pole goes the other way.–Field exerts a TORQUE on a compass needle.–Compass needle is a magnetic dipole.–North Pole of compass points toward the NORTH.MagnetismMagnetism2222Planet EarthPlanet EarthMagnetismMagnetism2323Inside it all.Inside it all.8000MilesMagnetismMagnetism2424On the surface it looks like this..On the surface it looks like this..MagnetismMagnetism2525Inside: Warmer than Inside: Warmer than FloriduhFloriduhMagnetismMagnetism2626Much Warmer than FloriduhMuch Warmer than FloriduhMagnetismMagnetism2727FinallyFinallyMagnetismMagnetism2828In BetweenIn BetweenThe molten iron core exists in a magnetic The molten iron core exists in a magnetic field that had been created from other field that had been created from other sources (sun…).sources (sun…).The fluid is rotating in this