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Magnetism Magnetism Presentation Transcript

  • MagnetismSTEM WorkshopDr. Tracey Wheeler
  • What is magnetism?Magnetism is the force of repulsion andattraction between two different substancescaused by the motion of charged particles.
  • The Law of MagneticAttractionO Force (push or pull) ofa magnet is thestrongest at it ends,which are called poles.O North-seeking- pointsto earth’s north poleO South-seeking-pointsto earth’s south pole.O When the two unlikepoles attract and twolike poles repel- law ofmagnetic attraction.
  • Magnetic FieldO Space around the magnetic also acts like amagnet which is a force referred to as amagnetic field.O The direction of the magnetic field is the directionin which the north pole of a compass needlepoints when it is placed in the magnetic field.O Magnetic fields can be represented by magneticfield lines which are imaginary lines that indicatethe direction and strength of the magnetic field.O Magnetic field lines form closed loops and nevercross.
  • Is this a misconception?O A magnetic field is a pattern of lines thatsurround a magnet- Why or Why Not?
  • Force of MagnetismO Magnetism is the result of the spinningmovement of the electrons in the atom.O Atoms of nonmagnetic materials- half ofelectrons spin in one direction, half in theopposite direction- cancels the magneticeffects.O Atoms of magnetic materials- more electronsspin in one direction than the other- makingthe atom a tiny electromagnet.- atoms grouptogether (domains) line up in north and southseeking poles.O When opposite poles of a magnet are broughttogether, the lines of force join up andmagnets pull together.
  • MagnetsO Natural magnet (ex. Lodestone) has many poles.O Ferromagnetic substances-spontaneous magnetismexists in the substance even in the absence of amagnetic field.O Examples-iron, steel, cobalt, nickel, and a few rareelements dysprodium and gadolinium can be madeinto magnetsO Magnets are attracted to metals that contain ferrous,mainly iron and steel.O Artificial magnets can be made from ferromagneticsubstances. Sometimes aluminum when mixed withnickel and cobalt.Lodestone
  • MisconceptionO Are all metalsattracted tomagnets?O Examples?
  • Permanent MagnetsO Permanent magnets are oftenmade from steel- iron-carbonalloy.O Electrons align themselvesand spin in the same directionwhile orbiting their nucleus.This produces a smallmagnetic field. As moreelectrons align themselves, themagnetic field becomesstronger. In the case ofpermanent magnets, electronstend to stay aligned, unlessheated temperature and thencooled.Misconception or Reality?Permanentmagnetics canbe made byplacing themin a strongmagnetic field
  • Magnets losing theirmagnetismO Dropping or strikingthemO 2. heating themO 3. placing the northseeking poles side byside or on top of eachother. The moleculeswill be thrown out ofalignment.
  • Keep magnets strongO Piece of soft iron across thepoles of a U shape magnetO Attach magnets to a metalsurfaceO Store them in pairs withopposite ends attractingseparated by nonmagneticdivider (wood, plastic)O Disk or ring magnets pairswith opposite poles together
  • MisconceptionOLarger magnets arestronger than smallermagnets
  • MaglevO Maglev (magnetic levitation) vehicles aretrains that are lifted, propelled, and guided byfast-moving magnetic fields. Speeds 248 mphor more.O Use linear electric motors built into theguideway to generate a magnetic field thatattracts the vehicle, allowing the train to move