O slideshow foi denunciado.
Utilizamos seu perfil e dados de atividades no LinkedIn para personalizar e exibir anúncios mais relevantes. Altere suas preferências de anúncios quando desejar.

Magnetism

16.989 visualizações

Publicada em

Publicada em: Educação, Tecnologia, Negócios
  • Entre para ver os comentários

Magnetism

  1. 1. Magnetism
  2. 2. Magnets <ul><li>A magnet is any material that produces a magnetic force (push or pull) on a magnetic material (such as iron) </li></ul><ul><ul><li>closely related to electricity, but different </li></ul></ul><ul><ul><ul><li>Where there is electricity, there's a magnetic field </li></ul></ul></ul><ul><ul><ul><li>Where there's magnetic field, electricity can be created </li></ul></ul></ul>
  3. 3. Magnetic Poles <ul><li>Every magnet has two poles </li></ul><ul><ul><li>North & South </li></ul></ul><ul><ul><ul><li>same poles repel </li></ul></ul></ul><ul><ul><ul><li>opposites attract </li></ul></ul></ul>
  4. 4. Magnetic Fields <ul><li>Lines show areas of force exerted in a region around a magnet </li></ul><ul><ul><li>closer lines show greater force </li></ul></ul><ul><ul><li>force is strongest near the magnet </li></ul></ul><ul><li>Force originates from N pole and moves towards S pole </li></ul>
  5. 5. Magnet Interactions <ul><li>Like poles repel </li></ul><ul><ul><li>North repels North </li></ul></ul><ul><ul><li>South repels South </li></ul></ul><ul><li>Opposite poles attract </li></ul>
  6. 6. Magnetic Domains <ul><li>The spin of electrons create tiny magnetic regions called domains </li></ul><ul><ul><li>In some atoms, these domains cancel out </li></ul></ul><ul><ul><li>In magnets, domains are all lined up in same direction </li></ul></ul><ul><li>Whenever all electrons spin in the same direction, a magnetic field is produced </li></ul>
  7. 7. <ul><li>Domains stay aligned within the magnet </li></ul><ul><ul><li>dipoles present in each new piece </li></ul></ul>What would happen to the poles if we cut this magnet in half?
  8. 8. Magnetic Materials <ul><li>Not all metals are magnetic </li></ul><ul><ul><li>3 Are naturally magnetic ( ferromagnetic ) </li></ul></ul><ul><ul><ul><li>Iron </li></ul></ul></ul><ul><ul><ul><li>Nickel </li></ul></ul></ul><ul><ul><ul><li>Cobalt </li></ul></ul></ul><ul><li>Aluminum is NOT magnetic </li></ul><ul><li>Some Lanthanides form strong magnets </li></ul><ul><ul><li>Rare Earth magnets </li></ul></ul><ul><ul><li>Neodymium & Samarium </li></ul></ul><ul><ul><li>Gadolinium is magnetic only at low temperatures </li></ul></ul><ul><ul><ul><li>Must be cooled to be magnetic </li></ul></ul></ul><ul><ul><ul><li>Used in MRIs (Magnetic Resonance Imaging) </li></ul></ul></ul>
  9. 9. Types of Magnets Alnico Magnets Flexible Magnets Ceramic Magnets Neodymium Rare Earth Magnets: (very strong) Samarium Cobalt (SmCo)
  10. 10. Magnetite <ul><li>Lodestone is magnetized magnetite </li></ul><ul><ul><li>means &quot;leading stone&quot; </li></ul></ul><ul><ul><li>used in early compasses </li></ul></ul><ul><ul><li>possibly made by lightning </li></ul></ul><ul><li>Naturally magnetic igneous rock </li></ul><ul><ul><li>found on black sand beaches and deserts </li></ul></ul><ul><ul><li>Largest US deposit in NY (Adirondacks) </li></ul></ul>
  11. 11. Cow Magnets <ul><li>Fed to young cows to prevent &quot;hardware disease&quot; </li></ul>Alnico Cow Magnets
  12. 12. Iron In Our Food <ul><li>Iron-fortified </li></ul><ul><ul><li>Cereal </li></ul></ul><ul><ul><li>Rice </li></ul></ul><ul><ul><li>Baby food </li></ul></ul><ul><li>Can extract from food with a strong magnet </li></ul><ul><ul><li>Neodymium </li></ul></ul>
  13. 13. Permanent Magnets <ul><li>Field can be lost or removed </li></ul><ul><ul><li>Heating to the Curie Point </li></ul></ul><ul><ul><li>Sending an Electric Current through </li></ul></ul><ul><ul><ul><li>Degaussing </li></ul></ul></ul><ul><ul><ul><li>Magnetic storage media erased </li></ul></ul></ul><ul><ul><li>Banging It </li></ul></ul><ul><ul><ul><li>dislodges aligned domains </li></ul></ul></ul><ul><li>Electron spins (domains) are aligned </li></ul><ul><li>Retains its own magnetic field </li></ul><ul><ul><ul><li>Examples: Refrigerator Magnets, Bar Magnets, Lodestone, Horseshoe Magnets, Hematite, etc… </li></ul></ul></ul>622 Iron Oxide (Fe 2 O 3 ) 358 Nickel (Ni) 1130 Cobalt (Co) 770 Iron (Fe) Curie temp °C Substance
  14. 14. Temporary Magnets <ul><li>Domains temporarily line up </li></ul><ul><li>Will keep magnetic field only until tampered with </li></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Paperclips, scissors, staples, thumb tacks, pins, screwdrivers, refrigerator door, car door locks, etc… </li></ul></ul></ul><ul><ul><ul><li>Anything that is magnetic, but will not keep its field </li></ul></ul></ul>
  15. 15. Making a Temporary Magnet <ul><li>Magnetic Induction </li></ul><ul><ul><li>domains are aligned by touching or bringing it near a magnet </li></ul></ul><ul><ul><li>only in some materials </li></ul></ul><ul><li>Strength of magnet determines: </li></ul><ul><ul><li>strength of induced field </li></ul></ul><ul><ul><li>how long induced magnetism lasts </li></ul></ul><ul><li>Object loses its magnetism once magnet is removed </li></ul><ul><ul><li>Temporary magnets can also be made using electric currents </li></ul></ul>

×