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MAGNETISM

Chapter 21. MAGNETISM. Magnetic Levitation Train ( Shanghai) Maglev uses powerful magnets to hold a train a few millimeters from the track and propel it with little noise or vibration. Earth’s Magnetic Field. Earth’s Magnetic Field. Properties of Magnets. 1. North and South Poles.

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MAGNETISM

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  1. Chapter 21 MAGNETISM

  2. Magnetic Levitation Train (Shanghai) Maglev uses powerful magnets to hold a train a few millimeters from the track and propel it with little noise or vibration.

  3. Earth’s Magnetic Field

  4. Earth’s Magnetic Field

  5. Properties of Magnets 1. North and South Poles

  6. Properties of Magnets 2. Law of magnetic poles Unlike poles attract

  7. Properties of Magnets 2. Law of magnetic poles Like poles repel

  8. LAWS OF ATTRACTION LIKE POLES REPEL UNLIKE POLES ATTRACT N S S N N S N S

  9. LAWS OF ATTRACTION LIKE POLES REPEL

  10. Properties of Magnets Testing a magnet 1. Bring one end of an unknown object to a suspended magnet. 2. If repulsion occurs, then the unknown object is a magnet since repulsion occurs between like poles.

  11. Magnetic Induction Magnetic Induction is the process of inducing magnetism in an unmagnetised ferromagnetic material without any contact with the magnet.

  12. Induced Magnetism • Making of magnetic materials (e.g. steel and Iron) into Magnets • Inducing magnetism in an ordinary piece of magnetic material • Induced magnetism is a temporary process

  13. Induced Magnetism The two iron nails become induced magnets and show a repulsion between the far ends

  14. Induced Magnetism Repulsion between the two iron nails increases as a bar magnet is brought towards the nails

  15. MAGNETIC POLES • A magnet is a dipole (two pole) • There is no monopole (single pole)

  16. MAGNETIC POLES • A magnet is a dipole (two pole) • There is no monopole (single pole)

  17. Magnetic Materials • Most materials are NOT magnetic • Naturally occurring magnetic materials are called FERROMAGNETIC (Iron-Like) • FERROMAGNETIC MATERIALS are • Iron, Steel • Cobalt • Nickel • Alloys of above metals

  18. Magnetic Domains These are small regions in a FERROMAGNETIC Material where all the magnetic fields of the atoms are aligned

  19. Magnetization If the domains are aligned, the material is polarized and becomes magnetized S N

  20. Magnetization Unmagnetised bar A magnetised bar

  21. Methods of Magnetisation & Demagnetisation Making a magnet by stroking Single Touch Divided Touch

  22. Methods of Magnetisation & Demagnetisation Making a magnet by stroking Single Touch

  23. Methods of Magnetisation & Demagnetisation Making a magnet by stroking Single Touch

  24. Methods of Magnetisation & Demagnetisation Making a magnet by electrically

  25. Methods of Magnetisation & Demagnetisation Making a magnet by electrically

  26. Methods of Magnetisation & Demagnetisation Polarity of the magnet determined by: (i) Right-Hand Grip Rule • Polarity of the • magnetised specimen

  27. Methods of Magnetisation & Demagnetisation Methods of demagnetising magnets • Heating • - misalignment of “tiny” magnets, increase vibration • of atoms • 2. Hammering

  28. Methods of Magnetisation & Demagnetisation Methods of demagnetising magnets 3. Alternating Current

  29. Methods of Magnetisation & Demagnetisation Methods of demagnetising magnets 3. Alternating Current

  30. Magnetic Fields & the Plotting Compass A magnetic field is the region where a magnetic force is exerted on any magnetic object placed within the influence of the field.

  31. Magnetic Fields & the Plotting Compass

  32. Magnetic Fields & the Plotting Compass

  33. Magnetic Fields & the Plotting Compass

  34. Magnetic Fields & the Plotting Compass X: neutral point

  35. Magnetic Fields & the Plotting Compass X: neutral point

  36. Magnetic Fields & the Plotting Compass

  37. Earth’s Magnetic Field

  38. Earth’s Magnetic Field

  39. Magnetic Properties ofIron & Steel Question: Comment on the magnetic properties of Iron & Steel

  40. Magnetic Properties ofIron & Steel

  41. Magnetic Properties ofIron & Steel

  42. Magnetic Field Near A Wire

  43. Magnetic Field Near A Wire

  44. Magnetic Field Near A Wire Right-Hand Grip Rule

  45. Magnetic Field Near A Wire

  46. Magnetic Field Near A Wire

  47. Magnetic Field Near A Wire

  48. Magnetic Field Near A Wire Iron Filings around a current-carrying wire

  49. Magnetic Field Near A Wire

  50. Magnetic Field Near A Loop Iron Filings around a current-carrying loop

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