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MAGNETISM

MAGNETISM. The Earth. Earth is a giant magnet. Geographic Poles North and South. Magnetic Poles North and South. Magnetic Declination. Inclinometer. An example of an inclinometer showing the Earth’s magnetic inclination. Compass Points. The direction of compass points in United States.

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MAGNETISM

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  1. MAGNETISM

  2. The Earth Earth is a giant magnet. Geographic Poles North and South Magnetic Poles North and South

  3. Magnetic Declination

  4. Inclinometer An example of an inclinometer showing the Earth’s magnetic inclination

  5. Compass Points The direction of compass points in United States

  6. Types of Magnets BAR LOADSTONE U COIL ALNICO

  7. Natural Magnet Material is Magnetite or Iron Oxide (Fe2 03)

  8. Magnets A very strong magnet can be made with a coil of wire and the flow of an electric current.

  9. Alnico An extremely strong Alnico permanent magnet with keeper

  10. Theory of Magnetism Molecular and Electron Theories

  11. Creating Magnets Methods used to create a magnet • The picture shows that a screwdriver does not pick up paper clips.

  12. Creating Magnets Stroking using a permanent magnet • However, after stroking the screwdriver with a magnet, the blade itself becomes magnetic and attracts the paper clips.

  13. Flux • Magnetic lines of force • Strongest at the poles

  14. Removing Magnetism Heat is one way to remove magnetism.

  15. Laws of Magnets Poles attract or repel

  16. Like Poles Repel

  17. Laws of magnets shown by flux lines Unlike poles attract Like poles repel

  18. Stray Lines of Force Controlling stray lines using a keeper

  19. Magnetic Lines of Force Magnetism will pass through any material • Notice how the materials are affected • Soft iron is a material that distorts flux

  20. Electromagnetism

  21. Electromagnets A 30-foot diameter electromagnet used in research for a superconductor A large electromagnetused to lift scrap metal

  22. Electromagnets The source of electromagnetism is electricity (current) flowing through a coil of wire.

  23. Electromagnets A coil of wire can be made into a magnet by passing an electric current through it. Without electricity, there is no magnetic force Electric current applied to a coil creates a magnetic field

  24. Electromagnetic Strength How can an electromagnet be made stronger? Increase the number of coils. Increase the electric current flowing through the coil. Add an iron core in the center of the coil.

  25. Electromagnetic Strength

  26. The left hand rule to determine North Pole NORTH POLE SOUTH POLE

  27. Making a Magnet An example of a very strong magnet

  28. The magnet is strong enough to lift this 50 pound engine cylinder head. Making a Magnet The coil of wire has been attached to a 12 volt DC power source making an extremely strong magnet.

  29. Saturation Knee Saturation Saturation of a magnetic field occurs when an increase of electric current flow does not increase the strength of the magnetic field as shown by the graph. The knee of the curve is the point that saturation occurs. Y Y- Axis Increasing Magnetic Force X X- Axis Increasing Electric Current

  30. MAGNETIC COIL LOSSES • Copper losses - resistance of copper coils. • Hysteresis - magnetic flux inducing a current in the core. • Eddy currents - magnetic polarity of the iron core is rapidly changed by an AC current causing friction and heat between the molecules

  31. ELECTROMAGNETIC DEVICES

  32. Electromagnetic Devices

  33. Electromagnetic Devices

  34. MAGNETIC TERMS • Flux - Invisible lines of force. • Poles - North and South where force is strongest. • Permeability – The ability of a material to conduct lines of force. • Residual Magnetism – The ability of a material to hold its magnetism for a long time.

  35. MAGNETIC TERMS • Ferromagnetic Material – A material easy to magnetize. (i.e., Iron Steel, Cobalt, Perm-alloy, and Alnico) • Paramagnetic Material- A material that can be slightly magnetized. • Diamagnetic Material – A material that is very difficult to magnetize. • Magnetic Laws – Simply stated: Like poles repel and unlike poles attract.

  36. Review • What are the poles of a magnet? • Name the magnetic lines of force. • List five types of magnets and their two families. • List the laws of magnets. • Explain two methods for making a magnet.

  37. Review • Explain two theories of magnetism. • Name five different types of devices that are associated with electromagnetism? • List three magnetic and three nonmagnetic materials. • What will remove magnetic lines of force?

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