Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine [e-mail]

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Introduction to Physical ScienceMonday,
Wednesday, ThursdayTom Burbinetomburbine_at_astr
o.umass.edu
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Magnetic Poles

• Like poles repel
• Opposite poles attract
• North pole
• South pole

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Magnetic Force

• 1) Between magnets, it is the attraction of
  unlike magnetic poles and the repulsion of like
  magnetic poles
• 2) Between a magnetic field and moving charge, it
  is the deflecting force due to the motion of the
  charge

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Difference between magnetic poles and electron
charges

• Electric charges can be isolated
• Protons and electrons can exist separately
• Magnetic poles cannot
• North magnetic poles cant exist without south
  poles

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• If you break a magnet in half, each half will act
  as a magnet
• If you break that piece in half, you will then
  have four magnets
• This suggests that the atoms themselves are
  magnets

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Magnetic Field

• The region of magnetic influence around a
  magnetic pole or a moving charged particle
• Field of force

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Motion of electric charges

• Electron spinning
• Electron revolution around the protons

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Electron spinning

• An electron spinning creates a magnetic field
• A pair of electrons spinning in the same
  direction creates a stronger magnet
• A pair of electrons spinning in the opposite
  direction work against each other

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Metals

• Materials such as iron, nickel, and cobalt have
  electrons whose spins do not cancel out
• Iron has four paired electrons
  that can have the same spin

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Magnetic domains

• Clusters of atoms line up with one another

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Permanent Magnet

• Place a piece of iron (or a similarly magnetized
  material) in a strong magnetic field

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• Moving charge produces a magnetic field
• A current of charge produces a magnetic field

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Electromagnetic Induction

• Electric current can be produced in a wire simply
  by moving a magnet into or out of a coil of wire
• A voltage is induced by the relative motion
  between a wire and the magnetic field

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Faradays Law

• The induced voltage of a coil is proportional to
  the number of loops multiplied by the rate at
  which the magnetic field changes within those
  loops

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• More practical to move the coil then move the
  magnet
• Generator has a rotating coil in a stationary
  magnetic field
• Converts mechanical energy into electrical energy

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• http//video.google.com/videoplay?docid3902466783
  636795302

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Any Questions?