Sources of the Magnetic Field...

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Sources of the Magnetic Field...

• ...moving charges, currents and other effects

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A Moving Point Charge

• Since a moving charge is effected by a magnetic
  field - is there a symmetry here? Just how
  does this interaction take place?
• Answer A moving charge establishes or creates a
  magnetic field!

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The Biot-Savart Law

• Currents produce magnetic fields

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Examples using the Biot-Savart Law(read
33.4-33.7 carefully!)

• The Current Loop
• The Solenoid
• Long Conducting Wire

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Examples using the Biot-Savart Law(read Example
33.5 carefully!)

• The Current Loop using Biot-Savart

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Forces on Conducting Wires

• Since a conducting wire creates a magnetic field,
  two conducting wires should interact...
• This leads to a precise definition of the Ampere

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Gauss Law for Magnetism

• The net magnetic flux through any closed surface
  is always zero...

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Amperes Circuital Law...

• When the current I is constantJust like
  Gauss Law, this is really only useful as a
  calculating method when there is a high degree of
  symmetry

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Magnetization in Matter

• Amperes Circulation Model explains magnetism as
  the result of amperian current which seems to
  anticipate the idea of magnetic dipole moments
  and leads to a definition of magnetization

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Magnetization in Matter

• In a magnetic field B the presence of a material
  affects the magnetic field in a manner described
  by

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Flavours of Magnetization

• Paramagnetic are materials for which a small
  increase in B (positive susceptibilty) occurs
  when placed in an external field
• Diamagnetic materials that have negative
  susceptibilty (Bisthmus for example)
• Ferromagnetic large (HUGE) suscpetibility

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More on Ferromagnetism...

• Domain Theory simulation of domains in a 10nm
  NiFe film undergoing rapid magnetization
  reversal
• Hysterisis and Soft and Hard ferromagnets
• Geological Field Reversal paleomagnetism