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Sources of the Magnetic Field...

Sources of the Magnetic Field. ...moving charges, currents and other effects. 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?

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Sources of the Magnetic Field...

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  1. Sources of the Magnetic Field... ...moving charges, currents and other effects

  2. 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!

  3. The Biot-Savart Law • Currents produce magnetic fields:

  4. Examples using the Biot-Savart Law…(read 29-1,2 very carefully!) • The Current Loop • The Solenoid • Long Conducting Wire

  5. 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

  6. Gauss’ Law for Magnetism • The net magnetic flux through any closed surface is always zero...

  7. Ampere’s Circuital Law... • When the current I is constant…Just like Gauss’ Law, this is really only useful as a calculating method when there is a high degree of symmetry

  8. Magnetization in Matter • Ampere’s 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:

  9. Magnetization in Matter • In a magnetic field B the presence of a material affects the magnetic field in a manner described by:

  10. 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

  11. 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

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