Lecture 24 - Magnetic materials

Lecture 24 - Magnetic materials - Back to current loops For...

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1 Lecture 24 Magnetic materials Magnetic materials. Back to current loops For a current loop of area A and current I : IA μ = G G z R G () μμ == ++ 2 00 3/2 3/2 22 2 2 B Rz ∼± 3 for Bz For large distances, Magnetic field produced by a current loop: Magnetic field by a dipole field lines for a current loop field lines for a magnet Somehow, it must be the same thing… DEMO: B field lines of a magnet Dipole-dipole interaction = G = Parallel currents: N S N-S: attraction N S = DEMO: Magnets attraction N S N S: attraction = Antiparallel currents: repulsion N S S N S-S (or N-N): repulsion Somehow, loops and magnets must be the same thing…
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2 Magnetism in materials Orbits of 1. Currents at atomic level within bulk matter Where are the currents in magnets?!? electrons about nuclei 2. Intrinsic “spin” of electrons (most important effect) In general, these atomic magnetic dipoles point in random direction, so material does not produce a net magnetic field. Magnetization Let be the total magnetic moment of the material in a sample with volume V .
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This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 24 - Magnetic materials - Back to current loops For...

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