1 / 12

Fields and Waves

Fields and Waves. Lesson 4.6. MAGNETIC MATERIALS. Magnetic Materials. Today’s Lesson:. linkage between H and B fields. M - magnetization. re-visit Ampere’s Law. boundary conditions. permanent magnets. Use simple, linear model. Vast majority of materials. Magnetic Materials.

atignor
Download Presentation

Fields and Waves

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fields and Waves Lesson 4.6 MAGNETIC MATERIALS Darryl Michael/GE CRD

  2. Magnetic Materials Today’s Lesson: • linkage between H and B fields • M - magnetization • re-visit Ampere’s Law • boundary conditions • permanent magnets

  3. Use simple, linear model Vast majority of materials Magnetic Materials Magnetic properties tend to either very strong or very weak • ferromagnets (Fe) and permanent magnets • exhibit strong non-linear effects • demonstrate “memory” or hysterisis effects Recall in electrostatics that most materials have moderate effect: 1 < e < 10

  4. e- I Magnetic Materials In Quantum mechanics, atoms have “spin” In the classical picture: • electron orbits the nucleus • acts like a current loop Usually in most materials, the loops has random orientation - so the net effect is small In ferromagnets, neighboring atoms have spins that are aligned - strong effects

  5. The individual current loops can be thought of as having a dipole moment, Magnetic Dipole Moment

  6. Relationship between & magnetization Sum over all atoms -flux due to all sources -flux due to atomic sources -flux due to free current In general, one can write: where, (e.g. conduction current, e-beam)

  7. Relationship between & these are free-currents If, Maxwell’s equation: • we can determine H without determining M In most general form: Values, most materials for iron

  8. Curves for & Typical B-H Curve for materials B H For course, use ideal curve:

  9. use then apply a Material 1 TOP h Material 2 BOTTOM Boundary Conditions Do problem 1a: Boundary Conditions: Normal component: Take h << a (a thin disc) • ignore contribution from the sides

  10. w Material 1 h Material 2 Surface currents - out of plane If non-conductor, Js = 0 ,then, If conductor in 1 and Boundary Conditions Boundary Conditions: Tangential component: h << w Inet can only be due to surface currents = Js.w or

  11. Magnetic Materials Do Problems 1b and 2 Problem 2 : Field lines exit normally in high m materials Also, field lines like to travel through high m materials • use IRON to direct flux Transformers : • primary and secondary windings intercept almost all the flux - no need for “smoothly-wound” coils • Noise reduction • increase Inductance with increasing m Do Problem 3

  12. The current loop approximates the dipole moment, E-field of electric dipole B-field of magnetic dipole Far-fields look the same for both types of dipoles Magnetic and Electric Dipole Moment

More Related