《磁性材料的特性》PPT课件.pptx

《《磁性材料的特性》PPT课件.pptx》由会员分享，可在线阅读，更多相关《《磁性材料的特性》PPT课件.pptx（12页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、CHAPTER16MAGNETICPROPERTIESOFMATERIALS16.1EffectonMagneticFieldbyMaterials16.2Magnetization16.3VectorHandItsCircuitalTheorem16.4MagneticShielding16.1EffectonMagneticFieldbyMaterialsTheinteractionbetweenmagneticfieldsandmaterialscanbeTheinteractionbetweenmagneticfieldsandmaterialscanbeobservedexperim

2、entally.Themostsimplemethodistousealongobservedexperimentally.Themostsimplemethodistousealongstraightwithvacuumorairinsidefirst(Fig.16.1(a)andmeasurethestraightwithvacuumorairinsidefirst(Fig.16.1(a)andmeasurethemagneticfieldinitwhencurrentIisflowinginthecoils.magneticfieldinitwhencurrentIisflowingin

3、thecoils.Nextfillthesolenoidwithsomematerialandthenmeasureagainthemagneticfieldinitwhenthesamecurrentisledinthecoils(Fig.16.1(a).LetB0andBbethemagneticfieldmeasuredinthetwocasesrespectively.Experimentalresultsshowthatthetwodifferfromeachotherandcanrelatedas16.2MagnetizationInanatom,theelectronsorbit

4、aroundthenucleusandhavealsospin.Inanatom,theelectronsorbitaroundthenucleusandhavealsospin.Thenucleusalsohasspin.ThesemotionallfromequivalentcircularThenucleusalsohasspin.Thesemotionallfromequivalentcircularelectriccurrents.Asawholethesemotionsofchargesinamoleculeelectriccurrents.Asawholethesemotions

5、ofchargesinamoleculemaybeconsideredasconstituteasinglemicroscopiccircularcurrentmaybeconsideredasconstituteasinglemicroscopiccircularcurrentcalledcalledmolecularcurrentmolecularcurrentiwithiwithmolecularmagneticmomentmolecularmagneticmomentm.m.Example16.1Alongstraightsolenoidofnturnperunitlengthisfi

6、lledExample16.1Alongstraightsolenoidofnturnperunitlengthisfilledinsidewithuniformmaterialofrelativepermeability.Findthesurfaceinsidewithuniformmaterialofrelativepermeability.Findthesurfaceboundcurrentdensityonthesurfaceofthematerialinthesolenoid.boundcurrentdensityonthesurfaceofthematerialinthesolen

7、oid.16.3VectorHandItsCircuitalTheorem16.4MagneticShieldingWhenabockofferromagneticWhenabockofferromagneticmaterialisputinamagneticmaterialisputinamagneticfield.Sinceitsisverylarge.field.Sinceitsisverylarge.ThesurfaceboundcurrentThesurfaceboundcurrentproducedbymagnetizationisproducedbymagnetizationis

8、verylarge.Thesuperpositionofverylarge.Thesuperpositionofthemagneticfieldproducedbythemagneticfieldproducedbytheseboundcurrentsonthetheseboundcurrentsontheoriginalexternalfieldwouldoriginalexternalfieldwouldchargethedistributionofthechargethedistributionofthelaterdrastically.Pictorially,thelaterdrast

9、ically.Pictorially,theresultantfieldlineswouldberesultantfieldlineswouldbeconcentratedorcollectedintheconcentratedorcollectedintheferromagneticmaterialasferromagneticmaterialasshowninFig.16.4.showninFig.16.4.Inthehollowspaceinthebox,themagneticfieldwouldbeveryweak.Thuswhensomethingisputintheclosedbox.Itwillnot(oronlyslightly)beaffectedbyexternalmagneticfields.Thisistheprincipleofmagneticshieldingusingironbox.SUMMARY