E物質(zhì)的磁性學(xué)習(xí)教案

1、會(huì)計(jì)學(xué)1E物質(zhì)物質(zhì)(wzh)的磁性的磁性第一頁(yè)，共16頁(yè)。(2) Paramagnetic medium 順磁質(zhì) manganese、chrome、oxygen etc.1rThe B in medium is larger than in vacuum.(3) Ferromagnetic medium 鐵磁質(zhì) iron、cobalt、nickel etc.1rThe B in medium is more lareger than in vacuum.(1) Diamagnetic medium 抗磁質(zhì)copper、plumbum、hydrogen etc.1rThe B in medium

2、 is less than in vacuum.Typically r differs from unity by only a few parts in 105第1頁(yè)/共16頁(yè)第二頁(yè)，共16頁(yè)。2 Magnetization 磁化強(qiáng)度磁化強(qiáng)度 Magnetic field intensity 磁場(chǎng)強(qiáng)度磁場(chǎng)強(qiáng)度(cchng qingd)1 The Magnetization of The motion of electron spin: 電子電子(dinz)自旋運(yùn)動(dòng)自旋運(yùn)動(dòng)： spin magnetic moment自旋磁矩自旋磁矩 ；The motion of electron orbit:

3、電子電子(dinz)繞核運(yùn)動(dòng)繞核運(yùn)動(dòng)：orbit magnetic moment 軌道磁矩；軌道磁矩；Molecular magnetic moment分子磁矩分子磁矩,固有磁矩：固有磁矩：所有所有(suyu)電子的軌道磁矩和自旋磁矩的矢量電子的軌道磁矩和自旋磁矩的矢量和。和。SIPmMolecular current：分子電流分子磁矩用等效的圓電流表示。(1) Molecular magnetic moment 分子磁矩分子磁矩第2頁(yè)/共16頁(yè)第三頁(yè)，共16頁(yè)。(2) Additional magnetic moment 附加附加(fji)磁矩磁矩In an external magneti

4、c induction, the every electron of molecule experiences force which is called Lorentz force.電子的運(yùn)動(dòng)狀態(tài)發(fā)生改變。這時(shí)，每個(gè)電子的運(yùn)動(dòng)，除了自旋運(yùn)動(dòng)和繞核運(yùn)動(dòng)之外，還要附加(fji)一個(gè)以外磁場(chǎng)為軸線的轉(zhuǎn)動(dòng)，稱為電子的進(jìn)動(dòng) the precessional motion of electron.BPMm無(wú)外磁場(chǎng)時(shí)，分子磁矩的排列(pili)雜亂無(wú)章；In an external magnetic induction, molecular magnetic moment experiences torq

5、ues It shows that the magnetic moment tends to orient itself parallel to the field分子磁矩沿外磁場(chǎng)方向排列(pili)-順磁性 paramagnetism mP第3頁(yè)/共16頁(yè)第四頁(yè)，共16頁(yè)。其方向總是(zn sh)與外磁場(chǎng)相反抗磁性 diamagnetism 用電磁感應(yīng)現(xiàn)象可以說(shuō)明附加磁矩方向與外磁場(chǎng)方向相反(xingfn)：If the flux through a circuit changes, an electromotive force is induced around it. The polar

6、ity of the induced emf is such as to oppose the change that caused it. The induced current always flows to create a magnetic field that opposite the change in flux through the circuit. Using the Lorentz force of electron experienced the diamagnetism can be explained too: 根據(jù)電子受力方向判斷電子進(jìn)動(dòng)形成的電流流向，從而確定對(duì)應(yīng)

7、的附加磁矩的方向mPThe motion of electron forms additional magnetic moment電子(dinz)的進(jìn)動(dòng)，形成附加磁矩第4頁(yè)/共16頁(yè)第五頁(yè)，共16頁(yè)。2 Magnetization and Magnetization currentVPMm單位體積(tj)內(nèi)分子磁矩或附加磁矩的矢量和。表征介質(zhì)的磁化(chu)程度Paramagnetic medium：mmPP分子磁矩起主要(zhyo)作用Diamagnetic medium：mP附加磁矩起作用(1) Magnetization (2) Magnetization current 磁化電流磁化電

8、流由于磁化而在磁介質(zhì)的邊緣形成的環(huán)形電流)()(dinLiLIlMLong solenoid：The relationship between magnetization current and magnetization第5頁(yè)/共16頁(yè)第六頁(yè)，共16頁(yè)。3 Gausss law in medium0BBB0d)(0SSB0d)(SSB0d) (d)(0)(SSSBBSBThe total magnetic flux through a close surface is equal to zero.4 4 Ampere circuital theorem in medium)(0)(00)(d

9、inLiinLiLIIlB:)(0inLiI: )(inLiIMagnetization currentConducting currentThe line integral of magnetization along with random closed path is equal to the sum of magnetization current through L.第6頁(yè)/共16頁(yè)第七頁(yè)，共16頁(yè)。)(0)(00)(ddLLiLlMIlB內(nèi))(0)(0d內(nèi)LiLIlMBMBH0)(0)(dinLiLIlHThe line integral of magnetic field int

10、ensity along a closed path L is equal to the sum of conducting current through L.Magnetic field intensity has nothing to do with magnetization current. magnetic field intensity磁場(chǎng)強(qiáng)度(cchng qingd)Ampere circuital theorem in medium:第7頁(yè)/共16頁(yè)第八頁(yè)，共16頁(yè)。5 5 The relationship between B and HMBH0MHB00Experiment

11、 show：HMmHBm0)1 (rm100)1 (rmHHBr0Paramagnetic medium：1r0mDiamagnetic medium：1r0mHB0In vacuum：In medium：HBr0第8頁(yè)/共16頁(yè)第九頁(yè)，共16頁(yè)。3 Ferromagnetic substance 鐵磁質(zhì)鐵磁質(zhì)Experiments express: The characteristics of ferromagnetics as follows:（1 1） r r11For high-permeability substance, r can be as high as 106Pure ir

12、on 純鐵：54102101（2 2）HB、非線性關(guān)系非線性關(guān)系(gun x)(gun x) r is not a constant.（3）the phenomenon of hysteresis 磁滯現(xiàn)象磁滯現(xiàn)象 B的變化的變化(binhu)落后落后H的變化的變化(binhu)（4）Curie point 居里點(diǎn)居里點(diǎn) 鐵磁質(zhì)轉(zhuǎn)化鐵磁質(zhì)轉(zhuǎn)化(zhunhu)為順為順磁質(zhì)磁質(zhì)B B is not a single-valued function of H.第9頁(yè)/共16頁(yè)第十頁(yè)，共16頁(yè)。1 1 鐵磁質(zhì)的磁化鐵磁質(zhì)的磁化(chu)(chu)規(guī)律規(guī)律Hysteresis loop Hysteres

13、is loop 磁滯回線磁滯回線接測(cè)量接測(cè)量(cling(cling) )儀表儀表在待測(cè)的磁性材料做成的圓環(huán)樣品上均勻地繞滿漆包導(dǎo)線，作在待測(cè)的磁性材料做成的圓環(huán)樣品上均勻地繞滿漆包導(dǎo)線，作為為(zuwi)(zuwi)初級(jí)線圈，再在其上繞若干圓漆包導(dǎo)線作為初級(jí)線圈，再在其上繞若干圓漆包導(dǎo)線作為(zuwi)(zuwi)次級(jí)線圈，接在回路中。次級(jí)線圈，接在回路中。 HBO SS HcBrHysteresis loopHc：coercive force 矯頑力Br：remanent magnetic induction 剩余磁感應(yīng)強(qiáng)度 剩磁 第10頁(yè)/共16頁(yè)第十一頁(yè)，共16頁(yè)。2 The clas

14、sification of ferromagnetic substanceAccording to coercive force ferromagnetic substance can be classified as two kinds:(2) Hard magnetic materials 硬磁材料：a larger coercive force 矯頑力大矯頑力大，意味著磁化后剩余磁感應(yīng)強(qiáng)度很大，稱為永磁鐵permanent magnet 或永磁體 permanent magnet material ：磁化后撤去外磁場(chǎng)(cchng)而仍能長(zhǎng)期保持較久磁性的物質(zhì)，電表，揚(yáng)聲器和錄音機(jī)等都離不

15、開(kāi)永磁體。碳鋼，鎢鋼，鉻鋼等各種合金第11頁(yè)/共16頁(yè)第十二頁(yè)，共16頁(yè)。鐵磁質(zhì)的磁性來(lái)源于電子的自旋磁矩。無(wú)外磁場(chǎng)時(shí)，鐵磁質(zhì)中電子的自旋磁矩可以在小范圍內(nèi)自發(fā)地排列起來(lái)，形成一個(gè)個(gè)小的自發(fā)磁化區(qū)Magnetic domain磁疇。由于熱運(yùn)動(dòng)，各磁疇的磁化方向不同，因而在宏觀上對(duì)外不顯磁性。當(dāng)鐵磁質(zhì)受到外磁場(chǎng)作用時(shí)，它將通過(guò)以下兩種方式實(shí)現(xiàn)磁化：外場(chǎng)(wichng)較弱時(shí)，磁化方向與外場(chǎng)(wichng)相近或相同的那些磁疇的體積將逐漸增大（疇壁位移）；外場(chǎng)(wichng)較強(qiáng)時(shí)，每個(gè)磁疇的自發(fā)磁化方向?qū)⒆鳛橐粋€(gè)整體，在不同程度上轉(zhuǎn)向外磁場(chǎng)方向；當(dāng)所有磁疇都沿外磁場(chǎng)方向排列時(shí)，磁化達(dá)到飽和。Ma

16、gnetic domain 磁疇磁疇第12頁(yè)/共16頁(yè)第十三頁(yè)，共16頁(yè)。Ex 1 Ex 1 如圖所示，相對(duì)磁導(dǎo)率如圖所示，相對(duì)磁導(dǎo)率(relative permeability)(relative permeability)為為r1r1的的無(wú)限長(zhǎng)磁介質(zhì)圓柱，半徑為無(wú)限長(zhǎng)磁介質(zhì)圓柱，半徑為R1R1，其中通以電流，其中通以電流I I，且電流沿橫截，且電流沿橫截面均勻分布。在磁介質(zhì)圓柱的外面有半徑為面均勻分布。在磁介質(zhì)圓柱的外面有半徑為R2R2的無(wú)限長(zhǎng)同軸圓柱的無(wú)限長(zhǎng)同軸圓柱面，該圓柱面上通有大小面，該圓柱面上通有大小(dxio)(dxio)也為也為I I但方向相反的電流。在但方向相反的電流。在圓

17、柱面和圓柱體之間充滿相對(duì)磁導(dǎo)率為圓柱面和圓柱體之間充滿相對(duì)磁導(dǎo)率為r2( r2( r1) r1) 的均勻磁的均勻磁介質(zhì)，圓柱面外為真空。試求介質(zhì)，圓柱面外為真空。試求B B和和H H的分布。的分布。（1）rR1：22101drRIIlHi21212RIrrH2112 RIrH210110112 RIrHBrr（2）R1 rR2：第13頁(yè)/共16頁(yè)第十四頁(yè)，共16頁(yè)。HrR1R2OHr curveBrR1R2OBr curve18104mAHcEx 2 Ex 2 有一鐵磁棒，矯頑力將它插入(ch r)長(zhǎng)12cm，繞有60匝的螺線管使去磁，此螺線管應(yīng)通多大的電流？IlNnIBAnHIc11108Ex 3 Ex 3 哪條曲哪條曲線線(qxin(qxin) )表示順表示順、抗、抗、鐵磁質(zhì)鐵磁質(zhì)？HB0BHIlNnIBHc第14頁(yè)/共16頁(yè)第十五頁(yè)，共16頁(yè)。Ex 4 Ex 4 一鐵環(huán)中心線的周長(zhǎng)為一鐵環(huán)中心線的周長(zhǎng)為30cm30cm，橫截面積為，橫截面積為1.0cm21.0cm2，在，在環(huán)上密繞環(huán)上密繞300300匝表面絕緣匝表面絕緣(juyun)(j