08导体与介质

1、AB无外电场无外电场加外电场：电子在电场力作用下运动加外电场：电子在电场力作用下运动导体的静电感应过程导体的静电感应过程0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应 E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应 E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应 E0E导体的静电感应过程导体的静电感应过程

2、0E外场外场感应感应E0E导体的静电感应过程导体的静电感应过程0E外场外场感应感应 E0E导体的静电感应过程导体的静电感应过程E静电平衡状态静电平衡状态0E E00EEEl静电平衡条件：静电平衡条件：0内E表面表EbabaUUl dEabU0E0 Ul dE 0l dE0U-静电平衡的导体是等势体静电平衡的导体是等势体PSSSdE00内Siq 0EQSSSdE00E0内Siq-S内无净电荷存在内无净电荷存在QbabaUUl dE0baUU abqQqqPSSSESSdESSdESE0S0ERrQqRrRQUR041RRR02440RRrqUr0410rrrRRr0RRRU0rrrU A0EAR

3、O q qqdxEEE0EE 0)(420idqidq20404qRdqU0RO q qqd0UUUdq04RqdqU0100440qdRq1ROqd1qURO q qqd12341P2PiEp)2222(0403020110iEp)2222(040302012413204132x1234qS)(21qS )(43SqSq43210 x04321041-电荷分布在极板内侧面电荷分布在极板内侧面Sq2Sq33241iE)22(03021iE)22(03022iSq023123x14003EqS)(210)()(4321032qS )(43Sq41413223123x14iE)22(04011iS

4、q0iE)22(040120iE)22(04013iSq014123xSq41 Sqq/ )(2141Sqq2/ )(2141112SqSqq21223Sq /121Sq /24312Sqq22114123234132xiE)2222(040302011iE)2222(040302012iE)2222(040302013i01iSqq0212i02iSqq0212i01iSqq0212Sqq2)(211Sqq22121412323x1r2r3r1rr 21rrr32rrr3rr 1r2r3rqqqQ01E02024rrqE03E02044rrQqE11rrdEU321202044rrrdrrQ

5、qdrrq321041rQqrqrq32142rrrrdErdE02024rrqE02044rrQqE1r2r3rqqqQ32rrdEU34rrdE3204rdrrQq304rQq21UUU210114rrq1r2r3rqqqQ3210141rQqrqrqU0321EEE02044rrQqE3421rrdEUUdrrQqr3204304rQq02024rrqE0431EEEqq2121rrrdEU)11(4210rrq21UUU1U3020101444rQqrqrqU0Qrrrrrrrrq12231312 q q qQ3024rQqU q q qQ1323210124rrrrrrrrQQrrr

6、rrrrrq122313120ep甲烷甲烷 CH4HHHHC水水 H2OHHOep0ep0E0Eep-转向极化转向极化1f2f0E0Eep0ip0ipipVpPi nPnPnnPldS000PSdSqdSdPsqdq外sSdPPdSn内外SqqSSdPEPe0PE EEE00EEEEEEEE0000E EPPn EPe0eEE10er1-相对介电系数相对介电系数rEE00E- 部分抵消部分抵消 的缘故的缘故E0E四、有电介质时的电场基本定理四、有电介质时的电场基本定理1. 环路定律环路定律0l dELEEE0- SSqSdE内01内内SSqq)(100内SSqSdPE00SSSdPq内PED0

7、SSqSdD内0-电位移电位移-有介质时的高斯定理或有介质时的高斯定理或 的高斯定理的高斯定理DD内SSqSdPE00PED，EPe0PED0EEDe00Ee)1 (0Er0r0ED-介质的介电常数介质的介电常数er1(1) DEDPED，R0qrSrDSdD240q240rqD0024rrqDDErD002004rrqrEPe0020004) 1(rrqrr02041rrqrrnPP2041RqrrR0qrnP02004rrqErer124 Rq 011qr-q与与q0反号，而且数值小于反号，而且数值小于q02041Rqrr221111r0V0E1D1E2D2E221111r1D1E2D2E

8、 00ESSSdD1SdD1下底dSD1下底SD1dEV00S111DrDE01122DdEdE2121EE r12r01022DE 221111r1D1E2D2ES02SSS2221221rr121r1225852r120221EE052052EdEV1dE05230052V1201011EPrnp110056E56561 P561PUqC -孤立导体的电容孤立导体的电容ABqqAUBUl定义定义: :BAUUqC-电容器的电容电容器的电容qABrSdqEBABAl dEUUEdSqdr0Sqr0BAUUqCdSr0ABARBRlrrEr02BABAl dEUUBARREdrBARRrrdr

9、02ABrRRln20BAUUqCABrRRlln20ABrRRlln20204rqErBRARABrBABAl dEUU)11(40BArRRqBARREdrBAUUqCABBArRRRR041.并联并联: :1C2C3CnCUUqC Uqqqn21nCCC21niiC12.串联串联: :UUqCnUUUq21nCqCqCqq/21nCCCC111121niiC11dCCCdrr111d2d3dd1C2C3CC201dSC102dSCr303dSC133221321CCCCCCCCCC3211111CCCC3210dddSrr1d2d3dd132ddddddCSdrr)1 (101dCCrr11dCCCrr1331221dEdEdEU301020dddrUqC US3210dddSrr同样可证同样可证1d2d3ddABdqqqE)(baUUdqdAdqCqABdqqqEQdqCqW0CQ2212)(21BAUUC)(21BAUUQUQC2)(21BAUUCW2)(21EddSVE 221dVWeVDEdVV21VWe221EDE21ED0内E2041rQE外Rr Rr QRVedVwWVdVE2021RdrrrQ222004)4(2