电感器的电动势线路的电流-ckw培训讲学.ppt

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1、电感器的电动势线路的电流-ckw27.1.InducedCurrents感應電流4resultsfromFaraday/Henry(1831)法拉第/亨利(1831)的四個結果Currentinducedincoilbymovingmagnetbar.移動磁鐵會在線圈引發(感應)電流。Movingthecoilinsteadofthemagnetgivesthesameresult.不移磁鐵，改移線圈有同樣結果。v=0,I=0v>0,I>0v>>0,I>>0v<0,I<0Aninducedcurrentalsoresultswhenacurrent-carryingci

2、rcuitreplacesthemagnet.把磁鐵換成線圈也會引發感應電流。Acurrentisalsoinducedwhenthecurrentinanadjacentcircuitchanges.旁邊線圈的電流改變也會引發感應電流。changingBinducescurrents(electromagneticinduction)改變B會引發電流(電磁感應)27.2.Faraday’sLaw法拉第定律Magneticflux磁通量Flux&InducedEMF通量和感應電動勢Magneticflux磁通量Magneticflux:磁通量：Reminder:提醒你：

3、ForauniformBonaflatsurface:均勻B在平面上：Movemagnetrightmorelinesthruloop磁鐵右移多些場線穿過廻路：Example27.1.Solenoid螺線管AsolenoidofcircularcrosssectionhasradiusR,一螺線管，其圓形截面的半徑為R，consistsofnturnsperunitlength,andcarriescurrentI.其捲線為每單位長度n轉，其電流則為I。Findthemagneticfluxthrougheachturnofthesolenoid.求通過管中每轉的磁

4、通量。BoutofplaneIB側面圖正面圖Example27.2.NonuniformField非均勻場Along,straightwirecarriescurrentI.一長而直的電線上有電流I。Arectangularwireloopofdimensionslbywliesinaplanecontainingthewire,withitsclosestedgeadistanceafromthewire,anditsdimensionlparalleltothewire.另一l乘w大的長方形線圈和電線在同一平面上，其最近的邊與電線相距a，其I長那邊與電線平行。Fin

5、dthemagneticfluxthroughtheloop.求通過線圈的磁通量。Areaelementforintegration積分的面積元素Flux&InducedEMF通量和感應電動勢Faraday’slawofinduction法拉第的感應定律:Theinducedemfinacircuitisproportionaltotherateofchangeofmagneticfluxthroughanysurfaceboundedbythatcircuit.一個線路的感應電動勢，與穿透任何由這線路圍住的表面的磁通量成正比。Note:dB/dtcanbedueto

6、註：dB/dt可能源自changingBcausedby下列因素所引起的B變化relativemotionbetweencircuit&magnet,線路與磁鐵的相對運動changingcurrentinadjacentcircuit,相隣線路內的電流變化changingareaofcircuit,線路面積的變化changingorientationbetweenB&circuit.B與線路間角度的變化CisCCWaboutS.C繞S逆時針轉Example27.3.ChangingBB在變Awireloopofradius10cmhasresistance2.0.一

7、個半徑為10cm的線圈的電阻是2.0。TheplaneoftheloopisperpendiculartoauniformBthat’sincreasingat0.10T/s.線圈的面垂直於一以0.10T/s增加的均勻B。Findthemagnitudeoftheinducedcurrentintheloop.求線圈內感應電流的大小。CCW逆時針SCIExample27.3.ChangingBB在變Awireloopofradius10cmhasresistance2.0.一個半徑為10cm的線圈的電阻是2.0。Theplaneof