17p1周六下午sat2和ap物理春季第6次课magnetism

SAT2Physics:Lecture6.D&LMagnetic磁MagneticFieldandMagneticInductionCompassesrevealthedirectionofthelocalmagneticMagneticInductionGeographicandGeomagnetic地理南极是地磁北地理北极是地磁南DDOfthefieldsshownbelow,whichisnotapossiblemagneticABECABEC onaonacurrent- 磁场强度的单位MagneticfieldBisaVECTORBismeasuredinteslasN/(A onamovingcharge FqvBsinθθvB的夹角F=qvBsiF的方Bv均垂负电荷受力方电荷在电场中一直受力电荷在电场中一直受力,Q1:Q1:R与v的关系?Q2:ifv2vRQ3:ifv2vTHowtoCreateaUniformB-FieldinElectromagnetichelicalWhatmustbethespeedoftheparticleifitistocrossthisregionwithoutbeingdeflected?MassMass测量电荷质可用于分离同位素 FIlBI只有垂B的分量才产生力F的方BI等于每个movingcharge的 的累 MagneticFieldsCreatedbyCurrent-CarryingWiresbylongstraightbyLongStraightCurrent-CarryingWire长直导μ0:vacuumpermeabilityr:distancefromthe Solenoid(Coil)通电螺线管/线圈匝数越多,磁场HowSpeakersEachelectroninanatomactslikeatiny原子轨道上的电子相当于一个环形电流,可以看作Whenthemagneticfieldsoftheelectronsinagroupofneighboringatomsareallalignedinthesamedirection,thegroupiscalleda 一群凑在一起、磁场方向相同的小小电磁铁称作磁畴 ElectromagneticConductingRodMovinginMagneticevB=EeΔV=EdΔV=MotionalEMF动生电电子的累积方接入外电路后Rod内部电流方向从负极到正极(相当于电池MagneticFlux磁通 Tm如果是solenoid,则ΦNBAΝ表上的Faraday’sLawofElectromagneticthemagnitudeoftheemfinducedinacircuitisequaltorateofchangeofthemagneticfluxthroughthe电路中感应电动势的大小,等于穿过电路的磁通ΔΦ=BΔΑ=表上的

ΔΦ/Δt=ΒlΔx/Δtε=BlvLenz’sLaw楞次Faraday’sLaw:计算emfLenz’sLaw:判断emf的方Theinducedcurrentwillalwaysflowinthedirectionthatthethechangeinmagneticfluxthatproduced感应生的磁场总是阻碍原磁通量Howtochange改变磁通量Φ的方改变改变感应电流方向判定(1分析磁通量如何变(2如果磁通量在减少则感应磁场磁铁如何受力原磁场方向相如果磁通量在增加,则感应磁场与原磁场方向相 ConservationofLenz‘sLawisoneconsequenceofthep