17p1周六下午sat2和ap物理春季第6次課magnetism

SAT2Physics:Lecture6.D&LMagnetic磁MagneticFieldandMagneticInductionCompassesrevealthedirectionofthelocalmagneticMagneticInductionGeographicandGeomagnetic地理南極是地磁北地理北極是地磁南DDOfthefieldsshownbelow,whichisnotapossiblemagneticABECABEC onaonacurrent- 磁場強度的單位MagneticfieldBisaVECTORBismeasuredinteslasN/(A onamovingcharge FqvBsinθθvB的夾角F=qvBsiF的方Bv均垂負電荷受力方電荷在電場中一直受力電荷在電場中一直受力,Q1:Q1:R與v的關系?Q2:ifv2vRQ3:ifv2vTHowtoCreateaUniformB-FieldinElectromagnetichelicalWhatmustbethespeedoftheparticleifitistocrossthisregionwithoutbeingdeflected?MassMass測量電荷質(zhì)可用于分離同位素 FIlBI只有垂B的分量才產(chǎn)生力F的方BI等于每個movingcharge的 的累 MagneticFieldsCreatedbyCurrent-CarryingWiresbylongstraightbyLongStraightCurrent-CarryingWire長直導μ0:vacuumpermeabilityr:distancefromthe Solenoid(Coil)通電螺線管/線圈匝數(shù)越多,磁場HowSpeakersEachelectroninanatomactslikeatiny原子軌道上的電子相當于一個環(huán)形電流,可以看作Whenthemagneticfieldsoftheelectronsinagroupofneighboringatomsareallalignedinthesamedirection,thegroupiscalleda 一群湊在一起、磁場方向相同的小小電磁鐵稱作磁疇 ElectromagneticConductingRodMovinginMagneticevB=EeΔV=EdΔV=MotionalEMF動生電電子的累積方接入外電路后Rod內(nèi)部電流方向從負極到正極(相當于電池MagneticFlux磁通 Tm如果是solenoid,則ΦNBAΝ表上的Faraday’sLawofElectromagneticthemagnitudeoftheemfinducedinacircuitisequaltorateofchangeofthemagneticfluxthroughthe電路中感應電動勢的大小,等于穿過電路的磁通ΔΦ=BΔΑ=表上的

ΔΦ/Δt=ΒlΔx/Δtε=BlvLenz’sLaw楞次Faraday’sLaw:計算emfLenz’sLaw:判斷emf的方Theinducedcurrentwillalwaysflowinthedirectionthatthethechangeinmagneticfluxthatproduced感應生的磁場總是阻礙原磁通量Howtochange改變磁通量Φ的方改變改變感應電流方向判定(1分析磁通量如何變(2如果磁通量在減少則感應磁場磁鐵如何受力原磁場方向相如果磁通量在增加,則感應磁場與原磁場方向相 ConservationofLenz‘sLawisoneconsequenceofthep