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(chǎng)強(qiáng)度的單位MagneticfieldBisaVECTORBismeasuredinteslasN/(A onamovingcharge FqvBsinθθvB的夾角F=qvBsiF的方Bv均垂負(fù)電荷受力方電荷在電場(chǎng)中一直受力電荷在電場(chǎng)中一直受力,Q1:Q1:R與v的關(guān)系?Q2:ifv2vRQ3:ifv2vTHowtoCreateaUniformB-FieldinElectromagnetichelicalWhatmustbethespeedoftheparticleifitistocrossthisregionwithoutbeingdeflected?MassMass測(cè)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(gè)movingcharge的 的累 MagneticFieldsCreatedbyCurrent-CarryingWiresbylongstraightbyLongStraightCurrent-CarryingWire長(zhǎng)直導(dǎo)μ0:vacuumpermeabilityr:distancefromthe Solenoid(Coil)通電螺線管/線圈匝數(shù)越多,磁場(chǎng)HowSpeakersEachelectroninanatomactslikeatiny原子軌道上的電子相當(dāng)于一個(gè)環(huán)形電流,可以看作Whenthemagneticfieldsoftheelectronsinagroupofneighboringatomsareallalignedinthesamedirection,thegroupiscalleda 一群湊在一起、磁場(chǎng)方向相同的小小電磁鐵稱作磁疇 ElectromagneticConductingRodMovinginMagneticevB=EeΔV=EdΔV=MotionalEMF動(dòng)生電電子的累積方接入外電路后Rod內(nèi)部電流方向從負(fù)極到正極(相當(dāng)于電池MagneticFlux磁通 Tm如果是solenoid,則ΦNBAΝ表上的Faraday’sLawofElectromagneticthemagnitudeoftheemfinducedinacircuitisequaltorateofchangeofthemagneticfluxthroughthe電路中感應(yīng)電動(dòng)勢(shì)的大小,等于穿過(guò)電路的磁通ΔΦ=BΔΑ=表上的

ΔΦ/Δt=ΒlΔx/Δtε=BlvLenz’sLaw楞次Faraday’sLaw:計(jì)算emfLenz’sLaw:判斷emf的方Theinducedcurrentwillalwaysflowinthedirectionthatthethechangeinmagneticfluxthatproduced感應(yīng)生的磁場(chǎng)總是阻礙原磁通量Howtochange改變磁通量Φ的方改變改變感應(yīng)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(yīng)磁場(chǎng)磁鐵如何受力原磁場(chǎng)方向相如果磁通量在增加,則感應(yīng)磁場(chǎng)與原磁場(chǎng)方向相 ConservationofLenz‘sLawisoneconsequenceofthep