电学基础Chap1培训讲学.ppt

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1、电学基础Chap11.1CircuitTheoryCircuittheoryisaspecialcaseofelectromagneticfieldtheory:thestudyofstaticandmovingelectriccharges.Threebasicassumptions:Electricaleffectshappeninstantaneouslythroughasystem.Thenetchargeoneverycomponentinthesystemisalwayszero.Thereisnomagneticcouplingbetweenth

2、ecomponentsinasystem.canholdequal,opposite,separatedchargeswithininstantaneouslycouplingThechargeisbipolar,meaningthatelectricaleffectsaredescribedintermsofpositiveandnegativecharges.Theelectricchargeexistsindiscretequantities,whichareintegralmultiplesoftheelectroniccharge,1.6022×10

3、-19C.Electricaleffectsareattributedtotheseparationofchargeandchargesinmotion.1.2VOLTAGEANDSomeimportantcharacteristicsofelectriccharge:REVIEW_______negativenineteenthpoweroftenCURRENTcharacteristicsbipolarTheseparationofchargecreatesanelectricforce(voltage)Voltageistheenergyperunitc

4、hargecreatedbytheseparation.Electriccurrentistherateofchargeflow.v=thevoltageinvoltsw=theenergyinjoulesq=thechargeincoulombsi=thecurrentinamperesq=thechargeincoulombst=thetimeinsecondsTheratioofwtoqindifferentialformThemotionofchargecreatesanelectricfluid(current).1.3THEIDEALBASICCI

5、RCUITELEMENTAnidealbasiccircuitelementhasthreeattributes:Ithasonlytwoterminals,whicharepointsofconnectiontoothercircuitcomponents.Itisdescribedmathematicallyintermsofcurrentand/orvoltage.Itcannotbesubdividedintootherelements.plussignminussign1.3THEIDEALBASICCIRCUITELEMENTii+v--v+Ass

6、ignthereferencedirectionforvoltageandcurrent.Thereferencedirectionisarbitrary.Onceassigned,wemustwriteallthesubsequentequationstoagreewiththechosenreferences.POSITIVEVALUEvvoltagedropfromterminal1toterminal2Orvoltagerisefromterminal2toterminallipositivechargeflowingfromterminal1tote

7、rminal2negativechargeflowingfromterminal2toterminal1NEGATIVEVALUEvvoltagerisefromterminal1toterminal2Orvoltagedropfromterminal2toterminallipositivechargeflowingfromterminal2toterminal1negativechargeflowingfromterminal1toterminal2interpretationofreferencedirection1.3THEIDEALBASICCIRC

8、UITELEMENTi+v--v+-v