电气工程及其自动化专业英语.pptx

文档介绍：Section1CurrentandVoltageTextNewWordsandExpressionsExercisesEndSection1CurrentandVoltageTwovariablesu(t)andi(t)ircuit,,,measuredincoulombs(C).Section1CurrentandVoltageWeknowfromelementaryphysicsthatallmatterismadeoffundamentalbuildingblocksknownasatomsandthateachatomconsistsofelectrons,protons,×1019C,;thatis,itcanbetransferredfromoneplacetoanother,(asourceofelectromotiveforce),pelledtomove;,thatis,oppositetotheflowofnegativecharges,-(l706~l790),,,urrentisthetimerateofcharge,measuredinamperes(A).Mathematically,therelationshipamongcurrenti,chargeq,andtimetisSection1CurrentandVoltageThechargetransferredbetweentimet0andtisobtainedbyintegratingbothsidesofEq.(1-1).WeobtainThewaywedefinecurrentasiinEq.(1-l)suggeststhatcurrentneednotbeaconstant-valuedfunction,chargecanvarywithtimeinseveralwaysthatmayberepresentedbydifferentkindsofmathematicalfunctions.(1-1)(1-2)Section1CurrentandVoltageVoltage,Energy,(emf),-