文档介绍：-thirdsthespeedoflightfrommeterspersecondtomilespersecond:23×108m100cm1in1ft1mile124,····=3:124,=1sxsTherefore,1100x===×10−3s=,$otation:$100billion=$100×henumberofmillisecondsinoneyear,againusingaproductofratios:1year1day1hour1min1sec1year····=×109msNowwecanconvertfromdollars/yeartodollars/millisecond,againwithaproductofratios:$100×1091year100·==$ש2010PearsonEducation,Inc.,UpperSaddleRiver,,storageinaretrieval1–1system,ortransmissioninanyformorbyanymeans,electronic,mechanical,photocopying,recording,(s),writeto:RightsandPermissionsDepartment,PearsonEducation,Inc.,UpperSaddleRiver,–.(),currentisthetimerateofchangeofcharge,ordqi=dtInthisproblem,,wemustintegrateEq.()tofindanexpressionforchargeintermsofcurrent:tq(t)=i(x)dxZ0Wearegiventheexpressionforcurrent,i,,welett→∞∞∞−5000x20−5000x20−∞0qtotal=20edx=e=(e−e)Z0−5000 0−5000 2020 =(0−1)===4000µC−.()thatcurrentisthetimerateofchangeofcharge,ordqi=,.():dqd1t1−αti==2−+2edtdtαααd1dt−αtd1−αt=2−e−2edtαdtαdtα1−αtt−αt1−αt=0−e−αe−−α2eααα11=−+t+e−αtαα=te−αtNowthatwehavea