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每天前20名注册可获免费名师辅导学英语记词汇练口语真人一对一教学抢注网址：www.englishvip.com/wenkxd.htm洛基国际英语竭诚为您服务ElectricityThemodernageisanageofelectricity.Peoplearesousedtoelectriclights,radio,televisions,andtelephonesthatitishardtoimaginewhatlifewouldbelikewithoutthem.Whenthereisapowerfailure,peoplegropeaboutinflickeringcandlelight,carshesitateinthestreetsbecausetherearenotrafficlightstoguidethem,andfoodspoilsinsilentrefrigerators.Yet,peoplebegantounderstandhowelectricityworksonlyalittlemorethantwocenturiesago.Naturehasapparentlybeenexperimentinginthisfieldformillionofyears.Scientistsarediscoveringmoreandmorethatthelivingworldmayholdmanyinterestingsecretsofelectricitythatcouldbenefithumanity.Alllivingcellsendouttinypulsesofelectricity.Astheheartbeats,itsendsoutpulsesofrecord;theyformanelectrocardiogram,whichadoctorcanstudytodeterminehowwelltheheartisworking.Thebrain,too,sendsoutbrainwavesofelectricity,whichcanberecordedinanelectroencephalogram.Theelectriccurrentsgeneratedbymostlivingcellsareextremelysmall?oftensosmallthatsensitiveinstrumentsareneededtorecordthem.Butinsomeanimals,certainmusclecellshavebecomesospecializedaselectricalgeneratorsthattheydonotworkasmusclecellsatall.Whenlargenumbersofthesecellarelinkedtogether,theeffectscanbeastonishing.Theelectriceelisanamazingstoragebattery.Itcanseedajoltofasmuchaseighthundredvoltsofelectricitythroughthewaterinwhichitlive.(Anelectrichousecurrentisonlyonehundredtwentyvolts.)Asmanyasfour-fifthsofallthecellsintheelectriceel’sbodyarespecializedforgeneratingelectricity,andthestrengthoftheshockitcandelivercorrespondsroughlytolengthofitsbody.AndrewCarnegieAndrewCarnegie,knownastheKingofSteel,builtthesteelindustryintheUnitedStates,and,intheprocess,becameoneofthewealthiestmeninAmerica.Hissuccessresultedinpartfromhisabilitytoselltheproductandinpartfromhispolicyofexpandingduringperiodsofeconomicdecline,whenmostofhiscompetitorswerereducingtheirinvestments.Carnegiebelievedthatindividualsshouldprogressthroughhardwork,buthealsofeltstronglytha
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