电力(Electricity)

themodernageisanageofelectricity.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-fifthsofallthecellsintheelectriceelsbodyarespecializedforgeneratingelectricity,andthestrengthoftheshockitcandelivercorrespondsroughlytolengthofitsbody.