电流和水流(The Flow of Electricity and Water)

详细内容

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theflowofelectricitythroughwiresandcablesfromthemainsupplycanbeparedwiththeflowofwaterthroughpipesfromawatertank.

whenthetapisturnedoff,thewaterdoesnotmove,butwhenatapisturnedontheheightofthewaterinthetankexertspressureonthewaterinthepipesandforcesitthroughtheoutlet.thiswaterpressureisparablewithvoltageinelectricity.therateofthewaterflow,similartotheflowofcurrent,iscontrolledbytwothings:thepressureandthesizeoftheoutlet.forexample,averynarrowsprayallowslesswagertoflowthanawidepipe.similarlyinelectricity,averythinwirerestrictsorresiststheflowofcurrent.

electriciansmeasurethisresistanceinohmsandtheflowofthecurrentinamperes