6physHW4

6physHW4 - A typical cell membrane ls 3 nm thick and has an...

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Unformatted text preview: A typical cell membrane ls 3 nm thick and has an electrical resistlylty bf 1-3 3-: ll}? flm {a} If the pbtential difference bet'w'een the lnner and cuter surfaces bf a cell membrane is T5 mil“, hcw much current fltiws thrnugh a square area bf membrane LII]I hm en a slde'l' Lb] Suppcse the thickness cf the membrane is dbublecl, but the resistlylty and pctential difference remain the same- Del-es the current increase nr decrease? Ely what factch Picture cf the prcuble m: A pntentlal difference driyes electric current acmss the membrane bfa cell wall- Strategy: Dhm‘s Law {equaticn 21-2} gives the relaticnship bet'u-reen pctential difference, current, and resistance fbr any circuit element. Tn sclye thls prcblem we can cbmbine equaticn 21-3, using the glyen reslstiyity cf the cell wall, with Dhm‘s law tn find the electric current that passes thrbugh an area A = {LII} 3-: lIIIIVEI m}2 = H} a Hill? mg- Sclutinn: {alflcmbine equatlbns 21-2 and 21-3 tn find I: _ 1; _ 1,: _ gr _[s5s1a-3 y]{l_asitr'1 m1] ___ ___—=12 ur‘is a pLIA as [Lssinin-mllsnsia'lm] K I {blIf the thickness L cf the membrane is dcubled, but p and la" remaln ccnstant, the current thrbugh the membrane wlll decrease by a factcr cufE- lnslght: A current bf Eli"; 11A dnesn‘t seem like much, but it is equivalent tn 4-5 milllbn electrcns passing thrcnugh a LEI um1 area every sectind.r ...
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6physHW4 - A typical cell membrane ls 3 nm thick and has an...

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