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The voltage across a membrane forming a cell wall is 80.0 mV and the membrane is 9.00 nm thick. What is the electric field strength? (The value is surprisingly large, but correct. Membranes are discussed in Capacitors and Dielectrics and Nerve Conduction—Electrocardiograms.) You may assume a uniform electric field.
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$8.89\times 10^{6}\textrm{ V/m}$
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OpenStax College Physics Solution, Chapter 19, Problem 18 (Problems & Exercises) (0:36)

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Video Transcript
This is College Physics Answers with Shaun Dychko. The voltage across a cell membrane is 80.0 millivolts, which is 80.0 times 10 to the minus 3 volts and the thickness of the cell membrane is 9.00 nanometers, which is 9.00 times 10 to the minus 9 meters and we are modeling this cell membrane as two conducting plates that are parallel and so finding the electric field between them means we divide the voltage by the thickness. So that's 80.0 times 10 to the minus 3 volts divided by 9.00 times 10 to the minus 9 meters and that's 8.89 times 10 to the 6 volts per meter.