Physics

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A simplified model for an erythrocyte is a spherical capacitor with a positive inner surface of area A and a membrane of thickness b. Use potential difference of 94 mV across the membrane and a dielectric constant K = 5.0. If the capacitance of the membrane is C = 0.15 pF, what is the radius of the erythrocyte? The thickness of the membrane is b = 90 nm.


The way I thought to solve for this question was that I found the area using the Capacitance of a dielectric eqn, then from there used A = pi*r^2 to solve for r...is this the correct approach? I'm just concerned because I'm not using the potential difference anywhere...

  • Physics -

    The membrane surface area should be
    A = 4 pi r^2
    for a spherical cell

  • Physics -

    Thanks, so there wouldn't be any need to use the potential difference anywhere right?

  • Physics -

    No, no V. Capacitance is not dependent on potential.

  • Physics -

    Isnt capacitance defined as how much charge per unit potential?

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