Physics
posted by Sandra on .
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...

The membrane surface area should be
A = 4 pi r^2
for a spherical cell 
Thanks, so there wouldn't be any need to use the potential difference anywhere right?

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

Isnt capacitance defined as how much charge per unit potential?