Assume that a red blood cell is spherical with a radius of 4.3 ×106 m and with w

Question

Assume that a red blood cell is spherical with a radius of 4.3 ×106 m and with wall thickness of 9.4 ×108 m. The dielectric constant of the membrane is about 5.0. The potential difference across the membrane is 0.080 V.

A) Assuming the cell is a parallel plate capacitor, estimate the capacitance of the cell. Express your answer to two significant figures and include the appropriate units.

B)Determine the positive charge on the outside and the equal-magnitude negative charge inside. Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

Here ,

Area , A = 4pi * (4.3 *10^-6)^2

A = 2.32 *10^-10 m^2

V = 0.080 V

d = 9.4 *10^-8 m

k = 5

A)

capacitance = k * epsilon * A/d

capacitance = 5 * 8.854 *10^-12 * 2.32 *10^-10/(9.4 *10^-8)

capacitance = 1.1 *10^-13 F

B)

magnitude of charge = C * V

magnitude of charge = 1.1 *10^-13 * 0.080

magnitude of charge = 8.8 *10^-15 C

positive charge on outside is 8.8 *10^-15 C

negative charge on the inside is -8.8 *10^-15 C

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