The membrane that surrounds a certain type of living cell has a surface area of 5.0 x 10^ -9 m^2 and a thickness of 1.0 x 10^ -8 m. Assume that the membrane behaves like a parallel plate capacitor and has a dielectric constant of 5.0. (a) If the potential on the outer surface of the membrane is +60.0 mV greater than that on the inside surface, how much charge resides on the outer surface? (b) If the charge in part (a) is due to K+ ions (charge +e), how many such ions are present on the outer surface?
2007-12-02 23:42:14 · 1 answers · asked by sunday 1 in Science & Mathematics ➔ Physics
Well, the capacitance of this capacitor is:
C = (Epcilon)A/d = 5.0*8.85x10^-12*5.0x10^-9/1.0x10^-8 = 2.2x10^-11 (Farad) = 2.2x10^-11(C/V)
(a) Q = CV = 2.2x10^-11*0.0600 = 1.3x10^-12 (C)
(b) The elementary charge is 1.6x10^-19C. Hence the number of K+ ions are:
1.3x10^-12 / 1.6x10^-19 = 8.3x10^6
2007-12-03 13:28:20 · answer #1 · answered by Hahaha 7 · 1⤊ 0⤋