Suppose that the resistance between the walls of a biologica

Suppose that the resistance between the walls of a biological cell is 3.00 109 ?.

(a) What is the current when the potential difference between the walls is 55 mV? ________A

(b) If the current is composed of Na+ ions (q = +e), how many such ions flow in 1.6 s? __________ions

Solution

(a) I = V / R = 55*10^-3 / 3*10^9 A = 1.833*10^-11 A = 18.33 pA

(b) I = q/t = 1.833*10^-11 C/s
So charge transferred in 1.6s = 1.6s * 1.833*10^-11C/s = 2.9328*10^-11 C

Each Na+ ion transfers 1.6*10^-19 C

so the number of NA+ ions is
2.9328*10^-11 C / 1.6*10^-19 C per ion = 18.33*10^7 ions