# Homework Help: Capacitance using an axon ?

1. May 4, 2010

### honor3

Capacitance using an axon.. :)?

1. The problem statement, all variables and given/known data
An axon membrane is 8.0×10-9 m thick.
a) Find the dielectric constant of the membrane, if the capacitance C is 100 nF for an area A = 10.0 square mm.
b) If the resting potential across the membrane is ΔV = - 90 mV, what is the charge ±Q on each surface A?
c) For this area of membrane at -90 mV, what is the stored electric energy?

2. Relevant equations
C=k(eoA)/D

3. The attempt at a solution
Basically plugging in the values however i do not know what eo is and the value of it.

2. May 4, 2010

### honor3

Re: Capacitance using an axon.. :)?

Okay so do i use eo to be ε0 = 8.85… × 10−12 F/m??

3. May 4, 2010

### nickjer

Re: Capacitance using an axon.. :)?

I have no idea how an axon membrane looks, but assuming it is a parallel plate capacitor then you have the right equation. And yes, that is the right constant in SI units.