What Is the Correct Sign for the Capacitance of a Spherical Capacitor?

[schattenjaeger]

Say you have a spherical conductor with radius 1 with charge -Q inside of another larger spherical conductor(with radius 2 to the inside edge of the conductor)with a charge +Q at the inside surface, what's the capacitance?

I used Gauss' law to find E in between the two conductors, then integrated with respect to r to find the change in potential, and did Q/that=C

I'm pretty sure I got the right actual answer, it was like 8*pi*Eo...and maybe something else(Eo is that constant), I don't remember off hand(this was on a test I took this morning)but my question...should it be positive or negative? That really confused me and I had all kinds of negatives floating around and finally fixed it up so that C came out positive, and it looked like it made sense

 

[berkeman]

Capacitance is always a positive value. Is that what you mean?

 

[schattenjaeger]

it is? Good then, that's what I figured at the time, but I got to thinking afterwards