**1. The problem statement, all variables and given/known data**

A spherical capacitor consists of a spherical conducting shell charge [itex]-Q[/itex] concentric with a smaller conducting sphere of radius [itex]4.0[/itex] cm and charge [itex]Q[/itex]. The larger conducting shell has inner and outer radii of [itex]11.0[/itex] cm and [itex]13.0[/itex] cm, respectively. What is the capacitance of the system in pF?

**2. Relevant equations**

[itex]C = \frac{Q}{\Delta V}[/itex]

**3. The attempt at a solution**

I don’t know what to do when the outer shell has a thickness. I know that when it doesn’t have a thickness you would do

[itex] -\int_{r_1}^{r_2} kQ\frac{dr}{r^2} [/itex]

where [itex]r_1[/itex] and [itex]r_2[/itex] are the inner and outer radii, respectively. But here what do you do for [itex]r_2[/itex]?

Thanks.

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