# Non-parallel plate capacitance

1. Oct 31, 2007

### ianmc7

Im having trouble calculating the capacitance of a non-parallel plate capacitor where seperation at one edge is d-a and the other it is d+a, assuming a<<d. I'm supposed to prove that C= epsilon_not A/d (1+a^2/3d^2). Thanks for the help.

2. Nov 1, 2007

### clem

The equations for the distance between the plates is x=d+ay/L.
The surface charge ~V/x.
Integrate V/(d+ay/L) from y=-L/2 to +L/2.
Expand the logarithm.