# Homework Help: Boundary conditions for P

1. Nov 12, 2009

### dsta

1. The problem statement, all variables and given/known data
Use a Gaussian surface and an Amperian loop to derive the electrostatic boundary conditions for the polarisation field P at an interface between electric media 1 and 2 of relative permittivities e1 and e2. (Hint: determine results for D and E first)

2. Relevant equations

3. The attempt at a solution
The boundary conditions for E and D I know. I know that the restrictions on P will have something to do with the bound charge at the interface, and I know that $$P = D - \epsilon_{o}E$$. I am not sure what Gaussian surface or Amperian loop I should use, and how I should use it.

2. Sep 7, 2010

### manyparticle

$$\int D \cdot ds=4\pi \rho$$