1. The problem statement, all variables and given/known data A sphere with radius R is charged with surface density σ. The charge found in a small surface Δs is repelled by the rest of the sphere, thus generating an electrostatic pressure. Find the pressure. 2. Relevant equations 3. The attempt at a solution I think I have to compute the field for the sphere, which can be done using Gauss' law. For Δs: Esph = σ/ε0 Then I think I have to find the field for Δs and subtract it, but I don't know how to find it. If field is constant, ten just multiplying QΔs = Δs·σ by the field would give the force. Thanks for your help!