1. The problem statement, all variables and given/known data First part of the problem was to work out E-field of uniformly charged spherical shell with charge Q and Radius R. This was fine : E = 0 for r<R and E = Q/(4*Pi*eps*r2) for r>R QUESTION: Find the pressure exerted on the shell due to the charges on its surface. 2. Relevant equations 3. The attempt at a solution I tried to do it using the principle of virtual work, I get an answer and was hoping someone could confirm it is right? I did this: u_s, Energy stored in Electric field = [tex]\int[/tex]eps*E2/2 (integrate over all space) I did this in spherical polar coordinates and get U_s = Q2/(8*Pi*eps*R) I then said (principle of virtual work:) F, Force*dR = [tex]\partial[/tex]U_s/[tex]\partial[/tex]R *dR and solved this to get: F = -Q2/(8*Pi*eps*R2) dividing by area of shell then gives pressure = Q2/(32*Pi2*eps*R2) is this right? If there's a mistake I think I may have not used the principle of virtual work correctly.... Thanks very much.