1. The problem statement, all variables and given/known data How to determine maximum voltage that coaxial cable, whose height is L and is filled with dielectric in such way that E is the same in the dielectric and in the part of the cable that isn't filled with dielectric (only vacuum),can handle if i have maximum electric field that is E=3MV/m, and i have inner radius a=2cm and outer b=2.72a. Dielectric is homogeneous and linear. 2. Relevant equations 3. The attempt at a solution I tried like this U=∫E*dl but since i know exact value of Emax and no data for εr and Qmax i can't solve this.