1. The problem statement, all variables and given/known data Two circular disks spaced 0.50 mm apart form a parallel-plate capacitor. Transferring 1.70 ×109 electrons from one disk to the other causes the electric field strength to be 3.50 ×105N/C. What are the diameters of the disks? 2. Relevant equations Refer to attachment 3. The attempt at a solution So I substitute everything into the formula and end up getting R = .5 mm. I then double this to find the diameter and still get the wrong answer. Any ideas?