Two circular disks spaced 0.50 mm apart from a parallel-plate capacitor. Transferring 1.90 x 10^9 electrons from one disk to the other causes the electric field strength to be 1.90 x 10^5 N/C. What are the diameters of the disks (in cm)?
E = Q / (e_o * A)
A = [pie]*r^2
The Attempt at a Solution
I though I went through the right process for this, but maybe I'm not using the right equations somehow? Here's what I did:
E = Q / (e_o * A) ==> Q = (8.85*10^-12 C^2 / N*m^2) * A * (1.9*10^5 N/C) = 3.04 * 10^-1
A = [Pie]*r^2 ==> 1.81 * 10^-4 = [pie]*r^2 ==> r = 0.00759 and thusly D = 0.1517m which is equal to 15.2 cm. This turned out to be wrong.
Where did I mess up?