Please help!!! Electric Field Problem due tomorrow 1. The problem statement, all variables and given/known data We want to analyze how a charged object picks up a neutral piece of metal. A small circular disk of foil is lying flat on a table. The foil has radius R and thickness t. A glass ball w/ positive charge Q is at height h above the foil. The ball's electric field polarizes the foil. The foil surfaces with charges +q and -q then act as the the plates of a parallel plate capacitor with separation t. But the foil is a conductor in electrostatic equilibrium so the electric field inside the foil must be zero. Write this condition as a mathematical statement and use it to find the charge on the upper surface of the foil. 2. Relevant equations 3. The attempt at a solution I know that the electric field of this sphere is Q/4[tex]\pi[/tex][tex]\epsilon[/tex]or^2 Should the electric field from the ball equal the electric field from the top surface of the plate? Ecapacitor = [tex]\eta[/tex]/[tex]\epsilon[/tex]o in the case of the foil disk [tex]\eta[/tex]=q/4[tex]\pi[/tex]r2 so the electric field is then q/4[tex]\pi[/tex]R2[tex]\epsilon[/tex]o If I set this equal to the electric field of the ball I get q/4[tex]\pi[/tex]R2[tex]\epsilon[/tex]o=Q/4[tex]\pi[/tex][tex]\epsilon[/tex]or^2 q=QR2/h2 The answer is actually q=QR2/4h2 Could someone help me understand this better?