1. The problem statement, all variables and given/known data http://imgur.com/sg8czUR An infinite sheet of charge has a charge density of σ= -2.1 uc/m2. (uc is micro-coulombs). The inner edge of the infinite conductor slab is 2.6 cm away. The outer edge is 4.2 cm away. The conductor slab has a charge density of σ= 74 uc/m2. What is the charge per unit area on the surface of the slab at 4.2 cm. (The outer edge) 2. Relevant equations Gauss's Law! 3. The attempt at a solution Well we know since the slab is a conductor the charges in it are going to move to make the electric field equal zero every inside of it. I have the inner being 2.1 uc/m2. The total charge of the slab must be 74 uc/m2. Therefore I thought the outer edge will have a charge of 71.9 uc/m2. But this is not the right answer. Any idea of what I am doing wrong here?