1. The problem statement, all variables and given/known data An infinite, charged plane/plate has a uniform positive charge density of σ. Another positively charged particle is found at a distant of D from the plane. In point P, positioned between the two, the electric field equals 0. A. What is the distance between point P and the charged particle q? B. The plane is removed and replaced with a new positively charged particle Q. What should be the value of Q in point A in order for the electric field to remain 0? 2. Relevant equations E=σ/2ε , E=k * Q/r^2 3. The attempt at a solution In A, I've calculated the electric field the plane exerts on point p, which is E=σ/2ε, and then added the electric field exerted by particle q, which is E=k * Q/(D-r)^2. E=k * Q/(D-r)^2 + σ/2ε =0 then found r. Am I right on this? Please help. In B, just use this equation E=k * Q/r^2 instead of E=σ/2ε, correct?