Three identical metal plates with large surface areas are kept parallel to each other.The leftmost plate is given a charge Q, the rightmost is given a charge -2Q & the middle one remains neutral.Find the charge appearing on the outer surface of the rightmost plate.
Answers
When electrostatic demonstrations are first presented to students, the demonstrator will often touch a piece of conducting material to the ground (earth) and declare that the excess charge has been removed. In fact, though, what has happened is that the potential has been set, by definition, to zero. Usually, but not always, this means that the excess charge has been removed. In the case of an isolated conductor, it's true that the excess charge has been removed, but if there are other charged objects nearby, the grounded conductor can still retain some excess charge. In this case we refer to it as induced charge. A capacitor is a pair of conductors.
Reference https://www.physicsforums.com/threads/earthing-of-a-system-of-parallel-metal-plates.851418/