Optimization of sphere and cyliners (Electrical physics)

  1. I recently noticed that I have blindly used optimization in some problems that involve symmetrical insulating/conducting spheres and cylindrical shells.
    For example, when calculating outer electric field caused by a spherical insulator/conductor, I just treated these as a simple point charge located at their center, and those ways rendered correct answers. Also, in a question involving an infinite cylindrical shell, (given charge density), I treated it as a simple line charge located at its center, and it also gave me a right answer. However, I am still not convinced how this works mathematically. Is it just a way of simplifying problem for faster calculation, or is there any theorem / definiton that fully explain the validity of this simplification?
    I would appreciate some help
  2. jcsd
  3. Simon Bridge

    Simon Bridge 15,473
    Science Advisor
    Homework Helper
    Gold Member

    Look up Gausses Law.

    You've noticed that the "optimization" only works for simple geometries, and only outside the objects in question.
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