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Homework Help: What is the charge density on the insulator?

  1. Feb 21, 2017 #1
    1. The problem statement, all variables and given/known data

    Insulator has a 3 cm radius and is a sphere. It has a total charge of -4.2 uC. I need to find the charge density of the insulator.

    2. Relevant equations
    sigma = total charge / volume.... I think?

    3. The attempt at a solution

    After using the above equation, I got -3.714E-8 C/m

    I am just not sure if this is the correct charge density for the insulator. I know that for conductors, I think the equation would be charge/area, but I think since an insulator contains the charge throughout the sphere and not just on the surface, you'd have to use volume correct? I am correct in my answer and thinking?
  2. jcsd
  3. Feb 21, 2017 #2


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    2017 Award

    Thinking is good, but I can't see your calculation (telepathic powers lacking) :smile: and the dimension of the answer seems a bit strange to me. Value also.
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