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Homework Help: Calculating flux when charge on vertex of cube

  1. Aug 24, 2010 #1
    1. The problem statement, all variables and given/known data

    A point charge q = 112 x 10^-9 C is placed at the centre of a cube of side l = 0.2 m.

    If the charge is moved all the way to one vertex of the cube, determine the flux
    through each of the faces.

    2. Relevant equations


    3. The attempt at a solution

    I looked at the answer:

    Flux through each face = Total flux / 24
    = 2 109.23 / 24
    = 527 Nm^2/C

    And dont understand why the 24 is used.

    I read somewhere that it said that the flux through the faces adjacent to the vertex where the charge is placed = 0, but I dont understand why? I think this might be why I dont understand the use of the "24". Could someone please help?
  2. jcsd
  3. Aug 24, 2010 #2
    Sorry forgot to attach a diagram

    Attached Files:

    • Cube.jpg
      File size:
      25.9 KB
  4. Apr 28, 2012 #3
    Flux through the faces touching the charge is zero because the Electric field is parallel to them. And flux through each face = ∅/24, since you have 24 faces in the cube diagram you attached.
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