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Calculate the flux through a cube of size 1.0 m

  1. Feb 3, 2013 #1
    An E field exists in a region of space and it can be described by:
    [tex] \bar{E} = \hat{i}xy^2 [/tex]

    Calculate the flux through a cube of size 1.0m, with one end extending into the positive x,y and z directions.

    Find the charge enclosed.

    I have no idea how to start this? can someone point me in the right direction please?

    I know that:
    [tex] \Phi = EA [/tex]

    But what does it mean that the E field exists in a region of space?

    All help is appreciated.

    And im not looking for a solution, but all help will be appreciated.

  2. jcsd
  3. Feb 3, 2013 #2


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    Staff: Mentor

    This applies only if ##\vec E## has the same magnitude everywhere on the surface, and is perpendicular to the surface everywhere. If these are not true, you have to integrate:

    $$\Phi = \int {\vec E \cdot \hat n da}$$

    Does this ring a bell?
  4. Feb 3, 2013 #3
    Sorry, not really.
    What values do I put in for for [itex]\hat{i}[/itex]?
    And what's the [itex]\hat{n}[/itex]? And do I pull E out of the integration as a constant? Then integrate da just to a?
    I'm sorry, I just got into this class two weeks late, and this is due tomorrow. But I'm gonna spend this week catching up.
    Last edited by a moderator: Feb 4, 2013
  5. Feb 4, 2013 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    You really just need to sit down with your textbook and learn the basics. After all, if you don't even understand what the notation means, how can you expect to solve the problem? The examples in your textbook should answer most of your questions.
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