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Homework Help: Help with Electric Field and Flux

  1. Jul 5, 2004 #1
    This problem is quite annoying considering I see it testing us in knowing when you can and cannot apply Gauss Law.

    The loop shown here

    http://uploader.clausercorp.com/uploaded/Loops.JPG [Broken]

    (I tried to draw it best i could) has an area of A, held to the right of a positive point charge +Q. The surface bounded by the loop is a plane--- so the area vector (I didnt draw) would be pointing perpendicular to the "plane" that is inside that loop, to the right.

    Would the electric field flux thru the loop due to the charge be positive negative or zero?

    At first I would say yes, considering the field lines are coming out of +Q and are "flowing" thru the plane. IE: E dot A would be positive since the Area vector I drew would be facing the same direction as the x components of the field lines--- correct?

    But then I wonder if its possible to use Gauss Law at all since the charge isnt enclosed by the surface--- or am I getting my definition mixed up?

    Also say a +2Q charge is placed to the right of the loop, and the +Q charge was still to the left. Would the flux change?

    i understand there would be more field lines coming out of the + 2Q charge, but since i drew my area vector pointing to the right of the loop--- would the +2Q charge allow for the net flux due to both +Q and +2Q be negative?

    And another situtation is when the +2Q is negative instead--- IE -2Q. Would that change anything?

    THanks for your help--- conceptually i find it difficult...
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Jul 6, 2004 #2

    Doc Al

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    Staff: Mentor

    Why are you bringing up Gauss's law?

    The total flux through the loop will be the sum of the fluxes from each charge. So what do you think?
    What do you think? Does the flux depend on the direction of the field?
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