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Homework Help: Gauss' Law Help don't even know where to start

  1. Jan 27, 2013 #1
    An electric field is E = 250 N/C i for x > 0 and E = -250 N/C i for x < 0. A cylinder of length 20 cm and radius 3 cm has its center at the origin and its axis along the x axis such that one end is at x = +10 cm and the other is at x = -10 cm.

    What is the outward flux through each end?
    a) +x end
    b) -x end

    I tried integrating the surface area of the cylinder, then multiplying by the electric field within that area but it's not correct... so a starting point or walk-through would be greatly appreciated.
  2. jcsd
  3. Jan 27, 2013 #2

    Doc Al

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    Staff: Mentor

    What do you mean? Did you find the area of each circular end surface?
    That should work, assuming you have the correct signs.

    Show what you did.
  4. Jan 27, 2013 #3
    I figured it out actually. They were just looking for the flux through the very end, so I only needed to find the area of the end of the cylinder, then multiply that by the electric field. I was integrating the surface area of the entire cylinder and then multiplying the charge by that. Obviously a very different number.
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