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osanseviero

  • one year ago

Electric field question

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  1. osanseviero
    • one year ago
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    There is an electrical field. There is a line with constant density. We know L (how long is the line). At a distance a from the middle, there is a point. Which is the field there? |dw:1441428125288:dw|

  2. UnkleRhaukus
    • one year ago
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    is \(L\gg a\)?

  3. osanseviero
    • one year ago
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    Yep

  4. osanseviero
    • one year ago
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    It is not infinite though, so I don't think we can use Gauss here

  5. osanseviero
    • one year ago
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    Actually it does not say anything about the relationship between a and L

  6. UnkleRhaukus
    • one year ago
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    i don't know how to deal with the fringing effects the occur at the the end point of the line, i do know how to get the E field if the line if infinite, (good approximation if a<<L)

  7. UnkleRhaukus
    • one year ago
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    hmm i maybe if a is a point above the MIDDLE of the line , the fringing effect from both sides cancel

  8. osanseviero
    • one year ago
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    It is in the middle

  9. osanseviero
    • one year ago
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    So I would guess that in horizontal all of them cancel

  10. UnkleRhaukus
    • one year ago
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    |dw:1441430062457:dw|

  11. osanseviero
    • one year ago
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    So I would have to use Gauss?

  12. UnkleRhaukus
    • one year ago
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    yeah use this cylinder as your gaussian pill box

  13. osanseviero
    • one year ago
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    Doing that I have E(2pi*a*L) = Qin / epsilon. But they told me doing this was not correct

  14. UnkleRhaukus
    • one year ago
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    is Qin the total charge of the line?

  15. UnkleRhaukus
    • one year ago
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    i think you have to express the charge in terms of a linear charge density \(\lambda\) \[\lambda = q/L\]

  16. osanseviero
    • one year ago
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    E = lambda/(2 * pi * a * Eo) (Eo is the epsilon)

  17. osanseviero
    • one year ago
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    But still...how would you solve this without Gauss?

  18. UnkleRhaukus
    • one year ago
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    you mean like using Coulombs law?

  19. osanseviero
    • one year ago
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    Yep. Coulomb + Electric field

  20. osanseviero
    • one year ago
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    And charge distributions

  21. osanseviero
    • one year ago
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    Found an answer, thanks a lot

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