Anonymous asked in Science & MathematicsPhysics · 4 months ago

simple electric field question?

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2 Answers

  • 4 months ago
    Favorite Answer

    We know the field won't be zero outside the charges because their fields are in the same direction left of the origin (both point 180° and right of (1,0) where both point at 0°. There fields oppose between the charges and that is where E = 0 at the point where the fields are equal and cancel. Let r be the distance right from the origin.

    2.5/r² = 7.5/(1-r)²

    2.5(1-r)² = 7.5r²

    Take square roots of both sides

    √2.5(1-r) =+/- √7.5r

    √2.5 = √2.5r+√7.5r = r(√2.5 +√7.5)

    r = √2.5/(√2.5 +√7.5) = 0.366 <<<<<<

    Check the negative solution

    r = √2.5/(√2.5 - √7.5) = -1.366 which can't be right because the fields add left of the origin. Discard solution r = -1.366

    E = 0 at x = +0.366

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  • 4 months ago

    The field from A points towards B , and the (stronger) field from B ,points towards A. At some point between them, therefore there will be a point where their fields cancel out .

    From the definition of E being proportional to Q/D, you get :

    Q(a) / D = Q(b) / (1-D)

    • hoarseman
      Lv 7
      4 months agoReport

      My apologies for accidently dropping the "square" of the distances

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