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Homework Help: Relation between Electric Potential and Electric Field

  1. Sep 17, 2015 #1
    1. The problem statement, all variables and given/known data
    In a certain region of space, the electric field along the x-axis is given by:

    E = 1.2x - 3.06, where E is in N/C and x is in meters.

    If you set the electric potential equal to zero at (4.39 m,0), find the electric potential, in V, at the point (7.22 m,0).

    2. Relevant equations
    V = - ∫E * dl

    3. The attempt at a solution

    V = - ∫ (1.2X-3.06) dx

    ⇒ V = - [1.2X2/2 - 3.06X]02.83

    ⇒V=3.85 → which is http://www.dabur.com/odomos/images/wrong_sign.jpg [Broken] :oldfrown: ...any suggestions?
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Sep 17, 2015 #2


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    You have the wrong integration boundaries and you are missing the term due to the potential at x = 4.39 m.
  4. Sep 17, 2015 #3

    rude man

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    First, find the potential difference between the two points.
    Then set the one to zero & get the other.
  5. Sep 17, 2015 #4
    potential difference between the two points: Vba = - ∫4.397.22 (1.2X-3.06) dx

    ⇒ Vba = -[1.2X2/2-3.06X]4.397.22
    = -(9.184+1.870)
    = -11.054
    ⇒-11.054 = Vb - Va


    ⇒Vb = -11.054 V

    does that make more sense? :olduhh:
  6. Sep 17, 2015 #5

    rude man

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    A whole lot more! :smile:

    P.S. I didn't check the math.
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