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What is the electrical potential at point P?

  1. Mar 8, 2017 #1
    1. The problem statement, all variables and given/known data

    Three point charges of +6.00 μC, +4.00
    μC, and +6.00 μC are placed along the x-axis 0.200 m above the +4.00 μC charge as shown in the figure below. What is the electrical potential at point P (relative to infinity) due to these charges?

    Diagram:

    https://pbs.twimg.com/media/C6cPxGfU0AA9QMB.jpg:large [Broken]

    2. Relevant equations

    Vp = V1 + V2 + V3
    Vp= ##\frac {kQ} {r^2}## + ##\frac {kQ} {r^2}## + ##\frac {kQ} {r^2}##

    3. The attempt at a solution

    Vp= ##\frac {kQ} {r^2}## + ##\frac {kQ} {r^2}## + ##\frac {kQ} {r^2}##

    Vp= 8.99 x109 ⋅ 6 x 10-6 / 0.2832 + 8.99 x109 ⋅ 4.00 x 10-6 / 0.2002 + 8.99 x109 ⋅ 6 x 10-6 / 0.2832

    Vp = 2.24 × 106 V
     
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Mar 8, 2017 #2
    Your potential Energy defition is wrong It cannot be ##V_p=\frac {kQ} {r^2}##.Think about it.
     
  4. Mar 8, 2017 #3
    I'm not sure what other equation it would be. This is electrical potential (voltage). I know there are 3 charges and there is a distance r for each of them to the point P.
     
  5. Mar 8, 2017 #4

    haruspex

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    You are confusing it with the formula for the field. Your equation is dimensionally wrong.
     
  6. Mar 8, 2017 #5
    Oh okay I see my error. I squared the r, when it shouldn't be.
     
  7. Mar 8, 2017 #6

    haruspex

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    Right.
    Do you get the right answer now, or can't you tell yet?
     
  8. Mar 8, 2017 #7
    Yes I got the right answer. Thanks.
     
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