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Homework Help: Polar coordinates of an electric field

  1. Jan 30, 2012 #1
    1. The problem statement, all variables and given/known data

    Three charges are arranged as presented below. Q1= 5.00E-9C, Q2= 6.00E-9C and Q3= -7.00E-9C.

    http://img15.imageshack.us/img15/9250/physicskf.png [Broken]

    D) Find the direction of the above electric field using the polar coordinate system 0°< θ <360°

    2. Relevant equations

    tan θ = o/a

    3. The attempt at a solution

    I found my

    E1 = 500
    E2 = 5400
    E3 = -700

    Ex = 500 cos 18.4° + (-700) = -225.6
    Ey = 500 sin 18.4° + 5400 = 5557.8

    But the angle that I got was incorrect which was 24.63°.

    Help anyone?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jan 30, 2012 #2

    SammyS

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    You are finding the Electris Field at what location?
     
    Last edited by a moderator: May 5, 2017
  4. Jan 30, 2012 #3
    Oops, sorry about that. Point P (0.3m,-0.1m)
     
  5. Jan 30, 2012 #4

    SammyS

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    Review the signs of your components .
     
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