1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Point Charge and e-field

  1. May 22, 2010 #1
    1. The problem statement, all variables and given/known data
    Point charge q1= -5.00 is at the origin and point charge q2= +3.00 is on the -x axis at x= 3.00 cm. Point P is on the y-axis at y= 4.00 cm .

    Calculate the electric fields E1 and E2 at point P due to the charges q1 and q2. Express your results in terms of unit vectors.


    2. Relevant equations

    r = sqrt(x2 + y2)
    hat{r} = (vec{r} /r = x hat{i} + y hat{j}) / r
    vec{E} = (k * q)/r2 hat{r}


    3. The attempt at a solution
    E1 will be the vector from q1 to point P
    r = sqrt(02 + .042) = .04 m

    hat{r} = (0 hat{i} + .04 hat{j})/.04 = 0 hat{i} + 1 hat{j}

    E1 = (9*109) * (-5.00*10-9) / .042 (0 hat{i} + 1 hat{j})
    = 0 hat{i} - 2.81*104 hat{j}

    i did the exact same steps to find E2 and
    E2 = 6.47*102 hat{i} + 8.62*102 hat{j}

    Am I doing something wrong? According to the steps I used because my answers are wrong and i even followed the way the steps were in the book.
     
  2. jcsd
  3. May 22, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Is q2 at x = +3 cm or at x = -3 cm?
     
  4. May 22, 2010 #3
    q2 is at x=+3 cm = 0.03m
     
  5. May 22, 2010 #4

    Doc Al

    User Avatar

    Staff: Mentor

    So how did you end up with a positive i-component?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook