1. Limited time only! Sign up for a free 30min personal 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!

Find the electric field at the origin

  1. Jul 15, 2017 #1
    1. The problem statement, all variables and given/known data
    Given two charged particles:

    1) 5x10^-9 C, (-.03 m, 0 m)
    2) -20x10^-9 C (.04 m, .02 m)

    find the electric field at the origin.


    2. Relevant equations
    F = (kQq)/r^2
    E = (kQ)/r^2

    3. The attempt at a solution

    So I know since 1)'s charge is plus, its field vector is

    [itex] ( (8.99x10^{-9}) (Q) ) / (.03)^2 [/itex] i hat, meaning its going to the right

    I use arctan to find the angle between the origin and 2), it is 26.57 deg, and pathagorean theorem to find the distance r to be .045m

    since 2) is - charged, its electric field is going away from the origin at 26.57 degrees.

    [itex] ( (8.99x10^{-9}) (Q) ) / (.045)^2 [/itex]

    Now I can break it down in to components, but how am I suppose to find Q, the charge of the origin?

    If they gave me a value for the electric force between the origin and one of the particles I can find Q, but with this information I dont see any way I can find it?
     
    Last edited: Jul 15, 2017
  2. jcsd
  3. Jul 15, 2017 #2

    TSny

    User Avatar
    Homework Helper
    Gold Member

    There is no charge at the origin. In the formula E = kQ/r2, Q is the charge that is producing the electric field. Each of the two charges that are given in the problem is producing electric field at the origin.
     
  4. Jul 16, 2017 #3
    Thank you sir. I was wasting my time on this question for 2 hours already.. now my answer matches my books answer. TY.
     
  5. Jul 16, 2017 #4

    TSny

    User Avatar
    Homework Helper
    Gold Member

    OK, good work.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted