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!

Finding magnitude of two charge given midpoint

  1. Apr 28, 2017 #1
    1. The problem statement, all variables and given/known data
    Two positive point charges, A and B are 6m apart. The electric field intensity at point C, midway between the two charges is 5 N/C directed towards B and the potential at the same point is 45V. Find the magnitude of A and the magnitude of B.

    2. Relevant equations
    E = kQ/r2

    3. The attempt at a solution
    From what I visualize it:

    (+A)<---3m--->(-C)<---3m--->(+B)

    Using E = kQ/r2 where Q=Er2/k

    Q = (5 N/C)(3 m)2 / (9x109 Nm2/C2) = 5x10-9C

    which is the answer for A and B I suppose? But the answer key tells me that the answer in A is twice the B. How come? I'm quite confuse on how this works.
     
  2. jcsd
  3. Apr 29, 2017 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    The equation you applied is valid for the electric field of a single point charge. You have two charges, QA and QB, both contributing to the electric field and to the potential at point C.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted