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!

Homework Help: Zero potential, 3 charges

  1. Apr 8, 2014 #1
    1. The problem statement, all variables and given/known data
    Let us have a square ABCD (D is in the topleft corner) of size 1 m. Let us have 3 point charges situated in points B, C and D. The charges are following QB=2C, QC=-1C and QD=5C. The task is to find (a) the points/plane where the electric potential is zero and (b) two points where the electric intensity is zero.

    2. Relevant equations
    ψ = (1/(4*pi*epsilon))* (Q1/r1+Q2/r2+Q3/r3)=0

    3. The attempt at a solution
    According to the equation mentioned above I obtain the following equation
    But now what? Is my current procedure OK?
    Last edited: Apr 8, 2014
  2. jcsd
  3. Apr 8, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    Your procedure is OK. If (a) asks for the points in the plane where the potential is zero, you can write it out in x and y and try to solve. Expect to end up rather close to C. in 3D it becomes a deformed sphere.
  4. Apr 9, 2014 #3
    How do I write it in x,y? And why in 3D, I should find the points in 2D not 3D.
    Any hint to (b)?
  5. Apr 9, 2014 #4
  6. Apr 9, 2014 #5


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    "I should find the points in 2D not 3D" Good thing you tell us, because it's nowherer in the original posting.

    If (x,y) is a point in the x,y plane, what is the expression for rB ?

    Wrt (b), does the problem ask for electric intensity, or does it ask for electric field strength ? If so, do you have a relevant equation available ?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted