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: Electric Potential

  1. Jun 13, 2004 #1
    Hello everyone, I need alittle help with an assignment....I am given two charges one along the y axis and one along the x, and I am asked to find the electric potential at infinite distance...I found the electric potential at the origin, but I am unsure about the eletric potential at infinity.Since when r final= infinity then it is o V at f....So the electric potential is equal to 1/4piE (Q/r)....what I am not sure about is as how to treat this with two point like charges....To find the electric potential at infinity.....
    Thank you
  2. jcsd
  3. Jun 13, 2004 #2


    User Avatar

    The potential at infinity is just zero. Remember the definition of potential, as the integral of the electric field from infinity to the point in space you wish to calculate the potential. If that point happens to be infinity, you're moving from infinity to infinity, in other words, your not moving anywhere, and the potential is just zero, relative to infinity.
  4. Jun 14, 2004 #3
    Thank you :smile:
  5. Jun 14, 2004 #4
    I have another question about this problem...there is another part asking for the work done by electrical forces if the proton at the origin is moved from the origin to infinity?? Is it just the negative potential energy of the proton at the origin?
    Thank you
  6. Jun 15, 2004 #5
    Yes, because the work-energy theorem for conservative forces (such as the electric field force) is

    [tex] W_C = -\Delta ({\rm PE}).[/tex]

    So to find the work of all conservative forces acting on a particle as it moves from one point to another, find the change in potential energy between those two points.

    Don't forget the negative sign (which appears because conservative forces try to minimize potential energy). Note also that one of the potential energy values (at infinity) is 0.
  7. Jun 15, 2004 #6
    sorry I have another dumb question....Since the particle's PE is zero at infinity, so there is really no change and it is just the negative of the result I found at the origin where the particles is no?
  8. Jun 15, 2004 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes, this is correct.
  9. Jun 15, 2004 #8
    thanks :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook