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!

Surface charge distribution of two metal spheres

  1. Nov 19, 2008 #1
    1. The problem statement, all variables and given/known data

    A total charge Q is shared by two metal spheres of small radii R1 and R2, that are connected by a long thin wire of length L. Fin (a) the charge on each sphre and (b) the tension in the wire.

    Source: Haliday 4th edn chapter 26 q. 91, p. 738

    3. The attempt at a solution

    I'm a bit confused by this. I assume that since the potential must be uniform for a conductor, that we can make the equation

    [itex]\frac{rQ}{4\pi\epsilon_0 R_1} = \frac{(1-r)Q}{4\pi\epsilon_0 R_2}[/itex]

    from which we obtain

    [itex]Q_1 = \frac{Q}{1 + R_2/R_1}[/itex].

    But I suppose this is only valid if the length of L is sufficiently large that we can ignore the interaction energy of the two spheres right?
  2. jcsd
  3. Nov 19, 2008 #2
    Perhaps I am correct, and merely

    [itex]\mathrm{Tension} = \frac{Q_1 Q_2}{4\pi \epsilon_0 (L + R_1 +R_2)^2}[/itex]?
  4. Nov 19, 2008 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You're correct for both parts.

    However, they probably want tension in terms of the given parameter Q, not in terms of Q1 and Q2.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?