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!

Determining charge from electric potential

  1. Feb 18, 2013 #1
    1. The problem statement, all variables and given/known data
    A metal sphere with radius ra = 1.20 cm is supported on an insulating stand at the center of a hollow, metal, spherical shell with radius rb = 9.00 cm. Charge +q is put on the inner sphere and charge -q on the outer spherical shell. The magnitude of q is chosen to make the potential difference between the spheres 500 V, with the inner sphere at higher potential. Calculate q.


    2. Relevant equations

    ΔV=q/K [(1/ra)-(1/rb)]


    3. The attempt at a solution

    Solving for q from the eqn above I have reached q= ΔV/[(1/ra)-(1/rb)] * K. By simply plugging in the numbers given I reached a soln of q= 6.23*10^10 C. This answer seemed far too large to be right, and indeed it is not correct. Is this the proper equation to use in this situation? I double checked the math and it appears everything is right, does anyone see where I may have gone wrong? Any help is greatly appreciated.
     
  2. jcsd
  3. Feb 18, 2013 #2

    TSny

    User Avatar
    Homework Helper
    Gold Member

    Hi rmcgovern. Welcome to PF!

    Did you put the constant K in the correct location in your equation for ΔV?
     
  4. Feb 18, 2013 #3
    ah! I forgot that K=1/4∏ε0. a rather trivial error. thank you for your help.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Determining charge from electric potential
Loading...