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Homework Help: E.M , capacity of a conductor?

  1. Feb 8, 2006 #1
    Hello guys, well its that time of the week when Im busy working on my homework again!
    One of this weeks questions is that there are 2 hollow concentric conducting spheres which hold charges Q1 (inner shell, radius R1), and Q2 (outer shell, Radius R2 )

    1) Find the potential difference between them. I think this is (Q2-Q1)/4*Pi*E0*r ?

    2)If q1 is +ive, and a wire connection is made from inner to outer conductor, charge will flow. How does direction of flow depend upon the magnitude and sign of Q2?

    I think charge will flow from higher to lower potential, ie if Q2 is a smaller +ive charge, charge will flow from q1 to q2.
    Is negative charge a lower potential than a positive, I guess?

    But this next part really gets me: What is the capacity of the above pair of conductors? (Answer 4*Pi*E0*R1R2/(R2-R1) )

    What on earth does "capacity" mean, we havent come across that term before! I would appreciate a poke in the right direction for this! There is another part but I havent tried that yet so I wont post here.

    Any help and hints (but no solutions please it is assesed) are most appreciated :-)

    Thank you

  2. jcsd
  3. Feb 8, 2006 #2


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    Error: r not defined.

    What is the potential at the surface of shell 1? Of shell 2?
  4. Feb 8, 2006 #3
    Hi :-)
    Oh I see, r should actually be R2-R1 in the equation I posted for the potential difference?


  5. Feb 9, 2006 #4


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