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Homework Help: Current due to Potential Difference

  1. Mar 21, 2010 #1
    1. The problem statement, all variables and given/known data

    Consider a rectangular block of metal of height A, width B, and length C , as shown in the figure. If a potential difference V is maintained between the two A X B faces of the block, a current Iab is observed to flow.

    Find the current that flows if the same potential difference V is applied between the two B X C faces of the block

    http://session.masteringphysics.com/problemAsset/1126202/2/Walker4e.ch21.Pr023.jpg


    2. Relevant equations

    V=IR, R=rho(L/A)


    3. The attempt at a solution

    V=IR, R=rho(L/A)

    V=I*rho*(L/A)

    Iab=(V)/(rho*(C/AB))

    Ibc=(V)/(rho*(A/BC))

    I thought this last equation was right, but apparently it isn't. When I entered it, it said that B, V, and rho had no impact upon the answer. I'm not really sure what to do now...
     
  2. jcsd
  3. Mar 21, 2010 #2
    By the way, it wants the answer in "terms of some or all of the variables A, B, C, and Iab."
     
  4. Mar 2, 2011 #3
    the answer is Iab(C^2/A^2) due to the fact the voltages had to be set equal
    IabR =IbcR
    Iab(rhoL/A) =Ibc(RhoL/A)
    Iab(RhoC/AB) = Ibc(RhoA/BC)
    Rho's and B's cancel
    IabC/A = IbcA/C
    cross multiply
    IabC^2=IbcA^2
    Ibc =Iab(C^2/A^2)
     
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