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Homework Help: 2 capacitors

  1. May 2, 2009 #1
    1. The problem statement, all variables and given/known data
    2 capacitors of equal capacitance one charged to potential V, and other completely discharged. when the are connected in parallel what would be the potential of each one of them.

    2. Relevant equations

    E=1/2 (C.V^2)

    3. The attempt at a solution
    as they are connected in parallel potential of each wud be same... now by conservation of energy i got answer V/sqrt(2)
    am i right??
  2. jcsd
  3. May 2, 2009 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    What is the charge, Q, on the charged capacitor (in terms of C and V)?
    What is the total charge, Q', on the two capacitors when they are connected together?
    What is the capacitance, C', of the two capacitors when connected together (in terms of C)?
    What is the potential V' (in terms of Q' and C')?
    Now express the answer in terms of C and V.

  4. May 2, 2009 #3
    When you connect the two capacitors in parallel, energy will be lost due to the charges moving through the resistive wires. So conservation of energy doesn't apply in this case. But the total number of charges is conserved. So follow Andrew Mason's steps and you will get the right answer.
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