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Find time constant

  1. Apr 22, 2014 #1

    utkarshakash

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    Gold Member

    1. The problem statement, all variables and given/known data
    The time constant of charging for the capacitor shown in the figure is


    2. Relevant equations

    See attached diagram

    3. The attempt at a solution

    [itex]\tau = R_{eq} C [/itex]

    [itex]R_{eq} = R/2 [/itex]

    So the answer should be t= RC/2. But the correct answer is 0! :confused:
     

    Attached Files:

  2. jcsd
  3. Apr 22, 2014 #2

    gneill

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    Staff: Mentor

    Once the switch is closed all the components are in parallel, right? What's the rule for the potential across components in parallel?
     
  4. Apr 22, 2014 #3

    utkarshakash

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    They all have the same potential difference.
     
  5. Apr 22, 2014 #4

    gneill

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    Staff: Mentor

    Right. And if the voltage source is ideal and the wires have entirely negligible resistance, then the capacitor voltage immediately after the switch closes must be....
     
  6. Apr 22, 2014 #5

    utkarshakash

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    It should be V. Thus time constant must be 0. Thanks !
     
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