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What is resistance of a DC circuit has resistor n capacitor connect parallel

  1. Nov 19, 2008 #1
    1. The problem statement, all variables and given/known data

    the title says everything, any formula that to find resistance in a DC circuit of one resistor and one capacitor connect parallel, as well as the current through each of R and C (the known values are R C and V)

    2. Relevant equations

    seem to me i = (V/R)e^ (-e/RC), but it only say for series
    3. The attempt at a solution

    couldn't find answer in text and on any website
     
  2. jcsd
  3. Nov 19, 2008 #2

    Hootenanny

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  4. Nov 19, 2008 #3
    does that mean the current won't go through capcitor branch? and that means if i want to find resistance of the circuit, it's simply R?(nothin to do with C)
    and wat about time constant? T = RC? will it be the same like when capacitor n resistor connect series?
     
    Last edited: Nov 19, 2008
  5. Nov 19, 2008 #4

    Hootenanny

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    It means that after a very short time interval, no current will pass through the capacitor branch, all the current will flow through the resistor.
     
  6. Nov 19, 2008 #5
    what about time constant T = RC, will it be zero also?
     
  7. Nov 19, 2008 #6

    Hootenanny

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    There is no time-constant in this case since after the initial current spike through the capacitor branch, the circuit simply behaves like a a resistor connected across a potential difference.
     
  8. Nov 19, 2008 #7
    thanx a lot, that quite a lot info for me
     
  9. Nov 19, 2008 #8

    Hootenanny

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    No problem. If you need to we can treat the network more rigorously, so if you have any more questions please feel free to return.
     
  10. Nov 20, 2008 #9
    What happens if we remove the resistor so the circuit consists just of a charged capacitor? Going around the loop we get [itex]q/C = 0[/itex] so q = 0 (i.e., it discharges immediately). Hmm.
     
  11. Nov 20, 2008 #10

    Hootenanny

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    That is indeed the case.
     
  12. Nov 20, 2008 #11
    Which is why you should be careful while shorting capacitors in the lab :smile:
     
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