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Homework Help: Simple Time Constants

  1. Apr 18, 2010 #1
    1. The problem statement, all variables and given/known data

    Calculate the time constants of the following circuits

    I drew them in the attachment


    2. Relevant equations

    t=RC in a RC Circuit

    t= L/R in a RL Circuit







    3. The attempt at a solution

    Im not sure if in the first one, I would simply add the two resistors and multiply the total by the Capacitance ?

    If so, then it would be 45 k Ohm x 2 Micro Farads = 45000 Ohms x 2E-6 Farads = .09 Seconds


    The second one, I calculated the value of the parralell resistors as 30 ohm x 80 ohm / 110 ohm = 21.81 Ohms

    Then it would just be 50 milliHenries = .05 Henries / 21.81 Ohm = .0022 Seconds
     

    Attached Files:

  2. jcsd
  3. Apr 18, 2010 #2

    kuruman

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    Correct.
     
  4. Apr 18, 2010 #3
    For the first one, it doesnt matter that the second resistor comes after the capacitor ?
     
  5. Apr 18, 2010 #4

    kuruman

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    It doesn't matter. The resistors are in series. Whatever charges move through one resistor, have to go through the other.
     
  6. Apr 18, 2010 #5
    Cool, so I was correct on both attempts ? Good News




    Thanks
     
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