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Homework Help: Exponential decay of voltage

  1. May 28, 2008 #1
    Please Help!

    This is based on the time at any point on the curve during exponential decay of voltage.

    Could someone explain to me this formula?

    t=T1n(E/Vl)

    example:

    t=(7.5ms)1n(20v/14.57v)=2.38ms.

    I get 20/14.57=1.372683596
    (7.5)(1.372683596)=10.29512697
    where and how do you get 2.38, where does the 1n fall in and how? is there a numerical value for this statement? Please help?
     
  2. jcsd
  3. May 28, 2008 #2

    berkeman

    User Avatar

    Staff: Mentor

    Please don't multiple post the same question. Your question was answered in your original thread:

    https://www.physicsforums.com/showthread.php?t=237561

    What you are writing as 1n is actually LN, or the natural log. It is a button on your scientific calculator.
     
  4. May 28, 2008 #3
    it still does not work!
     
  5. May 28, 2008 #4

    berkeman

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    Staff: Mentor

    Yes it does.

    t=(7.5ms) * LN(20v/14.57v) = 2.38ms.

    Divide 20/14.57, take the natural log, then multiply by 7.5. I get 2.375something.
     
  6. May 28, 2008 #5
    Thank You!
     
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