Results 1 to 2 of 2

Math Help - exponential function

  1. #1
    Newbie
    Joined
    Jun 2008
    Posts
    12

    exponential function

    Given T(subscript1/2) to be .0247 seconds, how long should it take to reach 93.75% of maximum charge?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by karnold9 View Post
    Given T(subscript1/2) to be .0247 seconds, how long should it take to reach 93.75% of maximum charge?
    You are doing nobody any favours with this question, you have not provided enough context for anyone to answer without guessing what the question really is.

    Lets assume that T_{1/2} is the time to reach 1/2 maximum charge from flat for a charging model where the rate of charging is proportional to the difference between the maximum charge and the current charge.

    Then starting from zero charge the charge state at time t is:

    \frac{C}{C_{mx}}= (1-e^{-kt})

    Then we solve for k from:

    0.5= (1-e^{-k\times 0.247})

    Then having found k we solve for t is:

    0.9375= (1-e^{-kt})

    (the arithmetic is slightly easier if we write the charging law as:

    \frac{C}{C_{mx}}= (1-2^{-kt})

    which you can try if you like)

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: April 17th 2012, 10:50 AM
  2. Replies: 11
    Last Post: May 9th 2010, 08:55 AM
  3. Replies: 0
    Last Post: August 31st 2009, 02:02 AM
  4. Replies: 2
    Last Post: March 30th 2008, 02:28 PM
  5. Replies: 3
    Last Post: July 17th 2007, 11:06 AM

Search Tags


/mathhelpforum @mathhelpforum