Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Solving for Im

  1. Aug 22, 2010 #1
    1. The problem statement, all variables and given/known data

    I am trying to solve the equation for Im and am having trouble

    [tex]Im=(Im+Ie+Ia)e^{-t/T} +Ia)[/tex]

    [tex]Im-Ia = (Im+Ie+Ia)e^{-t/T})[/tex]

    [tex]ln^{Im-Ia}= Im+Ie+Ia[/tex]

    this is were I get to but cant get the equation to work. Have I don't something incorrect in the second line when moving e^-t/T across to the other side?

  2. jcsd
  3. Aug 22, 2010 #2


    User Avatar
    Gold Member

    Going from the second to the third line, there's something wrong.

    Keep in mind [tex]\frac{1}{e^{-x}}[/tex] = [tex]e^{x}[/tex]. But expanding line 1 and rearranging the terms to make Im the focus may be the better alternative.
  4. Aug 23, 2010 #3


    User Avatar
    Science Advisor

    Since you are not solving for t or T there is no reason to take a logarithm. Just treat [itex]e^{-t/T}[/itex] as a single number and divide both sides by it:
    [tex]Ime^{t/T}- Iae^{t/T}= Im+ Ie+ Ia[/tex]

    Can you solve from there?

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook