1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: How they say that it is the solution

  1. Apr 19, 2010 #1
    they said that the solution of

    [tex]-dn=-\frac{1}{\tau}ndt\\[/tex]

    is

    [tex]n=n_0e^{-\frac{t}{\tau}}[/tex]



    i got a totaly different answer

    [tex]-dn=-\frac{1}{\tau}ndt\\[/tex]
    [tex]\int -dn=\int -\frac{1}{\tau}ndt\\[/tex]
    [tex]\int \frac{-dn}{n}=\int -\frac{1}{\tau}dt\\[/tex]
    [tex]-\ln{n}=-\frac{t}{\tau}\\[/tex]
    [tex]\ln{n^{-1}}=-\frac{t}{\tau}\\[/tex]
    [tex]e^{-\frac{t}{\tau}{={n^{-1}}[/tex]
     
  2. jcsd
  3. Apr 19, 2010 #2

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Are you sure the negative sign in front of dn in the original equation is supposed to be there? You also forgot the constant of integration.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook