Re: Mathematica and RC circuits

*To*: mathgroup at smc.vnet.net*Subject*: [mg56919] Re: Mathematica and RC circuits*From*: dh <dh at metrohm.ch>*Date*: Tue, 10 May 2005 03:42:22 -0400 (EDT)*References*: <d5hu1r$jtc$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, your "question" is not exactly very clear, but I try my best. If you want a good answer, you should put some effort into putting a good question. See below Sincerely, Daniel 1s1kjake wrote: > I am trying to use Mathematica 5.1.1 to solve an RC circuit, and I am > having problems. When ever I use I or i for the current the program > keeps running untill it close down. I is used as the imaginary unit and can not be used as a variable name. As for i, there is no problem using it as a variable name. Then other problem, how do I set > up Mathematica to solve this equation for dvdt, i = v/r + c dv/dr. Guessing from your equation I think you have a parallel circuit of an resitor and a capacitor. But then the term dv/dr should read dv/dt. A sensible question is to ask for the voltage, given the current. As you have a first order DG you also need a starting value, say v[0]==0. Well, this gives the following equations: eq={i[t]==v[t]/r+c v'[t], v[0]==0}; Lets make an example by choosing: i[t_]=1; r=1; c=1; this is solved for the time {0,1} by: sol= v/. NDSolve[eq,v,{t,0,1}][[1]]; and plotted: Plot[sol[xt],{t,0,1}] > Then I want to plot this equation based on diferent current imputs. > thanks >