
Re: capacitor equation solution not working
Posted:
Jun 18, 2011 4:48 PM


Do NOT type your code into email. Ever. Copy it from Mathematica and paste it into email.
Sometimes it's useful to Copy > As plain text.
Bobby
On Fri, 17 Jun 2011 12:16:13 0500, J and B <noslowski@comcast.net> wrote:
> Sorry for not typing my code in correctly. I have the same code as you, > that is mentioned in this email > i[t_] := If[t < 10  t > 60, 0, 1] > eq = v'[t] == i[t]/c; > c = 1; > soleq = v[t] /. First@NDSolve[{eq, v[0] == 0}, v[t], {t, 0, 100}]; > Plot[soleq, {t, 0, 100}] > But I thought it had to be wrong, since the capacitor never came back to > zero. I did not realize that I had to have a resistor in the circuit, as > several people pointed out. > Thanks for your help > > > Original Message > From: DrMajorBob [mailto:btreat1@austin.rr.com] > Sent: Friday, June 17, 2011 5:53 AM > To: mathgroup@smc.vnet.net > Subject: Re: capacitor equation solution not working > > Surely that is NOT your code; it has at least four misspellings and two > fatal syntax errors  == where you need = (as in Soleq = ...) and the > comma > before [[1]]. > > If you ran that code, you'd see error messages, not just a constant plot. > > This works, however: > > i[t_] := If[t < 10  t > 60, 0, 1] > eq = v'[t] == i[t]/c; > c = 1; > soleq = v[t] /. First@NDSolve[{eq, v[0] == 0}, v[t], {t, 0, 100}]; > Plot[soleq, {t, 0, 100}] > > I'd also suggest THIS for the first line: > > i[t_] := Boole[10 <= t <= 60] > > Bobby > > On Thu, 16 Jun 2011 23:09:13 0500, J and B <noslowski@comcast.net> > wrote: > >> I am trying to solve a very simple circuit, one that has only a >> capacitor in it. What am I doing wrong? The final graph should show >> that the capacitor has discharged, but its staying constant. I have >> current starting at t=10 and ending at t=60. >> I hope I have used the correct way to put in my code, I am using a new >> computer and I having trouble with my email program. Any advice would >> be appreciated. >> >> Thanks >> >> My code. >> I[t_]:= If[t<10t>60,0,1] >> Plot[i[t],{t,0,100}] >> Eq=v'[t]==i[t]/c >> c=1; >> Soleq==v[t]/.NDSolve[{eq,v[0]==0},v[t],{t,0,100}],[[1]] >> Plot[soleq,{t,0,100}] > > >  > DrMajorBob@yahoo.com > >
 DrMajorBob@yahoo.com

