Re: capacitor equation solution not working

*To*: mathgroup at smc.vnet.net*Subject*: [mg119716] Re: capacitor equation solution not working*From*: "J and B" <noslowski at comcast.net>*Date*: Sat, 18 Jun 2011 06:22:14 -0400 (EDT)*References*: <201106170409.AAA28826@smc.vnet.net> <201106170953.FAA02174@smc.vnet.net>

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 at austin.rr.com] Sent: Friday, June 17, 2011 5:53 AM To: mathgroup at smc.vnet.net Subject: [mg119716] 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 at 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<10||t>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 at yahoo.com

**References**:**capacitor equation solution not working***From:*"J and B" <noslowski@comcast.net>

**Re: capacitor equation solution not working***From:*DrMajorBob <btreat1@austin.rr.com>

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**Re: capacitor equation solution not working**