Re: capacitor equation solution not working

• To: mathgroup at smc.vnet.net
• Subject: [mg119701] Re: capacitor equation solution not working
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Fri, 17 Jun 2011 05:53:09 -0400 (EDT)
• References: <201106170409.AAA28826@smc.vnet.net>

```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

```

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