Re: capacitor equation solution not working

• To: mathgroup at smc.vnet.net
• Subject: [mg119717] Re: capacitor equation solution not working
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Sat, 18 Jun 2011 06:22:25 -0400 (EDT)
• References: <201106170409.AAA28826@smc.vnet.net>
• Reply-to: drmajorbob at yahoo.com

```Do NOT type your code into e-mail. Ever. Copy it from Mathematica and
paste it into e-mail.

Sometimes it's useful to Copy > As plain text.

Bobby

On Fri, 17 Jun 2011 12:16:13 -0500, J and B <noslowski at 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 at austin.rr.com]
> Sent: Friday, June 17, 2011 5:53 AM
> To: mathgroup at 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 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
>
>

--
DrMajorBob at yahoo.com

```

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