Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Re: capacitor equation solution not working

• To: mathgroup at smc.vnet.net
• Subject: [mg119716] [mg119716] Re: capacitor equation solution not working
• From: "J and B" <noslowski at comcast.net>
• Date: Sat, 18 Jun 2011 19:56:03 -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] [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>