Date: Jun 18, 2011 4:48 PM
Author: noslowski
Subject: Re: capacitor equation solution not working
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

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<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@yahoo.com