Re: capacitor equation solution not working

*To*: mathgroup at smc.vnet.net*Subject*: [mg119695] Re: capacitor equation solution not working*From*: michael partensky <partensky at gmail.com>*Date*: Fri, 17 Jun 2011 05:52:04 -0400 (EDT)*References*: <201106170409.AAA28826@smc.vnet.net>

Sorry, my last comment is irrelevant for your setting where the current is a given function (which is unusual but formally valid). Best MP On Thu, Jun 16, 2011 at 11:49 PM, michael partensky <partensky at gmail.com>wrote: > >> On Fri, Jun 17, 2011 at 12:09 AM, 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 >>> >>> I did not check the rest , but fixing two formatting errors can >> be helpful. >> > >> > My code. >> > I[t_]:= If[t<10||t>60,0,1] >> > Plot[i[t],{t,0,100}] (* you use different letters for the current, iand >> I; btw, I is reserved for the imaginary unit *) >> >> *Eq*=v'[t]==i[t]/c >> c=1; >> > >> > c=1; >> > Soleq==v[t]/.NDSolve[{*eq*,v[0]==0},v[t],{t,0,100}],[[1]] >> > Plot[soleq,{t,0,100}] >> ( **Eq* and *eq* are also different *) > > Btw, your circuit without a resistor is "short": the capacitor will > discharge instantly. > Be also aware that the derivative of a step function is expressed though > the so called delta-function which must be handled with extreme care. > > Best > MP > >

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