Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

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

Search the Archive

Re: How to set up a diff equation for circuit with a diode?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62809] Re: How to set up a diff equation for circuit with a diode?
  • From: dh <dh at metrohm.ch>
  • Date: Mon, 5 Dec 2005 13:41:31 -0500 (EST)
  • References: <dn0v2m$8g2$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,
your question mnust be rephrased. The diode either has no effect or 
blocks all current.
If the diode has no effect, the initial current of I0 changes with time 
exponentially to V/R. For this case we have (I call the current C 
because I already has a meaning):
L C'[t]  + R C[t] -V == 0

the analytic solution to this is (in its full glory):
\!\(\(\[ExponentialE]\^\(-\(\(R\ t\)\/L\)\)\ \((C0\ R + \((\(-1\) + \
\[ExponentialE]\^\(\(R\ t\)\/L\))\)\ V)\)\)\/R\)

Using NDSolve, you will first have to give numerical values to the 
constants and then you would write:

rep = {R -> 1, L -> 1, V -> 1, C0 -> 2};
NDSolve[{L C'[t] + R C[t] - V == 0, C[0] == C0} /. rep, C, {t, 0, 2}]

this gives an InterpolatingFunction that can be plottedt e.g. by:

Plot[(C /. res[[1]])[t], {t, 0, 2}]


Daniel

siliconmike wrote:
> I'm kind of curious how to set up a nonlinear differential equation and
> then solve it using NDSolve in case of the following setup:
> 
> Battery V in series with a diode, R and L.
> 
> To simplify, we may assume that diode is a pure conducting device in
> forward direction and pure blocking device in the reverse direction.
> 
> Now how to set up a differential equation for the current I(t), that is
> solvable using NDSolve?
> 
> Thanks
> Mike
> 


  • Prev by Date: Re: A question about algebraic numbers using Mathematica
  • Next by Date: Re: FixedPoint stops "when elements no longer change"?
  • Previous by thread: Re: How to set up a diff equation for circuit with a diode?
  • Next by thread: How to set up a diff equation for circuit with a diode?