[SI-LIST] Fwd: Re: heat v. radiation Re: FEM/BEM/MoM

From the same web site, click on "Energy Stored."
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng.html#c1

The last sentence of the last paragraph states:
For a finite resistance, one can show that half of the
energy supplied by the battery for the charging of the
capacitor is dissipated as heat in the resistor,
regardless of the size of the resistor.

My point was not that it depended on the size of the
resistor, just that there was one.

-Mike

--- Harry Selfridge <harrys@xxxxxxxxxxxxxxxxxxxxx>
wrote:
> Date: Fri, 29 Aug 2003 10:33:38 -0700
> To: si-list@xxxxxxxxxxxxx
> From: Harry Selfridge <harrys@xxxxxxxxxxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: heat v. radiation Re:
> FEM/BEM/MoM
> 
> The charge, energy, and voltage distribution stated
> in the original problem 
> do not depend on circuit resistance.  The "missing"
> energy was expended in 
> doing the work of moving charge (Work = q x
> delta-V).  You can't move the 
> charge from one capacitor to another without doing
> work against the charge 
> accumulating on the plates.  The energy wasn't
> radiated or dissipated as 
> power in real resistance - it was used to move
> charge against an increasing 
> field.
> 
> Take a look here for the basic theory:
> 
>
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng2.html#c2
> 
> At 09:54 AM 8/29/03 -0700, you wrote:
> >Rather it's heat v. radiation has nothing to do
> with
> >the "paradox."  Even an electrical engineer cannot
> do
> >a transient circuit analysis as it was described
> >below.  Without any lossy elements there is no way
> to
> >calculate voltage or current over time.  The
> paradox
> >(more of a fallacy) comes from looking at the
> starting
> >point and the ending point without looking at what
> >happened in between.  You could have the same heat
> v.
> >radiation discussion about any circuit and any
> >stimulus; that's not the point.
> >
> >Where did the 1/4 Joule go?  It was dissipated in
> the
> >inductive and resistive elements obmitted in the
> >problem statement.  The point is, you cannot omit
> >them; they are not negligible.  If physically you
> have
> >two caps and a switch, electrically you have much
> >more.
> >
> >- Mike
> >
> >--- "Pratt, Gary" <gary_pratt@xxxxxxxxxxx> wrote:
> > > Lets just say the energy is lost to radiation
> (heat
> > > (infrared), RF,
> > > visible (fire and/or arc), sound, etc).  Then
> > > everyone is correct ...
> > > Unless ...  Any energy lost to chemical changes
> (or
> > > gained through
> > > fire)?  Any energy transformed to mass, or mass
> to
> > > energy?  sub-atomic
> > > effects?  These questions, I will gladly defer
> to
> > > the physicists.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Lin Li [ mailto:lilin@xxxxxxxxxxxxx
> > > <mailto:lilin@xxxxxxxxxxxxx> ]
> > >
> > > Sent: Thursday, August 28, 2003 4:18 PM
> > > To: Feldman, Richard
> > > Cc: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: heat v. radiation Re:
> > > FEM/BEM/MoM
> > >
> > >
> > > Richard,
> > > You are absolutely right.
> > >
> > > I drew my conclusion based on assumption that
> > > impedance is negligible
> > > which
> > > is likely the real situation.
> > > If the circuit is not that lossy, then most
> energy
> > > is lost by radiation
> > > eventually if it could be.
> > >
> > > Thanks for your comment!
> > >
> > > Lin
> > >
> > > -----Original Message-----
> > > From: Feldman, Richard [
> mailto:rfeldman@xxxxxxxxxxx
> > > <mailto:rfeldman@xxxxxxxxxxx> ]
> > > Sent: Thursday, August 28, 2003 3:19 PM
> > > To: lilin@xxxxxxxxxxxxx; gary_pratt@xxxxxxxxxxx
> > > Cc: si-list@xxxxxxxxxxxxx
> > > Subject: RE: [SI-LIST] heat v. radiation Re:
> > > FEM/BEM/MoM
> > >
> > >
> > > Lin, I respecfully disagree with your statement.
> > >
> > > The lost energy can be partitioned arbitrarily
> > > between heat and electromagnetic radiation,
> > > depending on the circuit's geometry, R, and L
> > > values.
> > > It's trivial to do the experiment and get mostly
> > > heat.
> > > But I'm guessing that with some design effort,
> > > one could get mostly radiation.
> > >
> > > The transient behavior after switch closure is
> > > generally oscillatory, damped according to
> losses.
> > >
> > > Rich
> > >
> > > > -----Original Message-----
> > > > From: Lin Li [ mailto:lilin@xxxxxxxxxxxxx
> > > <mailto:lilin@xxxxxxxxxxxxx>
> > > ]
> > > > Sent: Thursday, August 28, 2003 12:31 PM
> > > > To: gary_pratt@xxxxxxxxxxx
> > > > Cc: si-list@xxxxxxxxxxxxx
> > > > Subject: [SI-LIST] Re: FEM/BEM/MoM
> > > >
> > > >
> > > > Heat transformation is not likely to happen
> unless
> > > the switch
> > > > cable has very
> > > > large resistance.
> > > >
> > > > We know at the moment of the electrons
> transfer,
> > > there will
> > > > be a transient
> > > > which will induce radiation. That is where the
> > > energy goes.
> > > >
> > > > I cannot deny heat effect but it is minor.
> > > >
> > > > Best,
> > > >
> > > > Lin
> > > > **********************
> > > > Lin Li
> > > > Ph.D. candidate
> > > > 3123 Glenn Martin Hall
> > > > Mechanical Engineering
> > > > University of Maryland
> > > > College Park, MD 20742
> > > > Ph: 301-405-5588
> > > > ***********************
> > > >
> > > > -----Original Message-----
> > > > From: si-list-bounce@xxxxxxxxxxxxx
> > > > [ mailto:si-list-bounce@xxxxxxxxxxxxx
> > > <mailto:si-list-bounce@xxxxxxxxxxxxx> ]On Behalf
> Of
> > > Pratt, Gary
> > > > Sent: Thursday, August 28, 2003 1:08 PM
> > > > To: arafi001@xxxxxxx; si-list@xxxxxxxxxxxxx
> > > > Subject: [SI-LIST] Re: FEM/BEM/MoM
> > > >
> > > >
> > > > The quarter-Joule turns into heat when the
> switch
> > > is vaporized into a
> > > > cloud of smoke.
> > > > Whats the paradox?
> > > >
> > > > Gary L. Pratt, P.E.
> > > > Product Manager
> > > > High-Speed Design Kits
> > > > Mentor Graphics
> > > > (503) 685-1177
> > > > gary_pratt@xxxxxxxxxx
> > > >
> > > >
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Abdulrahman Rafiq [
> mailto:arafi001@xxxxxxx
> > > <mailto:arafi001@xxxxxxx>
> > > > < mailto:arafi001@xxxxxxx
> > > <mailto:arafi001@xxxxxxx> > ]
> > > > Sent: Thursday, August 28, 2003 12:36 PM
> > > > To: si-list@xxxxxxxxxxxxx
> > > > Subject: [SI-LIST] FEM/BEM/MoM
> > > >
> > > >
> > > > Geoff,
> > > >
> > > > Could you ellaborate on this a little more, as
> I
> > > am afraid i
> > > > can't quite see what happened to the 1/4 Joule
> of
> > > energy.
> > > > Perhaps if you could do a quick back of the
> > > envelope
> > > > calculation as an example.
> > > >
> > > > -----------------
> > > >
> > > > Just a little diversion to show the error in a
> > > schematic:
> > > > An old example often quoted is the problem of
> > > connecting two
> > > > one farad
> > > > capacitors together by a switch; one is at 1V
> > > potential, the
> > > > other zero.
> > > > The initial energy is 1/2 CV**2 =3D 0.5 joule.
> > > After closing
> > > > the switch th=
> > > > ere
> > > > is charge distribution, and energy =3D 1/8
> +1/8
> > > =3D 0.25
> > > > joule.  Where did =
> > > > the
> > > > missing 0.25 joule go?  If you did an
> electrical
> > > degree,
> > > > you'd see the
> > > > paradox.  If you studied high frequencies,
> you'd
> > > know the
> > > > answer.  (I did a
> > > > Physics degree, then built RF circuits, so for
> me
> > > a capacitor
> > > > is not a
> > > > capacitor.)
> > > >
> > > > The answer is
> > > > 1) it's not physically possible to put two
> > > capacitors
> > > > together at one point
> > > > 2) therefore they are separated by a distance
> > > > 3) therefore on closing the switch, the
> discharge
> > > current
> > > > travels a distance
> > > > 4) the conductors have finite conductivity
> > > > 5) therefore there is a varying
> electromagnetic
> > > field and
> > > > energy is
> > > > dissipated and radiated
> > > > 6) please don't talk about too much about
> > > inductance because
> > > > it's only an
> > > > approximation.
> > > > -------------------
> > > > ---------------------------------------
> > > > Abdulrahman Rafiq
> > > > Department of Physics
> > > > University of California
> > > > Riverside, Ca. 92521
> > > > Email: arafi001@xxxxxxx
> > > > URL: www.geocities.com/arafiq786
> > >
> > >
> >=== message truncated ===
> snip
> 
>
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