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Re: [Phys-L] circuit analysis : a simpler approach?



I agree with you.

After I sent my "test" mail, I was wandering if there are problems with
"solutions" that obey KL (and constitutive relations ex: V_drop= I R) , but
there are not what you are searching for.

In:
https://www.av8n.com/physics/kirchhoff-circuit-laws.htm

Prof. Denker shows circuits in which KL are wrong (non constant magnetic
fields), so I was searching circuits in which KL was OK but the solution
could be wrong.

So there are examples of circuits "problems" in which KL are wrong and
others in which there are not enough.

There are also problems in which you need to add another condition, for
example $\sum dI/dt =0$, ok you can say that this is a derivation of one
of K laws, but ...


2015-09-02 11:42 GMT-03:00 Carl Mungan <mungan@usna.edu>:


On Sep 2, 2015, at 9:37 AM, Diego Saravia <dsa@unsa.edu.ar> wrote:

I was wrong, KL are not universal testing device.

Lets have a batery in a loop with 2 condensers. battery 1.5 V C1=1.5V
C2=0V

Its ok? ...... NO

if the previous conditions were B=1.5V C1=0V C2=1V, when you have a
switch
open, and close it


There are several conditions that satisfies KVL, but are not correct. all
VC1+VC2=1.5V


Well, doesn’t it depend on what you mean by “testing”?

C1=1.5 V and C2=0 V *is* a valid solution.

It’s just that it’s not the particular solution that is also consistent
with the initial conditions.

KL only checks that any given steady-state solution is physically allowed.
Time dependence is a separate issue.

-----
Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363
mailto:mungan@usna.edu http://usna.edu/Users/physics/mungan/

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--
Diego Saravia
Diego.Saravia@gmail.com
NO FUNCIONA->dsa@unsa.edu.ar

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