>>** My position is that AC circuit-analysis is valid
today, was valid
before I was born, and will be valid long after I am
outta here.<<
That would be a good assumption to re-think. "AC
circuit-analysis" (by this, I assume you are referring
to sinusoidal steady-state analysis using phasors,
neglecting the real part, because I actually don't
think anybody on this list has ever mentioned
performing the calculations in their indigeonous
LaPlacian space) is based on the notion that we can
take an analysis technique developed for DC, apply
some approximation equations to reactive impedances,
and all will be well as we perform algebraic
manipulation.
Those who created equations such as Xl=2*pi*L*F and
Xc=1/(2*pi*C*F) knew full well that they are not
exact, they are mere approximations, because
capacitance and inductance, as we know them, are
defined only at DC. Those approximation equations
fall apart when the physical dimensions of our
components begin to approach a fraction of a
wavelength. Because we have a lot of technicians
attempting to perform engineering work, all manner of
patchwork gets done, patching up the flawed models of
components, claiming that we can "model" a "capacitor"
by adding an inductor and a resistor in series with
it. In many ways, we are forced to do such things,
because the analysis tools we are given, depend on
such models.
The reality is that there is no such thing as a
capacitor that behaves according to that equation over
all frequencies, but you can certainly create a
transmission line model of that capacitor that works
over all frequencies.
At frequencies other than DC, we are always working
with fields, not volts, amps and ohms. We have been
fortunate, thus far, to operate at frequencies where
we can patch our so-called "AC circuit analysis" and
make do with it, but that time will draw to an end
before many of us have passed on. Thankfully,
computer power is now reaching a point where it is
possible to envision a time when our "circuit solvers"
are actually performing 3D Maxwell field solutions.
For about four years, my own professional work has
been completely untenable with the so-called AC
circuit analysis.
Not that this is germaine to any discussions on AMPS,
but it is critical, in any scientific/engineering
discussion, to understand the limits of the models we
use.
So-called AC circuit analysis began life as an
approximation which was necessary in order to fit
things into the limited ability we had to understand
and solve real-world problems. And it will always be
an approximation, nothing more. To claim it is valid,
one MUST be able to elucidate its many limitations.
73,
Dave W8NF
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