On Jan 27, 9:45*am, Cecil Moore wrote:
Keith Dysart wrote:
Not at all. The equations don't just stop working at 0 frequency.

As a matter of fact, EM waves cannot exist without
photons. There is zero wave activity at DC. Therefore,
the forward power and reflected power is zero at DC
steady-state.

And yet all the circuit theory derivations of reflection
coefficient, power, voltage and current distributions
work just fine for DC (or, if you prefer, low rate pulses).

Digital designers use exactly that for solving real world
problems. They do not refuse to solve problems when the
conditions approach DC. The equations all work.

You really should try to stop thinking about photons
for just a short while.

Yep, you guys would like to sweep the technical knowledge
from the field of optical physics and quantum electro-
dynamics under the rug. One wonders why.

An intriguing accusation. Transmission lines can be
understood well, and real world problems solved without
reference to photons and EM waves. Just use the well
known circuit theory based equations. And they extend
all the way to DC.

For those who like EM waves and photons... Why do you
want to limit yourselves? Why won't you use the circuit
theory bases equations to solve problems for which they
work? Just because EM waves and photons do not?

Think of it as a long pulse. That should satisfy your
need to have 'waves'.

No, only photons will satisfy the definition of EM
waves. There are no photons. There are no waves. There
are no forward and reflected powers. There are no
changing E-fields or H-fields. There is not even any
movement of electrons associated with the source
voltage.

May be true. But why do you want to use that as an excuse
not to solve solveable problems?

...Keith