On Apr 17, 7:35*am, Cecil Moore wrote:
Keith Dysart wrote:
It was such a good example that it just stopped you in
your tracks.

Not at all. Everything I have said applies to a
distributed network. Since you insist on using a
lumped circuit source in a distributed network
example, further discussion is futile because
you are mixing apples and oranges.

So you are saying that ideal voltage sources work differently
in distributed networks than they do in lumped circuits.

Perhaps you could expand on the differences using the
following two circuits. This one is lumped.

50 ohms
+----------\/\/\/\/-----------+
+| +|
Vsl=100 VDC Vsr=50 VDC
| |
+-----------------------------+

And this one is similar but includes a transmission line.

50 ohms
+----------\/\/\/\/----+----------------+-------+
+| arbitrary +|
Vsl=100 VDC length, any Vsr=50 VDC
| impedance line |
+----------------------+----------------+-------+

After the circuit has settled how will the ideal voltage
sources on the right be behaving differently in the two
examples? If you think it matters, try 50 ohm line.

Where does the energy being absorbed by these ideal voltage
sources go?

What you perceive as the source absorbing energy is
the reverse traveling wave energy flowing back through
the source unimpeded. After all, how much energy can
be absorbed by 0+j0 ohms?

None. But pushing a current against a voltage (regardless of
the cause of the voltage) will definitely use energy.

The illusion of energy
absorption is the direct result of you refusing to
deal with the component wave energies.

These circuits are DC, but Vf and Vr still work. The line settles
to a constant (over length) 50 V regardless of the line impedance,
but the value of Vf and Vr will depend on the impedance of the line.
Why does it settle to 50 V? What else can it do? It is connected
to a 50 VDC ideal voltage source.

Using a line impedance of 50 ohms, compute Vr. Ooopppps. Vr is
equal to 0: no reflected power.

The ideal voltage source on the right, after the circuits settle,
will be absorbing 50 joules/s in both cases.

...Keith