Keith Dysart wrote:
In a stub driven with a step function, where is the
energy stored?

Depends upon which valid model one is using.

1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

2. The LCLCLC transmission line model - the energy
is alternately stored in the L's and C's.

3. The Sloshing Model - I'll let Roy handle that one.
--
73, Cecil http://www.w5dxp.com

On Jan 2, 3:44*pm, Cecil Moore wrote:
Keith Dysart wrote:
In a stub driven with a step function, where is the
energy stored?

Consider the state of the open circuited line
after settling.

Depends upon which valid model one is using.

1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

So it is stored only in the E field. Is it an
EM wave when only an E field is present?

2. The LCLCLC transmission line model - the energy
is alternately stored in the L's and C's.

Since there is no current, it is stored only in
the capacitance of the line.

3. The Sloshing Model - I'll let Roy handle that one.

The sloshing has stopped, so the answer is the same
as 2.

But the important question is: Do you consider it
to be an EM wave when only an E field is present?

...Keith

Keith Dysart wrote:
Cecil Moore wrote:
1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

So it is stored only in the E field.

Wrong! Please reference a book on EM waves. An
EM wave CANNOT have a stationary E-field in an
ordinary transmission line or in free space.

But the important question is: Do you consider it
to be an EM wave when only an E field is present?

No, that violates the definition of an EM wave. If
only an E-field is present in a transmission line or
in free space, it is NOT an EM wave, by definition.

For a single EM wave to exhibit a zero H-field, the
Z0 would have to be infinite which is clearly impossible
for free space or ordinary transmission lines.
--
73, Cecil http://www.w5dxp.com

On Jan 3, 12:43*pm, Cecil Moore wrote:
Keith Dysart wrote:
Cecil Moore wrote:
1. Reflection Model - the energy is stored in the
forward and reflected traveling waves.

So it is stored only in the E field.

Wrong! Please reference a book on EM waves. An
EM wave CANNOT have a stationary E-field in an
ordinary transmission line or in free space.

But the important question is: Do you consider it
to be an EM wave when only an E field is present?

No, that violates the definition of an EM wave. If
only an E-field is present in a transmission line or
in free space, it is NOT an EM wave, by definition.

For a single EM wave to exhibit a zero H-field, the
Z0 would have to be infinite which is clearly impossible
for free space or ordinary transmission lines.

Good answers. Exactly as I expected. Now please
explain the applicability of EM waves to the
state of an open circuited line excited with a
step function, especially after it settles to a
constant voltage (where only an E field will be
present).

...Keith

Keith Dysart wrote:
Good answers. Exactly as I expected. Now please
explain the applicability of EM waves to the
state of an open circuited line excited with a
step function, especially after it settles to a
constant voltage (where only an E field will be
present).

Before it settles to a constant voltage, there is
acceleration of electrons that results in an EM
photonic wave.

After it settles to a constant voltage, there is
no acceleration of electrons and the EM photonic
wave disappears.

Please see Maxwell's equations for further
enlightenment.
--
73, Cecil http://www.w5dxp.com

On Jan 3, 2:15*pm, Cecil Moore wrote:
Keith Dysart wrote:
Good answers. Exactly as I expected. Now please
explain the applicability of EM waves to the
state of an open circuited line excited with a
step function, especially after it settles to a
constant voltage (where only an E field will be
present).

Before it settles to a constant voltage, there is
acceleration of electrons that results in an EM
photonic wave.

After it settles to a constant voltage, there is
no acceleration of electrons and the EM photonic
wave disappears.

So when the edge of the step is travelling towards
the right, is there an EM wave to the right of the
step, to left of the step, at the step, or all three?
Similar question for when the step is travelling
back to the generator?

When the line has settled, how do you add the forward
and reflected wave to compute the voltage on the line,
or does the disappearance of the wave mean this is
now impossible?

If only the step itself has an EM wave, how are
voltages computed using reflection coefficient after
the step has reflected from the open end?

...Keith

Keith Dysart wrote:
So when the edge of the step is travelling towards
the right, is there an EM wave to the right of the
step, to left of the step, at the step, or all three?
Similar question for when the step is travelling
back to the generator?

You are confusing cause and effect. There is an EM
wave wherever there are photons being exchanged
among the electrons. Any speed-of-light movement
is evidence of the existence of photons.

When the line has settled, how do you add the forward
and reflected wave to compute the voltage on the line,
or does the disappearance of the wave mean this is
now impossible?

After all the photons have been absorbed or radiated,
there is no forward EM wave or reflected EM wave.
They simply cease to exist in the DC steady-state
where electrons are not being accelerated or
decelerated.

If only the step itself has an EM wave, how are
voltages computed using reflection coefficient after
the step has reflected from the open end?

If the step is reflected, the reflection consists
of photons. As long as anything is flowing at the
speed of light in the medium, photons exist.
--
73, Cecil http://www.w5dxp.com