"Waves of Average Power"
 

On 7 Nov, 08:41, (J. B. Wood) wrote:
In article , Richard Clark

wrote:
Energy propagates much as we expect it does; power - well, not always
(hardly ever).

73's
Richard Clark, KB7QHC

Hello, and the above statement is simply not true as any undergraduate
textbook in electromagnetics will point out. Transmission lines, for
example, be they 60 Hz or at RF due in fact transmit power from source to
load. At any point along the line the average power is given by 1/2 the
real part of the product of the voltage and complex conjugate of the
current. Voltage and current contain their respective components of
travelling waves in both directions (source-to-load and load-to-source).
Of course the transport medium doesn't have to be a transmission line - it
can be free space, say from a transmitting antenna to a receiving antenna.

I have no idea how many of those in our ham hobby have taken any courses
in electromagnetics (traditionally called "fields" by undergrad EE
students).


Oh I believe that there are quite a few who memorised what was taught
and what was in the books but now they are getting older and the
memory is failing where they didn't understand the basics.
Since you may be younger and have taken the EE course. Try adding a
time varient
to Gaussian statics law and thus show how it equals Maxwell's law.
But them you may be relying on memory as well and bypassed
mathematics.
Richard has come a long way by doing that and nobody is equiped in
mathematics to call his bluff.
Things were like that when I was in the military. Don't ask why
just put it into the memory box and follow orders. If you can't
remember
then follow the rest of the squad. Doesn't that sound like ham radio?
Art





Such courses are part of an undergrad EE program and if you
major in electrophysics (as I did) at the grad level you delve much deeper
into the subject. Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

"Waves of Average Power"
 

Richard Clark wrote:
On Wed, 07 Nov 2007 11:41:29 -0500, (J. B. Wood)

Hi John,

I majored in English. Yet and all that intellectually crippled, I
found you couldn't respond to heat (the expression of power by your
own choice) being the dissipation of energy in a load, and that energy
is the entity that propagates - not power.

As the topic has migrated away from your original thesis of heat and
the sun towards fields; I, as an English major, am at a loss to
discover the correlation that resolves how fields can resurrect the
missing heat in an Earth equivalent volume of space, or provide the
surplus heat found in a smaller volume of the moon - all from the same
source of those fields, the sun.

Are fields selectively powerful (like a god)? Do the fields of

Hello, Richard and all.

With regard to power (be it from the sun or some other source of
energy), strictly speaking I would agree that what is transported is
energy. Physicists and engineers usually include the ability to do work
(as well as the work itself) as part of the concept of power. For
example, we can have "available power" at the terminals of a receiving
antenna even though the antenna is not connected to a dissipating
termination. Radio/antenna engineers and physicists also use the
concept of "power density" (usually in units of watts per square meter)
at some distance from a transmitting antenna. We then speak of an
antenna having an effective "capture area" that can extract a portion of
this power from incident electromagnetic waves.

In this regard we speak of power being transmitted through a medium. If
we clock energy flow across a boundary for a specified time then the
quantity of energy divided by that time represents power flow across the
boundary.

With regard to the sun/volume question I'm not qualified to answer that.
The earth still retains its primordial inner sources of heat and
other forms of energy as manifiested in erupting volcanoes, geysers, and
deep sea thermal vents. Of course these are in addition to radiant
energy from the sun. Sincerely,

"Waves of Average Power"
 

On Wed, 07 Nov 2007 13:23:12 -0500, "J.B. Wood"
wrote:

In this regard we speak of power being transmitted through a medium.

Hi John,

You might be interested in the work of Debra R. Rolison, Ph.D. Naval
Research Laboratory -- Surface Chemistry Branch. The lead-in would be
the medium of aerogels where her presentation that I attended nearly 5
years ago was called "The Importance of Nothing in Nanostructured
Materials." You will learn from her that power in the form of Heat
(not many other forms left) does not transmit through aerogels.
However, for her research, that is one of those "People" magazine kind
of qwik-facts where her work investigates to a greater depth. She is
quite conversant and has a vice-like grip on the topic.

Ask about Phonons insofar as how Power moves through a medium.

73's
Richard Clark, KB7QHC

"Waves of Average Power"
 

J. B. Wood wrote:
Transmission lines, for
example, be they 60 Hz or at RF due in fact transmit power from source to
load.

The unit of power is the watt. If power is being
transmitted, the transmitted power would have units
of watts/sec or joules/sec/sec. What would be the
physical meaning of joules per second squared?
--
73, Cecil http://www.w5dxp.com

"Waves of Average Power"
 

Cecil Moore wrote:
J. B. Wood wrote:
Transmission lines, for
example, be they 60 Hz or at RF due in fact transmit power from source to
load.

The unit of power is the watt. If power is being
transmitted, the transmitted power would have units
of watts/sec or joules/sec/sec. What would be the
physical meaning of joules per second squared?

I have no idea what you're talking about, Cecil. (But then I haven't
read every post in this thread.) Sounds like you just coined a term for
energy acceleration, whatever that might apply to. If you don't object
I think I'll stick with what I've gleaned over the years as an engineer
and going back to my university days. You are free of course to provide
your own interpretation of electrical phenomena. Sincerely, and 73s,

"Waves of Average Power"
 

Hi Richard
I believe Fourier got that one in 1824.

"1824
Joseph Fourier calculates that the Earth would be far colder if it lacked an
atmosphere."
http://www.aip.org/history/climate/timeline.htm


"Richard Clark" wrote in message
...
On Wed, 07 Nov 2007 06:30:41 -0500, (J. B. Wood)
wrote:

Hello, Jim , and power (energy per unit time) doesn't propagate? Where do
we get all that radiant heat from 93 million miles away? Sincerely, and

Hi John,

Is the volume of space immediately to the left of planet Earth as warm
as planet Earth? A balmy 13° to 17° C?

Same source, the sun.
Same distance, 93 million miles away;
Same power (sic), energy per unit time;
Same propagation, speed of light without obstruction;

Same heat? Not even close - even when accounting for and removing the
core temperature of Earth. A rather absolute chilly of 3° K.

Substitute the Moon by placing it to the left of Earth. Is it as warm
as planet Earth? A balmy 13° to 17° C?

Same source, the sun.
Same distance, 93 million miles away;
Same power (sic), energy per unit time;
Same propagation, speed of light without obstruction;

Same heat? Again, not even close. A rather toasty 107° C!

Two examples in proximity to Earth, and yet both seem to exhibit that
the Sun does not propagate power linearly. What could possibly
account for this error when the path is unobstructed and the Sun's
radiation is uniform? Even more quixotic is that the smaller load of
the Moon exhibits a higher dissipation of radiation (and has virtually
no core temperature effect to elevate that result).

Well, albedo has something to do with all three; but that is load
dependant and has nothing to do with energy per unit time from the
source. Insulation has something to do with all three; and that too
has nothing to do with energy per unit time from the source.

So, is the Sun selectively powerful (like a god)? Is the Sun like
some really, really huge radiant lamp (the kind with a toaster wire
wound like a slinky in the middle of a radar reflector)? Point the
radiant lamp at you, and you get toasty, step aside, and the air that
replaces your volume does not - hmmm. Put a pane of glass in the same
region, same chilling result.

Something going on here and there seems to be only one commonality to
power - the function of the load in the presence of energy.

Energy propagates much as we expect it does; power - well, not always
(hardly ever).

73's
Richard Clark, KB7QHC

"Waves of Average Power"
 

J.B. Wood wrote:
Cecil Moore wrote:
The unit of power is the watt. If power is being
transmitted, the transmitted power would have units
of watts/sec or joules/sec/sec. What would be the
physical meaning of joules per second squared?

I have no idea what you're talking about, Cecil.

I know and you are not alone. I was taught about
power transmission in college but it was actually
energy transmission they were talking about. The
power company doesn't charge me for power - they
charge me for KWH, i.e. energy.

Consider a Bird wattmeter in a flat transmission
line. It is at a fixed point reading watts. Are
the watts moving? The Bird is displaying joules/sec
passing a fixed point. The joules are certainly
moving but are the joules/sec moving? As you noted,
it seems that if the joules/sec are moving then the
joules must necessarily be accelerating.

You can measure the number of cars passing over
a bridge in one hour and write that number on your
notepad. The cars are moving but is that cars/hour
measurement written on your notepad moving? If so,
where is it going?
--
73, Cecil http://www.w5dxp.com

"Waves of Average Power"
 

On 7 Nov, 14:40, Cecil Moore wrote:
J.B. Wood wrote:
Cecil Moore wrote:
The unit of power is the watt. If power is being
transmitted, the transmitted power would have units
of watts/sec or joules/sec/sec. What would be the
physical meaning of joules per second squared?

I have no idea what you're talking about, Cecil.

I know and you are not alone. I was taught about
power transmission in college but it was actually
energy transmission they were talking about. The
power company doesn't charge me for power - they
charge me for KWH, i.e. energy.

Consider a Bird wattmeter in a flat transmission
line. It is at a fixed point reading watts. Are
the watts moving? The Bird is displaying joules/sec
passing a fixed point. The joules are certainly
moving but are the joules/sec moving? As you noted,
it seems that if the joules/sec are moving then the
joules must necessarily be accelerating.

You can measure the number of cars passing over
a bridge in one hour and write that number on your
notepad. The cars are moving but is that cars/hour
measurement written on your notepad moving? If so,
where is it going?
--
73, Cecil http://www.w5dxp.com

Cecil,
Velocity and acceleration are two different things
Velocity is the amount of movement and accelleration
is the rate of change of movement dependent on the
number of samples taken over a period of time
Joules are not necessarily accelerating.
Think Newton....ut + 1/2 f(t sqd)
Art
Art

"Waves of Average Power"
 

Cecil Moore wrote:
Please apply the same irradiance equation that
optical physicists were using before you were born.
Any physics professor should be able to accomplish
that simple task. If optical physicists were in
error in using that equation 100 years ago, please
explain their error.

So far no response to this simple request. The
graphic of the non-reflected glass example is
at http://www.w5dxp.com/thinfilm.gif

We know that the reflections are 100% canceled
during steady-state.

The problem is: With the given data, calculate
the magnitude of the total reflection back toward
the source immediately after the first internal
reflection arrives back at the thin-film to air
surface at time t3 and is superposed with the
external reflection. The two superposed waves are
180 degrees apart.

The external reflection is 0.01 watts at a reference
angle of zero deg. This is the normal reflection
from the thin-film surface

The first internal reflection is 0.009801 watts
at 180 degrees. This is the first reflection from
the glass.

These two waves superpose at t3. The irradiance
equation, using P for power density, is:

Ptotal = P1 + P2 + 2*SQRT(P1*P2)cos(A)

where (A) is the angle between the two waves and
Ptotal is the total power density of the reflections
toward the source after the two waves are superposed.

Ptotal = 0.01 + 0.009801 + 2*SQRT(0.01*0.009801)(-1)

Ptotal = 0.019801 - 0.0198 = 0.000001 watt

There is 0.0198 watts of destructive interference
which, according to the conservation of energy
principle, must result in 0.0198 watts of
constructive interference in the opposite direction.

The magnitude of the reflection toward the source
drops from 0.01 watt to 0.000001 watt at the arrival
of the first internal reflection from the glass. That's
a five magnitude reduction in the reflections at the
time of the arrival of the first internal reflection.
The reflections back toward the source are eventually
completely eliminated during steady-state.

There was no vector math and no need to calculate
the magnitudes and phases of the electric and magnetic
fields - just a straight forward calculation to get
the answer.

As long as the source remains in place, the steady-
state cancellation of the reflections toward the source
is permanent. It is difficult to analyze how that could
happen unless the internal reflections interact with the
external reflection resulting in wave cancellation.

Everyone is invited to prove the above calculation to
be incorrect. Hint: if one actually performs a vector
analysis, the magnitude of reflection result will be
exactly the same as above.

The above method does not invalidate or replace a vector
analysis. Unlike a vector analysis, it simply shows where
the energy goes. Optical physicists knew this a century
ago - most RF engineers have yet to learn it.
--
73, Cecil http://www.w5dxp.com

"Waves of Average Power"
 

Cecil, W5DXP wrote:
"The cars are moving but is the cars/hour measurement written on your
notepad moving?"

A simple question deserves a simple answer. Yes it is moving downstream
to the next tallyman`s position.

Best regards, Richard Harrison, KB5WZI