On Jun 4, 10:39*pm, Keith Dysart wrote:
On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. since they
are not real waves that propagate and move energy the P=VI formula is
not correct. you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results.

On Jun 4, 7:54*pm, K1TTT wrote:
On Jun 4, 10:39*pm, Keith Dysart wrote:





On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. *since they
are not real waves that propagate and move energy the P=VI formula is
not correct. *you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results

My apologies for being insufficiently precise. Where ever I wrote
P=VI,
please substitute P(t)=V(t)I(t).

That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

....Keith

Keith Dysart wrote:
On Jun 4, 1:26 pm, K1TTT wrote:
On Jun 4, 2:12 pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.
definately. another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.



The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

The above example has current but no voltage, There are no storage
elements, only resistors.

Inductance and capacitance are storage elements. You might find those in
a model of a transmission line, but not in this example.



So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

I think you are looking to hard at a small part of the picture and not
seeing what else is going on.

On Jun 4, 8:23*pm, joe wrote:
Keith Dysart wrote:
On Jun 4, 1:26 pm, K1TTT wrote:
On Jun 4, 2:12 pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.
definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. *The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

An excellent example. Let's draw it.

A
+----\/\/\------+-----/\/\/\----+
| |
--- -
- ---
| B |
+---------------+---------------+

Between A and B the voltage is zero. I contend that there is no energy
flowing from the left half of the circuit to the right half. To
demonstrate this, compute the energy contributed by the battery on the
left. It is equal to the energy consumed by the resistor on the left.
Similarly for the battery and resistor on the rigtht. No energy flows
across the plane A-B.

If you still disagree, what is the power flowing across A-B?

....Keith

"Keith Dysart" wrote
...

I tend to agree. Wave is an overloaded term and this leads to some of
the confusion. There are some phenomena that transport energy which
have a wavy nature. This does not mean that every thing with a wavy
nature is transporting energy.

In particular, it does not mean that when there is a situation in
which
energy is not being transported (e.g. a zero on a transmission line),
that just because the conditions on the line can be described by
decomposing into two waves going in opposite directions, that these
two waves are.

Also each pulse in the wave is carrying energy.

Attempting to do this, and believing that these decomposed waves
actually represent energy flows leads to having to answer questions like
"where
does the reflected energy go"? When I first started lurking in this
group about a decade and half ago, the 'obvious' answer accepted by many was
that it went in to the final and fried the tube.

Members of this Group should know that in microwave oven are the standing
waves, In the Manual is " when the amount of food is small, sharp points and
sharp edges on metal objects can initiate a corona discharge, a "Saint
Elmo's Fire," which behaves the same as a flame and can set fire to the food
and the oven if allowed to continue for long. Aluminum foil can become a
blow torch!"

Each pulse of the both waves travelling in the opposite direction is
carrying energy. The energy cummulate and can destroy the tube or the oven.

Many have moved beyond this simplicity, but some have not yet moved as far
as they need to.

It is important to know that the standing waves are possible only in
compressible medium.
"Maxwell's equations" are for the incompressible electricuty.
S*

On Jun 5, 12:19*am, Keith Dysart wrote:
On Jun 4, 7:54*pm, K1TTT wrote:



On Jun 4, 10:39*pm, Keith Dysart wrote:

On Jun 4, 1:26*pm, K1TTT wrote:

On Jun 4, 2:12*pm, Cecil Moore wrote:
Thanks David, that's good news. It apparently means that the arguments
based on energy not crossing a current node boundary in a standing
wave are invalid - since that singular condition violates the boundary
conditions for Maxwell's equations. So does the "standing wave energy
standing still" argument. Not only does the photonic nature of EM
waves require them to travel at the speed of light in the medium, but
so does Maxwell's equations.

definately. *another simple condition shows this can't be correct
since current nodes correspond with voltage peaks in the standing wave
pattern, so while energy in the magnetic field is a minimum the energy
in the electric field is a maximum.

And yet....

It is generally accepted that power = volts times current (P=VI) and
that
power is energy flowing, so if the voltage or current is always 0,
there
must be no energy flowing.

The presence of voltage without current, or current without voltage is
an indication that energy is stored, not that energy is flowing.

So are you really prepared to give up on P=VI so that energy can be
flowing (i.e. there is power) when the voltage or current is zero?

...Keith

that is just another flaw in the 'standing wave' problem. *since they
are not real waves that propagate and move energy the P=VI formula is
not correct. *you must take the original traveling waves and study the
power and energy using them, from that you should see the proper
results

My apologies for being insufficiently precise. Where ever I wrote
P=VI,
please substitute P(t)=V(t)I(t).

That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

...Keith

right, and this brings up another key error that a detailed look at
standing waves points out. go look at one of the animations of
standing waves and you will note that in each cycle they go from tall
peaks to a flat line and then back to peaks. so if you use p=vi what
is the energy in the line when either field is zero from end to end?
if you answer zero, then where did it go? it is obviously impossible
for the energy in the line to go to zero everywhere every half cycle
as that would require propagation faster than light, and some external
place for all that energy to dump to. so calculating power that way
is worthless with standing waves.

The real die hard standing wave fanatics will look closer and realize
they can represent calculate power in each field separately and make
it slosh back and forth between electric fields and magnetic fields.
That representation may be interesting, but is nothing more than
studying the energy stored in a resonant LC circuit. it doesn't go
anywhere, it just alternates between the electric and magnetic fields.

Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. *The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

you need to go back to circuits 101 and retake the undergraduate lab
intro where they teach you about measuring current and voltage. your
basic problem statement above is malformed since you can not measure
the voltage 'at the center'. voltages always have to be taken between
two points.

now if you REALLY want to be confused, ignore circuits 101 and draw
any circuit with as many components in it as you want as long as there
is only ONE loop. so connect AC or DC sources, inductors, capacitors,
resistors, around in a circle. start measuring voltage across each
one as you go around the circle and add them up. the result will
ALWAYS be zero. (go read about Kirchhoff's laws, here is one
reference http://www.bowest.com.au/library/theorems.html).

Note that of course these do not apply to transmission line problems
or antennas.

On Jun 5, 7:42*am, K1TTT wrote:
On Jun 5, 12:19*am, Keith Dysart wrote:
That is, the power (i.e. energy flow) at any instant in time is the
voltage at that time times the current at that time. If, for all time,
the current or voltage is 0, then so is the energy flow.

...Keith

right, and this brings up another key error that a detailed look at
standing waves points out. *go look at one of the animations of
standing waves and you will note that in each cycle they go from tall
peaks to a flat line and then back to peaks. so if you use p=vi *what
is the energy in the line when either field is zero from end to end?

We need to carefully understand the meaning of the words. Power is
energy
that is moving; the SI unit is the watt or joule per second. The unit
for energy is the joule.

When the voltage or current is zero everywhere, there is no power,
that
is, no energy is moving. The energy is stored on the line where it
happens
to be. As the voltage or current rises again from zero, the energy is
now moving in the direction opposite to the direction it was moving
before
the line was zero everywhere. At a point where the voltage or current
is
always zero, no energy moves. The energy sloshes back and forth
between
the points in the line that it never crosses.

it just alternates between the electric and magnetic fields

This is true, but the energy also changes location as it does this,
leading
to energy flow (or power), but the energy does not cross any point
where
the voltage or current is always zero.

When the current everywhere is zero, no energy is flowing, and the
energy
is stored as voltage in the capacitance of the line. And those
voltages are
at maximum and will soon begin to decrease as the energy begins to
flow the
other way.

Similarly, when the voltage is zero everywhere, the energy is stored
as
current in the inductance of the line.

....Keith

K1TTT wrote:
Consider two equal valued resistors connected in series. Connect one end
of the pair to +12 volts, connect the other end of the pair to -12
volts. The voltage at the center is 0. There is certainly current
flowing. There clearly is power dissipated in the circuit.

you need to go back to circuits 101 and retake the undergraduate lab
intro where they teach you about measuring current and voltage. your
basic problem statement above is malformed since you can not measure
the voltage 'at the center'. voltages always have to be taken between
two points.


Funny, Keith understood exactly what I meant. I find it hard to believe
you couldn't figure out the implied reference point. (I.e., what the
supplies were connected to.)


now if you REALLY want to be confused, ignore circuits 101 and draw
any circuit with as many components in it as you want as long as there
is only ONE loop. so connect AC or DC sources, inductors, capacitors,
resistors, around in a circle. start measuring voltage across each
one as you go around the circle and add them up. the result will
ALWAYS be zero. (go read about Kirchhoff's laws, here is one
reference http://www.bowest.com.au/library/theorems.html).


Since you include AC sources, the voltages must all be measured at the
same time. Circuits 101 should tell you that.




Note that of course these do not apply to transmission line problems
or antennas.


Which was part of my point, picking at some details may not lead you to
the proper view of what is going on.

On Jun 4, 5:39*pm, Keith Dysart wrote:
... if the voltage or current is always 0,
there must be no energy flowing.

Keith, you keep leaving out the word "net". If the current on each
side of a zero-current point is not zero, all that zero current
measurement means is there is equal energy flowing in both directions
so there is no *net* energy flow. The fact that Maxwell's equations
cannot be used on your condition of interest should be a clue that
something is wrong with your concepts and/or logic. You are
essentially saying that there is no traffic on the Golden Gate Bridge
because the north and south traffic averages out to zero. It is a
faulty concept. That zero net traffic keeps on wearing out the
roadway.
--
73, Cecil, w5dxp.com