Obtaining electromagnetic radiation from accelerating electrons
 

Is it not true that if I were able to accelerate my cup of coffee at light
speeds at a frequency of 14Mhz my cup of coffee would radiate a 14Mhz
carrier?

Obtaining electromagnetic radiation from accelerating electrons
 

On Sun, 05 Jul 2009 13:24:20 +0100, Richard wrote:

Is it not true that if I were able to accelerate my cup of coffee at
light speeds

non sequitur. acceleration = rate of change of speed.

at a frequency of 14Mhz

non sequitur. frequency is not a measure of speed or acceleration.

my cup of coffee would radiate a 14Mhz carrier?

No.

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

On Jul 5, 5:24*am, "Richard" wrote:
Is it not true that if I were able to accelerate my cup of coffee at light
speeds at a frequency of 14Mhz my cup of coffee would radiate a 14Mhz
carrier?


No.
You don't have to go the speed of light . Bigger the acceleration,
bigger the amplitude of the radiated signal.

And, it's the vibrating your cup of coffee back and forth at 14MHz
that would do it.

Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.


Consider a balloon which you've charged up by rubbing it on your hair
(or that fuzzy sweater...) If you move it back and forth, and have an
electric field meter some small distance away, you'll see the field
changing. Move the meter farther away, and the field is still
changing, but the amplitude is smaller.

Now look at the time delay between your moving the balloon and when
you see the field change. That delay is the time it takes for the
changed field to "propagate" to the meter.. aka the speed of light.

Obtaining electromagnetic radiation from accelerating electrons
 

Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Obtaining electromagnetic radiation from accelerating electrons
 

I don't care if it works or not, YOU are the one that's gonna have
to clean up that @#$ coffee mess!
- 'Doc

Obtaining electromagnetic radiation from accelerating electrons
 

"Rich Griffiths" wrote in message
communications...
On Sun, 05 Jul 2009 13:24:20 +0100, Richard wrote:

Is it not true that if I were able to accelerate my cup of coffee at
light speeds

non sequitur. acceleration = rate of change of speed.

at a frequency of 14Mhz

non sequitur. frequency is not a measure of speed or acceleration.

my cup of coffee would radiate a 14Mhz carrier?

No.

--
Rich

If the cup was to move 5 meters left, then 10 meters right, then ten meter
left again that would be one cylcle. There are 14 million cycles in one
second. So, net speed of cup is speed of light.

Obtaining electromagnetic radiation from accelerating electrons
 

"Richard" wrote in message
...

"Rich Griffiths" wrote in message
communications...
On Sun, 05 Jul 2009 13:24:20 +0100, Richard wrote:

Is it not true that if I were able to accelerate my cup of coffee at
light speeds

non sequitur. acceleration = rate of change of speed.

at a frequency of 14Mhz

non sequitur. frequency is not a measure of speed or acceleration.

my cup of coffee would radiate a 14Mhz carrier?

No.

--
Rich

If the cup was to move 5 meters left, then 10 meters right, then ten meter
left again that would be one cylcle. There are 14 million cycles in one
second. So, net speed of cup is speed of light.

Actually the frequency ought to be 15 Mhz.

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 09:51:12 +0100, Richard wrote:

"Richard" wrote in message
...

"Rich Griffiths" wrote in message
communications...
On Sun, 05 Jul 2009 13:24:20 +0100, Richard wrote:

Is it not true that if I were able to accelerate my cup of coffee at
light speeds

non sequitur. acceleration = rate of change of speed.

at a frequency of 14Mhz

non sequitur. frequency is not a measure of speed or acceleration.

my cup of coffee would radiate a 14Mhz carrier?

No.

--
Rich

If the cup was to move 5 meters left, then 10 meters right, then ten
meter left again that would be one cylcle. There are 14 million cycles
in one second. So, net speed of cup is speed of light.

Actually the frequency ought to be 15 Mhz.

Nonetheless, you still have acceleration, speed, and frequency seriously
confused. If you want to do a "thought experiment" (or any experiment,
for that matter), you must formulate it properly if you want to draw
sound conclusions from it.

And the "clarification" about frequency also makes no sense.

Either the cup has infinite acceleration at each end of its motion, or it
accelerates steadily from zero speed to a maximum at the middle and then
decelerates to zero again. The first implies an infinite change in
momentum and kinetic energy. The second implies a speed higher than the
speed of light at the middle of the motion.

You can't postulate conditions that defy the laws of physics and then ask
what physics implies anyway.

This is all WAY off topic, so we should end it.

--
73
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

Cecil Moore wrote:
Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?

pH = -log hydrogen ion concentration

the pH is about 7, so hydrogen ion concentration is 1E-7. It's
neutral, so there's an equal number of negative ions. How many of them
are free electrons is another question.


But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 08:22:19 -0700, Jim Lux wrote:

Cecil Moore wrote:
Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?

pH = -log hydrogen ion concentration

the pH is about 7, so hydrogen ion concentration is 1E-7. It's
neutral, so there's an equal number of negative ions. How many of them
are free electrons is another question.


But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

The pH of water in contact with the atmosphere tends to be about 6.5, due
to CO2 dissolving in the water and forming carbonic acid. Other commonly-
occurring ions that "match" the H+ are sulfate and nitrate. Of course in
salt water, most of the ions are sodium (Na+) and chloride (Cl-). Not
many free electrons. The motion of any ions could create electromagnetic
radiation, but as you note, the net charge is zero, so no radiation,
regardless how the cup is accelerated or what speed it travels at ;-)

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be
used as an antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 13:19:09 -0500, Cecil Moore wrote:

Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be used as an antenna?

It just means that moving the water back and forth won't cause
radiation. Waves on the surface of the ocean don't make radio signals.
(C'mon, Cecil. You knew the answer to your question, didn't you? ;-) )

The column of water will conduct a current, which will radiate, but I
think I'd rather use copper or aluminum :-)

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

Rich Griffiths wrote:
(C'mon, Cecil. You knew the answer to your question, didn't you? ;-) )

Actually, I had never thought about it. I assumed that any
conductor would radiate.

I've been working on a particle beam that ionizes 33 feet
of air for use as an efficient mobile antenna on 40m. Have
I been wasting my time?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Obtaining electromagnetic radiation from accelerating electrons
 

"Cecil Moore" wrote

I've been working on a particle beam that ionizes 33 feet
of air for use as an efficient mobile antenna on 40m. Have
I been wasting my time?

Unless you can stuff that antenna into a container the size
of two shoe-boxes, and achieve a 9 point something dBi
gain on 160M at the same time, yeah, you're wasting time.
Art's already beat you to it. And Art's antenna doesn't
care one never-mind about the phase information in the
standing wave current ;) good luck in the contest.

Mike W5CHR
Memphis

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 15:39:34 -0500, Cecil Moore wrote:

snip

I've been working on a particle beam that ionizes 33 feet of air for use
as an efficient mobile antenna on 40m. Have I been wasting my time?

Wasting your time? Heavens no! That would be WAY cool!

Even if it didn't work as an antenna, think how exciting it would be for
birds, people watching the highway from overpasses, ....

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

"Cecil Moore" wrote in message
...
Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be
used as an antenna?

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the feedpoint.

Reductio ad absurdum

LXXIII,
Sal

Obtaining electromagnetic radiation from accelerating electrons
 

Sal M. Onella wrote:
"Cecil Moore" wrote in message
...
Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.
Does that mean a column of salt water could not be
used as an antenna?

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the feedpoint.


been done, been patented too, I think.

(conductive liquid as a changeable antenna element)

Obtaining electromagnetic radiation from accelerating electrons
 

"Jim Lux" wrote in message
...

snip

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the
feedpoint.


been done, been patented too, I think.

(conductive liquid as a changeable antenna element)

Aw, phooey! I never get to invent ANYTHING!

Obtaining electromagnetic radiation from accelerating electrons
 

Richard:

Actually [cfr: Feynman's Lectures on Physics] it is not the acceleration of
charge that produces photons (radiation), rather it is the rate of change of
the acceleration of charge that results in radiation.

As we all know, 'velocity' v is the rate of change of distance or space s,
expressed in terms of the differential calculus this would be written in
scaler form as (v = ds/dt) while 'acceleration' a is the rate of change of
velocity v, (e.g. a = dv/dt = d(ds/dt)/dt). In Engineering and Physics, the
next level of differential change or rate of change of acceleration is
usually termed 'jerk'. Jerk j then is j = da/dt. Jerk is not often
mentioned in elementary presentations of mechanics, but as far as I know
even with more in depth presentations there are apparently no 'standard'
terms for higher derivates of distance change than jerk. [distance,
velocity, acceleration, jerk, and then...]

Since, like their relative, the exponential functions, the sinusoidal
functions, sine, cosine, etc... "sort of" replicate each other every time
they are differentiated the higher order differentials of each such function
'look' simply like a scaled version of the other derivatives. Thus, for
sinusoidal waveforms, which are the usual functional form assumed for most
Engineering work, it is relatively easy for one to come up with a
mathematical expression which provides exact values for radiation levels in
terms of charge acceleration instead of charge jerk. Since of course if the
charge velocity is sinusoidal, so is the acceleration and so is the jerk.

Notwithstanding that there are well known formulas that relate radiation
levels to charge acceleration for sinusoidal waveforms, it is not charge
acceleration per se that causes radiation. Charge jerk causes radiation.

If one desires an exact formulation for radiation caused by charge motion
then perforce to be exact for general non-sinusoidal waveshapes such
formulae must be related to charge jerk not acceleration.

If you do not have access to Feynman' Lectures on Physics (I believe he
discusses this in Vol. 3) there was a recent more accessible discussion of
this topic by the editor of QEX in an article published in QEX several years
ago.

-- Pete k1po
-- Indialantic, FL


"Richard" wrote in message
...
Is it not true that if I were able to accelerate my cup of coffee at light
speeds at a frequency of 14Mhz my cup of coffee would radiate a 14Mhz
carrier?