Re: Maxwell's Displacement Current
From: Androcles (dummy_at_dummy.net)
Date: 10/26/04
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Date: Tue, 26 Oct 2004 11:53:14 GMT
"jahn" <suzysewnshow@yahoo.com.au> wrote in message
news:2u5d1pF26p6m2U1@uni-berlin.de...
: "Androcles" <dummy@dummy.net> wrote in message
: news:wSdfd.46034$i02.788@fe1.news.blueyonder.co.uk...
: >
: > "jahn" <suzysewnshow@yahoo.com.au> wrote in message
: > news:2u565dF261fgfU1@uni-berlin.de...
: > :
: [snip]
: > : > : Sue...
: > : > : Oh Yeah.. The topic... (I am easilsy distracted...BLUSH)
: > : > : > : > :
: http://farside.ph.utexas.edu/teaching/em1/lectures/node41.html
: > : >
: > : > Ugh... back to doing hard sums.
: > : >
: > : > (382) has solution in the form A.sin(wt + phi) and does not
: compel
: > : > E and B fields to be in phase. Remember to add a constant
: when
: > : > integrating.
: > : >
: > : > (383) .... oh, there it is .... j, a 90 degree phase shift.
: > : > Looks like I agree with Maxwell after all, if you plot it
: in the
: > : > complex
: > : > plane with a time axis.
: > : > I expect some people think the j refers to the two fields
: being
: > : > orthogonal,
: > : > but @E/@t tells all. It's phase shift.
: > :
: > : Right-Oh! (382) is from Faraday's law or the "orthogonality
: > relation"
: > : The + or - j in (383) is the advanced or retarded potential
: and is
: > : *imaginary*
: > : power transfer so has no obligation to respect the speed of
: light.
: >
: > Yep. And transformers don't respect it either.
: >
: >
: > : In converting cgs and Coulomb gauge to SI something gets
: terribly
: > : misstated because of this oversight but my own math skills
: leave
: > : me dependant on other's papers to try an describe it.
: > : http://www.reciprocalsystem.com/bpm/bpm15.htm
: > :
: http://scienceworld.wolfram.com/physics/MagneticVectorPotential.h
: tml
: >
: >
: >
: > :
: > : Anyway... It will cause any discussion of SR to run in circle
: unless
: > you
: > : can not only show the errors but also the fix.
: >
: > LOL. Very punny.
: > http://www.androc1es.pwp.blueyonder.co.uk/Radio%20Wave.htm
: > In the diagram, the time axis is out of the screen. Energy is
: the
: > radius.
: That's a good essay. You probably won't agree that is seems most
: accurate for a CP wave moving in a dielectric, but that's the
: way
: I see it.
Thank you, but I'll add:
I don't deny light travels in glass, water, diamond, etc. There
are dielectrics. I just refuse to call the vacuum of space a
dielectric,
I see need for it. Aether would be a dielectric and there is no
aether.
: >
: > :
: > : > Good research, Sue.
: > : Thank you. :-)
: > : Now if you one of you maths gurus will replace the "displaced
: > : ether" and "retarded potential" with a 177 ohm resistor I can
: > : Google up our Nobel lecture instead of some harried
: professor's
: > : scribblings.
: > :
: > : Sue...
: >
: > You'll have to explain that resistor to me in words of one
: syllable,
: > cos I can't see what it refers to.
:
: Maxwell and Hertz weren't quite on the same page when Maxwell
: was tweaking Ampere and Faraday's laws and inventing
: "displacement current".
Well, ok. To me, a voltage can exist, a capacitor can be charged
and there is no current flowing. Pressure without movement.
:
: If you arrange perfect reflectors so a dipole can't radiate the
: "displacement current" and radiation resistance would go to
: zero or infinitity because there is no energy lost to radiation
: which is what the 377 ohms represents.
: Maxwell didn't quite have the insight we do to see a quarter
: wavelength stub coupling his dipole to infinity.
: A short circuit at one end, looks like an open circuit at the
: other.
: An open circuit at one end, looks like a short circuit at the
: other.
: A resistor looks like itself if it matches the characteristic
: impedance of the stub.
I don't see a displacement current. I see a changing magnetic field.
Referring to impedance, that is frequency dependent.
There is a difference between resistance and impedance.
Resistance limits current in phase with the voltage. Impedance
limits current out of phase with the voltage, and for any given
C that current increases with frequency. For any given L it
decreases with frequency. For an LC circuit there is a balance
point where the current is maximized at some frequency.
This is the "characteristic impedance" frequency, for which
coax is designed. A 50 ohm or 70 ohm cable only has that
value at the optimum frequency, and yes, it can be terminated
with a suitable load for maximum power transfer, which is
maximum current in the resistor with maximun voltage
across it. When there is no resistor, there is no current.
:
: A realistic interpretation of his equations would need to
: dispense
: with the false notion of ether being displaced to explain current
: flow and instead show it's flow throught a resistive virtual
: cylinder
: surrounding the dipole. The dipole shouldn't know if it is
: heating a
: carbon cylinder or a plama cloud three galaxy's away but it
: should know if it is shielded by a conductive cylinder.
:
: Such interpretations may exist, but I am not sure I would
: even recognize them if I saw them.
: ----------
: Sue...
: >
: >
: > : > Androcles
: [snip]
:
:
:
:
:
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