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Standing morphing to travelling waves, and other stupid notions
On Jan 11, 2:12 pm, Jim Kelley wrote:
Cecil Moore wrote: On Jan 10, 9:23 pm, Jim Kelley wrote: A standing wave is an amplitude vs position envelope. A standing wave has an associated envelope but the envelope is *NOT* the wave itself. It's like saying the body of a car is the car itself but you have forgotten the thing that makes the car move - the motor. Sorry, that is a false statement. No, in the most general sense, it is a precisely accurate statement. The equation for a standing wave contains an omega*t term. The equation for standing waves that does not contain an omega*t term is the equation for the envelope. Quoting the following reference, page 32: "For problems in which we shall be concerned throughout with sinusoidal quantities, it is not necessary to write the factor e^jwt explicitly each time, since it will always be understood that all terms are multiplied by this factor;" Please reference "Fields and Waves in Communication Electronics" by Ramo, Whinnery, and Van Duzer, page 343. Ah. Apparently the only book you know of that contains the description of a standing wave. No, just the only book I brought on my trip. The equation for the standing wave voltage is: Ez = Efor*e^j(wt- Bz) + Eref*e^j(wt+Bz) You must belong to the Standing Wave Equation of the Week Club. Nice letter choices. :-) Ramo and Whinnery use E+ and E- but that looks too much like addition and subtraction when using ASCII characters. Ah. So according to Cecil, we have a new definition for a wave which now stipulates that it must only be expressed as a function of time. Nothing new. The actual standing wave equation is a function of time. Dropping the time term turns it into an envelope equation. An envelope is a wave envelope, not a wave. You need to learn to be a little more precise with the language you choose to use. Looks like you have forgotten that e^jwt is implied. You need to be a little more precise with your wording. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 11, 2:12 pm, Jim Kelley wrote: Cecil Moore wrote: On Jan 10, 9:23 pm, Jim Kelley wrote: A standing wave is an amplitude vs position envelope. A standing wave has an associated envelope but the envelope is *NOT* the wave itself. No, it's plot of the equation - just like any other plot one might make of it. It simply a plot of amplitude vs position at a fixed time. Jeez, Cecil. You really do need a life, man. By the way, you forgot to give the Poynting vector for a modulation envelope. :o() (it's a clown) :-) regards, ac6xg |
Standing morphing to travelling waves, and other stupid notions
On Jan 11, 12:06 pm, Gene Fuller wrote:
For a plane wave the E and H fields are perpendicular for either traveling waves or standing waves. For a coaxial cable operating in the normal TEM mode, the E field is radial and the H field is circular around the center conductor. Again, the E field and H field are always perpendicular. Unless one or both of the fields are exactly zero, the Poynting vector will be nonzero. It will have a magnitude and direction. True for traveling waves. ABSOLUTELY *FALSE* FOR STANDING WAVES. Those false concepts are the source of your (and others) confusion.You should have paid attention to my postings of those two very different equations. The E and H fields are 90 degrees apart for traveling waves. The cross product of ExH is the power density in watts/unit-area, i.e. the Poynting vector. For standing waves, the E and H fields are either in phase or 180 degrees out of phase. The cross product of ExH for standing waves is *ALWAYS* equal to zero, i.e. the Poynting vector for pure standing waves is always equal to zero. Please alleviate your ignorance on this subject and get back to us. There is ZERO real power in a pure standing wave. The Poynting vector for a standing wave is *ALWAYS* zero contrary to what you falsely assert above. Stating the same thing in voltage and current terms, for a traveling wave, the voltage and current are either in phase for forward waves or 180 degrees out of phase for reflected waves. Either way, the real power in the traveling wave is V*I watts. For a standing wave, the voltage and current are 90 degrees out of phase. The real power in the standing wave is ZERO! P = V*I*cos(90) = 0 -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 11, 4:04 pm, Jim Kelley wrote:
Cecil Moore wrote: A standing wave has an associated envelope but the envelope is *NOT* the wave itself. No, it's plot of the equation - just like any other plot one might make of it. It simply a plot of amplitude vs position at a fixed time. I'm glad you finally agree. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 11, 12:06 pm, Gene Fuller wrote: For a plane wave the E and H fields are perpendicular for either traveling waves or standing waves. For a coaxial cable operating in the normal TEM mode, the E field is radial and the H field is circular around the center conductor. Again, the E field and H field are always perpendicular. Unless one or both of the fields are exactly zero, the Poynting vector will be nonzero. It will have a magnitude and direction. True for traveling waves. ABSOLUTELY *FALSE* FOR STANDING WAVES. Those false concepts are the source of your (and others) confusion.You should have paid attention to my postings of those two very different equations. The E and H fields are 90 degrees apart for traveling waves. The cross product of ExH is the power density in watts/unit-area, i.e. the Poynting vector. For standing waves, the E and H fields are either in phase or 180 degrees out of phase. The cross product of ExH for standing waves is *ALWAYS* equal to zero, i.e. the Poynting vector for pure standing waves is always equal to zero. Please alleviate your ignorance on this subject and get back to us. There is ZERO real power in a pure standing wave. The Poynting vector for a standing wave is *ALWAYS* zero contrary to what you falsely assert above. Stating the same thing in voltage and current terms, for a traveling wave, the voltage and current are either in phase for forward waves or 180 degrees out of phase for reflected waves. Either way, the real power in the traveling wave is V*I watts. For a standing wave, the voltage and current are 90 degrees out of phase. The real power in the standing wave is ZERO! P = V*I*cos(90) = 0 -- 73, Cecil, w5dxp.com Cecil, That is utter nonsense. Back to school for you. You are confusing phase, vector direction, phasors, and most everything else. What a mess! Everything I said above is exactly correct. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 11, 12:10 pm, Gene Fuller wrote: What do you recommend as the definitive reference on "the nature of photons and photonic waves"? I personally like "Optics" by Hecht and his idea that standing waves maybe shouldn't be called waves at all. EM waves move energy and conserve momentum. Standing waves don't. -- 73, Cecil, w5dxp.com That was a joke. I doubt that Hecht even uses the exact term "photonic wave". For fun, try a Google on "photonic wave". Most of the entries are really weird stuff. Wave-particle duality means that light and other electromagnetic phenomena can be described in terms of waves or in terms of photons. There is no need to use both descriptions at the same time. The laws of physics are complete for either. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
On Jan 11, 8:32 pm, Gene Fuller wrote:
Wave-particle duality means that light and other electromagnetic phenomena can be described in terms of waves or in terms of photons. There is no need to use both descriptions at the same time. The laws of physics are complete for either. Actually, what you don't seem to realize is that exactly the same laws apply to both at the same time and all those laws are perfectly consistent. Photons cannot stand still. Therefore, standing waves are not photonic, i.e. they are not EM waves. That you assert the standing wave E-field and H-field are 90 degrees apart is insanity (in addition to being completely false). -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 11, 8:27 pm, Gene Fuller wrote:
Everything I said above is exactly correct. Sorry Gene, almost everything you said about standing waves is false and some simple math will prove it. Please stop acting like a spoiled brat long enough to understand the following facts of physics. Assume the forward wave and reflected wave have the same magnitude. At one point on the line: The forward voltage is 100v at 0 deg and the forward current is 1 amp at 0 degrees. The reflected voltage is 100v at 90 degrees and the reflected current is 1 amp at 270 degrees. Perform the simple phasor addition to find the magnitude and phase of the standing wave at that point. The standing wave voltage is 141v at 45 deg and the standing wave current is 1.414 amps at -45 deg. The standing wave voltage and current are *always* 90 degrees apart which means the standing wave E- field and H-field are necessarily either zero or 180 degrees apart. 141*1.414*cos(90) = zero watts = ExH = E*H*sin(A) = standing-wave Poynting vector Therefore, the angle A between the standing wave E-field and H-field is either zero or 180 degrees. That doesn't meet the definition of a TEM wave. Therefore, standing waves are *NOT* TEM waves and Hecht was right about that notion. Until you (and others) hit the books and correct your false concepts, you are going to continue to exhibit your considerable ignorance of this subject, your alleged education notwithstanding. I believe that, in the long run, the technical truth will will out over all the ignorance, obfuscation, and ad hominem attacks. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves. was r.r.a.a Laugh Riot!!!
"AI4QJ" wrote in
: "Michael Coslo" wrote in message ... And there are some sanctimonius people out there who are educated orders of magnitude beyond their intelligence, Gosh, I apologize. I did not realize I was communicating with someone of such a greater IQ than I. Can you tell me your MENSA number or perhaps where you recived your PhdD? ready to throw out veiled insults at the drop of a hat....... Fortunately no one like that is in this conversation, eh? Well, there was the one person who started this exchange with a very sarcastic comment. I'm not sure who it was but this mystery person said: "Oh darnit! Here I went and built several antennas designed with Eznec, and they have worked just like the program said they would. I guess I'll have to take the remaining ones down, since I was only supposed to discuss them, not actually make and use them. Thanks for the correction!" Unexpected and unnecessary sarcasm pointed in my direction tends to make me appear sanctimonious and to respond in kind. That was me. Forgive the sarcasm. Sometimes that doesn't come across well in posting. I'll be straightforward. Your comment about Eznec as you quoted... The NEC program is just a computer model, for discussion purposes only. End qoute That statement is absolutely wrong. I have designed antennas using the program. I have studied the presumed properties of these antennas. I have put these antennas together. Upon testing and use of these antennas, they have worked in a manner consistent with the way the program predicted that they would. - Mike - |
Standing morphing to travelling waves, and other stupid notions
On 9 Jan, 22:25, Roy Lewallen wrote:
After reading this, I understand why you find Art's material interesting. snip Roy Lewallen, W7EL You just cannot stop the sarcasm coming out against posters can you? What did you gain on this gotcha? Art |
Standing morphing to travelling waves. was r.r.a.a Laugh Riot!!!
"AI4QJ" wrote in
: Thanks Mike, such information makes me interested in trying it out and sorry on my part too for any miscommunication and statements about 11m. I am from a generation where computer models had many limitations but I am now convinced that EZNEC has probably long overcome the weaknesses of the past. I think you'll like it. There are some things that it won't do, but I think that on the whole, it is pretty capable. It took me from absolutely clueless to neophyte pretty quickly. I can't keep up when the gurus here start badgering each other, but I can put something up, and have some understanding about what I'm doing. - 73 de Mike N3LI - |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 11, 8:27 pm, Gene Fuller wrote: Everything I said above is exactly correct. Sorry Gene, almost everything you said about standing waves is false and some simple math will prove it. Please stop acting like a spoiled brat long enough to understand the following facts of physics. [Usual nonsense snipped] I believe that, in the long run, the technical truth will will out over all the ignorance, obfuscation, and ad hominem attacks. -- 73, Cecil, w5dxp.com Cecil, That is certainly an interesting characterization. Is your position that anyone who disagrees with you must be a spoiled brat? And who provided the ad hominem attack in this thread? You are of course able to believe anything you wish. However, all of your handwaving explanations about reflections and phase shifts and phasors will not be found in ordinary discussions about the Poynting vector. Your "simple math" proves nothing at all, not even close. It is not reasonable to substitute current and voltage for E-field and H-field when considering the Poynting vector. The vector nature of the fields is essential to properly determine the cross product. Go take a look at the actual field configurations for a TEM wave, which includes standing waves, and report back to us. Everything I said in my previous post is exactly correct. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 11, 8:32 pm, Gene Fuller wrote: Wave-particle duality means that light and other electromagnetic phenomena can be described in terms of waves or in terms of photons. There is no need to use both descriptions at the same time. The laws of physics are complete for either. Actually, what you don't seem to realize is that exactly the same laws apply to both at the same time and all those laws are perfectly consistent. Photons cannot stand still. Therefore, standing waves are not photonic, i.e. they are not EM waves. That you assert the standing wave E-field and H-field are 90 degrees apart is insanity (in addition to being completely false). -- 73, Cecil, w5dxp.com Cecil, You keep ignoring the "sloshing" explanation. Actually, you did not totally ignore it; you did indeed criticize the choice of the descriptive word "sloshing". The standing wave envelope may be stationary, but the fields are not. There is no conflict with your photonic requirements. Since this discussion about fields and waves seems to annoy some of the "good buddy" crowd around here, I will quit now and let you win by default. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 10:59 am, Gene Fuller wrote:
You keep ignoring the "sloshing" explanation. Actually, you did not totally ignore it; you did indeed criticize the choice of the descriptive word "sloshing". Look up the word "slosh" in the dictionary, Gene. It is impossible for EM energy to "slosh". While you are at it, you might as well assert that photons smell bad. EM (photonic) waves do NOT change direction unless a change in medium is encountered. "Sloshing" requires a change in direction in the complete absence of a medium change. It is a very ignorant, impossible concept. The standing wave envelope may be stationary, but the fields are not. There is no net energy movement in the kx direction as evidenced by the equation: cos(kx)*cos(wt). All the energy movement is between the E-field and H-field at any fixed point along the wire. There is no conflict with your photonic requirements. Of course there is and I proved it with math. If you want to prove me wrong, prove my math wrong. Good luck on that one. Since this discussion about fields and waves seems to annoy some of the "good buddy" crowd around here, I will quit now and let you win by default. Translation: I have discovered my error. The standing-wave E-field and H-field really are either 0 or 180 degrees apart. Drawing those fields on paper and superposing them proves it. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 10:53 am, Gene Fuller wrote:
Is your position that anyone who disagrees with you must be a spoiled brat? The day you decided that you already know everything there is to know is the day you started getting more and more ignorant and started acting like a spoiled brat. Instead of screaming in anger that I am wrong, I challenge you to produce the math that proves me wrong. It is not reasonable to substitute current and voltage for E-field and H-field when considering the Poynting vector. Please prove that strange assertion. Is the voltage not proportional to the E-field? Is the current not proportional to the H-field? For traveling waves, is not Z0 = V/I and proportional to E/H? Go take a look at the actual field configurations for a TEM wave, which includes standing waves, and report back to us. That's what I did already, Gene. You should take your own advice. It's a little harder to visualize than voltage and current but follows exactly the same concepts plus the right hand rule. Let's take two equal coherent TEM plane waves forming standing waves in free space as described by Hecht in "Optics". At one point the forward wave E-field is at 135 degrees which puts the H-field at -135 degrees. The reflected wave E-field is at 45 degrees which puts the H-field at -45 degrees. Efor at 135 deg + Eref at 45 deg = |Efor|+|Eref| at 90 degrees Hfor at -135 deg + Href at -45 deg = |Hfor|+|Href| at - 90 degrees For standing waves, the H-field is 180 degrees offset from the E- field. The power in the standing wave is ExH = E*H*sin(180) = ZERO. Your assertion that the E-field and H-field are 90 degrees apart for standing waves is simply FALSE! Please prove fact of physics that for yourself. Standing waves do not meet the requirements for an EM wave! Hecht was right about that. Feel free to do something besides wave your hands, mount ad hominem attacks, and engage in obfuscation. -- 73, Cecil, w5dxp.com c |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote: On Jan 11, 4:04 pm, Jim Kelley wrote: Cecil Moore wrote: A standing wave has an associated envelope but the envelope is *NOT* the wave itself. No, it's plot of the equation - just like any other plot one might make of it. It simply a plot of amplitude vs position at a fixed time. I'm glad you finally agree. I'm glad you finally understand. 73, ac6xg |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 2:37*pm, Cecil Moore wrote:
It is impossible for EM energy to "slosh". [gratuitous insult snipped] EM (photonic) waves do NOT change direction unless a change in medium is encountered. "Sloshing" requires a change in direction in the complete absence of a medium change. [gratuitous insult snipped] There is no net energy movement in the kx direction as evidenced by the equation: cos(kx)*cos(wt). All the energy movement is between the E-field and H-field at any fixed point along the wire. As you say, the energy moves between the E-field and the H-field, but the locations of maximum energy along the line for each of these fields is different, so the energy changes position on the line with each cycle. The energy at any point on the line is not constant. E-field energy will peak at the voltage maximums. H-field energy will peak at the current maximums. These are at different places (90 degrees apart). So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. http://www.eznec.com/misc/rraa/TLVis1.exe Demo #2 is a simulation that helps visualize this change in the location of the energy. ...Keith |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
Standing waves do not meet the requirements for an EM wave! Here's a perfect example of what you're saying: http://id.mind.net/~zona/mstm/physic.../StandingWaves A standing wave, yet presumably not an electromagnetic wave! ;-) ac6xg |
Standing morphing to travelling waves, and other stupid notions
Jim Kelley wrote:
... http://id.mind.net/~zona/mstm/physic.../StandingWaves A standing wave, yet presumably not an electromagnetic wave! ;-) ac6xg That page is coming up "Not Found." on my browser; Is there an error in the URL? I am asking because, too often, my browser is giving me this error on URLs' posted by people ... I can't find any reason for it. Thanks in advance, warmest regards, JS |
Standing morphing to travelling waves, and other stupid notions
On Mon, 14 Jan 2008 12:40:39 -0800 (PST)
Keith Dysart wrote: snip............... As you say, the energy moves between the E-field and the H-field, but the locations of maximum energy along the line for each of these fields is different, so the energy changes position on the line with each cycle. The energy at any point on the line is not constant. E-field energy will peak at the voltage maximums. H-field energy will peak at the current maximums. These are at different places (90 degrees apart). So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. I can understand no energy crossing a zero current point, but how do you justify no energy crossing a zero voltage point when current IS observed? Current is defined as movement of charges, and charges have energy by definition (how can they be charges without energy?). Another point, the current is observed to change directions during the cycles, polarity also changes on each side of the zero voltage point. Where might the polarized energy come from if it does not cross the zero voltage point? I can kinda see how like charges could repell so that waves of like polarity might "bounce" but I can't see how waves of opposite polarity might "bounce". If waves of opposite polarity "bounced", why would the polarity change during the cycle on each side of the "bounce" point? To me, it is much more rewarding to work with traveling waves that pass through one another, interacting to create standing waves. Would it help your visualization process to observe that when two waves of SAME POLARITY but traveling in opposite directions cross, the currents accompaning the waves are moving in opposite directions both before and after crossing? When two waves of OPPOSITE POLARITY but traveling in opposite directions cross, the currents are moving in the same direction both before and after crossing. If we were talking about water, water behind a dam is like voltage, with the height of the water the potential energy, measured in head (feet), or PSI if measured at the bottom of the dam. A pipe to the bottom of the dam will squirt water at a high velocity but no head or PSI. The potential energy of the water behind the dam has been converted to kinetic energy measued in velocity of a moving mass. The moving water can be stopped, and if carefully done, the static head reached by stopping the water will nearly reach the original water level behind the dam. It would reach the same level if it were not for friction losses. Electrical current is something like that moving water. http://www.eznec.com/misc/rraa/TLVis1.exe Demo #2 is a simulation that helps visualize this change in the location of the energy. ...Keith 73, Roger, W7WKB |
Standing morphing to travelling waves, and other stupid notions
Jim Kelley wrote: Cecil Moore wrote: Standing waves do not meet the requirements for an EM wave! Here's a perfect example of what you're saying: http://id.mind.net/~zona/mstm/physic.../StandingWaves A standing wave, yet presumably not an electromagnetic wave! ;-) ac6xg Sorry. Truncated URL. There's more. The correct URL is: http://id.mind.net/~zona/mstm/physic...ingWaves1.html jk |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 14, 10:53 am, Gene Fuller wrote: Is your position that anyone who disagrees with you must be a spoiled brat? The day you decided that you already know everything there is to know is the day you started getting more and more ignorant and started acting like a spoiled brat. Instead of screaming in anger that I am wrong, I challenge you to produce the math that proves me wrong. It is not reasonable to substitute current and voltage for E-field and H-field when considering the Poynting vector. Please prove that strange assertion. Is the voltage not proportional to the E-field? Is the current not proportional to the H-field? For traveling waves, is not Z0 = V/I and proportional to E/H? Go take a look at the actual field configurations for a TEM wave, which includes standing waves, and report back to us. That's what I did already, Gene. You should take your own advice. It's a little harder to visualize than voltage and current but follows exactly the same concepts plus the right hand rule. Let's take two equal coherent TEM plane waves forming standing waves in free space as described by Hecht in "Optics". At one point the forward wave E-field is at 135 degrees which puts the H-field at -135 degrees. The reflected wave E-field is at 45 degrees which puts the H-field at -45 degrees. Efor at 135 deg + Eref at 45 deg = |Efor|+|Eref| at 90 degrees Hfor at -135 deg + Href at -45 deg = |Hfor|+|Href| at - 90 degrees For standing waves, the H-field is 180 degrees offset from the E- field. The power in the standing wave is ExH = E*H*sin(180) = ZERO. Your assertion that the E-field and H-field are 90 degrees apart for standing waves is simply FALSE! Please prove fact of physics that for yourself. Standing waves do not meet the requirements for an EM wave! Hecht was right about that. Feel free to do something besides wave your hands, mount ad hominem attacks, and engage in obfuscation. -- 73, Cecil, w5dxp.com c Cecil, Enjoy your superiority! When you finally figure out that phasor angles (such as those used above) have no connection with the vector directions considered in the Poynting analysis then you will have found even more wisdom. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 3:40 pm, Keith Dysart wrote:
So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. Zero *NET* energy moves in a standing wave pattern whether it be at a node or anywhere else. Forward energy and reflected energy moves across a node and everywhere else because there are no reflections in a homogeneous medium. Please site a reference that says that reflections are possible in a homogeneous medium. Until you do that, you are preaching religion, not science. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 3:09 pm, Jim Kelley wrote:
Cecil Moore wrote: I'm glad you finally agree. I'm glad you finally understand. I've always known that a graph drawn with a pencil on a piece of paper is not an EM standing wave but, for awhile, you seem to have forgotten that simple fact. The envelope is also not the wave. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 4:22 pm, Jim Kelley wrote:
A standing wave, yet presumably not an electromagnetic wave! ;-) EM waves necessarily travel at the speed of light in a medium. Does a standing wave travel at the speed of light? If your answer is 'yes', where does it go? If your answer is 'no', it is not an EM wave. -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 8:10 pm, wrote:
Jim Kelley wrote: Sorry. Truncated URL. There's more. The correct URL is: http://id.mind.net/~zona/mstm/physic...es/standingWav... Sorry, it didn't change and is truncated again. Maybe you should just use two lines? -- 73, Cecil, w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 10:07 pm, Gene Fuller wrote:
Enjoy your superiority! When you finally figure out that phasor angles (such as those used above) have no connection with the vector directions considered in the Poynting analysis then you will have found even more wisdom. I challenged you to post the math, Gene, and you are apparently afraid to do so. I'll bet you $100 that I am right and can prove it. I showed that two plane waves in free space form standing waves with the total E-field either 0 or 180 degrees apart from the H-field, contrary to what you asserted. Please prove me wrong. If you cannot, please send me $100. If you would put aside your delusions of grandeur and simply sketch those fields on a piece of paper, you would see for yourself that I am right. When I get back home, I'll knock out a 3D graphic that will leave no doubt. -- 73, Cecil. w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote:
On Jan 14, 10:07 pm, Gene Fuller wrote: Enjoy your superiority! When you finally figure out that phasor angles (such as those used above) have no connection with the vector directions considered in the Poynting analysis then you will have found even more wisdom. I challenged you to post the math, Gene, and you are apparently afraid to do so. I'll bet you $100 that I am right and can prove it. I showed that two plane waves in free space form standing waves with the total E-field either 0 or 180 degrees apart from the H-field, contrary to what you asserted. Please prove me wrong. If you cannot, please send me $100. If you would put aside your delusions of grandeur and simply sketch those fields on a piece of paper, you would see for yourself that I am right. When I get back home, I'll knock out a 3D graphic that will leave no doubt. -- 73, Cecil. w5dxp.com Cecil, This is truly bizarre. The E-field and the H-field are always at right angles to each other in the plane wave case. They are also perpendicular to the propagation direction. The same is true for the TEM mode in a coaxial waveguide, which is the usual case discussed on RRAA. There is no 0 or 180 degree involvement. I don't know what you are so confused about, but you really need to rethink what you are saying. There is no need to sketch or calculate anything. A diagram showing the relationship of the E-field vector and the H-field vector is in every E&M and optics book I have ever seen. I presume that Hecht has the same diagram. 73, Gene W4SZ |
Standing morphing to travelling waves, and other stupid notions
Gene Fuller wrote:
... There is no need to sketch or calculate anything. A diagram showing the relationship of the E-field vector and the H-field vector is in every E&M and optics book I have ever seen. I presume that Hecht has the same diagram. 73, Gene W4SZ Gesus, e fields/h fields at right angles to each other? These are things which make our graphs make "sense" to us--as far as being "real", gawd--who knows? IDIOTS ALL! Regards, JS |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 7:19 pm, Roger Sparks wrote:
On Mon, 14 Jan 2008 12:40:39 -0800 (PST) Keith Dysart wrote: snip............... As you say, the energy moves between the E-field and the H-field, but the locations of maximum energy along the line for each of these fields is different, so the energy changes position on the line with each cycle. The energy at any point on the line is not constant. E-field energy will peak at the voltage maximums. H-field energy will peak at the current maximums. These are at different places (90 degrees apart). So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. I can understand no energy crossing a zero current point, but how do you justify no energy crossing a zero voltage point when current IS observed? Well I start with P = V * I, so whenever the current or the voltage is zero, there is no power. Specifically, V and I are measured at the terminals of a network and P will be the power flowing into or out of the network. In the case under discussion, there are two networks, one to the left of the point on the line and one to the right and we are measuring the power flowing between these two networks. For an example of current without power, consider a loop of superconductor with a current flowing in it. No voltage, no power, but there is current. Current is defined as movement of charges, and charges have energy by definition (how can they be charges without energy?). Consider an object flying through space. No work is being done (and therefore there is no power), but the object still has kinetic energy. Another point, the current is observed to change directions during the cycles, polarity also changes on each side of the zero voltage point. Where might the polarized energy come from if it does not cross the zero voltage point? A thought experiment I have found useful is to consider a simple resonant circuit made of an ideal capacitor and inductor. Charge the capacitor to 10 volts and then connect the inductor. A sinusoidal voltage and current will appear in the circuit. Just as the inductor is connected: - all the energy is stored in the capacitor - the voltage on the capacitor is maximum - there is no current in the inductor After connecting the inductor: - energy starts to transfer to the inductor - the voltage on the capacitor is dropping - the current in the inductor is increasing Some time later: - the voltage on the capacitor is 0 - the current in the inductor is maximum - there is no energy stored in the capacitor - all the energy is stored in the inductor - no energy is moving from the capacitor to the inductor But the inductor insists that current continue to flow: - the capacitor begins to charge with a negarive voltage - energy begins to transfer from the inductor back to the capacitor (note the change in the direction of energy flow) - the voltage on the capacitor is increasing negatively - the current in the inductor is dropping Sometime later: - the current in the inductor has dropped to zero - the capacitor has a maximum negative voltage - all the energy is in the capacitor And this continues forever at the resonant frequency of the capacitor and inductor circuit. But no energy is moving from the capacitor to the inductor when the voltage on the capacitor is zero and the current in the inductor is maximum. It is at these times that the direction of energy flow is changing, as well as when the voltage in the capacitor is maximum and the current is zero. I can kinda see how like charges could repell so that waves of like polarity might "bounce" but I can't see how waves of opposite polarity might "bounce". If waves of opposite polarity "bounced", why would the polarity change during the cycle on each side of the "bounce" point? An excellent counter-example. I may have fallen into the trap of looking at the examples that support the argument rather than looking for the ones that don't. This will take some cogitating. Maybe its the end of the line for the "bounce hypothesis". To me, it is much more rewarding to work with traveling waves that pass through one another, interacting to create standing waves. I don't object to this view, as long as the waves are viewed as having voltages or currents but no power. The difficulty is that some waves definitely transport energy while others do not and I do not see a good explanation for what turns the former into the latter, as happens, for example, when the pulses collide. Would it help your visualization process to observe that when two waves of SAME POLARITY but traveling in opposite directions cross, the currents accompaning the waves are moving in opposite directions both before and after crossing? When two waves of OPPOSITE POLARITY but traveling in opposite directions cross, the currents are moving in the same direction both before and after crossing. I do understand (at least I think I do) the methodology for superposing the waves of voltage and current, computing the results and deriving the power from the result. I just am not happy that this results in waves sometimes transporting energy and sometimes not, without a good explanation of the transition. If we were talking about water, water behind a dam is like voltage, with the height of the water the potential energy, measured in head (feet), or PSI if measured at the bottom of the dam. A pipe to the bottom of the dam will squirt water at a high velocity but no head or PSI. The potential energy of the water behind the dam has been converted to kinetic energy measued in velocity of a moving mass. The moving water can be stopped, and if carefully done, the static head reached by stopping the water will nearly reach the original water level behind the dam. It would reach the same level if it were not for friction losses. Electrical current is something like that moving water. Agreed. I have used this analogy as an aid to understaning though it becomes challenging at RF. ....Keith |
Standing morphing to travelling waves, and other stupid notions
On Jan 14, 10:42*pm, Cecil Moore wrote:
On Jan 14, 3:40 pm, Keith Dysart wrote: So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. Zero *NET* energy moves in a standing wave pattern whether it be at a node or anywhere else. Forward energy and reflected energy moves across a node and everywhere else because there are no reflections in a homogeneous medium. From your posts I have not been able to determine exactly what YOU mean by "*NET* energy moving". Several possibilities come to mind: 1) the time average of the instantenous power, P(x,t), at a particular point on the line. 2) the difference between the time average power in the forward and reflected waves. This would be equivalent to subtracting the forward and reflected power indicated by a Bird wattmeter. 3) the difference between the instantaneous forward and reflected power at a particular time and point on the line. 4) the time average of the difference between the instaneous forward and reflected power at a point on the line. 5) something completely different? It would be valuable if you could indicate which of the possible definitions of "*NET* energy moving" you mean. It would be even more illuminating if you could describe what measurements would need to be made on a line and exactly what calculations should be performed to compute your definition of "*NET* energy moving". A rigorous definition might reveal that there is actually agreement. ...Keith |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote: On Jan 14, 4:22 pm, Jim Kelley wrote: A standing wave, yet presumably not an electromagnetic wave! ;-) EM waves necessarily travel at the speed of light in a medium. Does a standing wave travel at the speed of light? If your answer is 'yes', where does it go? If your answer is 'no', it is not an EM wave. You didn't click on the link, did you. :-) ac6xg |
Standing morphing to travelling waves, and other stupid notions
On Tue, 15 Jan 2008 06:44:05 -0800 (PST)
Keith Dysart wrote: On Jan 14, 7:19 pm, Roger Sparks wrote: On Mon, 14 Jan 2008 12:40:39 -0800 (PST) Keith Dysart wrote: snip............... As you say, the energy moves between the E-field and the H-field, but the locations of maximum energy along the line for each of these fields is different, so the energy changes position on the line with each cycle. The energy at any point on the line is not constant. E-field energy will peak at the voltage maximums. H-field energy will peak at the current maximums. These are at different places (90 degrees apart). So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. I can understand no energy crossing a zero current point, but how do you justify no energy crossing a zero voltage point when current IS observed? Well I start with P = V * I, so whenever the current or the voltage is zero, there is no power. Specifically, V and I are measured at the terminals of a network and P will be the power flowing into or out of the network. I can see why you find "no power" at the zero voltage point, but does that imply that there is no energy flow and no power from every perspective? As I write, I am struggling how to clearly differentiate between "power" as "work done" and energy as "capacity to do work", and what "network" are we defining. Let's begin with the network. Drawing from your words below, we have two networks, one to the left and one to the right of our zero voltage point. When we test voltages on either side of the zero point, we find voltage. The question now is: "Which network did we join when we measured voltage?". The answer is: "We joined the network that we measured.". When we measure exactly in the center between networks, we join neither network. For another way of looking at the two networks, let us place our voltage probes on each side of the zero voltage point on a/the wire connecting the two networks. We will detect a voltage and a current for any of the standing wave systems we are discussing. By changing our points of reference, we find that power is applied to the zero voltage zone during the instant of time the measurement is made. I personally define power as a state/condition where "work 'is being' done", . Power must act over time and have a physical movement component. Voltage by itself does not fulfill this definition because no movement is observed. Current is movement, voltage is only an indication of where a concentration of charges is found. In the case under discussion, there are two networks, one to the left of the point on the line and one to the right and we are measuring the power flowing between these two networks. For an example of current without power, consider a loop of superconductor with a current flowing in it. No voltage, no power, but there is current. I agree. We could place voltage probes between any two points on the superconducting loop and not find voltage. Power is not being applied nor extracted from the superconducting loop system. I think we would all agree that energy is stored in the superconducting loop with current flowing. Current is defined as movement of charges, and charges have energy by definition (how can they be charges without energy?). Consider an object flying through space. No work is being done (and therefore there is no power), but the object still has kinetic energy. Another point, the current is observed to change directions during the cycles, polarity also changes on each side of the zero voltage point. Where might the polarized energy come from if it does not cross the zero voltage point? A thought experiment I have found useful is to consider a simple resonant circuit made of an ideal capacitor and inductor. Charge the capacitor to 10 volts and then connect the inductor. A sinusoidal voltage and current will appear in the circuit. Just as the inductor is connected: - all the energy is stored in the capacitor - the voltage on the capacitor is maximum - there is no current in the inductor After connecting the inductor: - energy starts to transfer to the inductor - the voltage on the capacitor is dropping - the current in the inductor is increasing Some time later: - the voltage on the capacitor is 0 - the current in the inductor is maximum - there is no energy stored in the capacitor - all the energy is stored in the inductor - no energy is moving from the capacitor to the inductor But the inductor insists that current continue to flow: - the capacitor begins to charge with a negarive voltage - energy begins to transfer from the inductor back to the capacitor (note the change in the direction of energy flow) - the voltage on the capacitor is increasing negatively - the current in the inductor is dropping Sometime later: - the current in the inductor has dropped to zero - the capacitor has a maximum negative voltage - all the energy is in the capacitor And this continues forever at the resonant frequency of the capacitor and inductor circuit. But no energy is moving from the capacitor to the inductor when the voltage on the capacitor is zero and the current in the inductor is maximum. It is at these times that the direction of energy flow is changing, as well as when the voltage in the capacitor is maximum and the current is zero. When the voltage on the capacitor is zero, the voltage on the entire system is zero, no matter our reference point. The system energy is completely contained in the moving current with a direction of energy flow completely defined. For an instant, the inductor is like a superconducting loop. From a traveling wave standpoint, the resonant capacitor/inductor system contains a positive wave and a negative wave, equally balanced energy wise. When the capacitor is completely charged, the positive and negative waves are at the reversal/mid point of the cycle where each wave is maximally displaced from center (which is at the electrical center of the inductor). When the capacitor is completely discharged, the two waves superimpose and both reside in the inductor at identical times. The energy of both waves is completely contained in the electromagnetic field that exists outside the wires containing the two traveling waves. Do the waves exist on the wire at this instant, or have they completely desolved into a space field we observe as magnetic force? The current seems to be flowing so I would say the waves both continue to exist. I can kinda see how like charges could repell so that waves of like polarity might "bounce" but I can't see how waves of opposite polarity might "bounce". If waves of opposite polarity "bounced", why would the polarity change during the cycle on each side of the "bounce" point? An excellent counter-example. I may have fallen into the trap of looking at the examples that support the argument rather than looking for the ones that don't. This will take some cogitating. Maybe its the end of the line for the "bounce hypothesis". To me, it is much more rewarding to work with traveling waves that pass through one another, interacting to create standing waves. I don't object to this view, as long as the waves are viewed as having voltages or currents but no power. Have you considered how energy is transfered between elements of the transmission line over time if we do not have an ongoing application of power? Doesn't one section of line apply power to the next successive section of line an instant of time later after it received applied power? We agree that a transmitter applies power at the input of a transmission line. Isn't the first section of transmission line just the power source for the second piece of line? I think of the traveling waves as transporting power and energy through time and physical distance. The highest voltage points physically "move" (found in a new location) as time passes, as do the highest current points, and always together in phase. The difficulty is that some waves definitely transport energy while others do not and I do not see a good explanation for what turns the former into the latter, as happens, for example, when the pulses collide. Some waves transport energy, and some do not! That distinction bothers me less now that I have participated in this thread for a while. For me, the traveling wave always has current and voltage in phase, and always carries power. If I can not find power, then we must have a standing wave. For me, traveling waves is all that we really have, they are primary. All other waves flow/result from the traveling waves. Another observation that has helped me is the recognition that "waves" are just statistical groupings of repetitious events. It is very convenient to treat waves as physical objects but they are really groupings of much, much smaller events. How small is the smallest event, no one seems to know, but the highest frequencies still seem to be electromagnetic events. If the "wave" is composed of a group of much smaller events (such as movement of electrons, or smaller), then it is not so hard to accept that we might detect passage of two waves as having a different voltage and energy level from what we would expect if the voltage and energy were static. Would it help your visualization process to observe that when two waves of SAME POLARITY but traveling in opposite directions cross, the currents accompaning the waves are moving in opposite directions both before and after crossing? When two waves of OPPOSITE POLARITY but traveling in opposite directions cross, the currents are moving in the same direction both before and after crossing. I do understand (at least I think I do) the methodology for superposing the waves of voltage and current, computing the results and deriving the power from the result. I just am not happy that this results in waves sometimes transporting energy and sometimes not, without a good explanation of the transition. If we were talking about water, water behind a dam is like voltage, with the height of the water the potential energy, measured in head (feet), or PSI if measured at the bottom of the dam. A pipe to the bottom of the dam will squirt water at a high velocity but no head or PSI. The potential energy of the water behind the dam has been converted to kinetic energy measued in velocity of a moving mass. The moving water can be stopped, and if carefully done, the static head reached by stopping the water will nearly reach the original water level behind the dam. It would reach the same level if it were not for friction losses. Electrical current is something like that moving water. Agreed. I have used this analogy as an aid to understaning though it becomes challenging at RF. ...Keith This discussion helps clarify things in my mind. I hope it helps you as well. 73, Roger, W7WKB |
Standing morphing to travelling waves, and other stupid notions
Cecil Moore wrote: I've always known that a graph drawn with a pencil on a piece of paper is not an EM standing wave but, for awhile, you seem to have forgotten that simple fact. A plot is simply the graphical representation of an equation. Since I was the one pointing it out to you, it seems you are the one who had "forgotten that simple fact". The envelope is also not the wave. It all comes from the same equation, Cecil. If the thing which amplitude modulates a wave cannot be called a wave, then what should it be called? ac6xg |
Standing morphing to travelling waves, and other stupid notions
On 15 Jan, 11:27, Roger Sparks wrote:
On Tue, 15 Jan 2008 06:44:05 -0800 (PST) Keith Dysart wrote: On Jan 14, 7:19 pm, Roger Sparks wrote: On Mon, 14 Jan 2008 12:40:39 -0800 (PST) Keith Dysart wrote: snip............... As you say, the energy moves between the E-field and the H-field, but the locations of maximum energy along the line for each of these fields is different, so the energy changes position on the line with each cycle. The energy at any point on the line is not constant. E-field energy will peak at the voltage maximums. H-field energy will peak at the current maximums. These are at different places (90 degrees apart). So energy does move within the line, though no energy crosses a point where the voltage or current is always 0. I can understand no energy crossing a zero current point, but how do you justify no energy crossing a zero voltage point when current IS observed? Well I start with P = V * I, so whenever the current or the voltage is zero, there is no power. Specifically, V and I are measured at the terminals of a network and P will be the power flowing into or out of the network. I can see why you find "no power" at the zero voltage point, but does that imply that there is no energy flow and no power from every perspective? *As I write, I am struggling how to clearly differentiate between "power" as "work done" and energy as "capacity to do work", and what "network" are we defining. Let's begin with the network. *Drawing from your words below, we have two networks, one to the left and one to the right of our zero voltage point. *When we test voltages on either side of the zero point, we find voltage. *The question now is: "Which network did we join when we measured voltage?". *The answer is: "We joined the network that we measured.". *When we measure exactly in the center between networks, we join neither network. * For another way of looking at the two networks, *let us place our voltage probes on each side of the zero voltage point on a/the wire connecting the two networks. *We will detect a voltage and a current for any of the standing wave systems we are discussing. *By changing our points of reference, we find that power is applied to the zero voltage zone during the instant of time the measurement is made. I personally define power as a state/condition where "work 'is being' done", . *Power must act over time and have a physical movement component. *Voltage by itself does not fulfill this definition because no movement is observed. *Current is movement, voltage is only an indication of where a concentration of charges is found. In the case under discussion, there are two networks, one to the left of the point on the line and one to the right and we are measuring the power flowing between these two networks. For an example of current without power, consider a loop of superconductor with a current flowing in it. No voltage, no power, but there is current. I agree. *We could place voltage probes between any two points on the superconducting loop and not find voltage. *Power is not being applied nor extracted from the superconducting loop system. *I think we would all agree that energy is stored in the superconducting loop with current flowing. Current is defined as movement of charges, and charges have energy by definition (how can they be charges without energy?). Consider an object flying through space. No work is being done (and therefore there is no power), but the object still has kinetic energy. Another point, the current is observed to change directions during the cycles, polarity also changes on each side of the zero voltage point. *Where might the polarized energy come from if it does not cross the zero voltage point? A thought experiment I have found useful is to consider a simple resonant circuit made of an ideal capacitor and inductor. Charge the capacitor to 10 volts and then connect the inductor. A sinusoidal voltage and current will appear in the circuit. Just as the inductor is connected: - all the energy is stored in the capacitor - the voltage on the capacitor is maximum - there is no current in the inductor After connecting the inductor: - energy starts to transfer to the inductor - the voltage on the capacitor is dropping - the current in the inductor is increasing Some time later: - the voltage on the capacitor is 0 - the current in the inductor is maximum - there is no energy stored in the capacitor - all the energy is stored in the inductor - no energy is moving from the capacitor to * the inductor But the inductor insists that current continue to flow: - the capacitor begins to charge with a negarive * voltage - energy begins to transfer from the inductor * back to the capacitor (note the change in the * direction of energy flow) - the voltage on the capacitor is increasing * negatively - the current in the inductor is dropping Sometime later: - the current in the inductor has dropped to * zero - the capacitor has a maximum negative voltage - all the energy is in the capacitor And this continues forever at the resonant frequency of the capacitor and inductor circuit. But no energy is moving from the capacitor to the inductor when the voltage on the capacitor is zero and the current in the inductor is maximum. It is at these times that the direction of energy flow is changing, as well as when the voltage in the capacitor is maximum and the current is zero. When the voltage on the capacitor is zero, the voltage on the entire system is zero, no matter our reference point. *The system energy is completely contained in the moving current with a direction of energy flow completely defined. For an instant, the inductor is like a superconducting loop. From a traveling wave standpoint, the resonant capacitor/inductor system contains a positive wave and a negative wave, equally balanced energy wise. *When the capacitor is completely charged, the positive and negative waves are at the reversal/mid point of the cycle where each wave is maximally displaced from center (which is at the electrical center of the inductor). *When the capacitor is completely discharged, the two waves superimpose and both reside in the inductor at identical times. *The energy of both waves is completely contained in the electromagnetic field that exists outside the wires containing the two traveling waves. *Do the waves exist on the wire at this instant, or have they completely desolved into a space field we observe as magnetic force? *The current seems to be flowing so I would say the waves both continue to exist. I can kinda see how like charges could repell so that waves of like polarity might "bounce" but I can't see how waves of opposite polarity might "bounce". *If waves of opposite polarity "bounced", why would the polarity change during the cycle on each side of the "bounce" point? An excellent counter-example. I may have fallen into the trap of looking at the examples that support the argument rather than looking for the ones that don't. This will take some cogitating. Maybe its the end of the line for the "bounce hypothesis". To me, it is much more rewarding to work with traveling waves that pass through one another, *interacting to create standing waves. I don't object to this view, as long as the waves are viewed as having voltages or currents but no power. Have you considered how energy is transfered between elements of the transmission line over time if we do not have an ongoing application of power? *Doesn't one section of line apply power to the next successive section of line an instant of time later after it received applied power? We agree that a transmitter applies power at the input of a transmission line. *Isn't the first section of transmission line just the power source for the second piece of line? I think of the traveling waves as transporting power and energy through time and physical distance. *The highest voltage points physically "move" (found in a new location) as time passes, as do the highest current points, and always together in phase. * The difficulty is that some waves definitely transport energy while others do not and I do not see a good explanation for what turns the former into the latter, as happens, for example, when the pulses collide. Some waves transport energy, and some do not! *That distinction bothers me less now that I have participated in this thread for a while. *For me, the traveling wave always has current and voltage in phase, and always carries power. *If I can not find power, then we must have a standing wave. *For me, traveling waves is all that we really have, they are primary. *All other waves flow/result from the traveling waves. * Another observation that has helped me is the recognition that "waves" are just statistical groupings of repetitious events. *It is very convenient to treat waves as physical objects but they are really groupings of much, much smaller events. *How small is the smallest event, no one seems to know, but the highest frequencies still seem to be electromagnetic events. *If the "wave" is composed of a group of much smaller events (such as movement of electrons, or smaller), then it is not so hard to accept that we might detect passage of two waves as having a different voltage and energy level from what we would expect if the voltage and energy were static. * Would it help your visualization process to observe that when two waves of SAME POLARITY but traveling in opposite directions cross, the currents accompaning the waves are moving in opposite directions both before and after crossing? *When two waves of OPPOSITE POLARITY but traveling in opposite directions cross, the currents are moving in the same direction both before and after crossing. I do understand (at least I think I do) the methodology for superposing the waves of voltage and current, computing the results and deriving the power from the result. I just am not happy that this results in waves sometimes transporting energy and sometimes not, without a good explanation of the transition. If we were talking about water, water behind a dam is like voltage, with the height of the water the potential energy, measured in head (feet), or PSI if measured at the bottom of the dam. *A pipe to the bottom of the dam will squirt water at a high velocity but no head or PSI. *The potential energy of the water behind the dam has been converted to kinetic energy measued in velocity of a moving mass. *The moving water can be stopped, and if carefully done, the static head reached by stopping the water will nearly reach the original water level behind the dam. *It would reach the same level if it were not for friction losses. *Electrical current is something like that moving water. Agreed. I have used this analogy as an aid to understaning though it becomes challenging at RF. ...Keith This discussion helps clarify things in my mind. *I hope it helps you as well. 73, Roger, W7WKB Roger you would be better to start off with first principles. Current is by definition a constant at all points where the imagianary vector is the angle or phase of a molecular dipole at the point of reference. Nothing is moving forward. The only movement of the molecular dipole is on of rotational movement about a static pont of reference. One you understand this you can then go on to magnetic fields created by multiple inherrant dipoles with respect to their phase angle which magnifies or nullifies the created magnetic field Best regards Art |
Standing morphing to travelling waves, and other stupid notions
Roger Sparks wrote:
I can see why you find "no power" at the zero voltage point, but does that imply that there is no energy flow and no power from every perspective? As I write, I am struggling how to clearly differentiate between "power" as "work done" and energy as "capacity to do work", and what "network" are we defining. Power at a particular point on the line is the rate of energy flow past that point. It does no imply that any work is done anywhere, since any energy flowing past the point can be stored. That is, in fact, exactly what happens with the open circuited line in my analyses and illustrated with TLVis1. You can see from the TLVis1 demo 4 that power is present at all times and places along the line except a few select points. No work is being done; energy is simply moving back and forth along the line and between the E and H fields. . . . I personally define power as a state/condition where "work 'is being' done", . Power must act over time and have a physical movement component. Voltage by itself does not fulfill this definition because no movement is observed. Current is movement, voltage is only an indication of where a concentration of charges is found. Of course you're free to define anything in any way you choose. But you've chosen a definition that's different from the one accepted in all of electrical circuit analysis and all textbooks. So you can expect to have a good deal of difficulty communicating with people who are acquainted with the universally understood definition and assume that's what you mean, rather than your own personal definition. To them, power is the time rate of energy flow, dE/dt, period. . . . Roy Lewallen, W7EL |
Standing morphing to travelling waves, and other stupid notions
Gene Fuller wrote:
This is truly bizarre. The E-field and the H-field are always at right angles to each other in the plane wave case. They are also perpendicular to the propagation direction. The same is true for the TEM mode in a coaxial waveguide, which is the usual case discussed on RRAA. There is no 0 or 180 degree involvement. I don't know what you are so confused about, but you really need to rethink what you are saying. What you are saying is 100% correct for plane EM traveling waves. What you are saying is 100% incorrect for standing waves. It just shows that Hecht was right when he said standing waves probably don't deserve to be called waves. Maybe you should try to understand why Hecht would say such a thing. There is no need to sketch or calculate anything. A diagram showing the relationship of the E-field vector and the H-field vector is in every E&M and optics book I have ever seen. Yes, and that diagram is for a *TRAVELING WAVE*, not for a standing wave. Please find a reference with the E-fields and H-fields diagrammed for a standing wave and get back to us. Better yet, consider there is a need to sketch the fields if for no other reason, just to prove me wrong. This is not rocket science, Gene. When the magnitude of the Poynting vector for the forward wave equals the magnitude of the Poynting vector for the reflected wave, the net Poynting vector is obviously zero. Since the Poynting vector equals ExH, the only way that the standing wave Poynting vector can be zero everywhere is for the cross product of ExH to be zero. The cross product is E*H*sin(A) and we know that E and H are not zero, so sin(A) must necessarily be zero. So A must necessarily be 0 or 180 degrees. Nothing else is possible. -- 73, Cecil http://www.w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Jim Kelley wrote:
You didn't click on the link, did you. :-) Yes, I did, and Firefox said it couldn't find the page. Why do you post URLs with ... at the end? -- 73, Cecil http://www.w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Jim Kelley wrote:
Cecil Moore wrote: I've always known that a graph drawn with a pencil on a piece of paper is not an EM standing wave but, for awhile, you seem to have forgotten that simple fact. A plot is simply the graphical representation of an equation. Yet you said it was "the wave". It is not the wave. It is simply some carbon rubbed on a piece of paper. Jim, you requested that I be more precise and that's exactly what I am being. -- 73, Cecil http://www.w5dxp.com |
Standing morphing to travelling waves, and other stupid notions
Keith Dysart wrote:
It would be valuable if you could indicate which of the possible definitions of "*NET* energy moving" you mean. Net energy is the difference between the average forward energy and the average reflected energy. Please forget instantaneous values. Instantaneous voltage and current are obviously valuable concepts. For the context of this discussion, seems to me instantaneous energy or power are just diversions away from the real issues. The real question is: Can an EM wave exist without energy? Roy implies that it can. I challenge him to produce an EM wave containing no energy. -- 73, Cecil http://www.w5dxp.com |
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