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In Reply to: RE: Your thoughts please. posted by zako on February 23, 2014 at 08:40:30
Electromagnetic waves are particles and waves. But when they act as particles what kind of particles are they? Hint: electromagnetic waves move at the speed of light in a vacuum.
Follow Ups:
Electromagnetic waves are particles and waves. But when they act as particles what kind of particles are they? Hint: electromagnetic waves move at the speed of light in a vacuum.
And, generally speaking, in the case of a closed circuit the electrons in a conductor move as slow as thick molasses down the wire.Agree?
Disagree?
Why?
Edits: 02/25/14
If one goes so far as to measure wire with appropriate gear, one finds the propagation speed is set by the repeated series L and parallel C effect of a long set of conductors. Once a set of wires is approaching a wavelength or more, it is / has transitioned into what in engineering is called a transmission line. Unless your 'Ma Bell or installing an antenna, you never deal with cables long enough to be transmission lines.
In coax cable (at radio frequencies all the aspects of cables are much more important as they increase in importance / magnitude with frequency) they often specify the "propagation velocity".
Lets say you have a coax cable that goes around the earth and it has a PV of 66% (slow coax) and now you put a signal in at one end and waited for it to emerge at the other end, you would have waited about 2/10 of one second for the signal.
In other words, cable propagation speed is not an issue withing a living room.
Cables do have effects but these can be easily measured and the effect they have on the signal can be measured or auditioned by listening to the difference between one end and he other or the effect they have on the driving source.
If your concerned about electron flow, that view, consider a wire is like a ridged pipe full of water, if you force water in at one end, nearly instantly (at the speed of sound in water) that pressure reaches the other end. The speed the "electron pressure" travels is near the speed of light.
"If your concerned about electron flow, that view, consider a wire is like a ridged pipe full of water, if you force water in at one end, nearly instantly (at the speed of sound in water) that pressure reaches the other end. The speed the "electron pressure" travels is near the speed of light."
tomservo
Part 2 Demolition of a Myth
2.1 The basic misconception
The core misconception, propagated by many text books, is that moving electrons (or some other
form of current) in the connecting wires carry energy from the battery to the globe. I can give at
least five arguments why that idea is conceptually unsound. You may be able to think of more.
Objection 1 is that that electrons are just too slow to carry the energy fast enough! When the switch
is closed the light globe comes on almost at once. Many text books discuss a model of electrical
conduction in which a “gas” or “sea” or electrons is pushed slowly along a wire by an electric field.
If you know the density of electrons (the number of conduction electrons per volume of wire), the
diameter of the wire and a typical current you can work out how fast the electron sea moves along.
In a typical example of a 1mm copper wire carrying a current of 100 mA the answer turns out to be
about 0.01 mm.s-1 which is much slower than a tortoise. If those electrons were picking up energy
from the battery and then carrying it all the way to the light globe, you would have to wait an
awfully long time to see the globe light up.Objection 2 looks at AC circuits in which electrons don’t go anywhere much; they just jiggle back
and forth. So they can’t carry energy from one place to another. It would be silly to have a basically
different theory for AC and DC.
http://www.bing.com/search?q=http://science.uniserve.edu.au/schoo...002/sefton.pdf&FORM=HPDTLB&PC=HPDTDF&QS=n
Edits: 03/09/14 03/09/14
Is there a point in your reference that relates to what i said?
"If your concerned about electron flow, that view, consider a wire is like a ridged pipe full of water, if you force water in at one end, nearly instantly (at the speed of sound in water) that pressure reaches the other end. The speed the "electron pressure" travels is near the speed of light."
tomservo
If you are saying electrons travel through a conductor at near the speed of light then that is wrong according to the information I quoted from the Link.
If that is not what you meant I apologize and would you please further explain what you meant.
Jim
What I mean is, we transmit signals through wires and if we measure how long it takes from the time a signal goes into one end and comes out the other, one has a “propagation velocity” of that cable.
To picture the situation, imagine you had a pipe full of marbles form one end to the other. You force an additional marble in one end and nearly instantly, a marble is displaced at the other.
You can repeat this long enough until your first marble exits the far end if you want, but “that” time is not the propagation velocity of a signal.
http://en.wikipedia.org/wiki/Velocity_factor
http://www.picwire.com/technical/velocity_factor.php
The phrase "flow of electricity" refers generally to the movement of electrons (or other charge carriers) through a conductor in the presence of potential and an electric field. The "speed" of this flow has multiple meanings. In everyday electronics, the signals or energy travel quickly, as electromagnetic waves, while the electrons themselves move slowly.
This is what I have been trying to understand.
Would you agree, an audio signal traveling down a wire is energy in the form of an electromagnetic wave. The electromagnetic wave moves at near the speed of light. The electrons are basically just wiggling back and forth. (In an IC or speaker cable. No DC component in the audio signal.)
Do you agree or disagree?
When it comes to the speed of signal propagation the movement of individual electrons is irrelevant, as every electron is identical to every other electron. Even the existence of electrons is irrelevant to this discussion. (The presence of individual electrons does matter when considering thermal noise, but that's a different discussion.)
There is no need to go too far down the rabbit hole. It is necessary to stop at some point if one wants to accomplish anything. There are different levels at which subjects can be discussed, according, for example, to the knowledge and intelligence of the participants. This accounts for various explanatory scenarios that sometimes appear to conflict. In trying to get into a new technical subject, I have found it helpful to explore a range of books until I can find one that is at the right level to give me an effective learning experience, neither too difficult (incomprehensible) or too simplified (inaccurate and/or boring). Sometimes I have found it necessary to read through several levels of books before I could understand current research papers and sometimes I have given up the effort as too difficult for my talents and available time.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
You probably missed my post of a couple days ago on the subject of electron velocity in copper wire.
Why the games?
You agree with my posted message or you don't?
Get off the fence.
Who would disagree with your post. It's not as if it's breaking news. Are you trying to convert me? ;-)
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