View Full Version : electron mass in an electrical circuit
Dave Cutler
Nov5-04, 08:21 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\n\nThis thread is very likely to be badly misinformed but anyway here\ngoes...\n\nIn an electrical circuit electrons travel at a significant\nproportion to the speed of light, in a super cooled circuit\nsignificantly faster ... so why doesn\'t the mass of the wire start to\nreach infinity. I know that this is probably a stupid question but\ntolerate me!\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>This thread is very likely to be badly misinformed but anyway here
goes...
In an electrical circuit electrons travel at a significant
proportion to the speed of light, in a super cooled circuit
significantly faster ... so why doesn't the mass of the wire start to
reach infinity. I know that this is probably a stupid question but
tolerate me!
Joseph.D.Warner
Nov6-04, 11:04 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Dave Cutler wrote:\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nElectrons in an electrical circuit doesn\'t travel at a significant\nproportion of the speed of light. Electrons average speed is the drift\nvelocity it has which extremely small compared to the speed of light for\nmost materials. (See the Handbook of Physics) Not for certain what you\nmean by a super cooled circuit but electrons group velocity never\nexceeds the speed of light.\n\nNow when you cool most electrical circuits the drift velocity goes up\nbecause scattering of the electrons in the metal goes down. It is the\nrate of scattering and the applied electrical field that determines the\ndrift velocity. Best to look up the term and definition of drift\nvelocity in a Solid State Physics book anyone of them will do.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutler wrote:
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
Electrons in an electrical circuit doesn't travel at a significant
proportion of the speed of light. Electrons average speed is the drift
velocity it has which extremely small compared to the speed of light for
most materials. (See the Handbook of Physics) Not for certain what you
mean by a super cooled circuit but electrons group velocity never
exceeds the speed of light.
Now when you cool most electrical circuits the drift velocity goes up
because scattering of the electrons in the metal goes down. It is the
rate of scattering and the applied electrical field that determines the
drift velocity. Best to look up the term and definition of drift
velocity in a Solid State Physics book anyone of them will do.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>try again.. individual electrons in a wire move extremely slowly compared to\nlight.\n\n"Dave Cutler" <dvdctlr@tiscali.co.uk> wrote in message\nnews:dada93ec.0411042005.5bd47460@posting .google.com...\n>\n>\n>\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>try again.. individual electrons in a wire move extremely slowly compared to
light.
"Dave Cutler" <dvdctlr@tiscali.co.uk> wrote in message
news:dada93ec.0411042005.5bd47460@posting.google.c om...
>
>
>
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
Richard Saam
Nov6-04, 11:07 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Dave Cutler wrote:\n\n>This thread is very likely to be badly misinformed but anyway here\n>goes...\n>\n> In an electrical circuit electrons travel at a significant\n>proportion to the speed of light,\n>\nactually, conventional electrical circuit electrons travel at a "drift\nvelocity" on the order of a cm/sec.\n\n>in a super cooled circuit\n>significantly faster ...\n>\nSupercurrents in high temperature superconductors may travel on the\norder of 10^5 cm/sec which is still considerably less than speed of light.\n\n>so why doesn\'t the mass of the wire start to\n>reach infinity. I know that this is probably a stupid question but\n>tolerate me!\n>\n>\n\nRichard Saam\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutler wrote:
>This thread is very likely to be badly misinformed but anyway here
>goes...
>
> In an electrical circuit electrons travel at a significant
>proportion to the speed of light,
>
actually, conventional electrical circuit electrons travel at a "drift
velocity" on the order of a cm/sec.
>in a super cooled circuit
>significantly faster ...
>
Supercurrents in high temperature superconductors may travel on the
order of 10^5 cm/sec which is still considerably less than speed of light.
>so why doesn't the mass of the wire start to
>reach infinity. I know that this is probably a stupid question but
>tolerate me!
>
>
Richard Saam
Igor Khavkine
Nov6-04, 11:07 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light,\n\nWrong. The speed of electrons is on the order of centimeters per second.\n\n> in a super cooled circuit significantly faster ...\n\nSignificantly faster than what? The speed of light? That\'s physically\nimpossible. Significantly faster than in a non-supercooled circuit?\nNot really, they just scatter less.\n\n> so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nI hope you can see that your supposed conclusion is false.\n\nIgor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google.com>...
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light,
Wrong. The speed of electrons is on the order of centimeters per second.
> in a super cooled circuit significantly faster ...
Significantly faster than what? The speed of light? That's physically
impossible. Significantly faster than in a non-supercooled circuit?
Not really, they just scatter less.
> so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
I hope you can see that your supposed conclusion is false.
Igor
Uncle Al
Nov7-04, 07:44 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nDave Cutler wrote:\n>\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light,\n\nNO!!!!! The *signal* travels at about lightspeed divided by the\nsquare root of the surrounding dielectric constant. The electrons\nphysically travel a few microns/second. Don\'t take my word for it!\nRun an ampere through a 1 mm diameter copper wire. Assume one valence\nelectron/atom in the conducton band. How fast are the electrons\nphysically traveling (assuming no scatter)?\n\nSound travels at 1/5 mile/sec in air or about 720 mph. How fast does\nthe air travel?\n\n> in a super cooled circuit\n> significantly faster ...\n\nNO!!!!! First, the electrons in Cooper pairs have conjugate momenta.\nOnly translation of their center of mass matters. Second, we\'re back\nto the wire argument above. Wound supercon magnets have a whole lot\nof amps/cm^2 as current. The net speed of charge propagation is\nunremarkable.\n\n> so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nFirst calculate the numbers, then speculate. An electron traveling at\n99.995% of lighspeed would manifest 100X its rest mass. That is a\nwhopping 1/18 of a proton\'s rest mass. 96,485.3 coulombs is only one\nmole of electrons. Even it it happened your way it wouldn\'t make much\nmass diffference - and Bremsstrahlung would be a right proper pisser.\n\n--\nUncle Al\nhttp://www.mazepath.com/uncleal/\n(Toxic URL! Unsafe for children and most mammals)\nhttp://www.mazepath.com/uncleal/qz.pdf\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutler wrote:
>
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light,
NO!!!!! The *signal* travels at about lightspeed divided by the
square root of the surrounding dielectric constant. The electrons
physically travel a few microns/second. Don't take my word for it!
Run an ampere through a 1 mm diameter copper wire. Assume one valence
electron/atom in the conducton band. How fast are the electrons
physically traveling (assuming no scatter)?
Sound travels at 1/5 mile/sec in air or about 720 mph. How fast does
the air travel?
> in a super cooled circuit
> significantly faster ...
NO!!!!! First, the electrons in Cooper pairs have conjugate momenta.
Only translation of their center of mass matters. Second, we're back
to the wire argument above. Wound supercon magnets have a whole lot
of amps/cm^2 as current. The net speed of charge propagation is
unremarkable.
> so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
First calculate the numbers, then speculate. An electron traveling at
99.995% of lighspeed would manifest 100X its rest mass. That is a
whopping 1/18 of a proton's rest mass. 96,485.3 coulombs is only one
mole of electrons. Even it it happened your way it wouldn't make much
mass diffference - and Bremsstrahlung would be a right proper pisser.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nDave Cutler wrote:\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nIndividual electrons don\'t move very quickly down a wire. They move\nsomething like a couple of millimeters per second I think. However the\nEM field disturbance travels down the wire at a much higher speed,\napproaching the speed of light. Thus there is no need to accelerate any\nelectrons to near the speed of light.\n\nThink of Newtons cradle - you know, the toy with a couple of metal\nballs hanging in wires and you drop one on the edge, the one on the\nother edge will fly out - even if the balls in the middle don\'t really\nmove (actually this is not just an analogy, mechanics is really EM\nbetween molecules).\n\n/BW\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutler wrote:
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
Individual electrons don't move very quickly down a wire. They move
something like a couple of millimeters per second I think. However the
EM field disturbance travels down the wire at a much higher speed,
approaching the speed of light. Thus there is no need to accelerate any
electrons to near the speed of light.
Think of Newtons cradle - you know, the toy with a couple of metal
balls hanging in wires and you drop one on the edge, the one on the
other edge will fly out - even if the balls in the middle don't really
move (actually this is not just an analogy, mechanics is really EM
between molecules).
/BW
Maurice Barnhill
Nov7-04, 07:45 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nDave Cutler wrote:\n\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nChanges in the electrical current do propagate at speeds near\nthat of light, and the associated electric and magnetic fields do\nalso. However, the electrons do not. What happens is that an\nelectron near the source of the change in the current nudges\nanother electron nearby, which nudges another a little further\nalong, which nudges .... The changes in speed are driven by\nelectromagnetic fields which can in fact travel near light speed,\nso the point at which the current increases can move quite\nquickly. The individual electrons, however, move at a velocity\nwhich is much smaller, and their relativistic mass increase is\nvery small.\n\nYou can see the same effect at an intersection where the light\nturns from red to green. The point at which the cars start\nmoving travels back from the light at a speed unrelated to the\nspeed of the cars. Indeed, the speed-change point has a velocity\nopposite that of the cars.\n\n--\nMaurice Barnhill\nmvb@udel.edu [Use ReplyTo, not From]\n[bellatlantic.net is reserved for spam only]\nDepartment of Physics and Astronomy\nUniversity of Delaware\nNewark, DE 19716\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutler wrote:
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
Changes in the electrical current do propagate at speeds near
that of light, and the associated electric and magnetic fields do
also. However, the electrons do not. What happens is that an
electron near the source of the change in the current nudges
another electron nearby, which nudges another a little further
along, which nudges .... The changes in speed are driven by
electromagnetic fields which can in fact travel near light speed,
so the point at which the current increases can move quite
quickly. The individual electrons, however, move at a velocity
which is much smaller, and their relativistic mass increase is
very small.
You can see the same effect at an intersection where the light
turns from red to green. The point at which the cars start
moving travels back from the light at a speed unrelated to the
speed of the cars. Indeed, the speed-change point has a velocity
opposite that of the cars.
--
Maurice Barnhill
mvb@udel.edu [Use ReplyTo, not From]
[bellatlantic.net is reserved for spam only]
Department of Physics and Astronomy
University of Delaware
Newark, DE 19716
Frank Hellmann
Nov7-04, 04:05 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nThe so called drift speed of electrons in a wire is small.\nhttp://www.google.de/search?hl=de&q=drift+speed+electrons\n\nYou can get the drift speed of electrons through meassurements of the\nhall effect. The magnetic force experienced is proportional to the\nvelocity of the electrons. For superconductors things are somewhat\nmore difficult:\n\nhttp://lists.nau.edu/cgi-bin/wa?A2=ind0302&L=phys-l&F=&S=&P=42880\n\nAnyway, before your electrons would reach anywhere near relativistic\nspeeds they would destroy or just leave the wire.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google.com>...
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
The so called drift speed of electrons in a wire is small.
http://www.google.de/search?hl=de&q=drift+speed+electrons
You can get the drift speed of electrons through meassurements of the
hall effect. The magnetic force experienced is proportional to the
velocity of the electrons. For superconductors things are somewhat
more difficult:
http://lists.nau.edu/cgi-bin/wa?A2=ind0302&L=phys-l&F=&S=&P=42880
Anyway, before your electrons would reach anywhere near relativistic
speeds they would destroy or just leave the wire.
Ian Taylor
Nov7-04, 04:05 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n> This thread is very likely to be badly misinformed but anyway here\n> goes...\n>\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity. I know that this is probably a stupid question but\n> tolerate me!\n\nWhen you say an electrical circuit I\'m not entirely clear whether you\nmean electrons travelling through a semiconductor or through a metal\nwire. Certainly for semiconductors it is simply not true that\nelectrons (or holes) travel anywhere near the speed of light. The\ndrift velocity of carriers in semiconductors is proportional to\nelectric field and the mobility is defined as the drift velocity\ndivided by the electric field. For typical semiconductors, mobilities\nare around 4000 cm^2/(Vs) which by my calculations means that typical\ndrift velocities are only around 0.4 m/s. Of course, instantaneous\ncarrier speeds can be much higher, but there are many scattering\nevents which occur which result in a low drift velocity. Of course,\nthe drift velocity also depends on the type of semiconductor, and\nwhether you are talking about electrons or holes. (A good reference\nis: K. Seeger, "Semiconductor Physics: An Introduction" Springer\nSeries in Solid-State Sciences 40)\n\nIan Taylor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google.com>...
> This thread is very likely to be badly misinformed but anyway here
> goes...
>
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity. I know that this is probably a stupid question but
> tolerate me!
When you say an electrical circuit I'm not entirely clear whether you
mean electrons travelling through a semiconductor or through a metal
wire. Certainly for semiconductors it is simply not true that
electrons (or holes) travel anywhere near the speed of light. The
drift velocity of carriers in semiconductors is proportional to
electric field and the mobility is defined as the drift velocity
divided by the electric field. For typical semiconductors, mobilities
are around 4000 cm^2/(Vs) which by my calculations means that typical
drift velocities are only around .4 m/s. Of course, instantaneous
carrier speeds can be much higher, but there are many scattering
events which occur which result in a low drift velocity. Of course,
the drift velocity also depends on the type of semiconductor, and
whether you are talking about electrons or holes. (A good reference
is: K. Seeger, "Semiconductor Physics: An Introduction" Springer
Series in Solid-State Sciences 40)
Ian Taylor
robert bristow-johnson
Nov7-04, 04:05 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine at\nigor.kh@gmail.com wrote on 11/06/2004 12:07:\n\n> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message\n> news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n>> This thread is very likely to be badly misinformed but anyway here\n>> goes...\n>>\n>> In an electrical circuit electrons travel at a significant\n>> proportion to the speed of light,\n>\n> Wrong. The speed of electrons is on the order of centimeters per second.\n\nokay guys,\n\nwhat is meant, when referring to a transmission line data sheet, that the\nvelocity factor is 0.78 . what is it that is moving at 0.78 c?\n\nwhen we electrical engineers design circuit boards for high speed devices\n(something i must admit i have never done), we often consider 1 foot of\ndistance to be about a nanosecond of delay. i know that could be off by a\nfactor of 2, but i doubt it\'s off by a factor of 10. what is it that is\nmoving along those PC board traces?\n\nnonetheless, since the electrons are not moving at 0.999 * c, they are not\ngoing to get appreciably heavy and since their rest mass is 1800 times less\nthan that of protons or neutrons, there is no relativistic arithmetic i can\nthink of that makes their mass appreciable.\n\nr b-j\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine at
igor.kh@gmail.com wrote on 11/06/2004 12:07:
> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message
> news:<dada93ec.0411042005.5bd47460@posting.google.com>...
>> This thread is very likely to be badly misinformed but anyway here
>> goes...
>>
>> In an electrical circuit electrons travel at a significant
>> proportion to the speed of light,
>
> Wrong. The speed of electrons is on the order of centimeters per second.
okay guys,
what is meant, when referring to a transmission line data sheet, that the
velocity factor is .78 . what is it that is moving at .78 c?
when we electrical engineers design circuit boards for high speed devices
(something i must admit i have never done), we often consider 1 foot of
distance to be about a nanosecond of delay. i know that could be off by a
factor of 2, but i doubt it's off by a factor of 10. what is it that is
moving along those PC board traces?
nonetheless, since the electrons are not moving at .999 * c, they are not
going to get appreciably heavy and since their rest mass is 1800 times less
than that of protons or neutrons, there is no relativistic arithmetic i can
think of that makes their mass appreciable.
r b-j
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>"robert bristow-johnson" <rbj@audioimagination.com> wrote in message\nnews:BDB2878C.1B52%rbj@audioimagination.c om...\n> in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine\nat\n> igor.kh@gmail.com wrote on 11/06/2004 12:07:\n>\n> > dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message\n> > news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n> >> This thread is very likely to be badly misinformed but anyway here\n> >> goes...\n> >>\n> >> In an electrical circuit electrons travel at a significant\n> >> proportion to the speed of light,\n> >\n> > Wrong. The speed of electrons is on the order of centimeters per second.\n>\n> okay guys,\n>\n> what is meant, when referring to a transmission line data sheet, that the\n> velocity factor is 0.78 . what is it that is moving at 0.78 c?\n>\n> when we electrical engineers design circuit boards for high speed devices\n> (something i must admit i have never done), we often consider 1 foot of\n> distance to be about a nanosecond of delay. i know that could be off by a\n> factor of 2, but i doubt it\'s off by a factor of 10. what is it that is\n> moving along those PC board traces?\n>\n> nonetheless, since the electrons are not moving at 0.999 * c, they are not\n> going to get appreciably heavy and since their rest mass is 1800 times\nless\n> than that of protons or neutrons, there is no relativistic arithmetic i\ncan\n> think of that makes their mass appreciable.\n>\n> r b-j\n>\n\nlook at it this way... fill a pipe with pingpong balls.. push another ball\nin one end and a ball gets forced out the other end... the ball that went in\ndidn\'t come out, but the force that you pushed on it with got transmitted\nall the way up the pipe to move that last ball. the same happens with\nelectrons, you push one in or pull one out of a wire and the force is\ntransmitted at some high percentage of c to the other end... its not\ninstantaneous or even 1.0c because the electrons are not packed in there as\ntight as rigid pingpong balls.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>"robert bristow-johnson" <rbj@audioimagination.com> wrote in message
news:BDB2878C.1B52%rbj@audioimagination.com...
> in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine
at
> igor.kh@gmail.com wrote on 11/06/2004 12:07:
>
> > dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message
> > news:<dada93ec.0411042005.5bd47460@posting.google.com>...
> >> This thread is very likely to be badly misinformed but anyway here
> >> goes...
> >>
> >> In an electrical circuit electrons travel at a significant
> >> proportion to the speed of light,
> >
> > Wrong. The speed of electrons is on the order of centimeters per second.
>
> okay guys,
>
> what is meant, when referring to a transmission line data sheet, that the
> velocity factor is .78 . what is it that is moving at .78 c?
>
> when we electrical engineers design circuit boards for high speed devices
> (something i must admit i have never done), we often consider 1 foot of
> distance to be about a nanosecond of delay. i know that could be off by a
> factor of 2, but i doubt it's off by a factor of 10. what is it that is
> moving along those PC board traces?
>
> nonetheless, since the electrons are not moving at .999 * c, they are not
> going to get appreciably heavy and since their rest mass is 1800 times
less
> than that of protons or neutrons, there is no relativistic arithmetic i
can
> think of that makes their mass appreciable.
>
> r b-j
>
look at it this way... fill a pipe with pingpong balls.. push another ball
in one end and a ball gets forced out the other end... the ball that went in
didn't come out, but the force that you pushed on it with got transmitted
all the way up the pipe to move that last ball. the same happens with
electrons, you push one in or pull one out of a wire and the force is
transmitted at some high percentage of c to the other end... its not
instantaneous or even 1.0c because the electrons are not packed in there as
tight as rigid pingpong balls.
Igor Khavkine
Nov8-04, 05:09 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>On Sun, 07 Nov 2004 22:05:34 +0000, robert bristow-johnson wrote:\n\n> in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine\n> at igor.kh@gmail.com wrote on 11/06/2004 12:07:\n>\n>> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message\n>> news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n>>> This thread is very likely to be badly misinformed but anyway here\n>>> goes...\n>>>\n>>> In an electrical circuit electrons travel at a significant proportion\n>>> to the speed of light,\n>>\n>> Wrong. The speed of electrons is on the order of centimeters per second.\n>\n> okay guys,\n>\n> what is meant, when referring to a transmission line data sheet, that the\n> velocity factor is 0.78 . what is it that is moving at 0.78 c?\n>\n> when we electrical engineers design circuit boards for high speed devices\n> (something i must admit i have never done), we often consider 1 foot of\n> distance to be about a nanosecond of delay. i know that could be off by a\n> factor of 2, but i doubt it\'s off by a factor of 10. what is it that is\n> moving along those PC board traces?\n\nNever having seen such data sheets, I cannot be certain. But I imagine\nthat what is given is the speed of propagation of a signal which is\ncarried by electromagnetic waves and density modulations of the electrons.\nBoth of these velocities are determined by the material properties, the\nspeed of electromagnetic is determined by the dielectric constant, while\nthe speed of electron density waves by the compressibility of the electron\ngas inside the wire.\n\nI guess there isn\'t much point in explaining how light propagates. But I\ncan draw a nice diagram for the propagation of a density disturbance in an\nelastic medium:\n\n* *** * * * * * * * * * * * * * * * * *\n* * *** * * * * * * * * * * * * * * * *\n* * * *** * * * * * * * * * * * * * * *\n* * * * *** * * * * * * * * * * * * * *\n* * * * * *** * * * * * * * * * * * * *\n* * * * * * *** * * * * * * * * * * * *\n* * * * * * * *** * * * * * * * * * * *\n* * * * * * * * *** * * * * * * * * * *\n* * * * * * * * * *** * * * * * * * * *\n...\n\nNotice that the disturbance (***) is moving faster than the medium itself (* *).\n\nHope this helps.\n\nIgor\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>On Sun, 07 Nov 2004 22:05:34 +0000, robert bristow-johnson wrote:
> in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine
> at igor.kh@gmail.com wrote on 11/06/2004 12:07:
>
>> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message
>> news:<dada93ec.0411042005.5bd47460@posting.google.com>...
>>> This thread is very likely to be badly misinformed but anyway here
>>> goes...
>>>
>>> In an electrical circuit electrons travel at a significant proportion
>>> to the speed of light,
>>
>> Wrong. The speed of electrons is on the order of centimeters per second.
>
> okay guys,
>
> what is meant, when referring to a transmission line data sheet, that the
> velocity factor is .78 . what is it that is moving at .78 c?
>
> when we electrical engineers design circuit boards for high speed devices
> (something i must admit i have never done), we often consider 1 foot of
> distance to be about a nanosecond of delay. i know that could be off by a
> factor of 2, but i doubt it's off by a factor of 10. what is it that is
> moving along those PC board traces?
Never having seen such data sheets, I cannot be certain. But I imagine
that what is given is the speed of propagation of a signal which is
carried by electromagnetic waves and density modulations of the electrons.
Both of these velocities are determined by the material properties, the
speed of electromagnetic is determined by the dielectric constant, while
the speed of electron density waves by the compressibility of the electron
gas inside the wire.
I guess there isn't much point in explaining how light propagates. But I
can draw a nice diagram for the propagation of a density disturbance in an
elastic medium:
* *** * * * * * * * * * * * * * * * * ** * *** * * * * * * * * * * * * * * * ** * * *** * * * * * * * * * * * * * * ** * * * *** * * * * * * * * * * * * * ** * * * * *** * * * * * * * * * * * * ** * * * * * *** * * * * * * * * * * * ** * * * * * * *** * * * * * * * * * * ** * * * * * * * *** * * * * * * * * * ** * * * * * * * * *** * * * * * * * * *
...
Notice that the disturbance (***) is moving faster than the medium itself (* *).
Hope this helps.
Igor
Mikko Kiviranta
Nov8-04, 05:10 PM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>Dave Cutlerwrote:\n> In an electrical circuit electrons travel at a significant\n> proportion to the speed of light, in a super cooled circuit\n> significantly faster ... so why doesn\'t the mass of the wire start to\n> reach infinity.\n\nOthers have already replied on the actual electron velocities in\nnormal wires, but there exists a vaguely related phenomenon present\nin, for instance, the "super cooled circuits" you refer to.\n\nOrdinarily, when you excite a current in a wire, you have do work on\nthe system which gets stored as energy in the static magnetic field\naround the wire. When you try to stop the current, there is a sort of\ninertia (the current would like to keep flowing) when the stored energy\ngets released. This storage is called \'inductance\'.\n\nWhen a superconducting wire gets very thin (thinner than the so-called\nLondon penetration depth) the density of superconducting charge carriers\ngoes down. For a given amount of current, the average speed of each\ncarrier goes up, because there are now fewer of them to do the job.\nAnother energy storage mechanism becomes significant now, namely the\nkinetic energy of the charge carriers with finite mass. This storage\nmechanism behaves like added inductance in the circuit, but it does\nnot couple to the magnetic field. It is called \'kinetic inductance\',\nand it may in certain types of wires be several times larger than\nthe magnetic inductance. It is already a significant correction which\nmust be taken in account in SQUID design, for instance.\n\nThis phenomenon has a bit of the flavor of your original question,\nbut even here the carrier velocities never approach even the Fermi\nvelocity (the pairs would break down), not to mention relativistic\nvelocities.\n\nRegards,\nMikko\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Dave Cutlerwrote:
> In an electrical circuit electrons travel at a significant
> proportion to the speed of light, in a super cooled circuit
> significantly faster ... so why doesn't the mass of the wire start to
> reach infinity.
Others have already replied on the actual electron velocities in
normal wires, but there exists a vaguely related phenomenon present
in, for instance, the "super cooled circuits" you refer to.
Ordinarily, when you excite a current in a wire, you have do work on
the system which gets stored as energy in the static magnetic field
around the wire. When you try to stop the current, there is a sort of
inertia (the current would like to keep flowing) when the stored energy
gets released. This storage is called 'inductance'.
When a superconducting wire gets very thin (thinner than the so-called
London penetration depth) the density of superconducting charge carriers
goes down. For a given amount of current, the average speed of each
carrier goes up, because there are now fewer of them to do the job.
Another energy storage mechanism becomes significant now, namely the
kinetic energy of the charge carriers with finite mass. This storage
mechanism behaves like added inductance in the circuit, but it does
not couple to the magnetic field. It is called 'kinetic inductance',
and it may in certain types of wires be several times larger than
the magnetic inductance. It is already a significant correction which
must be taken in account in SQUID design, for instance.
This phenomenon has a bit of the flavor of your original question,
but even here the carrier velocities never approach even the Fermi
velocity (the pairs would break down), not to mention relativistic
velocities.
Regards,
Mikko
Richard Saam
Nov9-04, 03:44 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nFrank Hellmann wrote:\n\n>\n>The so called drift speed of electrons in a wire is small.\n>http://www.google.de/search?hl=de&q=drift+speed+electrons\n>\n>You can get the drift speed of electrons through meassurements of the\n>hall effect. The magnetic force experienced is proportional to the\n>velocity of the electrons. For superconductors things are somewhat\n>more difficult:\n>\n>http://lists.nau.edu/cgi-bin/wa?A2=ind0302&L=phys-l&F=&S=&P=42880\n>\n>\n>\nUsing\n\nhttp://xxx.lanl.gov/abs/physics/9905007\n\nas a reference\n\nEquation 2.8.1 and 93K at Table 2.8.1 would indicate supercurrent at\n6.02E8 amp/cm^2 for a pure superconductor lattice (no imperfections).\nThe velocity of actual current carrying Cooper pairs would be 5.05E5\ncm/sec from Table 2.4.1. The dielectric of this pure superconductor\nlattice would be 182.17 from Table 2.5.1 and the velocity associated\nwith this dielectric would be 2.17E8 cm/sec from Table 2.5.2.\n\nIt is interesting to note that Cooper pair velocity is near earth\norbital velocity SQRT(g*earth_radius) or 7.9131E+05 cm/sec which\nsuggests the question as to whether specific geometrically oriented\n(not circular) supercurrents may influence the apparent weight of the\nsuperconductor lattice?\n\nRichard Saam\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Frank Hellmann wrote:
>
>The so called drift speed of electrons in a wire is small.
>http://www.google.de/search?hl=de&q=drift+speed+electrons
>
>You can get the drift speed of electrons through meassurements of the
>hall effect. The magnetic force experienced is proportional to the
>velocity of the electrons. For superconductors things are somewhat
>more difficult:
>
>http://lists.nau.edu/cgi-bin/wa?A2=ind0302&L=phys-l&F=&S=&P=42880
>
>
>
Using
http://xxx.lanl.gov/abs/http://www.arxiv.org/abs/physics/9905007
as a reference
Equation 2.8.1 and 93K at Table 2.8.1 would indicate supercurrent at
6.02E8 amp/cm^2 for a pure superconductor lattice (no imperfections).
The velocity of actual current carrying Cooper pairs would be 5.05E5
cm/sec from Table 2.4.1. The dielectric of this pure superconductor
lattice would be 182.17 from Table 2.5.1 and the velocity associated
with this dielectric would be 2.17E8 cm/sec from Table 2.5.2.
It is interesting to note that Cooper pair velocity is near earth
orbital velocity \SQRT(g*earth_radius) or 7.9131E+05 cm/sec which
suggests the question as to whether specific geometrically oriented
(not circular) supercurrents may influence the apparent weight of the
superconductor lattice?
Richard Saam
Mikko Kiviranta
Nov9-04, 03:44 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nrobert bristow-johnson wrote:\n\n> what is meant, when referring to a transmission line data sheet, that the\n> velocity factor is 0.78 . what is it that is moving at 0.78 c?\n\nThe electromagnetic field. You jerk an electron: even when the speed\nof the electron may never exceed a few cm per second, it\'s movement\n(corresponding to a current) sends (electro)magnetic field buzzing to\nall directions at the speed of light.\n\nRegards,\nMikko\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>robert bristow-johnson wrote:
> what is meant, when referring to a transmission line data sheet, that the
> velocity factor is .78 . what is it that is moving at .78 c?
The electromagnetic field. You jerk an electron: even when the speed
of the electron may never exceed a few cm per second, it's movement
(corresponding to a current) sends (electro)magnetic field buzzing to
all directions at the speed of light.
Regards,
Mikko
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\n\nrobert bristow-johnson:\n>in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine at\n>igor.kh@gmail.com wrote on 11/06/2004 12:07:\n>\n>> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message\n>> news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n>>> This thread is very likely to be badly misinformed but anyway here\n>>> goes...\n>>>\n>>> In an electrical circuit electrons travel at a significant\n>>> proportion to the speed of light,\n>>\n>> Wrong. The speed of electrons is on the order of centimeters per second.\n>\n>okay guys,\n>\n>what is meant, when referring to a transmission line data sheet, that the\n>velocity factor is 0.78 . what is it that is moving at 0.78 c?\n\nThe signal. Note that the speed of propagation depends on the dielectric.\n\n>when we electrical engineers design circuit boards for high speed devices\n>(something i must admit i have never done), we often consider 1 foot of\n>distance to be about a nanosecond of delay. i know that could be off by a\n>factor of 2, but i doubt it\'s off by a factor of 10. what is it that is\n>moving along those PC board traces?\n\nThe signal, i.e., the fields.\n\n\n>nonetheless, since the electrons are not moving at 0.999 * c, they are not\n>going to get appreciably heavy and since their rest mass is 1800 times less\n>than that of protons or neutrons, there is no relativistic arithmetic i can\n>think of that makes their mass appreciable.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>robert bristow-johnson:
>in article ab2dc45b.0411051504.6a62d054@posting.google.com, Igor Khavkine at
>igor.kh@gmail.com wrote on 11/06/2004 12:07:
>
>> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message
>> news:<dada93ec.0411042005.5bd47460@posting.google.com>...
>>> This thread is very likely to be badly misinformed but anyway here
>>> goes...
>>>
>>> In an electrical circuit electrons travel at a significant
>>> proportion to the speed of light,
>>
>> Wrong. The speed of electrons is on the order of centimeters per second.
>
>okay guys,
>
>what is meant, when referring to a transmission line data sheet, that the
>velocity factor is .78 . what is it that is moving at .78 c?
The signal. Note that the speed of propagation depends on the dielectric.
>when we electrical engineers design circuit boards for high speed devices
>(something i must admit i have never done), we often consider 1 foot of
>distance to be about a nanosecond of delay. i know that could be off by a
>factor of 2, but i doubt it's off by a factor of 10. what is it that is
>moving along those PC board traces?
The signal, i.e., the fields.
>nonetheless, since the electrons are not moving at .999 * c, they are not
>going to get appreciably heavy and since their rest mass is 1800 times less
>than that of protons or neutrons, there is no relativistic arithmetic i can
>think of that makes their mass appreciable.
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>iantaylor2uk@yahoo.co.uk (Ian Taylor) wrote in message news:<2eefbf19.0411061017.25c99385@posting.google. com>...\n> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google. com>...\n> > This thread is very likely to be badly misinformed but anyway here\n> > goes...\n> >\n> > In an electrical circuit electrons travel at a significant\n> > proportion to the speed of light, in a super cooled circuit\n> > significantly faster ... so why doesn\'t the mass of the wire start to\n> > reach infinity. I know that this is probably a stupid question but\n> > tolerate me!\n>\n> When you say an electrical circuit I\'m not entirely clear whether you\n> mean electrons travelling through a semiconductor or through a metal\n> wire. Certainly for semiconductors it is simply not true that\n> electrons (or holes) travel anywhere near the speed of light. The\n> drift velocity of carriers in semiconductors is proportional to\n> electric field and the mobility is defined as the drift velocity\n> divided by the electric field. For typical semiconductors, mobilities\n> are around 4000 cm^2/(Vs) which by my calculations means that typical\n> drift velocities are only around 0.4 m/s. Of course, instantaneous\n> carrier speeds can be much higher, but there are many scattering\n> events which occur which result in a low drift velocity. Of course,\n> the drift velocity also depends on the type of semiconductor, and\n> whether you are talking about electrons or holes. (A good reference\n> is: K. Seeger, "Semiconductor Physics: An Introduction" Springer\n> Series in Solid-State Sciences 40)\n\nFirst: I personally have worked with supercooled AlGaAs HEMTs with\nmobilities in the range 2x10^6 cm2/Vs to 4x10^6 cm2/Vs. In a\nmicrostructure, fields can be as high as you like, just make the\nchannel shorter, just like on the 90 nm(!) transistors you will be\nwriting this stuff on. 0.5 V over 90 nm is >10^6 V/m.\n\nYou can\'t take the voltage much above ~100uV before heating it to >1K.\nLet\'s take 1K as the ballistic limit. HEMTs can support ballistic\ntransport to 100\'s of microns at low temperatures - so the original\nquestion about supercooled stuff was totally valid. In ballistic\ntransport, talk about drift velocities is meaningless.\n\nNext, all of the answers posted by the other posters are not relevant\nto the original question, which was: what is the mass increase of an\nelectron? The drift velocity is purely net velocity after multiple\nimpacts. The mass increase is dependent purely on energy. Drift\nvelocity purely means after the random-walk, and what we want to\nmeasure is <v_field^2> - <v_zerofield^2>\n\nOne electron at a potential of one volt has an energy of one eV.\n(eV/c^2)/m_e = 10^-6. Translation - put a megavolt across a piece of\nwire and the electrons will be relativistic.\n\nThe wire will also get quite hot, which will mask the effect you are\nlooking for. Fundamentally, under macroscopic conditions the electrons\nare in thermal equilibrium with the lattice, so any mass increase of\nthe electrons is masked under the x1836 mass increase of the nuclei.\nBut it is small and there.\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>iantaylor2uk@yahoo.co.uk (Ian Taylor) wrote in message news:<2eefbf19.0411061017.25c99385@posting.google.com>...
> dvdctlr@tiscali.co.uk (Dave Cutler) wrote in message news:<dada93ec.0411042005.5bd47460@posting.google.com>...
> > This thread is very likely to be badly misinformed but anyway here
> > goes...
> >
> > In an electrical circuit electrons travel at a significant
> > proportion to the speed of light, in a super cooled circuit
> > significantly faster ... so why doesn't the mass of the wire start to
> > reach infinity. I know that this is probably a stupid question but
> > tolerate me!
>
> When you say an electrical circuit I'm not entirely clear whether you
> mean electrons travelling through a semiconductor or through a metal
> wire. Certainly for semiconductors it is simply not true that
> electrons (or holes) travel anywhere near the speed of light. The
> drift velocity of carriers in semiconductors is proportional to
> electric field and the mobility is defined as the drift velocity
> divided by the electric field. For typical semiconductors, mobilities
> are around 4000 cm^2/(Vs) which by my calculations means that typical
> drift velocities are only around .4 m/s. Of course, instantaneous
> carrier speeds can be much higher, but there are many scattering
> events which occur which result in a low drift velocity. Of course,
> the drift velocity also depends on the type of semiconductor, and
> whether you are talking about electrons or holes. (A good reference
> is: K. Seeger, "Semiconductor Physics: An Introduction" Springer
> Series in Solid-State Sciences 40)
First: I personally have worked with supercooled AlGaAs HEMTs with
mobilities in the range 2x10^6 cm2/Vs to 4x10^6 cm2/Vs. In a
microstructure, fields can be as high as you like, just make the
channel shorter, just like on the 90 nm(!) transistors you will be
writing this stuff on. .5 V over 90 nm is >10^6 V/m.
You can't take the voltage much above ~100uV before heating it to >1K.
Let's take 1K as the ballistic limit. HEMTs can support ballistic
transport to 100's of microns at low temperatures - so the original
question about supercooled stuff was totally valid. In ballistic
transport, talk about drift velocities is meaningless.
Next, all of the answers posted by the other posters are not relevant
to the original question, which was: what is the mass increase of an
electron? The drift velocity is purely net velocity after multiple
impacts. The mass increase is dependent purely on energy. Drift
velocity purely means after the random-walk, and what we want to
measure is <v_{field}^2> - <v_{zerofield}^2>
One electron at a potential of one volt has an energy of one eV.
(eV/c^2)/m_e = 10^-6. Translation - put a megavolt across a piece of
wire and the electrons will be relativistic.
The wire will also get quite hot, which will mask the effect you are
looking for. Fundamentally, under macroscopic conditions the electrons
are in thermal equilibrium with the lattice, so any mass increase of
the electrons is masked under the x1836 mass increase of the nuclei.
But it is small and there.
andrew.stewart@anu.edu.au
Nov16-04, 02:17 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>>In an electrical circuit electrons travel at a significant\n>proportion to the speed of light, in a super cooled circuit\n>significantly faster ... so why doesn\'t the mass of the wire start to\n>reach infinity. I know that this is probably a stupid question but\n>tolerate me! Dave Cutler\n\nThe mean speed of an electron in a metal is around the Fermi\nvelocity, usually a few per cent of the speed of light, much as it is\nin an atom. This motion is random as electrons will be scattered by\ndefects and boundaries to give a mean velocity of zero (electrons do\nnot move out of a metal spontaneously).\n\nWhen a macroscopic current flows, electrons acquire an extra drift\nvelocity of some few cm/s. This is negligible compared to the average\nspeed so the effect that Dave Cutler is looking for will be too small\nto be noticed.\n\nAndrew Stewart\n\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>>In an electrical circuit electrons travel at a significant
>proportion to the speed of light, in a super cooled circuit
>significantly faster ... so why doesn't the mass of the wire start to
>reach infinity. I know that this is probably a stupid question but
>tolerate me! Dave Cutler
The mean speed of an electron in a metal is around the Fermi
velocity, usually a few per cent of the speed of light, much as it is
in an atom. This motion is random as electrons will be scattered by
defects and boundaries to give a mean velocity of zero (electrons do
not move out of a metal spontaneously).
When a macroscopic current flows, electrons acquire an extra drift
velocity of some few cm/s. This is negligible compared to the average
speed so the effect that Dave Cutler is looking for will be too small
to be noticed.
Andrew Stewart
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