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Anonymous Poster

It probably sounds silly

02/12/2008 11:21 PM

First time user here.

Has serious thought or discussion ever occurred about the ramifications or possible benefits of increasing the speed of an electrical current in a conductor? Is there any point in doing it if it is possible? Any ideas anyone?

willip

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#1

Re: It probably sounds silly

02/13/2008 7:20 AM

It doesn't sound silly in any way, rather sounds good for accademic excercise.

But i've not thought of any benefit for now.

Cheers,

Ethobil

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#2

Re: It probably sounds silly

02/13/2008 7:36 AM

There are really two speeds in a conductor: the speed of the charge (speed of light) and speed of charge carrier (drift velocity). There's not too much you practically do about either and you don't really care about drift (it's slower than me paying a bill already).

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#3

Re: It probably sounds silly

02/13/2008 8:27 AM

In a transmission line there always is a velocity of propagation, which never equals the speed of light...

Its a quite valid question and an interesting one... the velocity of propagation is dependant on the lumped characteristics of the transmission line R, L and C forming the impedance of the line Z.

For a correctly terminated line the transmission speed is fixed, this is why some decades ago coaxial cables were used inside oscilloscopes to give a delayed signal, so that the leading edge of a high speed signal could be observed even though the edge triggered the 'scope!

In the back of many 'scopes there would be several metres of, usually 93 ohm, low loss coaxial cable to delay the signal by up to 20 nanoseconds.

So the only way to increase the speed of transmission is by altering the characteristics of the transmission cable...

I wonder if anyone on here has some experience of trying that??

John.

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#4
In reply to #3

Re: It probably sounds silly

02/13/2008 10:13 AM

Yeah, you're right. I thought I was saying it wrong, but I couldn't find my cloned neuron this morning (the original one is in a jar at the National Aviary). Thanks.

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#6
In reply to #3

Re: It probably sounds silly

02/14/2008 3:06 AM

2 comments:

1. it's 'distributed', not 'lumped' (charactersitics) ('parameters' better)

2. the propagation velocity of a transmission line is determined by the dielectric constant of the dielectric, i.e. the insulating material between the inner and outer (shield) conductors.

http://www.microwaves101.com/encyclopedia/permittivity.cfm#relative

Coaxial cable comes in all sizes and many impedances, most often using 2 dielectrics, either solid polyethelene or Teflon, or various 'foams' (incl Teflon, Gore, etc). The solid dielectrics exhibit propagation velocities around 72%, the 'foam' dielectrics, having more air in them, around 82%. So-called 'air line' for high power & high voltage (i.e. transmitter feed) gets above 90%

http://www.andrew.com/catalog/product_details.aspx?id=1464

You can probably already see where this is going. If you could evacuate the coaxial cable (vacuum having the dielectric constant of 1) and magically get the center conductor to hover precisely in the center of the cable , you'd be getting even closer to the speed of light.

So the bottom line is: in order to create a transmission line whose propagation velocity is higher than the speed of light, you first need to come up with a dielectric whose dielectric constant is less than 1!

-RF_G

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#29
In reply to #6

Re: It probably sounds silly

02/18/2008 7:40 AM

By the way RFGUY, re your posting #6 - you are getting close to my conductor design when you refer to the need to reduce the dielectric constant to below 1.

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#5

Re: It probably sounds silly

02/14/2008 2:37 AM

How much faster do you have in mind?

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#7

Re: It probably sounds silly

02/14/2008 8:03 AM

Just like the friction inside a pipe, the calculations are that same as for an electrical conduit. The friction and the wire resistance are the same. They both affect the "speed". Copper is a better conductor that iron. Gold is a better conductor than copper. So I think the biggest ramafication is $$$$$.

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#8
In reply to #7

Re: It probably sounds silly

02/14/2008 9:26 AM

Somebody pound me 6-feet under if I'm wrong on this, but... as I once was learnt and now "preach" in a class that I occasionally teach:

Silver (if it is 100% pure) is THE best conductor... followed by copper, THEN gold.

Since most all silver has trace contaminents in it, in that form it exhibits no better conductivity than copper.

Gold is "confused" as being "The Best" conductor (plating all your high-end stereo and TV connectors, etc). The reason for its use in these apps is SIMPLY because it does NOT corrode like the patina developed on copper over time. Thus, it will insure longevity of these sorts of connections.

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#14
In reply to #7

Re: It probably sounds silly

02/15/2008 1:41 AM

The resistivity of the conductors does have an influence on the propagation veolocity, but it is almost insiginifcant compared to that of the dielectric.

-RF_G

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#9

Re: It probably sounds silly

02/14/2008 10:56 AM

From the top of my head I believe electricity flows 4.5 times (might be 7.5) around the earth in 1 second. How much faster do you need?

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#10
In reply to #9

Re: It probably sounds silly

02/14/2008 2:36 PM

Well, 4.5 times is about 112,000 miles/second which is the propogation velocity of about 75% the speed of light so that sounds alright, but 7.5 times is above (just a bit) the speed of light.

I guess it all depends on the dielectric used in the cable eh??!!

John

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#11

Re: It probably sounds silly

02/14/2008 3:57 PM

Greetings, willp, hopefully you will see fit to register as a member, there are SO many 'guests', it gets hard to keep track! Anyway, welcome aboard, and hope you like the responses - it is a very interesting question...and not at all silly!

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#12

Re: It probably sounds silly

02/14/2008 9:15 PM

Gentlemen, As it was properly pointed out above, the speed of electricity in a pair of conductors depend on their impedance. The lower the impedance (down to the impedance of a wave traveling in vacuum) the closer we get to the speed of light. This is the limit! It is not practical to have an impedance too low as you won't find a suitable driving source. This means that practically, in telecom, the signals travel at about 80% of the speed of light. Inside a chip we get closer to 90%. At high speeds, the impedance of the conductors is mostly reactive. This means that using cupper or silver has very little effect on the final speed. How much should we spend to go a little faster? It only matters inside your computer.

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#13

Re: It probably sounds silly

02/14/2008 11:34 PM

Hi Guest,

It's not a silly question, but some of the answers are. The Speed of electricity refers to the relatively slow movement of free electrons through a conductor in the presence of an electric field, also known as drift velocity. When a DC voltage is applied the electrons will increase in speed proportional to the strength of the electric field. These speeds are on the order of millimeters per second.

So you see that it happens automatically when you apply voltage.

S

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#15
In reply to #13

Re: It probably sounds silly

02/15/2008 2:03 AM

Hi SGuy ,

The implication of what you say - 'millimeters per second' - is that we require a rather high electric field in order for electrons to get moving.

This is only the case if we're talking about *extremely* small electric fields (below some threshold whose name escapes me, hopefully someone else knows it off the top of their head).

Electric field strengths quivalent to millivolts (or less) are more than sufficient for propogation of signals in wires and cables at large fractions of the speed of light (per my previous post). That these velocities are reached is being constantly re-confirmed around us every moment.

RF_G

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#17
In reply to #15

Re: It probably sounds silly

02/15/2008 11:04 AM

Hi RF_guy,

You are talking about propagation velocity. The guest was asking about velocity of the current flow (drift velocity). My source is Wikipedia (click on the link). Your post 6 is no doubt confusing the guest with info he didn't care about and probably doesn't understand.

S

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#18
In reply to #17

Re: It probably sounds silly

02/15/2008 11:41 AM

Hi Standards_guy

hmm...ya think so? But...but...

ELECTROMAN STARTED IT!


...with 'transmission line'..

OP/'Guest' wrote 'electrical current in a conductor'..hmmm...well ok, so perhaps (s)he meant in any conductor..

So I clicked on your link, and...I couldn't believe it! Guess I slept during that physics lecture. Some other good links on the subject:

http://www.eskimo.com/~billb/miscon/speed.html
http://www.amasci.com/miscon/speed.html
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ohmmic.html

Thanks, StandardsGuy, I (re)learned something!

Now I wonder if Guest will (ever) come back and say which kind of 'conductor' (s)he meant..

Nice weekend

RF_G

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#19
In reply to #17

Re: It probably sounds silly

02/15/2008 11:48 AM

You may be right. On the other hand, one could just as easily assume that the guest is not easily confused, and cares about many things, and can understand many things. If on the other hand, the guest is superficially informed, then he is far more likely to think of the "speed of an electrical current" as being near the speed of light.

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#20
In reply to #17

Re: It probably sounds silly

02/15/2008 1:56 PM

Oi! RF-Guy!! that's it blame me, i always get the blame when my attempts at answering a question go wrong!!!

Come on you guys - the questioner hasn't given us much to go on and wires are like transmission lines ain't they?

They were in my days.... everything changes huh?... next you'll be telling me that the magnets on my car's fuel lines don't do naff all!!!!

John...

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#21
In reply to #20

Re: It probably sounds silly

02/15/2008 2:31 PM

Come on you guys - the questioner hasn't given us much to go on and wires are like transmission lines ain't they?

Right. For all we know he's thinking he'd like to speed up electricity so it reaches his compact fluorescent lamps more quickly. (He could be laughing hysterically now, saying to himself "These guys are all a bunch of frigging nut cases!! I can see just by turning on this light that the electricity takes about two seconds to get from the switch to a light 15 feet away. At the speeds they are talkin, it should take a couple hours. Moooorons!"

And your magnets have been proven (SCIENTIFICALLY PROVEN!) to work just fine for their intended purpose, which is to inflate the vendor's bank account.

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#22
In reply to #21

Re: It probably sounds silly

02/15/2008 3:15 PM

"And your magnets have been proven (SCIENTIFICALLY PROVEN!) to work just fine for their intended purpose, which is to inflate the vendor's bank account."

ROFLMAO!!! DNPMSL!!!

I just LOVE that scienterrific proof! But I don't think the original question was meant as a lark, or the thread would have a different title... So what is the ultimate decision, guys, can electricity, or can it not, be made to speed up in a conductor? Or was the original question different from that? I may have mis-interpreted it.

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#26
In reply to #22

Re: It probably sounds silly

02/18/2008 1:28 AM

IMPORTANT QUESTION

I know what ROFLMAO stands for, but what's 'DNPMSL' ?

I delight in these things...

:-o

happy Monday

RF_G

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#30
In reply to #26

Re: It probably sounds silly

02/18/2008 9:14 AM

Like you RF-guy, I was puzzled at first but decided DNPMSL must stand for Damn Near Pi$$ Myself Laughing...

Would be interested to know for sure though...

John

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#31
In reply to #26

Re: It probably sounds silly

02/18/2008 9:14 AM

DNPMSL = damned near p1553d my self laughing

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#25
In reply to #20

Re: It probably sounds silly

02/18/2008 1:25 AM

THOSE MAGNETS WORK, MAN!

cheers

RF_Guy

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#16

Re: It probably sounds silly

02/15/2008 5:48 AM

Hi, Guest!

My current computer (not even close to the stuff they're selling in the stores now) runs at 3.4 gigahertz. Just how fast did you want to go?

Mark

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#23

Re: It probably sounds silly

02/15/2008 6:17 PM

OK Willip (guest),

Tell us who is right (even if I'm wrong). There is a lot of money on the table. We won't bite. The most that will happen is you will be called a lot of nasty names, and you can take that, so give us your second post.

As for you, Electroman, may your fuel-line magnets forever be stuck in a Flux Loop. If you want to slow down the fuel flow, you need to parallel your magnets with flux capacitors.

And as for mister Fry, I smell a cynic.

S

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#24
In reply to #23

Re: It probably sounds silly

02/17/2008 7:19 PM

Hello Standards Guy

Thanks to you and all who have responded. Pheww! A bit to take in there. A couple of matters:- I have registered but haven't worked out where to go - ie to get out of the Guest regime.

To the contributer that said I haven't given much info --absolutely correct. Just being a bit cautious as you may deduce from my next question.

Next question(s). OK re the limitations but, if I said that I can speed it up anyway (to what degree not yet specified) is it really only in micro-circuits - computer stuff generally - where it could be useful? and what speed increase would be useful? eg. would above the speed of light have any interesting consequences?

I know this may appear to be a hypothetical exercise but I suppose I need to explore possible applications before committing to exposure. Once again, apologies for the cautious approach.

willip

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#27
In reply to #23

Re: It probably sounds silly

02/18/2008 1:31 AM

CYNIC, n.A blackguard whose faulty vision sees thingsas they are, not as they ought to be.A. Bierce

http://www.amazon.com/The-Devils-Dictionary/dp/B000FC1CO6/ref=sr_1_2?ie=UTF8&s=books&qid=1203316252&sr=8-2

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#28
In reply to #23

Re: It probably sounds silly

02/18/2008 7:22 AM

Second reply (Third posting)

Colleagues, I really appreciate all (nearly) the responses. How can I switch this discussion to my logged-in-member status?

What really interests me about the result of increasing the speed of the current in the (unspecified) conductor(s) - which it seems I can achieve - is the possibility that a circumstance may arise where the old Ohm's Law rules don't apply any more, ie the degree to which the current will flow in a particular conductor being dependant upon the applied voltage and the resistance (or impedance as the case may be) in the conducting material (keeping in mind of course the other limiting factors referred to by some of you).

Regards

willip

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