How fast does electricity travel?

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#1
It's been a very intense couple of weeks, and the stresses of running a business would be overwhelming if it was not for great music and passionate fans. However, it feels like the last two weeks have been filled by shoddy suppliers, intractable customers, and the final straw was 2 hours in a debate over the laws of physics.... :mad:

So, here's another great use of the What's Best Forum - cartharsis. Instead of resorting to Angry Birds, I thought that I'd come back to something I enjoy and I've missed for the past 2 weeks.

We can debate endlessly about whether you can hear/perceive something, but the laws of physics are immutable. It is absurd to argue that electrons travel at or anywhere near the speed of light because if anything is accelerated towards light velocity, its mass increases, and the mass will approach infinite mass as its velocity approaches the speed of light. To accelerate electrons or anything else to anywhere near light speed would require huge amounts of energy, and would approach infinity as we approach light speed.

So, really, how fast does electricity travel?

Let's talk about electrical current - which is defined as the ordered movement of charge. The charge that moves in a liquid or gas (non-conductors) could be an ionic charge, but we are concerned about electrons in a conductor.

So, we can refine the question further by asking "how fast does an electron move in a conductor?"

The unit of current is the Ampere. One ampere is defined as one Coulomb passing a given point in a circuit in a second. The Coulomb is the unit of charge that is equivalent to 6.25 x 10^18 electrons. That's a LOT of electrons, but electrons are very tiny.

If we use copper as an example, copper has 8.5 x 10^22 atoms per cubic centimeter, and it has 1 mobile electron per atom. Since we know that the charge of a single electron is 1.6 x 10^-19 coulombs, we can easily work out the number of electrons that would need to flow past a point to have a single Ampere of current.

The formula is so simple that it is trivial:

V = I/(Q * e * R^2 x pi)

where V = velocity of electron in cm/sec
I = current in Ampere
Q = number of mobile electrons per cubic cm
e = electron charge
R = radius of conductor in cm (12awg has radius of 0.1cm)

V works out to 0.00234 cm/sec. That's 3.3 inches per day. The velocity of electrons is really slow.

If you're playing music at an average of 2 Watts into a pair of 8 Ohm speakers - that's 0.5 Amperes. An electron (let's call him Fred) that goes into a pair of 9-foot speaker cable will take 130 days for Fred to come out the other side plus a few more days to travel through the voice coil, inductors, circuit board traces, internal wiring, etc.

That's for copper. If the wire was silver, the electrons will flow slower. This is because both copper and silver have one free electron per atom, but silver is denser than copper, and therefore silver has more free charge carriers within the same cross section.

However, why then can we pass such fast signals for music over wires? This is because it's not electrons moving that we are talking about, it's because the electrons are already in the wire waiting to move. Imagine having a pipe that is completely filled with marbles. When an extra marble is pushed in one end, a marble almost instantaneousness drops out the other end no matter how long the pipe is.

The effect of electrical current is almost instantaneous (it cannot be instant) due to the domino effect of the electron charge carriers knocking on from atom to atom. Think of a row of dominos, with a gap in between. The larger the gap, the slower the knock-on effect.

So, now we change the question to "how fast does electricity propagate through a conductor?"

When the current flows, electrons move from atom to atom. As an electron is a charged particle, they have a force field (an electrostatic field or E-field). This field has a force associated with it, and a direction. So, when a current flows, there is an E-field radiating from the wire that flows with it.

Also, when the current flows, a magnetic field (the H-field) is generated around the wire. The force of the electromagnetic field has a strength that is inversely proportional to distance (like the E-field) but is circular around the wire (the direction is according to the right-hand rule).

When a current flows, the E-field and the H-field must rack together with the flow of current. No one field can get ahead and wait for the other to catch up. So, the issue is not how fast the electrons can move within the conductor, it is how fast the E- and H-field can travel in the medium it is travelling through (hence our interest in the dielectric around the conductor).

Electromagnetic fields travel at the speed of light when in a vacuum (unlike an electron which is a particle, fields have no mass). They travel almost at the speed of vacuum in air, but slower in any other medium. The difference in speed is inversely proportional to the square root of the relative dielectric constant.

For example, if the wire was insulated by water, which has a relative dielectric constant of 80, it will travel almost 9 times slower. Teflon has a dielectric constant of 2.1 - and hence will slow down the electrical propagation by 1.4 times.

If you had a pair of speaker cables, one insulated by air, and the other insulated by teflon, there is no way that you can hear the difference in the speed of the cable. Even if it was insulated by water, the difference is way below any hope of perception.

Light travels at about 300million meters per second.

There is no way to argue that a cable is "faster" or "slower" based on speed of electricity in a conductor.

So there..... better than therapy :)
 

mojave

New Member
Oct 29, 2010
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0
Elkhorn, NE
#2
Do you think break-in has anything to do with the replacement of electrons in a cable or device? How much longer can the left speaker cable be than the right before one could audible tell a difference?
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#3
Do you think break-in has anything to do with the replacement of electrons in a cable or device?
I don't think so - electron drift is so slow that to replace all the electrons in a cable will take years. Also, I don't think that you can distinguish between two electrons, so you can't feed in "better" electrons to replace the ones already there.

How much longer can the left speaker cable be than the right before one could audible tell a difference?
I don't like to have one cable more than 3 times longer than the other, but there is a minimum length at which I like to have speaker cables which is a bit longer than 1.5m. However, whether it is possible to reliably hear a difference is a totally different matter. At this point, being as stressed as I am, I couldn't hear a difference when earlier I blew the negative power supply rail of a new amp I'm designing...... so I'm not your best guy for this.

Sorry....
 
May 30, 2010
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#4
(...) If you're playing music at an average of 2 Watts into a pair of 8 Ohm speakers - that's 0.5 Amperes. An electron (let's call him Fred) that goes into a pair of 9-foot speaker cable will take 130 days for Fred to come out the other side plus a few more days to travel through the voice coil, inductors, circuit board traces, internal wiring, etc. (...)
May be here you should remember people who are waiting for its arrival, that since music is alternative current, Fred will take much, much longer to arrive ... Unless you are using a solid state DC coupled amplifier with an high offset! :)
 

steve williams

Site Founder, Site Owner, Administrator
#5
Gary

I have a lot of friends who believe that cables and connections take quite a while to anneal. Not sure I do however based on what you just posted I suppose that this could be reason to accept cables annealing to their connections
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#6
May be here you should remember people who are waiting for its arrival, that since music is alternative current, Fred will take much, much longer to arrive ... Unless you are using a solid state DC coupled amplifier with an high offset! :)
True that music is AC. However, when delivering a current, it is still measured the same way even if Fred keeps changing his mind. He goes, then he comes, then he goes, but still takes two steps forward and one step back.

While we are talking about Fred.... electrons are negative and come from the ground. So, Fred is being sucked up from the ground by the amplifier and not pushed from the amplifier to the ground through the speaker.
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#7
Gary

I have a lot of friends who believe that cables and connections take quite a while to anneal. Not sure I do however based on what you just posted I suppose that this could be reason to accept cables annealing to their connections
Steve,

based on my own experience, cables and connections do take a long time to settle. I do find that solder joints take far longer to run in than crimped joints. So, your friends might be right that the connections anneal. Although, annealing based on electron drift might take thousands of years...... but I do hear cables and connections breaking in and sounding better.
 
Jul 1, 2010
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#8
So if I understood what you just said (a pretty big question), silver is not more/faster/better, fancy dialectics are not more/faster/better and even the length of the cable doesn't matter until you have a differential of 3 or more, what does make a difference?

Tim
 

Gregadd

WBF Founding Member
Apr 20, 2010
6,435
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Metro DC
#9

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#10
So if I understood what you just said (a pretty big question), silver is not more/faster/better, fancy dialectics are not more/faster/better and even the length of the cable doesn't matter until you have a differential of 3 or more, what does make a difference?

Tim
Not exactly. What I am saying is that "speed" - either in terms of electron drift, or propagation velocity cannot be used to account for any conductor being faster or better.

There may be other factors in play. For example, the capacitance of a pair of conductors in close proximity is directly proportional to the dielectric constant. However, we showed in the Cable Theory thread that the capacitance effects are too low to make a difference in the frequency response or phase response of a cable.
 
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garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#11
To amplify, phase shift due to speed EM fields move along conductor are not something we hear, we do hear the phase shift effects at different audio frequencies due to inductance, capacitance, etc, just like in an audio circuit with a real capacitor or inductor...like a bass/treble tone control uses...and the effects of these things on the amplifier via feedback and output resistance of amp blah etc blah..

Tom
I agree with you that we do hear the phase shift effects, and also cable store/release of energy. However, it was shown by simulations done by Amir that the capacitance/inductance effects on a cable are extremely low. It does not mean that they are not audible - just that the measurements suggest that they should not be audible.
 

JackD201

[WBF Founding Member]
Apr 21, 2010
10,995
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Manila, Philippines
#12
Actually, the EM fields travel both ways in AC....the electrons move ever slightly toward ground direction then ever so slightly away from ground direction....he leans one way then the other so to speak...so Fred is bi-sexual? Frederica?

Tom
Hahahahahahaha! This forum is on a roll today!
 
May 30, 2010
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#14
It is known that the classical parameters of cables (R, L and C) can not explain the sound of cables.
Unless we have a good accepted theory for the audibility and perceived effects of very small signals in audio we will never be able to explain it.

IMHO part of the cable "sound properties" are due to the electromechanical properties of dielectrics and conductors, that modulate the electrical signal, enhancing some aspects of the sound, and make the sound feel more "real". Otherwise how can we admit that the sound of the cable depends on cable length and some times we prefer to have a 4m speaker cable than no cable?

In a interview some 20 years ago Dr. Van den Hul, a well know dutch cable manufacturer, referred that he had developed special instruments able to resolve differences at the -140 dB level for his cable research.
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
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0
#15
It is known that the classical parameters of cables (R, L and C) can not explain the sound of cables.
Unless we have a good accepted theory for the audibility and perceived effects of very small signals in audio we will never be able to explain it.

IMHO part of the cable "sound properties" are due to the electromechanical properties of dielectrics and conductors, that modulate the electrical signal, enhancing some aspects of the sound, and make the sound feel more "real". Otherwise how can we admit that the sound of the cable depends on cable length and some times we prefer to have a 4m speaker cable than no cable?

In a interview some 20 years ago Dr. Van den Hul, a well know dutch cable manufacturer, referred that he had developed special instruments able to resolve differences at the -140 dB level for his cable research.
LCR do explain a lot of things .. Yet they can't explain Audio cables ?????? In application much more critical and I would dare say demanding , video for one ... L,C and R routinely explain a lot ..
One must first convince oneself of differences and then push science aside .. Only in High End Audio and that with the knowledge of said cable in the system...
 

ack

VIP/Donor & WBF Founding Member
May 6, 2010
5,152
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Boston, MA
#16
It is known that the classical parameters of cables (R, L and C) can not explain the sound of cables.
Sure it can - and very easily so. There is a thread here by garylkoh from last year that explains cable construction and how it relates to RLC characteristics, and aims to unlock the design "secrets" of various cable designs and what to expect.
 
Jul 1, 2010
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#17
This thread is a perfect example of why I like WBF. We have the true believers who are so common on audiophile forums, but we have as many pragmatists. Balance. I'll take it.

Tim
 
May 30, 2010
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#18
Sure it can - and very easily so. There is a thread here by garylkoh from last year that explains cable construction and how it relates to RLC characteristics, and aims to unlock the design "secrets" of various cable designs and what to expect.
Ack,

Sure it can ? If it is the thread I am thinking, it was a great and interesting thread but in the end Gary conclusions were:

"I agree - we had explored it thoroughly in the cable theory thread with simulations by Amir and a LOT of discussion. Any potential noise effects, frequency response non-linearity, phase effects, etc. are all far below the level at which we could possibly hear. What I have not been able to understand is why the two cables I proposed building in the OP sounds so very different. The differences seem to be consistent in nature, but not in level with different types of systems. That is what I was hoping to explore in this dialectic."
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,469
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#19
Quick question .. How do we know that the cables "sound so different"? Just by trust? Faith? If the differences are , to use an expression from Anyrk, so "earth-shattering" shouldn't they be able to be repeated reliably ... I repeat .. repeated ;)
 
May 30, 2010
13,971
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#20
So if I understood what you just said (a pretty big question), silver is not more/faster/better, fancy dialectics are not more/faster/better and even the length of the cable doesn't matter until you have a differential of 3 or more, what does make a difference?

Tim
Tim,

Just one detail. Fancy dielectric materials and metals in cables are not an audiophile mania. They are used in many applications, such as aeronautics, space research, radiation detectors and many others, because of reliability, consistency of manufacture, long term stability and capability of foreseeing any changes in electrical properties during its lifetime.

Surely there are no intrinsic faster/slower sound properties of electric materials.
 
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