I don’t know what the gauge of the leads is, but given that the total length of the two leads is about 8 feet I suspect the lead resistance is a significant contributor to the 0.1 ohms, together with round-off due to the limited resolution.
I got the same reading from my Fluke 87.
Regarding fuse resistance, you might find the information on page 2 of this Littelfuse datasheet to be of interest. For the 4 amp 250 volt slow blow 6.3 x 32 mm glass fuse which is among the many listed, the "cold" resistance (meaning the resistance with negligible current being conducted) is indicated as 0.0311 ohms. So for a design which puts say half the rated max current through it the voltage drop would be a bit more than 0.06 volts.
Al, I will check out the link you provided.
So for a design which puts say half the rated max current through it the voltage drop would be a bit more than 0.06 volts.
There’s that current again.....
Just a guess the more current, the more heat produced by the energy the load is consuming, the more the resistance of the fuse the greater the VD. Correct?
Or is it the more energy the load is consuming the greater the current. Which came first the chicken or the egg?
At any rate my understanding, it is, the energy the load is consuming, that if it, increases above the rating of the fuse, (given by the manufacture in amperes), the fuse link will melt breaking the circuit. IT IS the energy that melts the link, not the current. Sound about right? I hope.
I am still confused on the discussion of current in a closed circuit.
Here is part of a response herman posted in response to a post of mine.
Jea, There are positive and negative charges and they are what they are. They do not change from positive to negative. In the case of a wire there are negative charges in motion but in some mediums there are + charges in motion and in some there are both.
So it isn’t + 0 - 0 + 0 - as in the charges are changing polarity it is L 0 R 0 L 0 as in the negative charges are vibrating left and right around a zero point.
If electric current is the movement of charge what is wrong with using the word current in place of the word charge?
Any place you see "current" you can substitute "movement of charge." If you say movement of current you are saying movement of movement of charge. It is redundant.
Look at it this way. In order for something to move it must exist. Current is not a thing or a form of energy, it is a word that describes movement. If water stops flowing the water is still there but there is no current. Did the current just disappear? No, it never existed, it is a concept, not a thing.
With the load consuming power from the supplying alternating voltage source explain the process movement of current to the load.
Thank you, thank you, thank you for asking. That question is a perfect example of why "alternating current flow" is a very bad description of what is going on.
In a nutshell AC current does not move or flow to the load.. That is the very heart of my debate with simply_q.
As stated above current does not move. Current means something is moving. If we switch to charge instead of current then those don’t move to the load either. The charges in an AC circuit merely sit there and vibrate.
Power isn’t moving to the load either. Power is the rate at which we transfer energy. Power is not a thing, it is not energy, it cannot be moved or consumed.
So what’s moving from the source to the load? Energy. A wave of electromagnetic energy moves down the wire and the energy in it is transferred to the load. Charges are vibrating everywhere around the path but energy is flowing in one direction...source to load. It is converted into another form of energy like heat or light, or motion, or it is launched into space if the load is an antenna.
Quote:
As stated above current does not move. Current means something is moving. If we switch to charge instead of current then those don’t move to the load either. The charges in an AC circuit merely sit there and vibrate.
Later on down the page herman posted a responded again to a post of mine.
If you say the AC fuse blew because there was too much current flowing through it everybody nods in agreement even though that isn’t true. If you say the wire in the fuse melted because it got too hot after absorbing energy from the electromagnetic wave people look at you like you are insane and want to argue that vibrating electrons constitute current flow.
These really are confusing topics as we have discovered in this thread. People frequently confuse energy and power. Most people think current is a thing when it is not. It was pounded into our heads that current flow is the same everywhere in a series circuit so we incorrectly think charges are flowing through components in an AC circuit. Yea I know, I sound like a broken record, but you asked/
The problem is there are many technically incorrect phrases that are so ingrained that we can’t seem to get away from them. Everybody says it including me but power can’t really be consumed because it isn’t a thing, it is the rate at which energy flows, but if you say an amplifier consumes 100 watts of power everybody nods in agreement. If you correctly say energy flows into that amp at the rate of 100 Joules per second they look at you like you are nuts.
I always have great respect for Herman’s opinions and insights, and as usual I don’t disagree with any of his comments that you quoted. And as you’ve no doubt gathered over the years, like him I happen to be someone who generally tries to be as precise as possible with words and terminology, which he is certainly trying to be in the quoted passages.
However, it seems to me that there are circumstances which can make some latitude in the use of terminology appropriate. Including this one, given the extremely widespread use (or arguably misuse) of the term "current." As well as the fact that for nearly all practical purposes, other than perhaps providing fodder for Internet debates about wire directionality (which Herman has not expressed a strong opinion about either way), the more widely used concept of "current" works fine. So as I said earlier:
Almarg 9-1-2017 It is energy absorbed **from** the electromagnetic wave by the non-zero resistance of the conductor in the fuse, which as I said causes the Poynting vector to tilt slightly toward the conductor, that causes it to blow....
... Since the amount of energy that is absorbed from the electromagnetic wave by the conductor in the fuse and converted into heat (causing it to blow if excessive) is proportional to both the energy that is being conveyed by that wave and to "the current," it is reasonable (and of course far more practical) to analyze the situation in terms of amperes and ohms, rather than in terms of joules (a unit of energy) and Poynting Vectors.
And correspondingly, since in the case of electrical signals (or power) being conducted via wires the slow moving "current" and the very fast moving electromagnetic wave go hand-in-hand (as I’ve explained), IMO it would be meaningless to think of one but not the other as being the cause of the fuse blowing.
Now, regarding:
Geoffkait 9-2-2017 One thing I will sign up to is that if anything is traveling down the conductor it’s photons, not electrons. Free free to concur with comment, concur without comment or non concur.
As I’ve stated on previous occasions, I agree fully that the energy of an electrical signal (or power) being conducted via wires is conducted at near light speed in the form of an electromagnetic wave that is comprised of photons. We’ll have to agree to disagree, however, as to whether those photons propagate within or outside of the conductor, aside from the very small fraction of the photons corresponding to the very small amount of energy that is absorbed by the resistance of the conductor and converted to heat.
Geoffkait 9-2-2017 One thing I will sign up to is that if anything is traveling down the conductor it’s photons, not electrons. Free free to concur with comment, concur without comment or non concur.
As I’ve stated on previous occasions, I agree fully that the energy of an electrical signal (or power) being conducted via wires is conducted at near light speed in the form of an electromagnetic wave that is comprised of photons. We’ll have to agree to disagree, however, as to whether those photons propagate within or outside of the conductor, aside from the very small fraction of the photons corresponding to the very small amount of energy that is absorbed by the resistance of the conductor and converted to heat.
>>>>Uh, I’ve already stated that it’s a tie. As indicated by the mathematical paper from the Journal of Physics on the dodgy subject of whether the energy of the signal is located outside or inside the conductor the energy is actually partly outside and partly inside. And the mathematics for that conclusion is provided in the first couple of paragraphs. Don’t tell me you didn’t read it. GASP
Al, Herman is right - electric current (electricity) is a flow of electric charge. Current does not flow, current is - charge flows. The same is true in the river - water flows and current is. Unfortunately improper usage of "current flows" (instead of electricty flows) is so common, that I found myself using it. Improper became common.
Geoffkait 9-2-2-2017
Uh, I’ve already stated that it’s a tie. As indicated by the
mathematical paper from the Journal of Physics on the dodgy subject of
whether the energy of the signal is located outside or inside the
conductor the energy is actually partly outside and partly inside. And
the mathematics for that conclusion is provided in the first couple of
paragraphs. Don’t tell me you didn’t read it. GASP
Yes, I had read the paper you are referring to. There is nothing in it that is inconsistent with what I have said.
If you'll notice, it deals with a hypothetical situation in which the wire ***is*** the load. In other words, a single piece of "long" wire is connected directly across the terminals of a voltage source. (The numerous references in the paper to the wire being "long" presumably imply that its resistance is high enough to limit the resulting, um, current, to an amount that can be provided by the voltage source, and that would not cause the wire to melt).
In that situation the Poynting Vector would point inward to the conductor, at all points along its length, as shown in Figure 1 of the paper. The energy carrying photons would therefore enter the conductor, causing the conductor would heat up. Note the references to energy flowing **into** "the cylinder," resulting in "Joule heating." "The cylinder" referring to the geometry of the wire. As the paper says:
The picture that emerges from these considerations is that the electromagnetic field around a current carrying wire is such that the energy dissipated in the wire is brought into it by the corresponding Poynting vector through each point of its surface.
That is all perfectly consistent with what I have said on the subject previously, assuming a more real world scenario involving low resistance wires conducting energy to a resistive load. In that situation the electromagnetic wave, and the photons comprising it, travel outside the conductors, aside from (as I said in my previous post) "the very small fraction of the photons corresponding to the very
small amount of energy that is absorbed by the resistance of the
conductor and converted to heat."
Fermi velocity (random) applies only to materials when no current is applied. As I stated previously the very low Drift Velocity indicates that electrons do not (rpt not) travel rapidly at any time in the conductor. If they did the net velocity or average velocity whatever would be much higher than the centimeter per hour velocity observed.
Pop quiz, if electrons are changing direction with alternating current, why is there a net velocity in one direction along the axis? Shouldn’t there be zero net velocity? And why is the net electron velocity in one direction, not the other direction? Why do electrons favor one direction over the other, assuming vector of Drift Velocity is always in the same direction?
Geoff, re your pop quiz, as you appear to realize there is no **overall** net movement of the electrons, assuming that the DC component of the applied voltage is zero. However, within each half-cycle of the applied voltage there is net electron movement and net velocity in one direction or the other, the direction corresponding to the +/- polarity of the applied voltage at that instant. I had said that in one of my early posts in this thread.
Also, I believe that your statement that "Fermi velocity (random) applies only to materials when no current is applied" is incorrect, and that there is always random movement of some electrons, at Fermi velocity and in random directions. That is why the word "net" comes into play. Since the movements at Fermi velocity are in random directions, that velocity does not factor into (or average into) the drift velocity.
Therefore in this wire the electrons are flowing at the rate of 23 µm/s. At 60 Hz alternating current, this means that within half a cycle the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch.
By comparison, the Fermi flow velocity of these electrons (which, at room temperature, can be thought of as their approximate velocity in the absence of electric current) is around 1570 km/s.[2]
Therefore in this wire the electrons are flowing at the rate of 23 µm/s. At 60 Hz alternating current, this means that within half a cycle the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch.
You’re talking AGAIN about electrons. Electric current moves with the speed of electric charge (electric field) and not the speed of electrons or drift velocity. When you flip a switch electric charge moves thru conductor at the speed of light (remember stacked balls?) magnetic wave follows at the same speed. If electric current moves at the drift velocity then in very long cable electrons at the end would not even move since it would take hours or days for charge to get there. All electrons along the wire move together instantly like stacked balls. Electric and magnetic fields have to move with the same speed (electro-magnetic field) because one doesn’t exist without the other. Again, imagine pipe filed with ping-pong balls. When you push them at one side of the pipe they will start coming out at the other instantly. When there is no change (DC) electrons move at drift velocity. DC current is proportional to drift velocity while drift velocity is proportional to magnitude of electric field. Any sudden change at the one end of the wire will travel thru the wire at the speed of light and it will arrive almost instantly and not a few days later. It will travel as wave of electric charge inside of the wire (stacked balls) and wave of magnetic field outside of the wire at the same light speed (or close to it).
Kijanki, I of course agree with your post. I suspect, though, that Geoff intended his "Exhibit A" post to be a rebuttal (mainly in its second paragraph) of the second paragraph of my post which immediately preceded it. To recapitulate the relevant paragraphs:
Almarg 9-3-2017 Also, I believe that your [Geoff’s] statement that "Fermi velocity (random) applies only to materials when no current is applied" is incorrect, and that there is always random movement of some electrons, at Fermi velocity and in random directions. That is why the word "net" comes into play. Since the movements at Fermi velocity are in random directions, that velocity does not factor into (or average into) the drift velocity.
Geoffkait 9-3-2017 (quoting Wikipedia) By comparison, the Fermi flow velocity of these electrons (which, at room temperature, can be thought of as their approximate velocity in the absence of electric current) is around 1570 km/s.
My response to that, assuming it was intended as a rebuttal of my statement: The quoted Wikipedia paragraph, referring to Fermi "velocity in the absence of electric current," says nothing about whether or not random movement of electrons at Fermi velocity occurs when a current is present. And I believe that such movement does in fact occur when a current is present, which is why drift velocity corresponds to **net** electron movement, past any given point.
No one has answered my question, why is there a "net velocity" for electrons? Assuming electrons move back and forth with alternating current, which I’m actually not convinced they do. Also, the Fermi velocity is the *directionally random* quantum mechanical velocity of electrons when no current is present. To refer to a Fermi velocity when current is present makes no sense since electrons then travel axially, I.e., not randomly.
Geoffkait 9-3-2017 No one has answered my question, why there is a net velocity for electrons? Assuming electrons move back and forth with alternating current which I’m not convinced they actually do.
I believe I did answer that, Geoff:
Almarg 9-3-2017 ...there is no **overall** net movement of the electrons, assuming that the DC component of the applied voltage is zero. However, within each half-cycle of the applied voltage there is net electron movement and net velocity in one direction or the other, the direction corresponding to the +/- polarity of the applied voltage at that instant. I had said that in one of my early posts in this thread.
So yes, the electrons moving at drift velocity do move back and forth with alternating current, never moving very far from their original location, assuming no DC is present. The Wikipedia writeup you quoted even alluded to that: "... electrons flowing across the contact point in a switch will never actually leave the switch."
Also,
Geoffkait 9-3-2017 To say there is a Fermi velocity when current is present makes no sense since electrons travel axially.
Again, I believe that is incorrect. Under the influence of an applied voltage/electric field, I believe that ALL electrons do NOT travel axially, in a direction corresponding to the polarity of the applied voltage, just SOME of them do. I believe that some of them continue to move in a random manner, at the Fermi velocity.
If that were not true, how much voltage would have to be applied for ALL of the electrons to suddenly cease moving in a random manner at Fermi velocity, and obediently start moving in an axial manner at drift velocity? 1000 volts? 120 volts? 1 volt? 1 millivolt? 1 microvolt? 1 nanovolt? 1 picovolt? How much current is necessary to be able to say that "current is present"? 10 amperes? 1 ampere? 0.0000000000001 amperes?
I hope you see my point. In any event, barring further questions from others I’m done with this discussion.
Geoffkait: "Therefore in this wire the electrons are flowing at the rate of 23 µm/s. At 60 Hz alternating current, this means that within half a cycle the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch."
to which kijanki replied,
"You’re talking AGAIN about electrons. Electric current moves with the speed of electric charge (electric field) and not the speed of electrons or drift velocity. When you flip a switch electric charge moves thru conductor at the speed of light (remember stacked balls?) magnetic wave follows at the same speed. If electric current moves at the drift velocity then in very long cable electrons at the end would not even move since it would take hours or days for charge to get there."
>>>>>I never said electric current moves with the velocity of electrons. I already said I think electrons are the charge carriers. You are confusing me with someone else perhaps.
then kijanki wrote,
"All electrons along the wire move together instantly like stacked balls. Electric and magnetic fields have to move with the same speed (electro-magnetic field) because one doesn’t exist without the other. Again, imagine pipe filed with ping-pong balls. When you push them at one side of the pipe they will start coming out at the other instantly. When there is no change (DC) electrons move at drift velocity. DC current is proportional to drift velocity while drift velocity is proportional to magnitude of electric field. Any sudden change at the one end of the wire will travel thru the wire at the speed of light and it will arrive almost instantly and not a few days later. It will travel as wave of electric charge inside of the wire (stacked balls) and wave of magnetic field outside of the wire at the same light speed (or close to it)."
>>>>>EM waves travel at light speed but magnetic fields are stationary. Magnetic fields are induced by the current traveling through the wire. It’s the right hand rule. I never said electrons carry the current. And I’ve always said the EM waves are comprised of photons. All EM waves are comprised of photons. That’s why they travel at lightspeed.
Under the influence of an applied voltage/electric field, I believe that ALL electrons do NOT travel axially, in a direction corresponding to the polarity of the applied voltage, just SOME of them do. I believe that some of them continue to move in a random manner, at the Fermi velocity.
Al, Wikipedia definition, I posted before, explains it:
The drift velocity is the average velocity that a particle, such as an electron, attains in a material due to an electric field. It can also be referred to as axial drift velocity. In general, an electron will propagate randomly in a conductor at the Fermi velocity. An applied electric field will give this random motion a small net flow velocity in one direction.
Thanks, Kijanki. Yes, that explains it pretty well. Although I can see how that statement could be misinterpreted. The reference to "in one direction" should say something like "in one direction for a given direction of the electric field," the direction of the electric field of course alternating every half-cycle in the case of AC. Also, the reference to "average velocity" is a bit misleading, because it could be interpreted as meaning that the much faster Fermi velocity of 1570 kilometers/second or so is numerically averaged in, even though (as I mentioned earlier) it cancels out of the average (the "net flow") since it is in random directions.
Allow me to summarize. It doesn’t really matter what the velocity of electrons is since they are only the charge carriers. It doesn’t really matter what direction electrons are traveling since they’re only the charge carriers. And compared to the velocity of the EM - even if one considered electrons were moving at Fermi velocity - the relative velocity of electrons is negligible. Recall that the velocity of light (photons) is constant even if it’s measured from a rapidly moving rocket ship. 🚀
What is the stuff that flows through a light bulb and comes back out again through the other wire?
The answer to question #1 is ELECTRIC CHARGE. Charge is a "stuff" that flows through lightbulbs, and it flows around a circuit. Normally no charge is lost during the operation of a circuit, and no charge is gained. Also, charge flows very slowly, and it can even stop flowing and just sit there inside the wires. In an AC circuit, charge does not flow forwards at all, instead it sits in one place and wiggles forwards and back.
As often occurs when this kind of subject comes up, ambiguity and/or imprecise use of terminology muddles the issue. If you replace his use of the word "charge" with the words "charge carrier," I think what he says then becomes pretty much correct.
As explained by Kijanki with the balls in a tube analogy, and as alluded to in my long post in this thread dated 8-23-2017 at 7:08 p.m. EDT (although what I said in that post was stated in terms signal energy rather than charge), charge propagates at near light speed, while charge carriers (electrons, in the case of a metallic conductor) move very slowly. And current, defined in terms of amperes, is proportional to the average number of charge carriers traversing a given cross-section of the conductor per unit time.
@almarg this has become a fascinating thread. I’ve a quick question: I’ve built a few cables in consultation with Steve (williewonka) and his ideas. Basically, the neutral in his cables is doubled and wrapped around the signal or hot conductor. My question is this: to lessen inductance, typically cables are tightly twisted, since the induced magnetic field is strongest further out. If the two conductors are spaced widely enough apart, will this also lessen the effects of induction? What about orientation? I'm under the impression that cables crossing at right angles won't induce currents in each other.
Thanks. I’m trying to make sense of all this as well. I do like the performance of Steve’s design. I’d like to understand the ’why’ a bit more.
Thanks for your comments and your interest. Steve’s approaches, such as what you’ve described, sound like good ones to me. Regarding your questions:
Wider spacing of the two conductors will increase inductance and decrease capacitance.
The reason that inductance decreases when the conductors are twisted together, or at least brought closer together, is that since the currents in the two conductors are moving in opposite directions (one toward the load and one toward the source, at any given time, with the directions alternating between each half cycle of the signal in the case of AC), the magnetic fields created by those currents are in opposite directions and tend to cancel each other if the conductors are close together. To the extent that those fields do not cancel, the impedance presented to the signal will increase as the rate of change of the signal (i.e., its frequency) increases. For further explanation the Wikipedia writeup on Lenz’s Law may be helpful.
Regarding capacitance, a capacitor consists basically of two conductive plates separated by a non-conductive dielectric, with each of the two terminals of the capacitor connected to one of the plates. As explained in the Wikipedia writeup on capacitance the closer those plates are to each other the greater the amount of capacitance, everything else being equal. Similarly, cable capacitance presents itself as a shunt (aka parallel) phenomenon between the two conductors, and therefore increases as the conductors become closer together. While inductance and resistance present themselves as series phenomena.
In general, inductance is most likely to be significant in the case of speaker cables, to an increasing degree if the impedance of the speaker is low at high frequencies. (See my first post in this thread). Resistance may also be a significant factor in a speaker cable, of course, especially if the speaker has low impedance at many or most frequencies. Capacitance will usually be unimportant in the case of a speaker cable, unless it is very high, in which case it can cause problems for the amplifier. Especially if the amplifier is solid state and therefore most likely has low output impedance, and uses significant amounts of feedback, in which case even destructive oscillations can occur if the capacitance is extremely high.
In general, resistance and inductance will be unimportant in the case of a line-level interconnect, aside from the possibility that the resistance and inductance of the ground/signal return conductor can make a difference with respect to ground loop-related low frequency hum or high frequency buzz or noise, if the components involved are susceptible to ground loop issues. Capacitance can be important in the case of a line-level interconnect, especially if the output impedance of the component providing the signal is high. The interaction of that output impedance and cable capacitance will form a low pass filter, whose rolloff will usually begin in the ultrasonic or RF region, and therefore be inconsequential, but if those parameters are too high the filter can start rolling off and/or introducing phase shifts at frequencies that are low enough to have audible consequences.
For a given cable type, all of those parameters are of course proportional to length.
All of this, btw, pertains to analog cables. Completely different considerations and effects come into play in the case of digital cables.
And yes, crossing cables at right angles, or at least minimizing how much of their lengths are parallel and closely spaced, is good practice and will minimize or eliminate any effects the corresponding signals might otherwise have on each other.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
