Superconductivity at room temperature??

[johanfprins]

"Thus"? What's "thus"? There was no preceding statement from which you could draw such a conclusion.

You keep on making the same mistake, over and over and over again. A current through a material always consists of charge-carriers moving past ions of opposite charges. This requires that the charge density of the charge-carriers must match the charge-density of the ions. In turn, this means that when a constant equilibrium current is flowing, the charges per unit volume must cancel. The charge carriers thus move through a conductor in a similar manner that incompressible water moves through pipes. As long as the density, of the ionised charges, do not change, the density of the charge-carriers also do not change; only their speeds: So there cannot be any charge accumulation anywhere along the direction that the current flows.

Consider this (totally normal, classical) system, Johan:

          Q  <---- a fixed positive point charge

====================   
  ^ an isolated metal sheet with net zero charge

Is the charge density the "exactly the same" everywhere on the sheet?

This is a static image charge and this situation has nothing to do with a current flowing through a material which require from the charge-carriers and their opposite charges to minimize the electrical interactions between them. It is also this relative motion that causes a magnetic field around a conductor when a current is flowing through it.

How about if the sheet is grounded?

What has that got to do with a current flowing through a conductor?

 

[sol invictus]

A current through a material always consists of charge-carriers moving past ions of opposite charges. This requires that the charge density of the charge-carriers must match the charge-density of the ions.

Wrong.

As always, you assert a conclusion that does not follow. If the material is net neutral, then the average density of charge carriers must match the average density of ions (because the average density times the volume is simply the total number).

But the local density of charges can, of of course usually does, vary. A perfect example is provided by ben's drawing. Let's say there's a steady current flowing through the metal sheet (superconducting or not, it's not important). Now slowly (or not, up to you) bring the charge Q in from infinity. What happens to the charge density on the sheet? What happens to the current through it?

 

[The Don]

With regards to my description of your initial experimental results as anomalous.....

This is a very long thread and maybe I've lost track of the sequence of events but I thought it went something like this:

• You conducted an experiement in which you got a result that you interpreted as room temperature super conductivity. This was unexpected and exciting
• You subsequently developed a theoretical understanding which explained these results
• You've had great difficulty in getting acceptance of this theoretical understanding because of the intransigence of the physics community
• You have spent the last few months debating your theories on this board

Surely, if the results of the original experiment were not "inconsistent with or deviating from what is usual, normal, or expected", you'd have thought nothing more of it and wouldn't have bothered to develop the theoretical understanding.

The results of initial experiment WERE anomalous. Whether they have been subsequently explained by your theoretical work (which you claim they have, others claim not) does not change the fact that they were anomalous.

 

[johanfprins]

Yep. And the fact that the voltage is nonzero means that the power supply has to do work (integral I V dt) on the magnet. That's the work that gets stored as magnetic field energy (integral B^2 dV) and which can be turned back into electrical work later (in, e.g., a quench).

If Johan claims that you can ramp up a magnet without encountering an inductive voltage drop, he is inadvertently claiming that the magnetic field energy appears out of nowhere without requiring work from the current source.

Another lie! I have never said that that when you start up a current within a superconductor you must not do work in order to obtain an equiibrium current. What I am saying is that this work DOES NOT entail ACCELERATION of the charge-carriers, since charge-carriers that can be accelerated cannot cancel an applied electric-field.

The argument Ziggurat had made earlier was that there must be acceleration since a current must start to flow simultaneously at every point along the conductor. I pointed out correctly, that the apparent simultaneous onset of a current at every point around the whole circuit, can be explained by a displacement current at this initial stage. I never claimed that such a displacement current then remains.

I am glad Ziggurat gave me the information above: But this still does not mandate that the superconducting charge-carriers must be accelerated by an applied electric-field. The fact remains that charge-carriers that can be accelerated can NEVER cancel an applied electric field.

 

[johanfprins]

And how about if the sheet is a superconductor with current flowing through it?

An intresting question. When there is no current flowing through trhe superconductor, there will be no image charge since the superconductor will react to the external charge like a dielectric: There are now now free charges. When a current flows, the anchored charges can move by borrowing energy (delta)E for a time interval (delta)t. It is thus possible that while making a jump from one anchor position to the next the electric field of the external charge can affect the jumping time.

Bye for now

 

[sol invictus]

Another lie! I have never said that that when you start up a current within a superconductor you must not do work in order to obtain an equiibrium current. What I am saying is that this work DOES NOT entail ACCELERATION of the charge-carriers, since charge-carriers that can be accelerated cannot cancel an applied electric-field.

Johan, ramping up a superconductor means increasing the current that flows through it. Read that again: INCREASING THE CURRENT.

How do you increase a current without accelerating charge carriers? You do know what a current is, right?

 

[sol invictus]

An intresting question. When there is no current flowing through trhe superconductor, there will be no image charge since the superconductor will react to the external charge like a dielectric: There are now now free charges. When a current flows, the anchored charges can move by borrowing energy (delta)E for a time interval (delta)t. It is thus possible that while making a jump from one anchor position to the next the electric field of the external charge can affect the jumping time.

Incomprehensible gibberish.

 

[ben m]

An intresting question. When there is no current flowing through trhe superconductor, there will be no image charge since the superconductor will react to the external charge like a dielectric

First: you must realize that dielectrics can have (bound) unbalanced charge density. In a dielectric with non-constant polarization density P, there is an effective charge density rho = divergence(P), sometimes called bound charge. If you treat my "plate" as a dielectric, the polarization indeed has a divergence (at the top and bottom surfaces) which indeed gives you nonuniform charge density. The formation of that charge density has exactly all of the properties of---guess what?---an electric current. (d/dt rho = div J is exactly as true for bound charge as it is for free charge.)

Second: no, it does *not* behave like a dielectric. You can see this very clearly if (as I suggested) the plate is plugged into a ground connection. Start with a grounded plate, and no external charge. Now bring the external charge in from far away. In order to remain at ground potential, the plate needs to pull in an image charge; it does this by drawing ordinary, free current through its grounding cable. The resulting charge arranges itself on the plate top surface in a nonuniform way.

This is basic, basic E&M, Johan. This problem (induced charge on a plate with a point charge above it) is section 3.2.2 in Griffiths "Introduction to Electrodynamics"; a complete derivation of the induced charge density as a function of position, uses Coulomb's Law plus literally four lines of algebra.

There is nowhere in the problem where you care about presence of a DC current, nor about the nature of the conductor (metal, semimetal, plasma, superconductor, salt water, etc.), nor any of the other details you toss in as "objections" without actually thinking about.

If you disagree, this is the world's easiest test of your theory. Take a superconducting plate (you can but a cheap YCBO pucks from Edmund Scientific for about $30) Plug it into ground via a nanoammeter (old Keithleys are $100 on EBay) Wave a static-charged rod (glass rubbed with silk) up and down above it. Does the ammeter show the plate drawing current? If so, it's getting a nonuniform image charge as normal physics says. If not, the plate is behaving like a dielectric, any moving charge is of the bound/polarization variety, and you win the Nobel.

 

[johanfprins]

Wrong.

As always, you assert a conclusion that does not follow. If the material is net neutral, then the average density of charge carriers must match the average density of ions (because the average density times the volume is simply the total number).

And since it is in an equilibrium state, the opposite charges will “on average” remain as near to each other as possible. A large accumulation of charge-carriers are therefore not possible while a current is flowing.

But the local density of charges can, of of course usually does, vary.

Not by so much that it can cancel an applied electric-field between two contacts; which is what you all are claiming.

A perfect example is provided by ben's drawing. Let's say there's a steady current flowing through the metal sheet (superconducting or not, it's not important). Now slowly (or not, up to you) bring the charge Q in from infinity. What happens to the charge density on the sheet? What happens to the current through it?

A perfect example! Holy Mother of God! A single external charge in addition to the equal numbers of opposite charges within the material DOES NOT give a “perfect” example which proves that free charge-carriers can accumulate at an interface while a current flows through the interface. The latter is NOT possible; even when you have some local fluctuations in charge density.

I will be back

 

[ben m]

And since it is in an equilibrium state, the opposite charges will “on average” remain as near to each other as possible. A large accumulation of charge-carriers are therefore not possible while a current is flowing.

Nope. Any given charge carrier feels a total field of all charges nearby. You're focusing on neighbor-neighbor repulsion, which indeed by itself would tend to make charge spread out as much as possible, but you're ignoring the other charges I've explicitly put into the problem.

Given my free charge Q placed a distance D above a flat conductor, the result I described---a patch of excess charge of surface density -Q d/(2 pi (d^2 + r^2)^(3/2))---is the equilibrium state taking into account neighbor-neighbor repulsion as well as the attraction between Q and the charge carriers. It also takes into account the effect of a net current in the metal, which is no effect at all, because only the net charge density (not the current) matters.

 

[ben m]

Not by so much that it can cancel an applied electric-field between two contacts; which is what you all are claiming.

Baloney. I gave you the numbers already. There are huge numbers of available + and - charge carriers available---100 kilocoulombs per mole---in typical conductors. Real-world electric fields, even large ones---say 1 MV/m---are cancelled by excesses of microcoulombs per m^2.

This is not a subtle, modern, quantum point. This is Coulomb's Law. Your opposition to it is baffling. What do you think a Faraday cage is? Do you think the zero-field-inside-the-cage requires something other than Coulomb's Law? Can you show me an E&M textbook which contains this new law?

 

[johanfprins]

With regards to my description of your initial experimental results as anomalous.....

This is a very long thread and maybe I've lost track of the sequence of events but I thought it went something like this:

[*]You conducted an experiement in which you got a result that you interpreted as room temperature super conductivity. This was unexpected and exciting

It was unexpected because I did not use the well-established theory of Solid State Electronics before I did the experiment to its full extent. After I have found the result and could not understand it I went back to these equations and found that they in fact predict the result I discovered.

[*]You subsequently developed a theoretical understanding which explained these results

No! The results for electrons within a vacuum were adequately explained by the standard equations which are used every day to model Sold State Electronic Devices. At first I thought that it was a new type of superconductor. It was only much later that I realized that it also gave a clue how superconduction WITHIN materials are actually occurring. I then developed a new model to explain superconduction within materials which model ALL the materials that have been discovered to date.

[*]You've had great difficulty in getting acceptance of this theoretical understanding because of the intransigence of the physics community

Yes for superconduction within materials it became obvious that pair formation is not required at all. This was too much for the 'experts” to even contemplate after they have had for 50 years been fed on the latter claptrap.

[*]You have spent the last few months debating your theories on this board
Surely, if the results of the original experiment were not "inconsistent with or deviating from what is usual, normal, or expected", you'd have thought nothing more of it and wouldn't have bothered to develop the theoretical understanding.

The theoretical understanding was not developed for my electron phase in vacuum since it is adequately explained by the standard equations which are used in Solid State Electronics.

The results of initial experiment WERE anomalous. Whether they have been subsequently explained by your theoretical work (which you claim they have, others claim not) does not change the fact that they were anomalous.

They were unexpected, but once obtained were found NOT to be anomalous.

What surprises me about people like you is that you are willing to judge other people by using narrow preconceived ideas without first even attempting to get the full story. Since you studied physics, this mentality augers badly for our future on this planet.

 

[johanfprins]

Johan, ramping up a superconductor means increasing the current that flows through it. Read that again: INCREASING THE CURRENT.
How do you increase a current without accelerating charge carriers? You do know what a current is, right?

By increasing the rate at which you inject charge-carriers at the injection contact. If you did not believe that you are an "all-knowing god" and first read the extracts from my book on my website, you would not have asked such an utterly stupid question.

 

[ben m]

By increasing the rate at which you inject charge-carriers at the injection contact. If you did not believe that you are an "all-knowing god" and first read the extracts from my book on my website, you would not have asked such an utterly stupid question.

Nicely done, Johan, you've violated conservation of energy *again*. You've outlined a process which will create a high magnetic field (with energy density B^2/(2 mu0)), and you insist that no electrical work needs to be done on the coils responsible.

 

[ben m]

After rereading both posts #1824 and #1833, I retract the preceding post.

Johan is *not* straightforwardly claiming to inject charge in a way that violates energy conservation. I was mistaken to say that he did.

Instead, as far as I can tell, Johan is claiming to to fit six hydrocoptic marzul to the ambaphascient lunar wain shaft so that side fumbling is effectively prevented. I cannot tell whether this obeys energy conservation, or whether the malleable logarithmic casing has two spurving bearings in a direct line with the pentametric fan.

Sol was right, this isn't wrong, it's gibberish.

 

[Ziggurat]

The argument Ziggurat had made earlier was that there must be acceleration since a current must start to flow simultaneously at every point along the conductor. I pointed out correctly, that the apparent simultaneous onset of a current at every point around the whole circuit, can be explained by a displacement current at this initial stage. I never claimed that such a displacement current then remains.

But the acceleration DOES remain, making this irrelevant. Even after the displacement current vanishes, the current throughout the magnet continues to increase, at every point along the conductor. Which means that the acceleration is continuing inside the superconductor as well. Claiming that the acceleration only occurs at the injection site would mean that the current at both ends of the magnet would not match, and therefore the magnet would become electrically charged over time. But that's not what happens.

Hell, if it makes you feel better, consider ramping from negative current to positive current. As you pass zero current, the voltage remains constant, so there's no displacement current. But you're still changing from zero real current to nonzero real current everywhere within the superconductor at the same time. Which is quite simple to explain, really: there's an electric field, and charge carriers are accelerating in response to that field.

 

[johanfprins]

See post 1828

I am not going to argue about these points since they are very far from the fundamental conflict between our standpoints which has surfaced all along within this thread. Every time I have allowed myself to be seduced away from the real issue by arguments by you and others which just confuse the issue. So let us try and have a focused debate.

Let us define the most fundamental issue on which we disagree and then try and discuss this issue in an adult, scientific manner. I think that the fundamental issue relates to the motion of charge-carriers within conductors, both normal and super. As I see it the opposing standpoints are as follows;

1. Your standpoint:
You argue that the charge-carriers within a superconductor are “free” charge-carriers which can be accelerated when there is an electric-field within the superconductor; and that when an equilibrium current flows, the applied electric field is cancelled by the accumulation of charge carriers at the target contact that leaves opposite charges behind at the injection contact. The current that flows are then generated by injected charges which move all the way with a constant speed from the injection contact to the target contact, without any change in the cancellation of the applied electric field: As an example you gave the movement of charges within a van de Graaff tube.

2. My standpoint:
I argue that free charge-carriers that can be accelerated by an applied electric field can NEVER cancel an applied electric field within a conductor whether the charge carriers experience resistance to their motion or no resistance to their motion. Therefore I conclude that free charge-carriers that can be accelerated can never be responsible for equilibrium superconduction (an equilibrium current) which requires charge carriers to move without an electric-field being present and without generating an increase in entropy. There must thus be another mechanism that does not require charge-carriers which are free so that they can be accelerated.

Before proceeding any further, I will appreciate it if you could confirm that my summary above is acceptable to you: If not, please suggest changes to it.

 

[Reality Check]

2. My standpoint:
I argue that free charge-carriers that can be accelerated by an applied electric field can NEVER cancel an applied electric field within a conductor whether the charge carriers experience resistance to their motion or no resistance to their motion. Therefore I conclude that free charge-carriers that can be accelerated can never be responsible for equilibrium superconduction (an equilibrium current) which requires charge carriers to move without an electric-field being present and without generating an increase in entropy. There must thus be another mechanism that does not require charge-carriers which are free so that they can be accelerated.

Butting in a bit but your standpoint is too general.
Your first sentence is obviously wrong as a simple example shows:

Take a block of metal (superconducting or not). Apply an external electric field. The electrons in it are charged particles. The electric field exerts a force on them. The electrons move. They move to one side of the block and stop because there is no where else to go. A charge is created on that side of the block.

In your standpoint the charge continues to build up forever. There is always a current across the block

In the real world, an internal electric field is created between the ions and the electrons. This electric field is opposite to the external electric field. It eventually matches the external electric field and the current stops.
​

Another simple example refutes the rest:

The current in a superconducting ring is an equilibrium current. The free charge-carriers that have been accelerated are responsible for 'equilibrium' superconduction. They are moving without an an electric field being present and without generating an increase in entropy.
​

Your conclusion is thus wrong.

You need to give a specific example that demonstrates your standpoint. rather than generalizing to every possible situation where your standpoint can be refuted by examples.

 

[johanfprins]

You need to give a specific example that demonstrates your standpoint. rather than generalizing to every possible situation where your standpoint can be refuted by examples.

I have not asked for an analyis of my standpoint at this stage, but only from Ben (or whoever) to confirm that the two standpoints I have formulated represent our different models: WHETHER YOU AGREE WITH MY STANDPOINT OR NOT AT THIS POINT IS IRRELEVANT. Once it is agreed that I have summarised the two standpoints accurately, only THEN will we discuss them. Please read and try and comprehend before (as usual) shooting from the hip!

For clarity I should have added to the first sentence that I am talking about cancelling an applied electric-field while a current is flowing: But after the formulation of the opposite standpoint above I thought that this goes without saying.

 

[ben m]

Thanks Johan, this is a useful way of moving forward.

1. Your standpoint:
You argue that the charge-carriers within a superconductor are “free” charge-carriers which can be accelerated when there is an electric-field within the superconductor; and that when an equilibrium current flows, the applied electric field is cancelled by the accumulation of charge carriers at the target contact that leaves opposite charges behind at the injection contact. The current that flows are then generated by injected charges which move all the way with a constant speed from the injection contact to the target contact, without any change in the cancellation of the applied electric field: As an example you gave the movement of charges within a van de Graaff tube.

Let me clarify one point: it doesn't matter whether the "current" is made of individual charges that move "all the way". Charge is charge. Consider the "charge excess" at a contact with metal on the left and SC on the right. You could, for example, have the following:

a) a new charge is injected into the left side of the excess
b) a previously-static charge gets bumped out of the right side
c) the bumped-out charge cruises through the SC at constant speed.

That'd be fine with Maxwell, but it's different than what you state above.

I agree that this is not what happened in the Van de Graaff example (there the static and moving charges were physically separated and identifiably different) but in actual materials it's irrelevant. Again, Maxwell's Equations care about the total fields j and rho, not about subcomponents of them.