As the resistivity decreases one finds that it takes longer and longer times for the current to settle down to reach the conditions under which Ohm's law is valid. When you make the resistivity zero, the current keeps on increasing to infinity
You're assuming that the voltage never changes. This is a physically impossible assumption. Relax this assumption, and you'll find that there are no problems.
The fact that it seems to be valid for superconduction, does not explain superconduction
In the sense that it doesn't tell us how zero scattering can occur, sure.
The only reason why it will establish is the effect of contact-resistances: Without them, no equilibrium state is possible.
Anything which allows the voltage to drop can do that. A resistance anywhere in the circuit will work (it doesn't have to be at the point of contact), the decrease in separated charges which created the voltage will work (and the current is trying to do exactly that, BTW), whatever.
And I then pointed out that when you accelerate charges around a ring, you have a mini accelerator and must then emit cyclotron, or synchrotron radiation.
Again: ben's answer quite some time ago explained why this assertion is wrong.
You keep on trying to use "inductance" for a DC current. It does not apply.
You keep talking about a current which increases without bound for a DC current. It does not apply.
Your objection in this post is founded on what happens in a non-DC case (and DC here means constant current, not constant voltage). I think inductance is rather relevant to that.
If they accelerate you must measure a voltage: It is, however, the defining discovery that there cannot be such a voltage which Onnes used to identify superconduction. So you must be wrong.
Well, no. His discovery was for the DC case, which meant no acceleration. And if he
meant to include time-varying currents (which I doubt), he was wrong. As I said, you cannot simply ignore induction. It's an obvious case where superconductors are MEASURED to have non-zero voltage across them.
The only way in which a current through a superconductor between two contcats can be increased is to increase the rate at which charge-carriers are being injected.
You can't do that without accelerating the charge carriers already in the superconductor, or you will create a net charge in the superconductor. Which (by Gauss's law) will create an electric field within the superconductor, which will then... accelerate the charge carriers already in the superconductor.
You cannot avoid accelerating the charge carriers. Even if you assume they won't, you will find out that they must.
If an electric field were present you would have measured a voltage.
Yes. Now try to figure out how large an electric field you need for that.
It's pretty damned small.
Onnes's discovery that a voltage does not manifest over two points to superconductor while a current is flowing is incontrovertible proof that the charge-carriers are not accelerated by an electric field within a superconductor. Please stop contradicting impeccable experimental evidence.
It's not impeccable evidence. In fact, it's fundamentally limited. You can never prove zero resistance, all you can ever do is establish an upper bound. If that upper bound is sufficiently small, we assume it's zero, but that step is still an assumption. And in the case of the electric field needed to make a superconducting current bend, well, the required field is
damn tiny, so the inability of Onnes to measure it is of no consequence.
What you think is "direct observation of superconductors" is a misinterpretation of what you are seeing. If you cannot measure a voltage, there cannot be acceleration
That's simply not true. Our sensitivity to voltage in circuits is not unlimited. In fact, it's kind of crappy.
Ben is wrong: If he were correct that acceleration of charges without scattering cannot generate EM we would not have had synchrotron radiation.
Synchrotron radiation uses pulsed currents, so obviously his argument, which was formulated specifically to describe constant currents, doesn't apply.
I agree I made a booboo on this one by not being very clear about what I was trying to say when it comes to a superconductor and the presence of a magnetic field under these conditions. What I was trying to say, is that if there is any net magnetic field present within any region of such a material, that region cannot be superconducting.
Maxwell's equations, the region which contains the current MUST have a magnetic field, unless that region has zero volume. And a zero-volume current is not physical. So the obvious implication of what you're now arguing is that the current-carrying region of a superconductor is not superconducting. Which is a rather strange conclusion, don't you think?
What the main stream scientists are arguing is that a superconducting current flows through a surface layer (at a penetration depth lambda) in which the magnetic field is not cancelled. Now if this is so, why does superconduction stop in its tracks when a magnetic field is present within the whole superconducting layer. It just does not make experimental sense.
You have the sequence backwards. The superconducting phase always screens the field to a depth lambda. When the superconducting phase is destroyed because the field
within that depth is too large, then the material stops superconducting
and stops screening. You kill the superconducting phase, and THAT leads to a lack of screening. You cannot GET a magnetic field penetrating the entire sample until
after you hit the critical field within the screened region.
Since there is a magnetic field energy within this layer, this region is not superconducting anymore; and the current must flow beneath it, within the region where there is no magnetic field.
Again, this is not possible: whatever region the current flows through will have a field.
