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This is one of those mad Ideas I originally had decades ago, but somehow didn't think of posting it here until now.
Most everyone who knows something about electricity knows that when electrons flow through a wire, there is usually some resistance to their motion, which we can compare to (or analogize
as) "friction".
The phenomenon of superconductivity is thought to be the result of electrons behaving in a very special way. Pairs of them act together to, basically, cancel out each other's friction, as they move through a conductor. They are called "Cooper pairs" after the physicist who pulled that idea out of Quantum Mechanics.
Cooper pairs can be broken up by heat, and thus many superconductors only behave as such at extremely low temperatures (mostly below the temperature at which hydrogen gas freezes solid).
It came as quite a suprise in the 1980s when certain materials (mostly copper-oxide ceramics) demonstrated superconductivity at liquid-nitrogen temperatures. The mystery yet remains to be solved, regarding how Cooper pairs can still stay together as pairs, at that temperature. The evidence so far suggests that there is some special aspect of the physical structure of the material, that assists them.
Anyway, I may be mistaken, but I get the impression that a Cooper pair is a "lower-energy" state, for a pair of electrons, than when they are not paired. That means electrons would prefer to pair-up if only there wasn't so much thermal energy typically available at room temperature, to discourage them from doing that.
But it **also** means that a completely different approach toward achieving superconductivity might be possible.
Consider the concept of "pressure". It tends to cause things to occupy less space, whenever it is possible for those things to do that. A simple/common example is a "pressure cooker", which forces water to stay liquid at a temperature higher than its boiling point at ordinary atmospheric pressure.
Well, water, as a liquid, occupies something like 1/1600 the space of water-as-a-gas. Also, liquid water is typically a "lower-energy state" than steam. So, what pressure can do is force water to stay in the lower-energy state, despite the temperature of the water being such that it might "prefer" to be in the gaseous state.
I'm guessing that we can apply that principle toward making superconductivity work at higher temperatures. All we need is the right sort of "pressure".
So, start with a loop of metal. If current flowed in it, we would have a "closed" electric circuit. If it was a superconducting metal, it would generally be surrounded with liquid helium, to actually be used as a superconductor. It is my understanding that special care is taken, at the point where a superconducting wire interacts with a non-superconducting wire, to ensure that the superconducing wire **stays** superconducting.
One way to do that invovles "induction". If the electric current in either wire changes, then it will be associated with a magnetic field that also changes, and which can induce a similar changing current to flow in the other wire. So, the wires don't have to touch, for power to be transferred from one to the other. (Note: not all superconductors will cooperate as easily as I've just described; they tend to repel magnetic fields.)
That separation of electrical circuits is very important for this Idea!
What we want to do is start with our isolated "superconducting" loop of material, regardless of whether or not it is actually a superconductor when we do the next step --which is to give it a very strong negative electric charge. Basically, we are pressurizing the quantity of electrons within that closed and isolated loop of wire.
Which means, to the extent that Cooper pairs represent a lower-energy state for electrons, that pressure should encourage their formation.
To find out, we now cool the wire down toward the "transition" temperature at which we would expect it to become a superconductor. But while cooling it, we test it, to see if the transition temperature has changed. Will the loop of wire become a superconductor at a higher temperature than before?
To be determined by Experiment! --And, preferably, by a lot of experiments, to see what degree, if any, charging up a wire enhances its ability to superconduct. Maybe this method alone can let us achieve the dream of room-temperature superconductivity. (More likely, we would combine it with the highest-temperature uncharged superconductor that we can make.)
========Added March 20, 2012
Per an annotation, I should mention that "voltage" is the term normally associated with electrical "pressure". A Van de Graaff generator can easily apply a pressure of 400,000 volts to an object, and a Cockcroft-Walton "voltage multiplier" can go even higher, by using alternating current and diodes to build up a static charge. Keep in mind that such voltages can require lots and lots of insulation, to ensure the charged material retains that voltage-pressure!
I also neglected to mention that simply by testing for the ability of a material to exclude a magnetic field (typically indicated by the initiation of "magnetic levitation"), that is another way to determine if a material has become superconductive.
More information about superconductivity
http://en.wikipedia...i/Superconductivity
For anyone interested [Vernon, Mar 15 2012]
More on Pressure Cooking
http://en.wikipedia...ki/Pressure_cooking
For anyone interested. [Vernon, Mar 15 2012]
[link]
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Now, this is a better idea, and less than 1VU in
length! |
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Be aware, though, that the quantity of surplus
electrons which can be produced by even an
enormous electrostatic charge is absolutely tiny
compared to the total number of electrons in the
material. Still, interesting. |
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[MaxwellBuchanan], yes, I'm aware that we can't appreciably increase the total quantity of electrons in anything to which we give an electrostatic charge. However, the important thing here is the pressure. Like trying to pressurize liquid water, the pressure inside a container can be increased quite a lot with only a little extra water added to a full container. |
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Yes, fair point. Whether this would have any impact
on the formation of Cooper pairs, I have no idea, but
hey. |
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//Consider the concept of "pressure". It tends to cause things to occupy less space, whenever it is possible for those things to do that.// |
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So this idea hinges on whether or not Cooper pairs occupy "less space" than the corresponding 2 unpaired electrons would. |
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Compare: water/ice, which tends to melt under pressure as the solid form is larger, to more or less anything else, which tends to solidify under pressure for the opposite reason. |
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How "large" is a Cooper pair, compared to the unpaired form? |
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Does my question even make sense? |
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If your question makes no sense, then it makes no sense to speak of the size of a Cooper pair, and so you ask a sensible question. Therefore your question makes sense if and only if your question does not make sense. |
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More specifically, if electrons can interact in
Cooper pairs, does a general charge tend to favour
or discourage the formation of Cooper pairs? |
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This might be equivalent to asking whether the
formation of Cooper pairs has any influence on the
local electric field. Just as ice formation leads to
a change in volume (and therefore pressure
changes can encourage or delay ice formation), so
one would expect that if the Cooper pairing of
electrons has a large-scale effect on the electric
field, then the reciprocal must be true. |
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Naively and intuitively, I'd expect not, as conservation laws imply that the charge on a Cooper pair is exactly twice that on an electron. |
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Of course, naively applying intuition to phenomena in this scale is a bit, er, naive. |
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My first thought was also that a charge only takes a few electrons. Whether the "pressure" increases, and whether that affects pairing, are two possibilities, possibilities that seem likely only by comparison with water. |
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But electricity is like water in a lot of ways, and testing this idea is fairly easy. |
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Still ... if electricity is like water, what in water is comparable to Cooper pairs and superconductivity? Ice crystals and ice skating, maybe? |
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//And how do you propose to measure the
superconductivity ?// The idea itself was tldr, but I
think he suggested using induction to induce and
then detect the current, which would work. |
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[Vernon], I recant all of the rotten things I've said to/about
you; this idea is brilliant. It's the kind of thing that, given
just one tiny breakthrough in high-tech materials
fabrication, will change the world in a subtle but
significant way. The possible applications obvious even to
my relatively narrow view are stupendous. It could re-
revolutionize arc welding, for one. Please pursue it if you
have the means. |
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This doesn't mean I'm going to stop saying rotten things
about you, though. [+] |
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[Wrongfellow], the "less space" interpretation is not the whole of I was trying to describe. The important thing is whether or not a Cooper pair really is a "lower-energy state", when compared to higher-temperature unpaired electrons. If it is, then my analogy with water becomes fairly precise; pressure can keep hotter water in the lower-energy liquid state, so perhaps it can keep hotter electrons in the lower-energy Cooper-pair state. |
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All: Sorry, somewhere in the main text I should have mentiond the fact that with respect to electrical stuff, the term used, equivalent to "pressure", is "voltage". So, when a high voltage is applied to something, it can be given a significant static-electric charge, and thereby the electrons in that object would (if the charge is negative) be experiencing "static pressure", equivalent to what water can experience inside a pressure cooker. |
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I don't think applying a higher voltage (your
"pressure") will have any effect on the
superconductivity of the material. Increasing the
voltage simply increases the "pull" on the electrons -
increasing current, but also increasing resistance
(i.e. increasing the "friction" in the system, not
decreasing it). Increasing the voltage, basically, just
heats the wire up - the opposite of what you need
to get superconductivity. |
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// Increasing the voltage, basically, just heats the
wire up - the opposite of what you need to get
superconductivity.// |
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No, increasing the *current* heats up a wire,
unless it's superconducting. A net charge on the
wire won't (as far as I can see) have any such
effect. |
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There's a possible analogy that might help.
Suppose you have a wide pipe, inside which is
scrunched up chicken-wire. You take a bunch of
very small balloons (say, 2cm diameter) and try to
blow them through the pipe using a pressure drop
of (say) 1psi. The air pressure is pushing them
through, but of course the chicken-wire acts as a
resistance, and slows their movement (they have
to wiggle through the gaps in the chicken wire). |
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Now you repeat the experiment, but with an air
pressure of 101 psi at one end, and 100psi at the
other end. The net pressure drop trying to move
the balloons along is still 1psi, but the static
component of the pressure (100psi) will squash
the balloons, making them smaller and allowing
them to pass through more easily. |
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Of course, by analogy, pressure is voltage and, in
the second experiment, we're applying a static
voltage in addition to the voltage gradient which
induces the electrons (balloons) to move. |
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Having said all that, there's no evidence of which I
know to say that applying a static charge will
favour the formation of Cooper pairs, so it's still
all speculation. |
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// increasing the *current* heats up a wire, unless it's
superconducting. // |
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That's why something like this could revolutionize arc
welding. Many skilled welders can lay down perfect beads
at high speeds using wire-feeds, but this requires higher
amperage. High-end machines like the ones I own will
produce plenty of current, but the leads and couplings will
burst into flames because the arc creates a 'bottleneck', if
you will; methinks a superconducting contact element
would eliminate much of that resistance. Even having a
superconducting ground clamp would solve more mundane
stick-welding problems like sputtering and arc-blow. |
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