Please create an account to participate in the Slashdot moderation system

 


Forgot your password?
Close
typodupeerror
×
Science

Quantum Wires 235

Posted by CmdrTaco from the i'll-believe-it-when-they're-conducting-my-mojo dept.
Silverlancer writes "Room temperature superconductors have often been a hallmark of far-future science fiction. But fortunately for us, they're here today, according to MIT's Technology Review. Richard Smalley, winner of the 1996 Nobel Prize for the discovery of the buckyball, is currently heading a project to produce a prototype carbon nanotube superconductor. They've already produced some wires up to 100 meters long--the only thing left to do is figure out how to produce only a certain type of nanotube, the "5,5 armchair nanotube," that conducts so well that it can be considered a superconductor."
This discussion has been archived. No new comments can be posted.

Quantum Wires More

Quantum Wires

Comments Filter:

  • Armchair... (Score:5, Funny)

    by isny ( 681711 ) on Sunday April 17, 2005 @10:23AM (#12261929) Homepage
    I'm sure that in the next 5 minutes, the "5,5 armchair nanotube" will be criticized by the armchair physicists, the Slashdot equivalent of the armchair quarterback.

  • Superconductors (Score:4, Funny)

    by mrRay720 ( 874710 ) on Sunday April 17, 2005 @10:24AM (#12261937)
    100 times stronger than a normal conductor, and able to carry a thousand volts in a sinlge bound!

    That out the way, this is great news. There are so many useful scientific applications for superconducting wires that this is really cool news, once you get over the ethical dilemma caused by the fact that they are making them by *cloning* the orginals. It's ok to clone wires but not people? Hypocrites.

  • Dr. Smalley talks to the senate (Score:5, Informative)

    by Flywheels of Fire ( 836557 ) on Sunday April 17, 2005 @10:24AM (#12261938) Homepage
    Interestingly,Dr. Smalley [mithuro.com] talked about armchair nanotube technology at the senate Oversight hearing on sustainable, low emission, electricity generation Full Committee Hearing almost one year ago. The full text is here. [mithuro.com]

  • Dubious Logic (Score:2, Informative)

    by Anonymous Coward
    A superconductor is in a different league to a conductor, even a really good one. That's all this appears to be about, a really good conductor.

    • Nah, Monster Cable will capitalize on it! (Score:5, Funny)

      by PornMaster ( 749461 ) on Sunday April 17, 2005 @10:59AM (#12262158) Homepage
      Someone's gotta find a way to break the $2000 mark for speaker cables that some arrogant ass will insist makes the whole sound experience worth it.

      • Re:Nah, Monster Cable will capitalize on it! (Score:2, Funny)

        by Anonymous Coward
        Less than ten posts and:

        One uninformed, irrelevant and gratuitous knock against Slashdot - check

        One uninformed (+$2k cables are common), irrelevant and gratuitous knock against audiophiles - check

        Let me finish off with "teh gimp sux 'case it's not like Photoshop!" Now we have closure.

    • We might call them "quasi-superconductors". See, the difference between carbon nanotubes and common conductors is their crystaline structure that makes electrons travel in 1-D, as opposed to 3-D in common conductors. This nullifies heat dissipation, because, if there's no friction between the electrons, there's no energy loss.

      And think about this. Cold superconductivity is a temporary, artificial effect. And there's a limit on the amount of current that can flow thru a superconductor before it loses its su
      • > So I'd say this is the *REAL*
        > superconductivity...

        I'd say this is ultraconductivity or similar. The word "superconductivity" is already firmly attached to the phenomena described by the BCS theory.

        Question: what are the thermal properties of this stuff?
      • So I'd say this is the *REAL* superconductivity, and the phenomena discovered in near-0K conditions was just an attempt to it.Ah. So is this "REAL" superconductivity Type I or Type II superconductivity? Just to clarify.

    • Re:Dubious Logic (Score:5, Informative)

      by nrlightfoot ( 607666 ) on Sunday April 17, 2005 @11:33AM (#12262379) Homepage
      Actually, it's called a ballistic conductor. There is a small resistance when electrons pass through the ends of the nanotube, and while it is traveling along the rest of the tube there is no resistance.

  • wires... (Score:2, Funny)

    by dword ( 735428 )
    great! now i have something geekish to use for bondage with girls.

  • Power distribution efficiency (Score:4, Funny)

    by DmitryProletariat ( 876610 ) on Sunday April 17, 2005 @10:31AM (#12261987)
    Superconductivity will be a great boon to efficient power distribution. By spreading efficiency across the grid we'll see greater centralization of power, which can only lead to capitalist tyranny. Thus, be wary of Superconductivity. For while the Luddites were a conservative force against change, so too could they have weaved these carbon nanotubes into power cables capable of suppressing all revolutionary thought. Worldwide!

    In short, not all new technologies will help bring about the worker paradise. Scientist and their capitalist pig ways!!! Soon the proletariat will rise and all you carbon nanotube superconductor makers will find yourselves up against a brick wall...

    *bang!*

    • Re:Power distribution efficiency (Score:2, Funny)

      by Anonymous Coward
      Can I mod this +1 insane?
    • Superconductivity will be a great boon to efficient power distribution.

      Well, what will matter most for the average /.'er is that we can have CPU's wastly more efficient than today. No transport loss equals lower core voltage, and lower current. A cpu that only wastes power in transistors would be a great improvement. Remember, AMD and Big Blue changed from Aluminium Interconnects to Copper Interconnects in their CPU's to reduce heat output... So imagine what a super conductor (that is, 0 Ohm) would do to

  • Optical Computing versus Quantum Wires (Score:5, Interesting)

    by DanielMarkham ( 765899 ) on Sunday April 17, 2005 @10:35AM (#12262012) Homepage
    Seems like from one direction optical computing is advancing, from another we're working towards room-temperature superconductors.

    So what's the future look like? Quantum processors with superconducting and optical connections? I wonder how these various technologies will actually be deployed?

  • EMR from high tension power lines? (Score:4, Interesting)

    by bawol ( 626115 ) on Sunday April 17, 2005 @10:35AM (#12262015)
    While the effects are still debated, would this have any effect on radiation given off from high tension power lines? Would the electricity be carried at a higher or lower frequency?

    • Re:EMR from high tension power lines? (Score:5, Informative)

      by totoanihilation ( 782326 ) on Sunday April 17, 2005 @11:02AM (#12262173)
      At same voltage and current, the electromagnetic radiation should stay the same. The advantage of reduced resistance though come in two points:

      1. Lower losses in cables, so less power needs to be transmitted
      2. Lower resistance means we can pump more power into them. This becomes handy in electromagnetics (example: maglev trains). Less energy is wasted in heat, and less cooling is required.
      • If this is a real superconductor, higher voltages might need to be used to keep the current below the saturation threshold where the superconductor stops superconducting.

        On the other hand, big high voltage lines only carry a few dozen amps max anyway, so it might be an acceptable drop-in replacement.
    • Would the electricity be carried at a higher or lower frequency?

      The frequency most likely would not change, to maintain compatibility with the existing infrastructure.

      However, we mostly use AC to get around the fact that DC suffers massive losses when sent any useful distance. In a true superconductor (not sure if these nanotubes count, the wording used strikes me as very awkward - Something either has a resistance of zero or it doesn't), we could use DC just as efficiently as AC.
      • That's interesting. DC distribution = no EMFs generated. Whether or not EMFs have any real health effects, removing them would be good PR for the power companies.

      • Re:EMR from high tension power lines? (Score:4, Interesting)

        by John Hasler ( 414242 ) on Sunday April 17, 2005 @11:37AM (#12262404) Homepage
        > However, we mostly use AC to get around the fact
        > that DC suffers massive losses when sent any
        > useful distance.

        Not true. We mostly use AC because it is easy to step the voltage up and down with transformers. This way we can reduce the cost of transmission by stepping the voltage up and the current down (allowing the use of smaller, cheaper conductors) and then step the voltage back down for use. At the same voltage AC suffers _more_ loss in long-distance transmission due to radiation and skin-effect. For short to moderate distances this is more than offset by the low cost of voltage conversion. For very long distance transmission DC is sometimes used because the reduced losses make the extra expense of conversion worthwhile.
        • Correct me if I'm wrong, but aren't you quibbling over semantics? The reason that we step the voltage up and down is that it allows power to be transmitted farther. The reason we use AC is to facilitate stepping voltage up and down. So, we're using AC to transmit power farther.


          If we had superconducting wires, we wouldn't need to change voltage, so we wouldn't need AC, and hence it might be worth switching to DC. IANAElectrician though, so correct me if I've misunderstood something.

          • The electronics revolution has given us the means to step DC power almost as easily and as efficiently (more efficiently?) than an AC inductor.

            Also, DC in the home is a *bad* idea. Although I suppose if one had ground fault interrupt throughout the home it should be no more dangerous than today's juice.

            A few volts DC is enough to kill you; it locks your muscles and thus causes you to continue to hold on to the wire that you grabbed in the first place. Hence why all electric fences in the united states are
            • > The electronics revolution has given us the
              > means to step DC power almost as easily and as
              > efficiently (more efficiently?) than an AC
              > inductor.

              Solid-state DC-DC converters are much more complicated than transformers: they include semiconductor power switching devices, integrated circuits, resistors, capacitors, _and_ inductors. Mechanical DC-DC converters include motors and generators. Transformers are just copper, iron, and insulation.

              > A few volts DC is enough to kill you...

              Not tr

    • Re:EMR from high tension power lines? (Score:5, Informative)

      by MoralHazard ( 447833 ) on Sunday April 17, 2005 @11:19AM (#12262293)
      I assume you're talking about the different effects of resistance on AC and DC currents: as electricity travels through a conventional conductor, the resistance of the conductor gives up some of the electrical power as heat (as Ohm's law describes). That's why we use high-voltage AC to distribute electric power, and even higher-voltage AC to transmit power over long distances--by transmitting at high AC voltages, you don't lose quite as much power as you otherwise would.

      So if you could replace vast swaths of conventional copper electric transmission and distribution lines with superconductors, you could theoretically switch to DC power in these applications, which would have some interesting effects on the rest of the electrical distribution system.

      Strict DC voltage on the power lines would virtually eliminate the EM radiation. You would still get some EM when you turned things on or off, or if the amount of power the line carries changed at all, but there would be a HELL of a lot less.

      Lower voltages could be used, which would be safer (less chance of electrocuting people), and connectors (plugs, receptacles) designed with lowe voltages in mind would be cheaper to produce and certify.

      Also, many devices in the home (especially computer equipment, or anything with circuit logic in it) need to convert the 110V AC current into much lower-voltage DC (2-5V DC, usually) to operate chip logic. This in generally an inefficient process, with a lot of power given up in the transformers and inverters to heat. Granted, you'd have to redesign all the home devices that currently use AC power directly (mostly lights and appliances) to run on DC, it could be done.

      Really, the only problem would be the massive costs of switching over from one standard to another. All of those applicances and such would become useless on the new standard, which means everybody has to go out and buy new stuff. If you tried to switch the distribution over to DC in one go, I can see a lot of people having a lot of problems with it. And it wouldn't be practical to change the distribution bit-by-bit, either.

      If you just wanted to change the transmission side, and leave the consumer out of it entirely, you'd have to replace a lot of power generation infrastructure. This could be done more slowly, I'd imagine, but it would still be expensive.

      But then again, there's nothing that prevents you from continuing to run AC current on superconducting wires. That's probably what will happen, because it's the cheapest option.

      I don't see anyone caring too much about interference from power lines in the 60Hz frequency band, anyway--not like we use those frequencies for anything.

      • Many AC-DC converters are relatively efficient (> 90% efficiency). Since we won't be doing power distribution with 5VDC, we would still need several levels of voltage step-down, and computers would still need to convert the "home" intermediate voltage DC to the 12, 5, and 3.3 that they need. Given that, I suspect we are better off staying with AC.

        Furthermore, there is no good replacement for AC motors, which are considerable more efficient than DC, and generate less EMI.

      • We're already using DC [abb.com] for high power long haul transmission as it's more economical to do so in many cases. It's really the voltage that provides the saving. The reason we use AC is that it could easily be stepped up (and down again) to the required voltages by use of a transformer. Today we can do that using e.g. power semiconductors (or generate and use high voltage directly). So, they've already beat you to it, no carbon nano-tubes necessary. :-)

        • DC for high power long haul

          Yeah, I was going to point that out. For reference, there is at least one, and I think there are actually two high voltage DC lines running from the BPA (Oregon/Washington dams) to southern California.

          Problem is, current technology seems to limit DC to *ONE WAY* transfer of electricity. So you need to know that the power is always going to be flowing from A to B, and never from B to A.

          Obviously this has nothing to do with the wire itself; I'm wagering that the step-up/step-do

      • So if you could replace vast swaths of conventional copper electric transmission and distribution lines with superconductors, you could theoretically switch to DC power in these applications, which would have some interesting effects on the rest of the electrical distribution system.

        Replacing aluminum transmission lines with superconductor (or with this stuff) would have no sustantial effects that I can see on the tradeoffs between AC and DC for transmission. DC is used now for some very long distance

      • That's why we use high-voltage AC to distribute electric power, and even higher-voltage AC to transmit power over long distances--by transmitting at high AC voltages, you don't lose quite as much power as you otherwise would.

        I don't thnk so. We transmit at high voltages because that yields higher power througput at same current levels. P=U*I, right? If you lowered the voltage on major powerlines, they would have to conduct much higher current levels, and that would mean thicker wires, superconducting or n

        • And, BTW, Tesla (AC) vs. Edison (DC) happened at the end of the 19th century. Tesla won, game over. :-)

          Technically correct, but most sources I've seen have depicted Tesla as being far more interested in the scientific research and development than in the buisness side of things, which he left to his "partner" Westinghouse. Westinghouse's work to promote AC vs. Edison's DC (along with Tesla's assignment of his patents to Westinghouse for a paltry sum so that Westinghouse could make the whole thing econom

  • Article Summary: (Score:4, Funny)

    by Anonymous Coward on Sunday April 17, 2005 @10:35AM (#12262019)
    Superconducting wires are "here today", the only left to do is to make super conducting wires.

    In other news, I am now a billionaire with a super model trophy wife. The only thing left is for me to get a lot of money and a hot wife.

  • really a superconductor? (Score:5, Interesting)

    by Al+Clocker ( 687416 ) on Sunday April 17, 2005 @10:36AM (#12262025)
    The article says that there is "almost no loss of energy." But real superconductors truly have zero resistance. Once you start a current in a superconducting loop it runs for years without decreasing. AFAIK a decrease has never been observed. The article is unclear about whether this actually is a super-conductor or not. Does anyone know for a fact?
    • Well energy can come out of a superconducting wire. If it couldn't, then there'd be no way to introduce energy into the superconducting wire either. These things work both ways. Think things like mutual inductance and magnetic effects. These things can cause undesirable losses too.

      The key for superconducting is only that *resistive* losses are zero, as you said, for a given current n that is below the superconductor current saturation point.

      The article does seem to strongly imply this is a superconduc

    • Re:really a superconductor? (Score:5, Insightful)

      by fearofcarpet ( 654438 ) on Sunday April 17, 2005 @11:12AM (#12262234)

      No. Superconductors must be able to form so-called Cooper Pairs in order for electrons to move in the coherent manner in which no energy is lost. I gather the rules are a little different at really small scales where tunneling becomes a much bigger issue and some of the energy relationships are backwards, but the principle is still the same; if electrons bang into something they lose energy.

      Metallic carbon nanotubes, to the best of my knowledge, cannot be made crystalline (perfectly regular) over large enough domains for this to happen thus there is "minimal energy loss" and they are really just very, very, very low resistance conductors (you can tell the difference by looking at the temperature dependance of the resistance).

      The thing is, unless you want to build a mag-lev train, you don't really need a perfect super conductor. Right now the conductivities of the metals used in electronis are around 10^6 - 10^10 (inverse ohms per centimeter) and you can put your hand on your computer case to see just how much energy is dissipated as heat. If you increased those conductivities (with metallic carbon nanotubes for example) then your heat sink shrinks and your clock cycles come up... Assuming we can wire teeny tiny circuits with nanotubes. More importantly, you can drive portable electronics with less power, and thus smaller batteries.

      BTW (regarding the very first post), some of the Slashdot Armchair Scientists (there are other sciences besides physics too you know) out here in computer land have Masters and PhDs and have published or worked in the field. Some of us have even met and/or worked with the people mentioned in the articles. I wouldn't be so quick to push aside honest criticism, afterall that is what scientists are trained to do - be skeptical :)

      • ... "and you can put your hand on your computer case to see just how much energy is dissipated as heat" ...

        You seem to have forgotten that the heat loss in computers is due to the SEMICONDUCTORS inside. You know, those pesky little PN junctions made from doped silicon, germanium, or rust? Adding superconductors to the power subsystem in a computer would do nothing to reduce the radiated heat.

        --
        This space for rent. Inquire within.
        • > Adding superconductors to the power subsystem in
          > a computer would do nothing to reduce the
          > radiated heat.

          Much of the heat generated in integrated circuits is due to the resistance of the aluminum traces used to connect the transistors on the chip. Replacing it with superconductor or with this "ultraconductor" would substantially reduce power dissipation.
      • BTW (regarding the very first post), some of the Slashdot Armchair Scientists (there are other sciences besides physics too you know) out here in computer land have Masters and PhDs and have published or worked in the field. Some of us have even met and/or worked with the people mentioned in the articles. I wouldn't be so quick to push aside honest criticism, afterall that is what scientists are trained to do - be skeptical :)

        However, if when you remember the armchair product design and commerce experts [slashdot.org] o

    • Re:really a superconductor? (Score:5, Informative)

      by triplepoint217 ( 876727 ) on Sunday April 17, 2005 @11:49AM (#12262481)
      Carbon nanotubes are not superconductors. In an ideal (the kind they are trying to build), they have a resistance that is independent of length, however it is not zero like in actual superconductors. The resistance of an individual nanotube is about 20 kOhms, but because they are so small an array of a large number of them in parallel can have a small resistance, and still not be very large. Because the restance does not increase for longer tubes, they are similar to a superconductor, and would be useful for transmitting power over long distances. However, the physics behind the conduction is different.
      • Carbon nanotubes are not superconductors ... they have a resistance that is independent of length ... the resistance of an individual nanotube is about 20 kOhms

        So I guess you could say that the nanotube itself really is a superconductor, but each end has a resistance of around 10kOhm - and it's impossible to build a tube without ends.
        • So I guess you could say that the nanotube itself really is a superconductor, but each end has a resistance of around 10kOhm - and it's impossible to build a tube without ends.

          Of course it's possible. They're called doughnuts. :)

          -

        • Carbon nanotubes are not superconductors ... they have a resistance that is independent of length ... the resistance of an individual nanotube is about 20 kOhms

          So I guess you could say that the nanotube itself really is a superconductor, but each end has a resistance of around 10kOhm - and it's impossible to build a tube without ends.

          Why would it be impossible? Couldn't you join the ends of a tube to make it a torus?

          And if you did this, would the tube still have a 20Kohm resistance? If it didn't, you sh

          • Maybe you could give it a tail like a Q (depending, of course, on your font), and pump it up through the tail.

            What would be the magnetic properties of such a loop? Would the current circulate indefinitely? Does THIS emulation of a superconductor lose superconductivity in a strong magnetic field?

            I don't think that superconductor is the right term for this, unless the magnetic properties are the same as for the other superconductors. Hyperconductor, perhaps?
          • > And if you did this, would the tube still have a
            > 20Kohm resistance?

            I would think that such a loop would have zero resistance.

            > If it didn't, you should be able to induce a
            > current in the loop, and it continue to flow,
            > just like superconducting magnets.

            Interesting. If there were no electons inside the tube no current could flow. If there were some they would move faster and faster as the external field ramped up in order to generate a canceling field. What would be the upper limit?

  • So much work (and funding) is being poured into finding alternative energy sources, I wonder how much the discovery of a scaleable, inexpensive, widely deployable (as in converting the world's energy grid) superconducting power distribution system has been quantified.

    I do understand that this isn't that, and that there are a million barriers to be overcome, and that fossil fuels need a replacement Real Soon Now, but I do wonder if anyone knows of any studies out there trying sort out how much energy is currently lost in the distribution of consumer power, and how much less we'd need to generate if a practical superconducting solution is found.

    Factoring in a reasonable probability of success in both sides, it would be interesting to see whether the potential cost/benefit of investments in finding superconducting solutions all the way to the last mile might be as or more efficient in the long run than funding research in new power sources.

    I know, it shouldn't be either or in any case, but it's just a thought...

    • We need both. Most of the alt fuel sources are relatively low power density compared to say a 1000MW coal fired power station and often further from the places people live. So a high transmission efficiency technology such as this makes alt-energy sources much more viable. By the same token it cuts the need for power overall. A lot of power is wasted in transmission.

      You make a good point, though. Right now though, there are lots of viable alt-energy sources and this is far from ready to roll. So let's kee

    • I think you overestimate the amount of funding being poured into alternative energy research.

    • In the UK (Score:3, Informative)

      by Colin Smith ( 2679 )
      on average around 2% of energy is lost during transmission over power lines. It'll be different in different countries. It all depends how far you are from the station.

      On the other hand, convertng fuel to heat in order to generate electricity is typically around 40% efficient with a 60% loss of energy. Combined cycle power stations are closer to 60% efficient with a 40% loss of energy. The laugh is that the single largest use of electricity is to produce heat, but we're only doing it at around 40% efficien

      • Re:In the UK (Score:3, Insightful)

        by zCyl ( 14362 )
        CHP and DH systems have already been in use in northern european countries (Denmark, Finland etc) for decades, they are nothing new. I guess the UK and USA literally have money to burn.

        It's a geographical problem. How are you going to ship heat 200 to 2000 kilometers without electricity? Big pipes? At what point does the resource expenditure of constructing this enormous lossy infrastructure pay off for a country like the U.S. that only heats 4-5 months a year, sometimes less, depending on location? W
        • "How are you going to ship heat 200 to 2000 kilometers without electricity?"

          Don't be obtuse. You put the power stations where the requirement for heat and electricity is. i.e. locally.

          "lossy infrastructure"

          *Lossy* infrastructure? It's *WASTE* heat. You're pumping this waste heat into rivers, the oceans and the atmosphere *right* now! Anything which is used is saved energy.

          "that only heats 4-5 months a year, sometimes less, depending on location?"

          And the rest of the time burns electricity in order to co

  • The armchair nanotube... (Score:4, Funny)

    by Anonymous Coward on Sunday April 17, 2005 @10:41AM (#12262056)
    The armchair nanotube is great for those lazy electrons who put up a lot of resistance to doing work.
    So if that electron in your life is giving you heat about the pressure they are under this new product from LazyBoy is the perfect gift for them!

  • superconductor != 0 resistance (Score:5, Informative)

    by joostje ( 126457 ) on Sunday April 17, 2005 @11:04AM (#12262191)
    conducts so well that it can be considered a superconductor

    The most essential thing about a superconductor isn't the zero resistance, but the meissner effect [gsu.edu]. So if they manage to create wires with near-zero resistance, they will not have created `near-superconductors'.

    For energy transportation and storage it doesn't matter all that much, cause zero resistance (even without superconductivity) would make energy transportation and storage better

    • nooooooooooo, actually, the concept of superconductivity was proposed LONG before we had ever achieved it. And we didn't know about the Meissner effect until around that time.

      'Tis defined as transfer without loss: zero resistance. The only *question* would be to what is it superconductive to? Electricity, heat, mice etc.

      Science fiction usually concentrated on superconductive materials that would transfer heat without resistance; reality has given us materials that transfer electrons (or whatever happens i

  • LEDs (Score:5, Interesting)

    by Interrupt18 ( 839674 ) on Sunday April 17, 2005 @11:06AM (#12262203)
    There was a discussion [slashdot.org] yesterday about using LEDs to replace incandescent lights. One thing that came up was the power losses associated with stepping down the mains voltage to voltages required by LEDs.

    Even if the carbon nanotubes are not technically superconductors, if their resistance is much lower than copper they might be ideal for low voltage home wiring. You could step the mains down to 5 or 12 volts in a central location in your house, and power the all your low voltage electronics without having to worry about I^2R losses.
    • True. And the conversion from mains to 5 or 12V could be much more efficient if the transformers used to convert the voltages had 0 resistance ;)

      And they could be much smaller.

      Heck, you could fit your 120-to-5V transformer _inside_ your appliance ;) or in the plug of your power cable... Or power bar. Or PSU in your computer.

      Mix this with that battery that can charge in a minute from a few weeks back, and you have cars/iPods/Laptops that plug directly into the wall, charge instantly and don't heat up ;)
      S

      • Re:LEDs (Score:3, Funny)

        by 3waygeek ( 58990 )
        Zero-resistance is the holy grail of electrical systems. I really hope they can do it!

        Of course they'll do it; after all, resistance is futile.
      • A transformer typically has about half its volume in iron and half in wire. Don't expect transformer volume to fall by much more than half.
        • I wonder, though, whether it won't be possible to replace the iron with something else...
          Iron isn't the only ferro-magnetic thing...perhaps something could be created with magnetic properties superior for the purpose of transformers, at least for small ones.

          • Re:LEDs (Score:2)

            by zCyl ( 14362 )
            Iron isn't the only ferro-magnetic thing...perhaps something could be created with magnetic properties superior for the purpose of transformers

            A supermagnetor? :)

  • Superconductivity in nanotubes (Score:3, Informative)

    by karvind ( 833059 ) <karvind@NoSPAM.gmail.com> on Sunday April 17, 2005 @11:20AM (#12262298) Journal
    Article on Physics Web [physicsweb.org] (1999) which explains why carbon nanotubes can be superconducting where as most of the other molecules aren't.

    Two years later Sheng et al demonstrated superconductivity in carbon nanotubes [physicsweb.org]. The experiment was conducted below 20K and the data collected was consistent with the Bardeen-Cooper-Schreiffer (BCS) theory of superconductivity.

    For practical applications one wants the superconducting phenomenon to occur at much higher temperature. A material becomes superconducting when its electrons pair up. Normally such negatively charged particles would repel each other, but in a positively charged crystal structure, vibrations called phonons help them get together. In carbon nanotubes, the frequency of these vibrations is very high, which, in theory at least, means superconductivity at higher temperatures.

    • Mmph. 20K is hardly room temperature, as advertised. Of course, that was 1999, but the linked article doesn't mention ANYTHING about the temperature required.

      If it requires 20 Kelvin, it's not even a high-temperature superconductor, much less one that could work in liquid nitrogen. And THAT'S a long way from room temperature.
  • Well, if anyone needs the visual proof that carbon nanotubes are very electrically conductive, here's a video. [wisc.edu]
  • I had actually read this article yesterday or the day before off of Google News (guess I should have submitted it). I was surprised that it didn't clarify in more detail how this "Near Super Conductivity" works, but I believe I had seen this mentioned years ago and is called "Balistic Conduction" [nih.gov]. There is resistance entering and leaving the Bucky Nano Tube, but near zero resistance as the electron travels down the tube. One might imagine the electrons zipping through the hollow center, though I suspect
  • They've already produced some wires up to 100 meters long--the only thing left to do is figure out how to produce only a certain type of nanotube, the "5,5 armchair nanotube," that conducts so well that it can be considered a superconductor."

    Does the amount of conductivity depend on how you set the little lever on the side of the armchair?

  • The Smalley nanotube effort: the accurate version (Score:5, Informative)

    by dr. loser ( 238229 ) on Sunday April 17, 2005 @02:02PM (#12263317)
    I'm at Rice University, and I can tell you what the real situation is. Smalley has DARPA and NASA money to try to do something he calls continued growth: to take an existing carbon nanotube, and increase its length in a gas-phase chemical vapor deposition process. They are having limited success. Don't go buying your space-elevator stock yet.

    Separately, Smalley and collaborators have been working on spinning fibers from ropes of nanotubes (basically short (less than 1 micron) tubes bundled together by van der waals forces). Those are the fibers that can be meters long. These fibers do not consist of meter-long tubes!

    Finally, metallic nanotubes are not room temperature superconductors. In fact, they are not even ballistic over length scales larger than a micron. Smalley's habit of implying otherwise is really annoying to any physicist who knows anything about these systems.

    Now, a long fiber of only metallic nanotubes would still have conductivity better than copper at much less the weight, and would therefore be very important industrially if it could be made economically. There is a huge difference between that and having no electrical resistance, though.

  • The linked article doesn't seem to say room temperature.

    It's true it does say:
    quantum wires could perform at least as well as existing superconductors--without the need for expensive cooling equipment.

    But that is subject to multiple interpretations, and an earlier post said that his report in 1999 featured data collected at 20 Kelvin. Nitrogen liguifies at about 70K, and Oxygen at about 90K. So that probably means liquid Helium, but not extremely cold Helium. Unless this is based on something else,

  • Maybe someone knows the answer to this (Score:3, Interesting)

    by Gnaythan1 ( 214245 ) on Sunday April 17, 2005 @04:29PM (#12264152)
    If you coil a superconductor into a torus, it sounds like it will loop around the torus forever with no losses. How much electricity can you feed into it? Is the size of the coil a significant factor? If there is an easy way to feed electricity into it, and later pull electricity from it, have we created a perfect battery?

  • DC Mains Power (Score:4, Interesting)

    by JonoPlop ( 626887 ) <meNO@SPAMJonathonMah.com> on Sunday April 17, 2005 @05:41PM (#12264636) Homepage
    If powerlines could have negligible resistance, then it will be viable to transmit power as DC. (At the moment, AC is used to minimize power loss during transmission.) This could mean that devices could plug into a (say) 12V DC outlet right in the wall, eliminating all the heat loss from each individual transformer, and getting rid of the bulk. Imagine, your computer wouldn't need some massive AC-DC power supply! (Obviously it'd still need a small, simple one to transform down to 5V, etc.)

Slashdot Top Deals

The truth of a proposition has nothing to do with its credibility. And vice versa.

Close