Re:Maybe someone knows the answer to this
on
Quantum Wires
·
· Score: 1
yes, you can create a perfect battery with a superconducting coil but between the need for cooling and the limitation on current density it isn't yet practical.
Re:really a superconductor?
on
Quantum Wires
·
· Score: 1
> Maybe you could give it a tail like a Q > (depending, of course, on your font), and pump > it up through the tail.
Thinking about it a bit more it seems likely that the tube contains a fixed number of "conduction band" electrons per unit length. You couldn't just pump electrons in via your Q tail: that isn't how current works.
> Hyperconductor, perhaps?
Ultraconductor.
Re:really a superconductor?
on
Quantum Wires
·
· Score: 1
> 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? Something well short of the speed of light, I presume. There also must be a limit on the number of electrons per unit length of tube, so there must be a hard upper limit on current density.
Re:EMR from high tension power lines?
on
Quantum Wires
·
· Score: 2, Informative
> 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 true. According to UL it takes more than 5 milliamperes to be dangerous and your skin resistance is too high to permit that much current to flow at a potential of "a few volts". Try grabbing both posts of a car battery.
>...it locks your muscles and thus causes you to > continue to hold on to the wire that you grabbed > in the first place.
60Hz will do that as well if the current is sufficient, and 60Hz is actually slightly more likely to stop your heart than DC.
> Hence why all electric fences in the united > states are required by law to be pulsed...
Pulsed or limited to less than 5ma of current. Current-limited fencers are sometimes sold as "pet fencers" but only fools and the ignorant will buy them. They are ineffective on large animals but will kill very small ones.
> Unable to let go, the would take many minutes > to die from low-voltage current.
There are basically two ways to die from electrocution: heart failure and severe burns from very high current. The former can happen at 120V but the latter usually involves tangling with transmission lines.
> I suspect that if the wire is in a magnetic > field it will lose it's superconductivity > - thus it wouldn't work in an electric motor.
1) Superconductors only lose their superconductivity when exposed to a field strength in excess of the threshold for the material they are made of. Superconductors are, in fact, used to produce extremely strong magnetic fields for things like MRI machines. Motors and generators (some very large) _have_ been made with them and they have real advantages: they are just not cost effective in most applications.
2) We are not talking about superconductors. I see no reason why ballistic ultraconductors should not work in high magnetic fields.
Both are *REAL* superconductivity. This is something else. I propose we call it ultraconductivity, for no good reason at all.
Re:really a superconductor?
on
Quantum Wires
·
· Score: 2, Informative
> 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.
Re:EMR from high tension power lines?
on
Quantum Wires
·
· Score: 1
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 transmission lines where it is cost-effective but high-power high-voltage DC-DC converters are _much_ more expensive than transformers.
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.
The EMI comes from corona discharge and arcing. Changing to DC would not reduce it at all. You _would_ hear it less on your AM radio because it would not be modulated at 120Hz (it would most likely be modulated at 360Hz but at a much lower amplitude).
Re:EMR from high tension power lines?
on
Quantum Wires
·
· Score: 3, Interesting
> 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.
> If you use this tool... there are those who > would assert you are not holding up your end of > a "social contract"
None of the ad-supported sites that I occasionally visit advertise anything I want. How is blocking ads I am never going to click on for products I am never going to buy breaching some purported contract? Or am I contractually obligated to buy crap I don't want?
> Since you do not have to pay FICA, Medicare, or > income taxes on the capital gains associated > with stock sales, they stand to substantially > decrease their tax burden.
This is true. One does not pay taxes on income that one does not receive.
> Is this a breech of the company's "do no evil" > mission statement...
Sigh. If they had kept their salaries they would have received salary income, paid taxes on it, and _also_ made money on stock sales. Now they will only make money on stock sales (and pay the relevant taxes). How is the latter more "evil" than the former?
>...or just an example of people who love their > jobs so much they don't need to be paid to go > to work?"
It is an example of how some people have chosen to manage their money. I know damn well that if you could rearrange your income so as to increase the amount left after taxes you would.
> This ruling has the unusual effect of > ambivalence.
No it doesn't. It is a straightforward interpretation of trademark law. Companies should not be allowed to treat trademarks as though they were copyrights. No one can own a simple string of letters.
Since it is "field trash", it may be economical in small scale. You need to compare the generated energy with the more fertilizer you will need for the next crop and see if it is better. My guess is that for corn it will be, but for soybean it will not because of the little amount of trash generated.
The primary reasons for leaving trash on the field are erosion control and tilth improvement. The minerals returned are a minor factor. The whole plant is used for silage, and some dairy farmers bale stalks for bedding and even forage.
Short-season corn (maize for you Europeans) might compete with grass and legumes as a fuel crop.
> Don't alfalfa fields get 2 or 3 cuttings minimum > per season?
Depends on the climate, among other things. Here in Wisconsin I get three cuttings a year of my mixed alfalfa/brome, but I am trying for an optimum combination of nutrition for horses, tonnage, and stand life. Many of my neighbor dairy farmers cut their pure alfalfa every 28 days. This gives them higher protein at the price of slightly lower tonnage and shorter stand life. If I was growing hay for fuel I would be trying to maximize dry weight without concern for nutritional value and would choose what to plant and how to harvest it on that basis.
> I don't see any studies coming out asking "Why is > the percentage of women so low amongst asphalt > pouring crews" or anything like that. I also > don't see any studies asking whey more men aren't > going into nursing.
Slashdot Mirror
yes, you can create a perfect battery with a superconducting coil but between the need for cooling and the limitation on current density it isn't yet practical.
> Maybe you could give it a tail like a Q
> (depending, of course, on your font), and pump
> it up through the tail.
Thinking about it a bit more it seems likely that the tube contains a fixed number of "conduction band" electrons per unit length. You couldn't just pump electrons in via your Q tail: that isn't how current works.
> Hyperconductor, perhaps?
Ultraconductor.
> 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? Something well short of the speed of light, I presume. There also must be a limit on the number of electrons per unit length of tube, so there must be a hard upper limit on current density.
> The electronics revolution has given us the
...it locks your muscles and thus causes you to
> 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 true. According to UL it takes more than 5 milliamperes to be dangerous and your skin resistance is too high to permit that much current to flow at a potential of "a few volts". Try grabbing both posts of a car battery.
>
> continue to hold on to the wire that you grabbed
> in the first place.
60Hz will do that as well if the current is sufficient, and 60Hz is actually slightly more likely to stop your heart than DC.
> Hence why all electric fences in the united
> states are required by law to be pulsed...
Pulsed or limited to less than 5ma of current. Current-limited fencers are sometimes sold as "pet fencers" but only fools and the ignorant will buy them. They are ineffective on large animals but will kill very small ones.
> Unable to let go, the would take many minutes
> to die from low-voltage current.
There are basically two ways to die from electrocution: heart failure and severe burns from very high current. The former can happen at 120V but the latter usually involves tangling with transmission lines.
> I suspect that if the wire is in a magnetic
> field it will lose it's superconductivity
> - thus it wouldn't work in an electric motor.
1) Superconductors only lose their superconductivity when exposed to a field strength in excess of the threshold for the material they are made of. Superconductors are, in fact, used to produce extremely strong magnetic fields for things like MRI machines. Motors and generators (some very large) _have_ been made with them and they have real advantages: they are just not cost effective in most applications.
2) We are not talking about superconductors. I see no reason why ballistic ultraconductors should not work in high magnetic fields.
Both are *REAL* superconductivity. This is something else. I propose we call it ultraconductivity, for no good reason at all.
> 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.
> 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.
> 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?
> If you use this tool ... there are those who
> would assert you are not holding up your end of
> a "social contract"
None of the ad-supported sites that I occasionally visit advertise anything I want. How is blocking ads I am never going to click on for products I am never going to buy breaching some purported contract? Or am I contractually obligated to buy crap I don't want?
They are, but so are the media companies.
> Makes you wonder where your tax information is
> going...
To the IRS. Via USPS. Only an idiot would file his tax return via the Web.
> I'm not sure what they're afraid of from
> genetically modified rice.
They are afraid that the anti-GM loons will launch a scare campaign about how drinking Bud will cause your kids to have three eyes.
> And if we did, would there be any way to protect > the planet?
Half of the planet would be protected by the mass of the planet itself, of course.
> Since you do not have to pay FICA, Medicare, or
...or just an example of people who love their
> income taxes on the capital gains associated
> with stock sales, they stand to substantially
> decrease their tax burden.
This is true. One does not pay taxes on income that one does not receive.
> Is this a breech of the company's "do no evil"
> mission statement...
Sigh. If they had kept their salaries they would have received salary income, paid taxes on it, and _also_ made money on stock sales. Now they will only make money on stock sales (and pay the relevant taxes). How is the latter more "evil" than the former?
>
> jobs so much they don't need to be paid to go
> to work?"
It is an example of how some people have chosen to manage their money. I know damn well that if you could rearrange your income so as to increase the amount left after taxes you would.
> This ruling has the unusual effect of
> ambivalence.
No it doesn't. It is a straightforward interpretation of trademark law. Companies should not be allowed to treat trademarks as though they were copyrights. No one can own a simple string of letters.
> Don't alfalfa fields get 2 or 3 cuttings minimum
> per season?
Depends on the climate, among other things. Here in Wisconsin I get three cuttings a year of my mixed alfalfa/brome, but I am trying for an optimum combination of nutrition for horses, tonnage, and stand life. Many of my neighbor dairy farmers cut their pure alfalfa every 28 days. This gives them higher protein at the price of slightly lower tonnage and shorter stand life. If I was growing hay for fuel I would be trying to maximize dry weight without concern for nutritional value and would choose what to plant and how to harvest it on that basis.
> Just like I can shop elsewhere if I don't like
> being captured on a store's video surveillance
> camera.
Yes. You can. Contrary to common belief, your choices are not limited to Walmart and Kmart.
Get a patent on HTTP.
> I remember a professor here at CMU saying that
> you could do localization for forklifts by
> pointing a camera at the floor.
You could use the guts of an optical mouse for that.
> I don't see any studies coming out asking "Why is
> the percentage of women so low amongst asphalt
> pouring crews" or anything like that. I also
> don't see any studies asking whey more men aren't
> going into nursing.
You aren't looking very hard.
...When I can't get past the first page.
The thing is broken.