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Pushing 800W of Wireless Power at 5 Meters
Joe Decker writes "The Nevada Lightning Laboratory has experimented with Nicola Tesla's methods of wireless power transmission to push 800 Watts over 5 meters, besting MITs mark of 60W over 2 meters last year. (May I dream of wireless laptop power? I hate power cords.)"
The Mythbusters tried the metallic ink in an MRI myth. There isn't enough metal in the ink to have any sort of effect at all. The person with the tattoo who had the MRI said that there was no pain or heat or anything.
A metal plate might do something, though.
Learn something new.
Nope. Standing-wave microwaves are absorbed by water molecules, and re-radiated as heat.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
Wrong way. The power should decrease with the inverse of the square. 2/5 = 0.4, 0.4^2 = 0.16.
So 60*0.16 = 9.6W at 5m.
That's an increase of nearly a hundredfold.
Though I am not an electrical engineer / physicist and I don't know if the inverse square law is necessarily applicable.
Tasers operate at extremely high voltage and extremely low current. This is why, they must be in contact with the target and preferably penetrating the skin to overcome the natural resistance of human skin. The farther an arc travels over the preposterously high resistance of an air gap the more current required. The more current that is involved the more likely that the target will be killed as opposed to stunned.
The amount of current required to deliver 95,000 volts across a 6' air gap is sufficient to produce lightning strike like effects on the target.
You clearly do not know anything about Cyrillic. The 'H' you refer to is actually an 'n' and the backwards 'N' is actually a 'i' type sound. The 'C' is an 's'.
The MIT group is not proposing to use omnidirectional (or directional) radiative energy transfer, which indeed would radiate most of the energy into the environment, and only a small fraction into the receiver, and even that could be eliminated if something (e.g. a person) walks between the source and receiver.
They are proposing non-radiative resonant energy transfer, in which both the source and receiver are resonant oscillators at a particular frequency coupled via the near field (non radiatively), and hence preferentially transfer energy compared to anything else that is not resonant (with a long lifetime) at the same frequency. Furthermore, they are using resonators that only couple through their magnetic fields (the electric fields are largely within capacitors inside the device), which further reduces absorption of energy by the environment (because most materials are non-magnetic, energy dissipation is largely via ohmic heating, i.e. by the electric fields). Because of this, almost all of the losses take the form of resistive heating in the devices themselves; only a miniscule fraction is dissipated in the surrounding environment (e.g. a person).
Of course, this being Slashdot, it's not surprising that most posters never RTFAed and post nonsense "it's just like an inductive transformer" (nope, those don't use resonance) or "it's just like an antenna" (nope, that is radiative transfer) or "Tesla looked at this a century ago" (nope, people like Tesla were concerned with power transfer over long distances, which necessitates radiative mechanisms and hence low efficiency).
If a thing is not diminished by being shared, it is not rightly owned if it is only owned & not shared. S. Augustine
When I was in the Canadian Military we had a sat dish we could hook up to our PABX in the field, and it stated in the manual that you should not stand in front of the thing when it was operational or the transmitted signal from it "might cause sterility" or something to that effect. It had a hazard sticker on it that should have warned people to stay clear. Try as we might we couldn't get people to stop walking in front of it (even if we put up a tape barrier, people would just step over it rather than walking the 8 feet or so required to go around it).
In the end I had to sketch up a sign of someone with their balls being blown off their body and large letters warning "RADIATION HAZARD - SAY GOODBYE TO YOUR CHANCE TO EVER HAVE KIDS" and post it over top of the dish where it was clearly visible. That and the tape finally got people to stay out of the hazardous area.
"The first time I got drunk, I got married. The second time I bought a chimpanzee, after that I stayed sober" Arian Seid
Cell phones, cordless phones, and remotes might also be good to charge via this method as well.
Heck, making AA, AAA, C, and D sized "batteries" that just receives "wireless power" from the "wireless transmitter" would let you power some of those kids toys for as long as you have the wireless transmitter plugged in. That would be much better than running down the batteries really quickly and then either having to recharge or get new ones.
You don't need 800W to charge a couple of small batteries. The "problem" that you describe is already solved with inductive power. Most electric tooth brushes with batteries work on this principle.
The audible snapping and popping likely has nothing to do with RF radiation from the lines. High tension power lines actually get a DC charge on them from capacitance between the conductor and ground, and the snapping and popping is from ionic discharge (artificial lightning).
Although it *is* an electrical field, it is a static field that does not radiate RF energy. It can not be harvested inductively and therefore it has nothing to do with what some people are paranoid about.
Isn't this how smart cards work already?
;)
I thought that smart cards had a tiny chip on them with no power supply, they get the energy to perform the transaction from the antenna built into the card when it's held over the point of sale device.
Which gives it just enough juice to perform the job at hand and then go back to sleep when the card it put away. So we already use it and need it to survive
Personally I welcome our new wireless power overlords......
I was talking about the MIT group (who explicitly discuss the differences between what they are doing and what Tesla considered), not the group in the article here. And you're right that Tesla also looked at non-radiative schemes for very short distances, e.g. Tesla coils, but at the time of Tesla most of the interest was in long-range power delivery (which never worked out because of the problems with radiative transfer, and in any case such schemes were supplanted by the wired electrical grid).
Tesla coils involve large electric fields between the source and receiver device, and so (a) are quite different from the magnetically-coupled resonators the MIT group proposes and (b) are impractical for the short-distance power-delivery applications considered here because they can dissipate too much energy into the environment.
If a thing is not diminished by being shared, it is not rightly owned if it is only owned & not shared. S. Augustine
As TFA cleary states, far fields decrease in power linearly, not by the inverse square, to the distance. Wires also lose power linearly.
But why should you bother considering the actual problem and solution? You already know everything that can be known about electric transmission.
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make install -not war