4 ms·
Right, if our best regular conductors (used in your ohmmeter) are ~10^-8 and superconductivity is (by convention) less than 10^-11, one can see right away the s
by frisco 3y ago
Right, if our best regular conductors (used in your ohmmeter) are ~10^-8 and superconductivity is (by convention) less than 10^-11, one can see right away the simple regular methods won’t work and some cleverness is needed.
- someplaceguy 3y ago> superconductivity is (by convention) less than 10^-11, Ah, so you're saying that superconductivity is not actual zero resistance, but something close to it, and in fact only a factor of 1000x less resistive than the best conductor? If that is so, this is something that I had previously thought would make a lot more sense to me. But in that case it's not intuitive to me how SMES is possible with a 0% discharge rate. Shouldn't a significant fraction of the electrons looping around the coils be lost after many loops? (I know very little about electricity, as you can probably tell, never mind superconductors).
- mort96 3y agoNo, I believe it's literally zero but we don't have a measurement apparatus with infinite precision so we need some cut-off.
- someplaceguy 3y agoThanks, that makes sense.
- deleted 3y ago[deleted]
- fooker 3y agoIt's only literal zero for superconductors close to 0K temperature. For high temperature superconductors (50-70+K), it's not literal zero for superconducting mechanisms discovered so far.
- crote 3y agoThe conductors of your ohmmeter are not that important, though. You can work around that by using four-terminal sensing, and you can of course also calibrate your probes by directly touching them together. Even if your ohmmeter conductors have a resistance of several ohm, you could still get an accurate measurement if your tool has a high enough resolution. A bigger issue is going to be sample size. A 1mm-diameter 1mm-long rod of silver has a resistance of about 20 μΩ (or 2e-5) at room temperature. That's already getting tricky to measure with lab-grade equipment without pushing insane currents through it, let alone anything even smaller. If you want to measure a 1m-diameter 1m-long silver rod (which would be 0.02μΩ or 2e-8) you could just push a few thousand amps through it and reliably measure that using a household multimeter in the mV range - but do that with a small sample and it'll evaporate.
- jacquesm 3y ago> Even if your ohmmeter conductors have a resistance of several ohm, you could still get an accurate measurement if your tool has a high enough resolution. Not that low in range though, you will end up seeing thermal noise that dwarfs your measurement.
- dclowd9901 3y agoHow about the wires connected to your probes? Or the internal electronics that are used to gauge resistance? How do you work around those?