5 ms·

I’m a noob when it comes to SC. Sorry to ask this question here and hope someone could explain. I can’t get any answer from Google. What is the excitement aroun

I’m a noob when it comes to SC. Sorry to ask this question here and hope someone could explain. I can’t get any answer from Google. What is the excitement around seeing floating magnets? My understanding is that we can have 2 regular magnets float if position them in opposite polarity, right?

ceejayoz 3y ago
Levitation demonstrates the superconductivity, but that's not all it's useful for. https://en.wikipedia.org/wiki/Technological_applications_of_superconductivity https://en.wikipedia.org/wiki/Technological_applications_of_...
golergka 3y ago
Basically, all of the electronical devices humanity uses, from nuclear power plants to smart watches, are about to get efficiency improvements in double digits. This is trillions of dollars per year, and a couple of degrees in average Earth temperature.
- AdamH12113 3y ago
  Unfortunately, this is not even close to correct. Resistive losses in wires are not the only cause of wasted energy, and in most battery-powered devices they aren't very important at all. How is a superconductor supposed to help with e.g. switching losses in a buck converter, or reduce the amount of energy stored in a transistor's gate capacitance?
  - jacquesm 3y ago
    > How is a superconductor supposed to help with e.g. switching losses in a buck converter That one I can answer for you: because it would reduce the time to go from 'on' to 'off' due to the much more rapid flow on account of reduced resistance. The currents in a buck converter can be very high because they are short, but that is also exactly where you'll find the losses: in the transition from 'off' to 'on' and vice versa. So this won't do anything for the MOSFET losses but it could seriously shrink inductor losses and those are the other major factor.
    - AdamH12113 3y ago
      Sure, the inductor conduction losses would go away (and that's a substantial improvement!), but I'm not sure what you're talking about with regard to reducing switching time. I don't think the MOSFET gate drive is limited by the wire that connects to it.
      - jacquesm 3y ago
        It isn't but the capacitor that is sitting on the far end of that circuit is limited by how fast you can pump current in or out. And if your current can go up considerably then the capacitor will charge that much faster and so your losses will be smaller because for the same 'on' duration of the MOSFET you can move more charge. Clearer now?
        AdamH12113 3y ago
        The output capacitor in a buck converter is charged through the inductor, whose current is continuous. I think we must be talking about different things.
whoisburbansky 3y ago
With the regular magnets, you'd have to hold them in places, since otherwise they'd rotate in place and fall back down, attracted to each other.
iefbr14 3y ago
I think they use a shard of the end of an ferrite loopstick antenna to fake the so called levitation. With some help, as seen in the video, it will orient itself in the field lines of the magnet.
mhb 3y ago
No. It is impossible for an ordinary magnet to float freely over any number of other stationary ordinary magnets.
ajnin 3y ago
No, you can't float a regular magnet above another magnet or any number of magnets, that is not stable (it can be proven mathematically). You can float a diamagnetic material but you need at least 2 magnets, it wouldn't be stable with only one either. Note however that in the video the material is not completely floating, one corner is touching, that would be enough to stabilise a diamagnetic material for example so it's not a sufficient proof of superconductivity by itself.

ceejayoz 3y ago

Levitation demonstrates the superconductivity, but that's not all it's useful for. https://en.wikipedia.org/wiki/Technological_applications_of_superconductivity https://en.wikipedia.org/wiki/Technological_applications_of_...

golergka 3y ago

Basically, all of the electronical devices humanity uses, from nuclear power plants to smart watches, are about to get efficiency improvements in double digits. This is trillions of dollars per year, and a couple of degrees in average Earth temperature.

AdamH12113 3y ago
Unfortunately, this is not even close to correct. Resistive losses in wires are not the only cause of wasted energy, and in most battery-powered devices they aren't very important at all. How is a superconductor supposed to help with e.g. switching losses in a buck converter, or reduce the amount of energy stored in a transistor's gate capacitance?
- jacquesm 3y ago
  > How is a superconductor supposed to help with e.g. switching losses in a buck converter That one I can answer for you: because it would reduce the time to go from 'on' to 'off' due to the much more rapid flow on account of reduced resistance. The currents in a buck converter can be very high because they are short, but that is also exactly where you'll find the losses: in the transition from 'off' to 'on' and vice versa. So this won't do anything for the MOSFET losses but it could seriously shrink inductor losses and those are the other major factor.
  - AdamH12113 3y ago
    Sure, the inductor conduction losses would go away (and that's a substantial improvement!), but I'm not sure what you're talking about with regard to reducing switching time. I don't think the MOSFET gate drive is limited by the wire that connects to it.
    - jacquesm 3y ago
      It isn't but the capacitor that is sitting on the far end of that circuit is limited by how fast you can pump current in or out. And if your current can go up considerably then the capacitor will charge that much faster and so your losses will be smaller because for the same 'on' duration of the MOSFET you can move more charge. Clearer now?
      - AdamH12113 3y ago
        The output capacitor in a buck converter is charged through the inductor, whose current is continuous. I think we must be talking about different things.

whoisburbansky 3y ago

With the regular magnets, you'd have to hold them in places, since otherwise they'd rotate in place and fall back down, attracted to each other.

iefbr14 3y ago

I think they use a shard of the end of an ferrite loopstick antenna to fake the so called levitation. With some help, as seen in the video, it will orient itself in the field lines of the magnet.

mhb 3y ago

No. It is impossible for an ordinary magnet to float freely over any number of other stationary ordinary magnets.

ajnin 3y ago

No, you can't float a regular magnet above another magnet or any number of magnets, that is not stable (it can be proven mathematically). You can float a diamagnetic material but you need at least 2 magnets, it wouldn't be stable with only one either. Note however that in the video the material is not completely floating, one corner is touching, that would be enough to stabilise a diamagnetic material for example so it's not a sufficient proof of superconductivity by itself.