Specifically, this compound was developed. It contains yttrium, barium, copper, and the seven minus n next to the oxygen means that there are seven or fewer oxygen atoms associated with this compound, depending on what kind of oxidation states find themselves in. >> But this material is a superconducting ceramic. >> Now to say more about the importance of that is to say a little bit more about what superconductivity if you run a current of electricity through a wire, and then if you were foolhardy enough to touch the wire, you'd notice that it was pretty hot. That he comes from the current of electricity encountering electrical resistance as it flows with a y. >> If you like, you can think of it as the friction that's created when the electrons come in contact with the material the wires made up. >> Now, even though metals are good conductors of electricity, they still have some electrical resistance. So when you're trying to conduct energy through that wire, some of it gets lost in the form of a superconducting material conducts electricity without any loss of energy due to heat. Now, for awhile, it was believed that superconductivity was only possible at extremely low temperatures when the phenomenon was first discovered by a Dutch scientist by the name of Henry camera. >> Really honest, suffice it to say that he needed liquid helium. >> Temperature is approximately four Kelvin to be able to make this happen. So for a long time, it was believed that this was only possible at extremely low temperatures until this material was discovered. And it was found that it became superconducting at still low temperatures, but a somewhat higher temperature than the others. >> It's so-called transition temperature. The point at which it becomes superconducting is about 90 Kelvin. >> Now the significance of that is that liquid nitrogen is at a temperature 77 kilohertz. >> So liquid nitrogen, which is much cheaper than liquid helium, is able to make this material superconductor. >> And that's what I want to demonstrate to you for our second demonstration today. Let's zoom in on what we have here. Look at what's going on here. >> Alright, it's hard to see the pellet because there's all kinds of tape on top of it. >> But this black material over here is the superconducting material. Except it's not superconducting right now because we haven't cooled down to low temperatures. >> Sitting on top of that, we had a little samarium cobalt magnet, which is a small but strong magnet like this. >> You are commonly used in various electronic components in people used to listen to music and stuff like that. >> But suffice it to say for right now, just a strong magnet. And what I want to demonstrate to you is a phenomenon called the Michener effect Now suffice it to say that what this means is that when the material becomes superconducting, it will not allow a magnetic field to pass through it. >> Now, if I take a piece of paper and just try to write, now, slide it between the pellet and the magnet. You can see that I nudge the magnet across. >> And obviously I can't just slide the piece of paper between the pellet and the magnet, because the pellet with magnets sitting on top of them. >> But what I'm gonna do is, or myself some liquid nitrogen that I had leftover from earlier in the week. >> And part of the reason we have this set up on a Styrofoam cup, like you can see here is because when I pour the liquid nitrogen on top of this, then the lip of the Styrofoam cup should hold it in place long enough for the pellet to become superconducting, that he's going to take about a minute or so to just be a little patient here. >> But the point is when the palate becomes superconducting, then hopefully it will exclude the magnets magnetic field, which means the magnet should levitate off the pallet load above it. Not a huge distance, but that's why we're zooming in here to give you a better work than what you might get otherwise. >> See if we're there yet. >> And if I take this piece of paper notebooks still sitting, and ponder a little bit more liquid nitrogen. >> Let's try it now. >> As you can see, I can in fact find a piece of paper in-between the magnet in the pellet with no problem, because the pellet is actually floating above the surface of the magnet. >> That fear on screen. >> Okay, that's the phenomenon called the bystander effect when it's brought about by the superconducting properties of the material in question. Applications of this phenomenon include the possibility developing things like railroad train their ranks and therefore don't lose anywhere near as much energy to friction or electrical resistance or anything like that. >> Anyway, phenomenon called my further alright.
Meissner Effect.mov
From Dana Chatellier March 03, 2020
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