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October 19, 2011
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Joanne Manaster is a university level cell and molecular biology lecturer with an insatiable passion for science outreach to all ages. Enjoy her quirky videos at www.joannelovesscience.com, on twitter @sciencegoddess and on her Facebook page at JoanneLovesScience Follow on Twitter @sciencegoddess.
This video demonstrating the power of superconductivity has been making the rounds this week and is an example of how video is really the best way to capture and share with thousands of viewers the amazing power of science!
You will notice that the video is a demonstration without the science explained live. It was a missed opportunity in my opinion. Thankfully, Tel-Aviv University, who is responsible for the demonstration, has posted an explanation of the Meissner Effect as demonstrated by a liquid nitrogen cooled disc composed of a sapphire wafer coated thinly with yttrium barium copper oxide. Supercondutivity and magnetism are usually in opposition to each other. In this case, where the disc is extremely thin, it’s possible for the magnetic field to penetrate the disc via tiny flux tubes which somehow (biologist hand-waving here) are what’s responsible for the levitation we see over the track. Jump below the video to read their explanation and catch a Quicktime video of the physics.
The video is courtesy of the Association of Science-Technology Centers (ASTC), representing the science center and museum field worldwide. You can follow them on Twitter at @ScienceCenters.
The explanation from Tel -Aviv University’s website:
“Superconductivity and magnetic field do not like each other. When possible, the superconductor will expel all the magnetic field from inside. This is the Meissner effect. In our case, since the superconductor is extremely thin, the magnetic field DOES penetrates. However, it does that in discrete quantities (this is quantum physics after all! ) called flux tubes.
View the Quicktime link to what is happening: Magnetic field expulsion
Inside each magnetic flux tube superconductivity is locally destroyed. The superconductor will try to keep the magnetic tubes pinned in weak areas (e.g. grain boundaries). Any spatial movement of the superconductor will cause the flux tubes to move. In order to prevent that the superconductor remains “trapped” in midair.”
Even if the explanation opportunity was missed in the video, the awe inducing wonder of the demonstration will hopefully capture the attention of non-scientific viewers and intrigue them enough to explore further!
Levitation and Field Lines
Image is courtesy of Tel-Aviv Univeristy http://www.quantumlevitation.com/levitation/The_physics.html
About the Author: Joanne Manaster is a university level cell and molecular biology lecturer with an insatiable passion for science outreach to all ages. Enjoy her quirky videos at www.joannelovesscience.com, on twitter @sciencegoddess and on her Facebook page at JoanneLovesScience Follow on Twitter @sciencegoddess.
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The effect is really amazing! How can he hold a liquid nitrogen cooled superconducting disc in his bare hands?
Link to thisPeople can briefly hold an object that has been frozen in liquid nitrogen (or dunk their hand or pour it over their skin) because of a phenomenon called the Leidenfrost Effect. The natural warmth of the body helps create an insulating vapor layer on the skin when a much cooler liquid encounters it, so brief handling of very cold substances are possible. This effect is lost if the skin is wet or if the skin is exposed to the cold for much too long.
Link to thisRe: 2. Don’t try this at home kids!
Link to thisAre you sure? Looks more like insulating effect of the frost on the puck.
Link to thissciencegoddess. In your explanation of the Leidenfrost Effect, it is the moisture in your hand that provides the protection, so some water in necessary, but too much and the water will freeze you to the object as anyone who has tried the tongue to cold metal pole has found out. You can touch the same pole with your hand. In the case of liquid nitrogen, it is the evaporating nitrogen that provides the insulating layer. I have tried all these experiments. I do not recommend the tongue to pole one. It is however a test of patience, pain tolerance, and the hotness of your breath as you try to warm up your tongue and the pole. It took several minutes in the experiment I conducted. It also leads to thoughts of “idiot” and that some theories should not be tested.
Link to thisActually freezing isn’t the Leidenfrost effect, so I don’t see where the insulating vapour is coming from when he is handling the puck. It is the insulating frost that is protecting him, and if directly on the liquid nitrogen temperature puck directly, the contact would have to be very brief and low thermal conductivity of the skin would afford some protection as long as the hand is not wet.
Link to thisJoanne loves science and I love Joanne
Link to thisInteresting………
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