Editing Meissner Effect

{| class="wikitable" style="color:black; background-color:#ddd; margin-left: auto; float:right"
| [[Physics]]:
| Meissner Effect, Superconductive Materials
|-
| Grade Range:
| [[Middle School]], [[High School]]
|-
| Format:
| [[Hands-on]], [[Stage]]
|}



== Materials ==

* YBCO Superconductor Disk
* Superconducting Wire
* Liquid Nitrogen
* Petri Dish
* Tweezers
* Small Neodynium Magnet
* Copper Wire for Comparison

== Safety Precautions ==

Please read the Cryogen Safety section of the [[Demonstration Safety]] page before performing this demonstration.

This demonstration requires: safety glasses, cryogen gloves, small blast shield

== Demonstration ==

*''Note: this demonstration is performed the same way for a hands-on event or a stage show. For a stage performance, you will want to include a desktop camera & projector to make it more visible to the audience.''

# Set the Superconductor in the petri dish. Put on the safety glasses and cryogen gloves, and pour liquid nitrogen into the petri dish, slowly adding more in until it stops rapidly boiling out.
# Pick up the magnet using the tweezers, and carefully place it above the superconductor. It will float in the air above the superconductor! You can show that the magnet can be re-positioned at different angles and stays suspended, so long as the superconductor is cold enough!
# Mention that superconductors can conduct large amounts of electricity with very little resistance. Show the copper wire next to the superconducting wire, and explain how they are comparable to the superconductor in your petri dish!

== Why This Works ==

===Short Explanation===
''Superconductors'' are materials that are able to send large amounts of current with very little or no resistance. This property makes them ideal for laboratories where they use huge amounts of electricity, since it lets them use all of the current and not lose much of it to the wire heating up or resistance in the wire. This tiny superconducting wire, when cooled, is able to carry the same amount of current as the giant copper wire next to it! 

When a material starts superconducting, it will resist outside magnetic fields in order to stay superconducting. This means that we can put a magnet above the superconductor, and the superconductor will create a magnetic field to resist the magnet, causing it to float! This unique property to resist electromagnetic fields is known as the ''Meissner Effect''

===Full Explanation===

Yttrium barium copper oxide (YBCO) is a ceramic high temperature superconductor. "High temperature" in this case means that it starts superconducting at 90K, which means liquid nitrogen can work since it boils at 77K. This makes YBCO much easier to use than other superconductors, most of which need to be cooled to 23K or below. ''Superconductors'' are materials which, when cooled below a certain temperature, start to exhibit very low or near zero resistance when a current is run through them. This property makes superconductors extremely useful in several research and industrial applications, where large currents normally need to be sent through thick wires to compensate for the loss due to resistance. By using superconductive materials, one can run a comparable current through a much smaller wire, as included with this demonstration, and get the same output as the massive copper wire next to it! YBCO is an extremely useful superconductor since it can be cooled with liquid nitrogen, which is inexpensive, unlike typical superconductors which need to be cooled with liquid helium.

When a material starts superconducting, it also becomes perfectly ''Diamagnetic'', meaning the total magnetic field is zero inside of them. This means that, if you put a superconductor within a magnetic field, the superconductor will resist it by generating an opposite magnetic field. This unique property of superconductors not only plays into why they are superconducting, but also explains how the ''Meissner Effect'' works. When a magnet is placed near the superconductor, the magnetic field from the magnet pushes on the superconductor. The superconductor will then generate an opposing magnetic field, which dispels the magnet's field and magnetically "locks" it in place. This results in the magnet being levitated above the superconductor, unable to fall out of the position on its own! If the superconductor were to be picked up and moved around, the magnet would stay locked in the position above it the whole time!

== Additional Information ==

* This demonstration pairs well with the [[Liquid Nitrogen]] demos, as well as the [[Accelerators]] demonstration.
* This demonstration is a part of the [[Nuclear Physics Show]]