The meissner effect pdf

Precautions 1. When pouring liquid nitrogen please be careful to prevent any splashing. Conduct the experiments in a well-ventilated room. Do not touch any items immersed in the liquid nitrogen with your hand until they have warmed to room temperature.

Use the provided tweezers to add and remove items from the liquid nitrogen. This experiment can also be conducted by placing the magnet on top of the superconductor before it is cooled in liquid nitrogen. As predicted by the Meissner Effect, the magnet will levitate when the temperature of the superconductor falls below its Critical Temperature. As explained earlier, there is no material other than a superconductor which could have shown this effect. If you carefully set the magnet rotating, you will observe that the magnet continues to rotate for a long time.

This is a crude demonstration of a frictionless magnetic bearing using the Meissner Effect. The rotational speed of a cube-shaped magnet can be increased by using a plastic drinking straw to blow a stream of air at one of the edges or corners of the cube. Another way to increase the magnet's rotational speed is to cut out a small rectangular hole in a piece of paper.

The hole is positioned over the levitated magnet such that half of the magnet projects above the plane of the paper. A stream of air directed along the upper surface of the paper will cause the magnet to rotate rapidly. The cubical magnet naturally is slowed by the resistance of air. Consequently, it can be expected to stop after a while.

A cylindrical magnet will rotate for much longer since it is rotationally streamlined. However, the cubical magnet makes this demonstration much more graphic. A research group at Cornell University has demonstrated a frictionless superconducting bearing that can turn at a rate of one million rotations per minute. All Kits from Colorado Superconductor Inc. Both superconductors exhibit the Meissner Effect, however, if the disks are carefully removed from the liquid nitrogen bath, while magnet is still levitated, the bismuth-based material will continue levitating the magnet for a considerably longer time than the yttrium-based superconductor.

This is because the bismuth-based superconductor has a significantly higher Critical Temperature than to the yttrium-based one. Some Questions 1. Why does the liquid nitrogen boil when you pour it into the dish? Why does it boil when you put the superconductor disk into it? When the nitrogen has evaporated, the magnet stays levitated for a short while longer. Why is this so? Can you think of any other experiments using this fact? If you push the levitated magnet with the tweezers so as to move it across the superconductor, it will resist movement.

Why does this happen? How can you improve the operation of the model frictionless bearing in your Kit? Think of a gallon jug, filled with water, that has a small pin hole in the bottom. The jug is the superconductor, the water is the magnetic field. This superconducting material will not allow a magnetic field to pass though it, in much the same way the jug will not allow the water to pass though it.

However, the tiny non superconducting regions will allow the magnetic field to pass though, in the same way the pin hole in the jug allows the water to pass though.

The string in this case is the magnetic field, and the weight is the superconductor. Meissner Effect Demonstration The procedure below, will guide the experimenter through a demonstration of the Meissner Effect in a cookbook fashion, step by step. The shallow dish-like depression in the styrofoam container for the kit, or a third of an inch high portion of the bottom of a styrofoam coffee cup, can be used for holding liquid nitrogen for the experiment.

To project a sharp image of the Meissner Effect with an overhead projector, use a very small dish so that the levitated magnet is less than an inch from its glass plate. Procedure 1. ACTION: Carefully pour a small amount of liquid nitrogen into the dish or styrofoam cup until the liquid is about a quarter of an inch deep.

Wait until it stops boiling. ACTION: Using the provided tweezers, carefully place the black superconductor disk flat in the liquid until its top is just flush with the surface of the liquid nitrogen. Wait until this boiling stops too. ACTION: Again using the tweezers, pick up the provided magnet, and attempt to balance it on top of the superconductor disk.

This is a demonstration of the Meissner Effect. Precautions 1. When pouring liquid nitrogen please be careful to prevent any splashing. Conduct the experiments in a well-ventilated room. Do not touch any items immersed in the liquid nitrogen with your hand until they have warmed to room temperature. Use the provided tweezers to add and remove items from the liquid nitrogen.

This experiment can also be conducted by placing the magnet on top of the superconductor before it is cooled in liquid nitrogen.

As predicted by the Meissner Effect, the magnet will levitate when the temperature of the superconductor falls below its Critical Temperature. As explained earlier, there is no material other than a superconductor which could have shown this effect. If you carefully set the magnet rotating, you will observe that the magnet continues to rotate for a long time. This is a crude demonstration of a frictionless magnetic bearing using the Meissner Effect. The rotational speed of a cube-shaped magnet can be increased by using a plastic drinking straw to blow a stream of air at one of the edges or corners of the cube.

Another way to increase the magnet's rotational speed is to cut out a small rectangular hole in a piece of paper. The hole is positioned over the levitated magnet such that half of the magnet projects above the plane of the paper. A stream of air directed along the upper surface of the paper will cause the magnet to rotate rapidly.

The cubical magnet naturally is slowed by the resistance of air. Consequently, it can be expected to stop after a while. In both cases the details of the interaction between the magnet and superconductor are complicated and cannot be fully explained by classical physics. Check out this video of the demo in action. The superconducting disc sits in the bottom 5mm segment of a Styrofoam cup, which itself rests on a whole inverted cup; this is well insulated as well as providing a white backdrop for the YBCO disc and the neodymium magnet.

Place the magnet on the disc. The YBCO and the magnet should only be handled with tweezers. Use a camera with a macro lens to compose a shot of the interior of the cup. Slowly pour the liquid nitrogen into the cup so that it barely immerses the disk; the YBCO will transition suddenly to superconducting after about seconds, at which time the magnet will rise about 7mm above the disc.

This is a commercially available ceramic superconductor. Purcell, Edward and David Morin.