Description: Cool a superconductor with liquid nitrogen and a small magnet floats on it due to magnet repulsion.
- Meissner effect apparatus
- Small neodymium magnet
- Dewar flask for LN2
- Safety gloves and tongs
- (Optional) Video Camera
- Fill the flask with LN2.
- If a video camera is requested, connect it to the AV equipment.
- Pour LN2 into the Meissner effect apparatus up to the top of the Styrofoam.
- Using tweezers, delicately place the magnet above the superconductor.
- Note that it will be stationary above the superconductor, for as long as the temperature of the superconductor is below the critical temperature.
Concept: The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. When a superconductor is cooled below superconducting temperature, it prevents any magnetic flux from going through its surface. Since magnetic flux is conserved, the exterior magnetic flux increases to balance the canceling effect within the conductor. The increase in magnetic flux outside of the conductor is what makes the magnet float in this demonstration.
Use caution when working with liquid nitrogen, as it is very cold.