Eddy Currents and Supercurrents in Rotating Metal Spheres at Liquid Helium Temperatures

These experiments show that large eddy currents are set up in a tin sphere rotating at 4.6 or more revolutions per second in the earth's magnetic field and at 3.8^∘{}K. Within experimental determination, the eddy currents have the same magnitude and distribution on the sphere as the supercurrents which cause the Meissner effect at 3.7^∘{}K. These results are in accord with classical electromagnetic theory for a normal conductor and with the London theory for a superconductor. The Meissner effect has been produced in bulk tantalum metal by rotating the specimen while cooling through the superconducting transition temperature.