Magnetic Torque on a Rotating Superconducting Sphere

摘要

Using the London theory of superconductivity, the torque on a superconducting sphere rotating in a uniform applied magnetic field is calculated exactly. The London theory is combined with classical electrodynamics for a calculation of the direct effect of excess charge on a rotating superconducting sphere. Classical electrodynamics with the assumption of a perfect Meissner effect is used to calculate the torque on a superconducting sphere rotating in an arbitrary magnetic induction;this "macroscopic" approach yields results which are correct to first order in X/R, where A is the London penetration depth and R is the sphere radius. Using the same approach, the torque due to a current loop encircling the rotating sphere is calculated.