Thermodynamic Explanation of the Meissner-Ochsenfeld Effect in Superconductors

The thermodynamic principle of superfluid flow – that the energy is minimized at constant entropy – is applied to superconducting currents to derive the Meissner-Ochsenfeld effect in which magnetic fields are expelled from superconductors. The principle gives a modified form for the first London equation that does not trap magnetic fields within a superconductor. The physical mechanism by which a critical magnetic field destroys superconductivity is identified.