London equations

The London equations, developed by the brothers Fritz and Heinz London in 1935, are constitutive relations describing a superconductor's superconducting current in terms of the electromagnetic fields in and around it. Whereas Ohm's law is the simplest constitutive relation for an ordinary conductor, the London equations play the same role for superconducting phenomena and underlie most modern introductions to the subject, including their central role in explaining the Meissner effect, in which a material expels internal magnetic fields as it crosses the superconducting threshold. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/