Second London Equation, which is supposed to represent the current in a superconductor. (SI units) ∇×j=-(ns e2/m) B. Lets have a look at a super-conducting wire. The magnetic field is: B=μ0Ir/(2πr) Where Ir is the current enclosed by the radius r. We are talking about the current at some depth, not assuming its infinitely thin. The problem is, the second London equation predicts the curl of the current is opposite the magnetic field, which conflicts with the direction of the current initially specified. It would predict a relationship between the magnetic field and current that seems impossible.