  The law of entropy increase postulates the existence of irreversible
processes in physics: the total entropy of an isolated system can increase but
cannot decrease. The annihilation of an electric current in normal metal with
the generation of Joule heat because of a non-zero resistance is well-known
example of irreversible process. The persistent current, an undamped electric
current observed in a superconductor, annihilates after the transition into the
normal state. Therefore this transition was considered as irreversible
thermodynamic process before 1933. But if this transition is irreversible then
the Meissner effect discovered in 1933 is experimental evidence of a process
reverse to the irreversible process. Belief in the law of entropy increase
forced physicists to change their understanding of the superconducting
transition, which is considered a phase transition after 1933. This change has
resulted to the internal inconsistency of the conventional theory of
superconductivity, which is created within the framework of reversible
thermodynamics but predicts Joule heating. The persistent current annihilates
after the transition into the normal state with the generation of Joule heat
and reappears during the return to the superconducting state according to this
theory and contrary to the law of entropy increase. The success of the
conventional theory of superconductivity forces to consider the validity of
belief in the law of entropy increase.
