Understanding Resistivity in Superconductors

[TWest]

What is the Resistivity of YBCO in superconductive state because it is not zero, or there would be not heat created so what is it or am I wrong? Explain to me where the heat from a current passing into a superconductor comes from.

 

[f95toli]

The DC resistivity for YBCO in the SC is indeed zero.
The AC resistivity is not equal to zero, meaning there will some dissipative losses, but this is mainly an issue at quite high frequencies, i.e. microwave frequencies and above (this is true for all superconductors).

I am not sure what "heat" you are referring to. There are situations where e.g. cable might warm up if you pass too much current through it, but this a "non-ideal" situation where the heat could be generated from e.g. weak-links formed across high-angle grainboundaries going normal; flux moving between pinning sites can also cause dissipation.
However, these effects don't really have anything to do with superconductivity as such; it is more of a materials science issue.