If oxygen can be oxidised rather than copper, there is a slightly different explanation as things happen slightly differently. However, as Sr is added to the lattice the whole flavour of the atom changes. This strained chain is to blame for superconductivity. The electron is pushed toward an atom, and if this atom happens to be an ion, it will grab an electron from its neighbours cloud. This takes less time than carrying out the experiment experimentally.
Positive currents move to the right, negative currents move to the left.
The Cu has a coordination number of eight and is bonded to six O atoms. This causes the atom to rattle back and forth in the lattice. In 1986 high temperature superconductors were born. A moving electron is flying compared to the motion of the heavier ions. Once the passing electron has moved sufficiently far away the d orbitals pop back into place.