The Little–Parks effect consists in a periodic variation of the T c with the magnetic flux, which is the product of the magnetic field (coaxial) and the cross sectional area of the cylinder. T c depends on the kinetic energy of the superconducting electrons. More precisely, the T c is such temperature at which the free energies of normal and superconducting electrons are equal, for a given magnetic field. To understand the periodic oscillation of the T c, which constitutes the Little–Parks effect, one needs to understand the periodic variation of the kinetic energy. The kinetic energy oscillates because the applied magnetic flux increases the kinetic energy while superconducting vortices, periodically entering the cylinder, compensate for the flux effect and reduce the kinetic energy. Thus, the periodic oscillation of the kinetic energy and the related periodic oscillation of the critical temperature occur together.