1. Calculate the free energy decrease when a transition from the normal state to the superconducting state takes place.
See text for the working out. The final expression is ![](SA4-2_clip_image002.gif)
2. Is the transition from the normal state to the superconducting state in the absence of a magnetic field a first or a second order transition? What is the order in case a magnetic field is present ?
In the absence of a magnetic field, the superconducting transition is a second order transition. On the other hand, in a magnetic field the Tc reduces and there appears a jump in free energy as for a first order phase transition.