There are two main theories in superconductivity: i) Microscopic or (BCS) theory whichrndescribes why materials are superconducting, ii) The phenomenological theory which describesrnthe properties of superconductors in magnetic fields; Unlike the microscopic (BCS)rntheory the phenomenological theory is based on a so-called phenomenological order parameter.rnMost physical problems in physics can not be solved exactly, and hence they need tornbe dealt with approximately. The principles of variations as developed for providing anrnelegant description of a wide variety of physical phenomena; Here we are using this methodrnto solve problems related to the phenomenological theory of superconductivity, whichrnincludes London’s equation, first and second Ginzburg-Landau equation and in the casernof weak superconductivity, the penetration of the magnetic field on Josephson’s contactrnbetween two superconductors, when there is an insulator between them, i.e Ferrell-Prangernequation and the physical phenomena on the junction