Superconductor critical electrical current density

The most distinguishing features of superconductive materials are the sudden and complete disappearance of electrical resistance below T, the high critical current density J ), which allows superconductors to conduct with no power loss and the high critical magnetic fields (H 2) in which superconductivity can exist. The relationship among these features is shown in Figure 3,... 

Direct transport measurements are generally employed on thin films, tapes and coated conductors. They quickly reach their natural limits as the currents go up and/or the cross-section of the conductor increases. They are fast, i.e., can be started immediately after the magnetic field is set, and trace the I-V characteristics, which is of course most valuable if flux creep or thermally assisted flux flow (Kes et al. 1989) prevails, because the electric field is directly determined. On the other hand, must be defined by a criterion e.g., 1 [xV/cm. It will be affected by the presence of stabilising materials, the silver tube or conducting substrates, and thus generally refers to the overall Jc, wfrich can be converted to the critical current density of the superconductor if the shape and the volume fraction of the superconducting material are known. 

When a magnetic field is applied to a superconductor below the critical superconducting transition temperature T, electric currents flow in the material without resistance, creating a magnetic field opposing the applied field (the Meissner effect). There is a critical current density above which superconduction halts. Also, there is a maximum magnetic field above which superconduction ceases. In general, as the temperature is... 

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