Critical Current Density in Superconductors One problem with some of the newer high-temperature super conductors is getting a large enough current density for practical use without causing the resistance to reappear. The maximum current density for which the material will remain a superconductor is called 1he critical current density of the material. In 1987, IBM research labs had produced 1hin films with critical current densities of 1.0 X 105 A/cm2.
(a) How much current could an 18- gauge wire (see Example 25.1 in Section 25.1) of this material carry and still remain superconducting?
(b) Researchers are trying to develop superconductors with critical current densities of 1.0 X 106 A/cm2. What diameter cylindrical wire of such a material would be needed to carry 1000 A without losing its superconductivity?