One problem with some of the newer high-temperature superconductors is getting a

Question

One problem with some of the newer high-temperature superconductors 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 the critical current density of the material. In 1987, IBM research labs had produced thin films with critical current densities of 1.0 105 A/cm2.

(a) How much current could an 18-gauge wire of this material carry and still remain superconducting? (18-gauge has a nominal diameter of 1.02 mm.) A

(b) Researchers are trying to develop superconductors with critical current densities of 1.0 106 A/cm2. What diameter cylindrical wire of such a material would be needed to carry 929 A without losing its superconductivity? mm

Explanation / Answer

1) current density = 1.0105 A/cm^2

18 -gauge material have diameter of 1.02mm , so, area of cross section = 8.17128*10^-3 cm^2

current = 8.17128*1.0105*10^-3 A= 8.257*10^-3 A

2)current density = 1.0106 A/cm^2

current = 929A ,

required diameter= 342.116 mm

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