For a superconducting material at a temperature T below the critical temperature TC, the critical field HC (T), depends on temperature according to the relationship

where HC(0) is the critical field at 0 K.

(a) Using the data in Table 20.7, calculate the critical magnetic fields for tin at 1.5 and 2.5 K..

(b) To what temperature must tin be cooled in a magnetic field of 20,000 A/m for it to besuperconductive?

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Critical Magnetic Flux Density Bc (tesla)“ Critical Temperature Tc (K) Material Elements 0.02 Tungsten Titanium 0.0001 0.0056 0.0105 0.40 Aluminum Tin Mercury (a) Lead 1.18 3.72 4.15 7.19 0.0305 0.0411 0.0803 Compounds and Alloys 10.2 10.8 Nb-Ti alloy Nb-Zr alloy РЬМо,Ss V3GA Nb3Sn Nb3Al Nb,Ge 12 11 45 22 14.0 16.5 18.3 18.9 23.0 22 32 30 Ceramic Compounds 92 110 YBażCu3O7 BiżSr2Ca2Cu3O10 TЬВa:Сa-CuзОто HgBa2CazCu2O8 125 153