Question

Many metals become superconductors (zero resistance, zero loss, zero heating) at low temperatures. If they are warmed above the critical tempareature, the superconductivity is lost. Also, if the metal experiences a magnetic field above a critical value, the superconductivity is lost. Consider an aluminum wire with 1 mm diameter below its critical temperature of 1.2 Kelvin. It's critical magnetic field is 0.01 Tesla. What is the maximum current in Amps that you can send down this wire for it to remain superconducting?

Answer 1

r=d/2 =0.5 mm =0.0005 m
I(max) = B(cr) c r /2 = 0.01•3•10⁸•0.0005 /2 = 750 A