The critical magnetic flux density of a long superconducting wire is 10 mT at 0K. a) Calculate the critical current of the wire if the radius is 1 mm. b) What is the critical current density of the wire if the penetration depth is 500 nm in 0K? c) If the penetration depth is 400 nm at 5K what is the critical temperature of this superconductor.

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The saturation curve of a particular core material shows that at a magnetic field intensity of 1250 At/m and the flux density is 0.80 Tesla. Determine the relative permeability of the core material.

1.2 Magnetic Circuits The figure shows a ferromagnetic core whose mean path length is 40cm. There is a small gap of 0.05 cm in the structure of the otherwise whole core. The cross-sectional area of the core is 12 cm², the relative permeability of the core is 4000, and the coil of wire on the core has 400 turns. Assume that fringing in the air gap increases the effective cross-sectional area of the air gap by 5 percent. Mr = 4000 N=400 turns ·25.4m² Il=0.0005m A=0.0012 m² Given this information: a) Find the total reluctance of the flux path (iron plus air gap). b) Find the current required to produce a flux density of 0.5 T in the air gap. c) Qualitatively describe the effect of the air gap on the magnetic circuit.