申論題

1.Fig. 1 shows a ferromagnetic core whose mean path length is 30 cm. There is a small gap of 0.02 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 2000, and the coil of wire on the core has 100 turns. Assume that fringing in the air gap increases the effective cross-sectional area of the air gap by 5 percent. Given this information, find: