计算电流环产生的磁场分布实例，电流环在y-z平面上，环心过原点O，半径RH，通过电流I0，Z=0处x-y平面上的磁场分布-Calculate the distribution of the magnetic field produced by current loop example, the current ring in the yz plane, ring heart through the origin O, the radius RH, by current I0, Z = 0 Chu