Magnetic field due to nuclear spin

[luxiaolei]

Hi all.

Can anyone tell me why in the equation of the magnetic field due to a nuclear's spin has radius dependence? How come?

B=-u0 uI / 2 pi R^3

(sorry about the typing, I don't know how to type a porper equation..)

Thanks in advance

 

[alxm]

See http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/hydfin.html#c4", for instance.

 

[luxiaolei]

Thanks alxm, great answer, I am now understood. Thank you