An insulated wire is wound so that it forms a flat coil with N=100 turns. The radius of the innermost turns is `R_(1)=4 cm` . What magnetic moment will this coil have when a current of I=10 mA flows in it ?

Answer

`m=(1)/(3)piNI(R_(1)^(2)+R_(1)R_(2)+R_(2)^(2))=2.2 xx 10^(-3)A m^(2)`