Answer to Question #86826 in Electricity and Magnetism for vikas

Question

Metallic iron contains approximately 1029 atoms per cubic meter. The magnetic moment
of each iron atom is 1.8 × 10−23 Am−1
. If all the dipoles were perfectly aligned what
would be the magnetisation M and the magnetic moment of a bar 10 cm long and 1cm2
in
cross-section?

Answer 1

Magnetization is the magnetic moment of a unit volume, so that M = 10²⁹*1.8*10^-23 = 1.8*10⁶ (A/m), and the magnetic moment of the bar is M_b = MV = 1.8*10⁶*0.1*10^-4 = 18 (Am²).