Question

Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magnetons (1 Bohr magneton equals 9.27 x 10^-24A-m²). The density of atoms in iron is 8.52 x 10²⁸atoms/m³. (a) Find the maximum magnetization I in a long cylinder of iron, (b) Find the maximum magnetic field B on the axis inside the cylinder.

Answer 1

f = 8.52 × 10²⁸ atoms/m³

For maximum ‘I’, Let us consider the no. of atoms present in 1m³ of volume.

Given: m per atom = 2 × 9.27 × 10^–24A–m²

I = net m/V = 2 × 9.27 × 10^–24 × 8.52 × 10²⁸ ≈ 1.58 × 10⁶A/m

B = μ₀ (H + I) = μ₀I [∴ H = 0 in this case]

= 4π × 10^–7 × 1.58 × 10⁶ = 1.98 × 10^–1 ≈ 2.0T