An iron bar of length 10 cm and diameter 2 cm is placed in a magnetic field of intensity 1000 Am^(-1) with its length….

Q: An iron bar of length 10 cm and diameter 2 cm is placed in a magnetic field of intensity 1000 Am-1 with its length parallel to the direction of the field. Determine the magnetic moment produced in the bar if permeability of its material is 6.3 × 10-4 T mA-1

Sol: We know that, μ = μ0 (1 + χ)

χ = μ/μ0 – 1

χ = (6.3 × 10-4)/(4π × 10-7 ) – 1 = 500.6

Intensity of magnetisation,

I = χ H = 500.6 × 1000 = 5 × 105 Am-1

∴ Magnetic moment, M = I × V = I × π r2 l

= 5 × 105 × 3.14 × (10-2)2  × (10 × 10-2) = 17.70 A-m2