A B-H curve is use to show the Relationship between Magnetic Flux Density (B) and Magnetic Field Strength (H) for a Particular Material B=µ0µrH where µ0 is Permeability of air µr is Relative permeability and Relative Permeability of air is 1. ∴ B=µ0H The shape of curve is straight line passing through origin because Magnetic field applied to air and air never structure.