Different laws for calculating magnetic field-Biot-Savart law; We know that any current carrying conductor produces a magnetic field. A magnetic field ℜ is characterized either byH, the magnetic field intensity or by B, the magnetic flux density vector.These two vectors are connected by a rather simple relation:B=μ_rμ_oH;

where  μ=4π*10^-7 H/M  is called the absolute permeability of free space and μ_r, a dimensionless quantity called the relative permeability of a medium (or a material). For example the value of μ_r is 1 for free space or could be several thousands in case of ferromagnetic materials.