Relation between Magnetic Flux density ( B ) and Magnetic Field Strength ( H )


Magnetic flux density ( B )

  • It is defined as the magnetic flux per unit area of surface at right angle to the magnetic field. Its unit is weber per meter square

       B = Φ / A

      Where Φ = Flux in weber and

                  A = Surface area

Magnetic field intensity ( H )

  • The magnetic field intensity is the force required to maintain magnetic flux and it will produces particular value of magnetic flux. 
  • The magnetic field strength is measure of magnetic field produced by electrical current flows through coil. 
  • The magnetic flux density is directly proportional to magnetic field intensity.

      B α H

      B = μH

      Where μ = Constant

                 μ = μ0 μr

      Where μ0 = Permeability of free space

                     = 4π × 10 – 7 weber / ampere - meter

               μr  = Relative permeability of the medium

Relative Permeability of different Medium


Relative Permeability



Carbon steel


Electrical steel


Super conductor



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