Electrical Engineering ⇒ Topic : Relation between the Magnetic Field Intensity (H) and the Magnetic Flux Density (B)

Relation between the Magnetic Field Intensity (H) and the Magnetic Flux Density (B)

The magnetic flux density (B) at any point in a medium is related to the magnetic field intensity (H) at that point by the following relationship

                                  B = μH          ..........(1)

The value of Air = 1 for air and varies from 1000 to 10,000 for special irons.Equation (1) is very similar to the equation for electric flux density (D).

           D = εE as shown in Eq. (2.10) of Chap. 2. From these two equations, it is clear that the magnetic flux density B is analogous to D, the electric flux density and the magnetic field intensity H is analogous to the electric field intensity E. The relative permeability of any medium μ_r = μ/μ_o.

The relation between B and H as given by Eq. (1) is nonlinear in nature and is shown in Fig. (b), for different magnetic materials. The relative permeability of the material also depends upon the working magnetic field intensity (H) and the magnetic flux density (B) as shown in Figs (c) and (d). It attains maximum value for a certain value of (B) and then decreases with a increase in the value of either B or H.

 FIGURE (b) Variation of magnetic flux density (B) with magnetic field intensity (H) for different magnetic materials

FIGURE (c) Variation of relative permeability with magnetic field intensity (H) for different magnetic materials

FIGURE (d) Variation of the relative permeability with magnetic flux density (B) for different magnetic materials