Electrical Engineering ⇒ Topic : Magnetic flux density

Magnetic Flux Density

The magnetic flux density is defined as the magnetic flux passing normally per unit area i.e.

The SI unit of magnetic flux density is Wb/m² or *tesla. Flux density is a measure of field concentration i.e. amount of flux in each square metre of the field. In practice, it is much more important than the total amount of flux. Magnetic flux density is a vector quantity.

(1) When the plane of the coil is perpendicular to the flux direction [See Fig. (a)], maximum flux will pass through the coil i.e.

                                       Maximum flux, Φ_m = B A Wb

                                     (a)                                                                                                  (b)

                                                                            figure 

 When the plane of the coil is inclined at an angle θ  to the flux direction [See Fig. 7.4], then flux (Φ)  through the coil is

                                     Φ= B A sin θ Wb

When the plane of the coil is parallel to the flux direction, θ = 0 so that no flux will pass through the coil (Φ) = BA sin 0 = 0).

Magnetic flux density (B). It is defmed as the flux (Φ) or lines of force passing per unit area (A) through any substance through a plane at right angles to the direction of magnetic flux ; it is measured in Wb/m² (or T, i.e., Tesla)

Mathematically, B = Φ / A

MAGNETIC FLUX DENSITY (B)

Consider a specimen of a conductor as shown in Fig. (a), in which the magnetic flux (Φ) lies normal to the cross section (A). Then,

The unit of magnetic flux density (B) is Wb/m². Sometimes, B is also expressed in Tesla (1 Tesla = Wb/m²).

                                                 FIGURE (a) Magnetic flux (Φ) in the specimen of a conductor