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444 ⏐⏐⏐ MAGNETIC CIRCUITS
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
B (T)
B (T)
H 1 H 2
H x
materials in Fig. 11.23, is called the normal magnetization curve. An
expanded view of one region appears in Fig. 11.24.
A comparison of Figs. 11.19 and 11.23 shows that for the same value
of H, the value of B is higher in Fig. 11.23 for the materials with the
higher m in Fig. 11.19. This is particularly obvious for low values of H.
This correspondence between the two figures must exist since B � mH.
In fact, if in Fig. 11.23 we find m for each value of H using the equation
m � B/H, we will obtain the curves of Fig. 11.19. An instrument
that will provide a plot of the B-H curve for a magnetic sample appears
in Fig. 11.25.
It is interesting to note that the hysteresis curves of Fig. 11.22 have
a point symmetry about the origin; that is, the inverted pattern to the left
of the vertical axis is the same as that appearing to the right of the ver-
H 3
H S
FIG. 11.22
Defining the normal magnetization curve.
Cast iron
Sheet steel
Cast steel
300 600 900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500
FIG. 11.23
Normal magnetization curve for three ferromagnetic materials.
H (At/m)
H(At/m)