# What Is Magnetization Curve?

Hysteresis Loop, also known as Magnetization Curve, is a curve or loop plotted on B-H coordinates that displays the variation in magnetization of a ferromagnetic material when subjected to a periodically reversing magnetic field.

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## Non-Magnetic Materials

It has been found that the density of flux has no effect on the reluctance of non-magnetic materials. The magnetic flux () and flux density (B) are proportional to the magnetic field strength (H) and the magnetic moment (IN), respectively.

The graph of B versus H for non-magnetic materials will be a straight line because B varies directly with H.

## Magnetic Materials

A curve can be seen when the B values are plotted against the H values for a magnetic material. The data for the iron sample are shown in Table 1.

Table 1 Magnetization Curve for a Magnetic Material

Figure 1 depicts a graph drawn from these data. Since B values are plotted against H values, the graph is called a B/H curve or magnetization curve. These curves are frequently employed in the evaluation of magnetic properties of various materials.

## Magnetic Saturation

When the magnetizing force (H) is low, a small increase in H results in a large increase in the flux density (B), as shown in the B/H curve in Figure 1. (B). The steeply sloping part of the curve illustrates this point.

It can be seen that as both H and B grow larger, the effect of H on B becomes smaller and smaller. As H is increased to its maximum value, H3, only a marginal increase (from B2 to B3) is produced. The flux density decreases as magnetization approaches 2000 A T/ m. Saturation of the magnetic field is evidenced by this.

At a flux density close to the middle of the ‘knee’ of the B/H curve, it is said that saturation occurs. Magnetizing steel past its magnetic saturation point is impractical from a cost perspective. There is no point in increasing the magnetizing current if it only increases the flux density by a small amount because that is a waste of electrical power.

Different flux densities have different effects on the permeability of ferromagnetic materials. By solving the basic magnetic equation, we can show that for a given flux density, permeability (μ) is equal to the ratio B/H.

Iron typical B and H values can be found in Table 1. Permeability can be determined for any given flux density and magnetizing force in this way. Table 1 columns 3 and 4 show the calculated values for and r based on the given values for B and H.

Figure 1 shows the r/H curve calculated by plotting r values against H values. According to the graph, the permeability curve sharply increases to a peak. At this maximum permeability point, the curve drops off sharply. The permeability decreases as H is increased past the point of magnetic saturation.

## Comparison of B/H Magnetization Curves

Magnetic susceptibility curves for silicon steel, cast steel, and cast iron are shown in Figure 2.