How is the strength of a magnet measured?

In: Applications of magnets On: Hit: 1661

To describe the most important characteristics of magnets, there are three values ​​that are crucial: the maximum energy product, the value without load or gauss of surface and its maximum traction force.

Strong magnets and their properties

A permanent magnet displays its properties in a visible and tangible way when different metallic materials approach their magnetic field. In order to define the strength of this magnetic field, a diagram is used to represent the magnetic flux density along the axis "B" and the magnetic field intensity in "H" (in Gauss).

If a magnetic material is magnetized, it is exposed to a magnetic field strength, but if it is demagnetized again, the magnetization curve shows a different course to the characteristic curve of demagnetization. This phenomenon is called hysteresis and extends to the four quadrants of the HB diagram. This hysteresis causes a certain residual magnetism in the demagnetization and a value H = 0 as a positive B value, which is also known as remanence.

In the later course of the demagnetization curve at a value B = 0, a negative H value is obtained, which bears the name of coercive force. If these two values ​​are multiplied (remanence * coercive force), their maximum power is obtained, which is measured in Mega Gauss Oersted (MGOe).

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Measurement of important characteristics of magnets

To describe the most important characteristics of magnets, there are three values ​​that are crucial: the maximum energy product, the value without load or gauss of surface and its maximum traction force.

To determine the maximum energy product, the remanence value and the coercive force must be determined experimentally. This is done with the help of a hysteresis graph test machine. If the magnet to be tested is in the hysteresis graph test machine, this is called a closed circuit. With the help of the test machine, it is possible to adjust the intensity of the magnetic field to the value 0 and read the associated retention value. The coercive force is determined in a similar way by establishing the magnetic flux density at 0.

If the magnet to be tested is removed from the hysteresis graph machine, this is called an open circuit. In this state, the magnetism decreases to a much smaller value, namely the no-load or gauss-surface value, which is determined by means of a Gauss meter and a Hall probe. The amount of this unloaded value is largely determined by the geometry of the magnet, ie the relationship between its surface and its relative length. The smaller the magnetic poles and the longer the magnet, the greater the density of the flow in vacuum.

The maximum tensile force is determined in a tensile testing machine and is defined as the force needed to vertically detach the magnet from a flat steel plate. To determine the exact relationship between the resulting air gap and the associated tension force, it is subjected to different measurements made in air spaces of different sizes.

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Magnets and their effects of force

Neodymium magnets produce the strongest magnetic fields compared to all other magnetic materials. Neodymium magnets are available in different qualities such as, N35 to N55. A neodymium magnet N55 has 50% more magnetic field than a neodymium magnet N35. Strong magnets of this type characterize the product of maximum energy with the letter N. The measurements of magnetic flux density, provide an overview of the different magnetic materials and their magnetic fields.

• The strength of the earth's magnetic field is 0.5 Gauss on its surface.

• A standard fridge magnet has approximately 100 gauss.

• Magnets made of ferrite (ceramic) have a magnetic flux density of 3,700 Gauss.

• A magnet of samarium cobalt grade 2:17, has 11,000 gauss.

• A grade 5 Alnico magnet has 12,500 Gauss.

• A neodymium magnet N42 can reach 13,000 gauss.



The two vectors of magnetic field intensity and magnetic flux density have the same direction. The intensity of the magnetic field can be considered as concentric circles around a current conductor. When the current flow enters the plane, these magnetic field lines run in the direction of a screw, to the right.

In contrast, the magnetic flux density takes into account the influence of an iron filler around the current carrying conductor. Therefore, for the correct detection of a magnetic field, the two variables must always be included: the magnetic field strength and the magnetic flux density.

The acquisition of magnetic fields and the correct interpretation of their properties require a high degree of experience, which we have acquired through many years of study and numerous experiments.

Therefore, do not hesitate to take advantage of our experience and contact us.


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