Estimating magnetic field based on pull force

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SUMMARY

This discussion focuses on estimating the magnetic field strength in gauss based on the pull force of a magnet. The user compares their magnet's pull force with that of a similar magnet, using the relationship between pull force and magnetic energy density. The formula provided indicates that the pull force is roughly proportional to the square of the magnetic field strength (F ≈ k*B²), where k is a constant. The user emphasizes that this estimation is valid at the center of the magnet's flat face and acknowledges the non-linear nature of magnetizing curves.

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  • Understanding of magnetic field concepts, specifically in gauss
  • Familiarity with the relationship between pull force and magnetic energy density
  • Knowledge of magnetizing curves and their non-linear characteristics
  • Basic grasp of the formula Edens = ½*B*H for energy density
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Engineers, physicists, and hobbyists interested in magnetics, particularly those involved in designing or testing magnets and their applications in various fields.

EddieP
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I am trying estimate the approximate value in gauss of the magnetic field of a magnet I have based on its pull force, and I am wondering if anyone can comment on the validity of my method.

I have tested the pull force of my magnet by weighing the heaviest object it can hold. I have also found data on another magnet made of the same material online. This data contains the pull force of the magnet in grams, and also the magnetic field in gauss. The two magnets are of similar shape, but obviously different masses.
By comparing the pull force values of the two magnets, can I then estimate the magnetic field of my magnet? For example, if my magnet has half the pull force of the magnet online, will the magnetic field also be roughly half?

(The two magnets are cylindrical, and I am thinking about the magnetic field value at the point in the center of the flat face at the end of the magnet - not at any distance away from the magnet)
 
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EddieP said:
(The two magnets are cylindrical, and I am thinking about the magnetic field value at the point in the center of the flat face at the end of the magnet - not at any distance away from the magnet)
The attraction of some load is proportional to the magnetic energy density at the end of the magnet:

Edens = ½*B*H [ J/m3 ]

B = μ0 * H →

Edens = ½*B*H = ½*μ0*B2

So (roughly) F ≈ k*B2 , k is some constant. The B-value found is the mean flux density over the cross section area at the end of the magnet, not at the center or at the edge.

"Roughly" because the magnetizing curves are not linear.
 

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