# Estimating magnetic field based on pull force

• EddieP
In summary, the individual is seeking to estimate the magnetic field of their magnet by comparing its pull force to that of another magnet of similar shape and material. They have found data online that provides pull force and magnetic field values for the other magnet. They plan to use the formula Edens = ½*μ0*B2 to estimate the magnetic field, but note that this may only provide a rough estimation due to non-linear magnetizing curves.

#### EddieP

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)

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.

## 1. How is the pull force related to the magnetic field?

The pull force is directly related to the strength of the magnetic field. As the magnetic field becomes stronger, the pull force will also increase. This means that the greater the pull force, the stronger the magnetic field is in that area.

## 2. What factors can affect the accuracy of estimating the magnetic field based on pull force?

There are several factors that can affect the accuracy of estimating the magnetic field based on pull force. These include the distance between the magnet and the object, the material and shape of the object, and any external magnetic fields that may be present in the surrounding area.

## 3. Is it possible to estimate the direction of the magnetic field using pull force?

No, pull force alone cannot determine the direction of the magnetic field. Additional measurements, such as the angle of deflection of a compass needle, are needed to determine the direction of the magnetic field.

## 4. How can I measure the pull force accurately?

The best way to measure the pull force accurately is to use a specialized instrument called a magnetometer. This device is designed specifically for measuring magnetic fields and can provide precise measurements of the pull force in a given area.

## 5. Can pull force be used to estimate the strength of any type of magnetic field?

No, pull force can only be used to estimate the strength of a static magnetic field. It cannot accurately estimate the strength of a changing or alternating magnetic field, such as those produced by electromagnets or alternating currents.