Calculate Force Between Neodymium Magnets

[eddybob123]

hi, I was wondering if there is an equation out there that let's you calculate the force between two neodymium magnet. thanks, i would really appreciate an answer.

 

[Low-Q]

hi, I was wondering if there is an equation out there that let's you calculate the force between two neodymium magnet. thanks, i would really appreciate an answer.

If there is an equation, this must also consider the shape of the magnets. Two magnets with same mass and grade will have different "center of magnetism".

Say you have two cube magnets, N40, with the volume of 1cm^3. These will not get closer to the center than approx 5mm. To pull them apart require a given force.

Say you have two square magnets measuring 1mm x 31.6mm x 31.6mm (1cm^3), and you put them together surface to surface, it will require greater force to separate them. If you put them together edge to edge, it will require less force to separate them.
In addition, there will be different force required between magnetized through thickness, and through length. Surface to surface, and magnetized through length will allow the magnetic flux to have a tighter and more dense flux loop, which also require even greater force to separate.

However, at greater distance both shapes will attract practically equal for both shapes.

I have done a lot of experiments with this.

Vidar

 

[chrisbaird]

hi, I was wondering if there is an equation out there that let's you calculate the force between two neodymium magnet. thanks, i would really appreciate an answer.

Finding the answer is more detailed than I think you are expecting. The force will depend on the shapes, sizes, and strengths of the magnets, as well as their relative position and orientation. The equations that describe the interacting fields are Maxwell's equations, but they have to be applied to a specific problem.

 

[eddybob123]

Let's just say that the magnets are cylindrical and the face is 2 cm in diameter, and the height is 5 cm.

 

[Low-Q]

Let's just say that the magnets are cylindrical and the face is 2 cm in diameter, and the height is 5 cm.

The magnetic force is generally exponential to distance. If you know the force at 10cm distance, the force is increased 4 times at 5cm distance.

The general equation would be this: Force_initial x (initial distance / new distance)^2
Example:
Initial distance D_i is 10cm.
New distance D_n is 7cm
Initial force F_i is 2N
New force F_n is unknown

F_n = F_i(D_i / D_n)^2 =
2N(10cm/7cm)^2 = 4.08N


Vidar

 

[eddybob123]

But assume the magnets are stationary?

 

[bbbeard]

The magnetic force is generally exponential to distance.

Magnet-magnet interactions like the OP is asking about are dipole-dipole interactions and go like 1/r³, not exponential.

BBB

 

[eddybob123]

How do you get those number?