Exploring the Effects of Combining Small Magnets in a Cube or Sphere Shape

  • Thread starter Thread starter Energize
  • Start date Start date
  • Tags Tags
    Magnets
AI Thread Summary
Combining small magnets into a cube or spherical shape increases the overall magnetic field strength, allowing them to lift heavier objects. This is supported by domain theory, which explains that larger magnets are collections of smaller, weaker magnets working together. The lifting force is influenced by the contact area between the magnet and the object, with a formula indicating that the force increases with surface area. However, the magnetic field strength just outside the magnet does not depend on the area. The effectiveness of the magnets also diminishes if they are too thin, as the effects of their faces can cancel each other out.
Energize
Messages
30
Reaction score
0
If you combine many small magnets together in a cube or spherical shape (say those 1.5 tesla rare Earth magnets), is the resulting magnetic field able to affect even heavier objects, or is there no difference in the range/energy of the field?
 
Last edited:
Physics news on Phys.org
Energize said:
If you combine many small magnets together in a cube or spherical shape (say those 1.5 tesla rare Earth magnets), is the resulting magnetic field able to affect even heavier objects, or is there no difference in the range/energy of the field?

Well I know that the magnetic field definitely does get stronger when you make a big cube out of many small magnetised cubes because I've tried it.

Makes sense really, the domain theory says that a magnet that you can hold in your hand is just a collection of very tiny microscopic (weak) magnets all side by side, and end to end. Put them all together and you can pick up comparatively gigantic objects(compared to the size and strength of the domains) .

So yes, the more you have the stronger the field.
 
If you build a cube out of rectangular magnets, The lifting force will be increase as the contact area of a face of the cube and the face of the object to be picked up.
In gaussian units, F=2pi M^2 A for the lifting force of a magnet of magnetization M on a high mu object, with A the contact area.
 
clem said:
If you build a cube out of rectangular magnets, The lifting force will be increase as the contact area of a face of the cube and the face of the object to be picked up.
In gaussian units, F=2pi M^2 A for the lifting force of a magnet of magnetization M on a high mu object, with A the contact area.

So this would mean that for 2 magnets with the same volume, the one with the biggest surface-area would have the strongest field. Is that correct?
 
Not quite. The B field just outside the magnet does not depend on the area.
The lifting force ~B times the area of contact between the magnet and the flat surface of an iron object.
One other thing. The formula I gave is only if the magnet is large enough that effect of the distant face can be neglected. If the magnet is too thin, the the effects of the close face and the distant face tend to cancel.
 
This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'
Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
Back
Top