I Permanent Magnetic Dipole in an electromagnetic field

AI Thread Summary
Calculating the forces between a permanent magnet and an electromagnetic field can be complex, often leading to nonsensical results if incorrect formulas are applied. Understanding the history and design challenges of linear motors is crucial, as they involve both horizontal and vertical forces that can affect performance. Field mapping and material considerations are also essential for accurate calculations. Recommended resources include "A History of Linear Electric Motors" and "Linear Synchronous Motors: Transportation and Automation Systems." Engaging with these materials may provide the necessary insights for approximating the math involved in such systems.
Aviax98
Messages
2
Reaction score
0
I've been trying really hard to calculate the forces between a permanent magnet that is within an electromagnetic field.
I have tried every formula under the sun, but it seems I am just not using the right ones, as my results always end up nonsensical.

To be clear, I am trying to understand the math behind a project like this one:
https://kevinlynagh.com/pcb-stepper/
However, the math here just doesn't look right. The OP seems to just drop off terms from the formulas and make strange jumps in their logic.

Would anyone be able to point me in the right direction as to what formulas I would need to figure out the math behind a system like this? I don't even need it to be perfectly accurate, just an approximation would suffice.
Thanks all!
 
Physics news on Phys.org
Welcome to PF.

It seems you are getting into linear induction or stepper motors.

First, you need to understand the history of linear motors and why they are difficult to design. There are not only horizontal forces along the plane, there are also vertical forces, that can stick the carriage to the track, or throw it up in the air.
A History of Linear Electric Motors. Eric R. Laithwaite. 1987.

Second, you need to understand the materials, do some field mapping, and then some calculations. Take a look at;
Linear Synchronous Motors: Transportation and Automation Systems. 2'nd Edn, 2012.
Jacek Gieras, Zbigniew J. Piech, and Bronislaw Tomczuk.
 
Hi Thanks for your reply and your suggestions!
I will have a read of those and see how I go.
 
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...

Similar threads

Back
Top