Longitudinal magnetic forces in conductors

[TrickyDicky]

Is there a simple way to understand within classical electrodynamics (or QED) the experiments that show longitudinal forces in conductors that are capable of breaking wires when enough current is conducted and are not due to melting or pinch effect?

 

[harrylin]

I think that this relates to an old issue about a possibly missing term in Maxwell's laws, based on experiments with such things as rail guns.
You can find a rather old paper about it in the Journal of Applied Physics:
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5114236&abstractAccess=no&userType=inst

I see that this links to a more recent paper by Moyssides, which I had not seen and may give sufficient answer:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1211177&navigation=1

 

[TrickyDicky]

Only the first paper seems to be directly related to the OP, anyway I haven't subscriptiom.
I read somewhere these longitudinal forces could be accounted for using the Maxwell stress tensor and I was wondering if anyone knew how.

 

[Meir Achuz]

Graneau has misinterpreted his experiments. I looked in detail at his papers some years ago. In each case, the geometry has current moving in a non-longitudinal direction. He considered this negligible but it isn't.

 

[sardar]

Yes, there is a simple explanation within classical electrodynamics for the longitudinal forces observed in conductors. These forces, also known as Lorentz forces, arise from the interaction between moving charges and a magnetic field.

When a current flows through a conductor, the moving charges experience a force due to the magnetic field created by the current. This force is perpendicular to both the direction of the current and the direction of the magnetic field. However, if the current is not uniform along the length of the conductor, there will be a component of the force that is parallel to the direction of the current. This is known as the longitudinal force.

The strength of the longitudinal force depends on the magnitude of the current, the strength of the magnetic field, and the length of the conductor. If the current is high enough, the longitudinal force can become strong enough to break the conductor. This is because the force is exerted over the entire length of the conductor, leading to a large net force on the material.

This explanation is consistent with classical electrodynamics and does not require the use of quantum electrodynamics (QED). The melting or pinch effect that can also cause wires to break is a result of the high temperatures and pressure generated by the intense current, and is not directly related to the longitudinal forces described above.