NIB Magnet Dropped in a Cu tube - Forces

AI Thread Summary
A strong magnet drops slowly through a conducting copper tube due to the generation of Eddy currents, which create opposing magnetic fields. The discussion highlights confusion regarding the direction of these induced currents and their resultant forces. The right-hand rule is mentioned as a tool for determining the direction of the magnetic fields, but there are concerns about its application in this scenario. The relationship between the induced currents and the forces acting on the magnet is explored, questioning whether the formula I X B = F is applicable. Understanding these interactions is crucial for explaining the magnet's slow descent through the tube.
MrLiou168
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Homework Statement


I'm trying to figure out and explanation as to why a strong magnet drops so slowly through a non-magnetic but conducting Cu tube. The attached diagram shows the original B field, induced Eddy currents, and secondary B field as a result of those Eddy currents, but I can't figure out my Force vectors. Any help greatly appreciated.


Homework Equations


F = qvB
F = qv X B
F = IL X B

The Attempt at a Solution


See attached diagram...
 

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I think after studying the following,

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

that your drawing has the induced currents going the wrong way? The induced magnetic field looks right though (note something is wrong as the right-hand rule does not apply to your drawing (induced current and secondary magnetic field)). The induced magnetic field below the falling magnet repels the falling magnet and the induced magnetic field above the falling magnet attracts the falling magnet.
 
Thanks for the response. Those examples are all of coils, and not solid conductors. Does this make a difference?

And in terms of the directions of the Eddy currents, is it correct to use I X B = F?
 
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