Electrons and positrons free fall within a superconducting cylinder

AI Thread Summary
Electrons and positrons in a superconducting cylinder experience distinct electric fields that affect their motion differently. Electrons feel an electric field that balances their weight, effectively freezing them in place, while positrons experience a negative electric field resulting in a net acceleration of 2g. This behavior seems to contradict Lenz's law, which typically suggests that induced currents should dampen motion rather than reinforce it. The discussion raises questions about the spontaneous appearance of these fields and their implications for both particles. Overall, the phenomenon challenges conventional understanding of electromagnetic interactions in superconducting environments.
lalbatros
Messages
1,247
Reaction score
2
I read about electrons and positrons free fall within a superconducting cylinder, in this book (p 105):

https://www.amazon.com/dp/0521675537/?tag=pfamazon01-20

I don't understand what I read.

Apparently, electrons would feel an electric field mg/e that would actually freeze them in the cyclinder. This is already not totally clear. But I assume that any motion would create huge reacting currents in the cylinder to balance the motion. This would be the usual Lenz law. But I would like to that understand better.

Where I really don't understand is when positrons are discussed.
Apparently they would feel a -mg/e field that would in total result in a 2g acceleration. I feel this is very strange since this is contradictory to my usual understanding of the Lenz law: the induced current would then re-inforced the motion instead of damping it.

Any suggestion ?

Thanks
 
Last edited by a moderator:
Physics news on Phys.org
WIthout further details one can only speculate But it sounds like an electric field (E) is set up in which case the magnitude of the electric force on both the electron and positron would be the same(Ee).In the case of the electron Ee acts up to balance its weight
(mg=Ee) and for the positron Ee acts down making a resultant force(mg+Ee=2mg).
This reminds me of Millikans experiment where e was measured.
 
Dadface,

It seems that a field appears spontaneaously.
This is not totally surprising.
What is surprising if the effect on positrons.
I would expect the same effect both for e- and p+, since the effect should actually counter-act on the motion of the particle.

Here is what I don't fully understand:

http://www.geocities.com/l.albatros/pictures/epfreefall.jpg

http://www.geocities.com/l.albatros/pictures/epfreefall2.jpg
 
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...

Similar threads

Back
Top