[Phys-L] Re: Lenz's law

[Chuck Britton <britton@NCSSM.EDU>]

I had a similar experience some years back.
The mid-eighties was my first exposure to the cow magnet dropped
through a copper tube.
(well before the Neodymiums became so available).
The thicker the tube wall, the slower the drop.
Terminal velocity is quickly reached.

We drilled some holes in the tube to watch the fall (and time with
photogates).
For some reason I got the idea of slitting the copper pipe along it's
entire length.
This certainly CHANGED the the paths of the induced currents, but
didn't effect the speed of the fall as much As I would have thought.

I surmised - much as Denker has - that the current path is still
continuous but instead of a clockwise loop above and a cc loop below
the magnet (for instance) that the two loops are now joined by currents
running along the edges of the slit - up on one edge and down on the
other. The magnetic effect of these two currents cancel, leaving the
two opposing  loop currents circulating above and below the falling
magnet.

(Ain't these NdFeBo magnets NEAT!)



On Apr 11, 2005, at 5:49 PM, Mangala Joshua wrote:

> I have a question about a demonstration showing  Lenz's Law. While a
> ring is hanging  if we bring a fairly strong magnet towards it the ring
> repels and  when the  magnet is moved out  the ring attracts. We
> usually
> don't see this effect if we have a ring that has a slit in it. However
> today I used a very strong magnet and I was able to move the ring with
> the slit. Any thoughts on this
> Mangala Joshua
> Mesa Community College
_______________________________________________
Phys-L mailing list
Phys-L@electron.physics.buffalo.edu
https://www.physics.buffalo.edu/mailman/listinfo/phys-l