Re: [Phys-L] hands-on activity: Dirac String Trick

[brian whatcott <betwys1@sbcglobal.net>]

On 4/4/2020 8:17 PM, Zani, Gerald wrote:
> /snip/
> There is a patent device based on this that is described in an AJP
> article: Some mechanisms related to Dirac’s strings Edgar Rieflin Citation:
> American Journal of Physics 47, 379 (1979)
>   And Dick Berg has a good page about the Dirac Rope Trick here:
> https://physicslearning2.colorado.edu/QOTWSite/services/demos/demosp2/p2-61.htm
> /snip/
I found Berg's video clip helpful. I tried with a pair of cords, and 
even a single cord held firmly from rotating.
It came to me that I could never find an instance of a method of 
connecting signals to a rotating turn table without slip rings or rotary 
transformers that I read of, long ago. If I recall, it consisted of a 
cable anchored under the turntable to a pedestal, which looped outside 
the disk perimeter to be fixed near its top center. When the table spun, 
the cable rotated around the table perimeter, but did not tangle.
If I have even remembered this correctly, (did the cable come up through 
the hollow spindle possibly?) this would seem to be an application of 
the same effect. Perhaps the AJP would describe this? I have no access, 
unfortunately.

Brian W