Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] Poynting Vector

On 06/30/2008 08:11 AM, chuck britton wrote:

This is not intended to reproduce Feynmann's example

From where I sit, it looks essentially identical to Feynman's

The main difference is the use of a capacitor (a bilayer of charge)
whereas Feynman used a single layer of charge.

Another wrinkle is that he used insulated dots of charge, so there
would be no questions about eddy currents in the capacitor plates.
The doesn't affect the long-term outcome, because the eddy currents
will eventually die out, and angular momentum is conserved. Or
you could just cut some slits in your coaxial capacitor.

but I am
(perhaps incorrectly) assuming the same phenomena are involved.

Looks the same to me!

The idea for the coaxial capacitor was cribbed from Feynman. I was
hoping somebody would notice the correspondence.

... a short, superconducting solenoid in free space.
Short, because we must make use of the non-zero field outside the

You don't want to make it too short. You want its length to be comparable
to the length of the coaxial capacitor ... and you want the capacitor to
be reasonably long because otherwise you'll have lots of fringing fields
that are hard to keep track of.