Re: [Phys-l] non-conservative --> non-grady ???

[Brian Whatcott <betwys1@sbcglobal.net>]

At 08:40 PM 2/19/2008,  John D., you wrote, in part:

> >> 2) You can change the sum of KE and PE of a system by doing work
> >>  with a conservative force
> ....
>
> Example 1: ...
>  *) Define "the system" to be a charged particle, initially at rest, but
>   free to move.
>  *) Apply an electric field, initially zero, then nonzero, then zero again.
>  *) The particle picks up a nonzero kinetic energy.  BTW it also
>   picks up nonzero momentum.  Energy and momentum were transferred
>   across the boundary of "the system".
>  *) Potential is the same before and after, so the *sum* of KE and PE
>   is changed, not just KE at the expense of PE.

If I apply a voltage, and see a momentary current
(the charged particle moves)  then I am dispensing electrical energy
 across some boundary to a particle. I can see this, yet I still do not
understand the point in question. Perhaps I could ask:
What is the point that this example illuminates?



Brian Whatcott    Altus OK    Eureka!