Re: The Capacitor problem - once more

[brian whatcott <inet@INTELLISYS.NET>]

At 09:23 6/3/99 -0400, Michael Edmiston wrote:
> I disagree with Jack Uretsky's analysis that the person connecting the
> capacitors absorbs the energy.  In his experimental description he may
> be correct, but he has changed the experiment drastically.
>
> I think my spring pendulum analogy can help us here.
>
> In the original case, simply connecting the two charged capacitors
> together is like letting loose of a stretched spring pendulum.  The
> spring pendulum either oscillates forever (no friction) or dissipates
> kinetic energy into thermal energy over some period of time.  Likewise
> the suddenly-connected capacitors oscillate forever (E-energy to
> B-energy and vice-versa) or else energy is radiated via some
> combination of thermal energy or as E&M waves.
>
> The process Jack describes is not the same.  Rather, his process is
> like slowly letting go of the spring pendulum.  Rather than simply
> letting go, keep holding onto the spring-pendulum mass and move it
> toward equilibrium, and only let go once it is at equilibrium.  In this
> case the person has "absorbed" all the energy that had been stored in
> the spring.  There is no oscillation and there is no generation of
> thermal energy (other than in the person)....

> Michael D. Edmiston

The physicist's strength in simplifying and idealizing, can be his
Achilles heel, if he moves from a (realistic) physical picture of a
pendulum losing a little energy each swing, to an (idealized) picture
of a pendulum being brought to rest so gradually that no energy is lost
thermally. This is the physicist's favorite idealization:
"In the limit..."

 So to differ with Michael, there is always (practically) some energy
lost thermally to air turbulence etc. in setting a pendulum still.

brian whatcott <inet@intellisys.net>
Altus OK