Re: non-dissipative circuitry

[Bernard Cleyet <anngeorg@PACBELL.NET>]

Sorry.  I conflated the current discussion (charging a cap.) with
discharging one slowly or rapidly (through a large value or zero
resistance).

The answer must be yes to conserve energy, yes?  As you answer,
indirectly, in part B.

I haven't followed closely the latter part of this thread, but ...
would connecting a cap to a chemical cell at low temp. and raising
veerrry slowly the temp. be a method of charging with low dissipation?

bc  who heard liquid air was used to disarm Jerry UXBs during the blitz.

"John S. Denker" wrote:

> Bernard Cleyet wrote:
>
> > Is this confirmation or .... of my claim that the total energy
> > dissipation (radiation + I^2*R) is constant.
>
> If the answer concerns constancy of the dissipation,
> we need to be rather explicit about what the
> question is.
>
> A) If the question is what's the minimum dissipation
> for bicharging a capacitor C to a voltage V, then
> the answer is _not_ .5 C V^2 or any other constant.
>
> The dissipation could be very small, using methods
> discussed in previous notes.
>
> B) If you really want the answer to be .5 C V^2,
> then you can cobble up a suitable question,
> perhaps along the lines
>   -- voltage source V, switch, resistor R, capacitor C
>   -- V = constant
>   -- no other circuit elements
>   -- no variable capacitances
>   -- et cetera.
> and then you can make it possible to prove, using
> conservation of charge, conservation of energy, etc.,
> that there will be dissipation of .5 C V^2, independent
> of R.
>
> It is a question of taste whether you choose to
> restrict the question as in (B).  Choose what
> you like, but remember that others may choose
> differently.  Remember that it is a choice, not
> a law of nature.
>
> I've had the experience of being yelled at by
> an entire roomful of "experts" who "knew" that
> .5 C V^2 dissipation was a law of nature.  And
> they had a stack of textbooks to "prove" it.
> ... But all their yelling didn't change the
> facts.  There really are low-dissipation ways of
> charging a capacitor.