Re: [Phys-L] circular definition of "success" .... was: standard DC circuits

[brian whatcott <betwys1@sbcglobal.net>]

On 12/2/2013 1:40 AM, John Denker wrote, in part:
> /snip/
Not all springs obey Hooke's law. There exists such a thing as a 
constant-force spring, where the force is independent of x. Such things 
are an article of commerce; ...In contrast, a Hooke's-law spring is less 
than ideal, because the force changes as a function of x. The same 
concepts apply to the other terms on the RHS of equation [1]. An ideal 
heat bath maintains a constant temperature, independent of S. Now ... an 
important term has been left out of equation [1]. It would be better to 
write dE = T dS - P dV - F dx + (voltage) d(charge) .... etc. [2] The 
fourth term on the RHS can be taken as an implicit /definition/ of 
voltage, much as the first and second terms can be (and often are) taken 
as implicit definitions of temperature and pressure. Again the same 
concepts apply. An ideal battery, by definition, maintains a constant 
voltage at its terminals, independent of how much charge goes in or out. 
It is profoundly analogous to an ideal anvil, and to an ideal heat bath. 
Consider the following statements: "An ideal tensioner maintains a 
displacement and a force." "An ideal heat bath maintains a certain 
entropy and temperature." «A battery maintains a charge separation and a 
potential difference.» The first time I see a statement like that I just 
assume it is a typo and laugh it off. However, when somebody makes a 
concerted effort to defend such a statement, I say wow, we are dealing 
with some serious misconceptions. /snip/
    ***************************

This is a beautifully stated description of a misconception, but it is 
not certain whose misconception is in question.
I see that Bruce understands that charge separation can be a static 
entity, in much the same way that immense force applied on a stiff 
bulkhead provides a displacement /displacement/ with no subsequent work 
done like a large constant electric field can provide a charge 
separation indicated by a displacement /current/ with no subsequent 
energy expenditure.
   I get the impression that John is conceiving the term "charge 
separation" to be a solely dynamic entity dQ/dt rather than comprising 
the static dQ/dx in addition, which is called polarization.

Sincerely

Brian Whatcott   Altus OK