Re: E or U continued

[Brian McInnes <bmcinnes@PNC.COM.AU>]

Hi Jim and All,
The use of U for internal energy is what is found in most "pure"
thermodynamic texts.  I don't know how far back this goes (perhaps it
does extend from early papers) but it certainly is enshrined in
Zeemansky's work. He really drew our attention to the distinction
between internal energy and heat and emphasized the need to be clear
in using the term "heat" - a message that you, Jim, have taken to
heart so well, congratulations. In so doing his presentation left most
of his users in no doubt that U was the term for internal energy.

More recently, however, those who are drawing our attention to the
marriage of energy conservation and the first law are using E as the
internal energy symbol.  When Arnold Arons writes down the FLT as
delta E  = delta E(therm) + delta E(chem) + delta E(kin) + delta E
(pot) + delta E(misc)  + ....    = Q  +  W  he really needs a
different symbol to U.
I see that Randall Knight in his Physics: A Contemporary Perspective
adopts the same symbols. And, as you point out, so does Reif>

So perhaps the day of U domination as the internal energy symbol is
passing.

More importantly, the day of applying energy conservation is mechanics
to particle systems only and worshipping at the temple of the
work-energy theorem and being unable to deal with simple situations
such as pushing off a wall or walking and running up a hill are gone
(well, I hope they have).

By the way, if I mystify anyone about this, please buy, borrow or
steal and then read Albert Arons' book "Teaching Introductory
Physics".  It is any physics teacher's best investment.
Brian McInnes
----------
> From: Jim Green <JMGreen@SISNA.COM>
> To: PHYS-L@LISTS.NAU.EDU
> Subject: E or U continued
> Date: Thu, 27 May 1999 2:21 AM

> The response to this previously posted question --
>
> |Please vote on the following intergalactically important question:
> |Should the internal energy of a system be written as U or as E?
>
> -- both public and private -- has been unanimously in favor of my friend
> the U
>
> But the E is also my friend and he tells me that he is a bit miffed -- Why,
> he asks, does the U get both internal energy and potential energy?   He
> wonders why there is this great fondness for the U.  Is this some sort of
> pedantic momentum which extends from the first papers and textbooks on
> thermodynamics?  Or is there some good reason for this choice?  And suppose
> that one wants to talk about the potential energy contribution to the
> internal energy, what then?  Would it really unnerve people to use E as the
> internal energy?  After all Reif does.
>
> Come to think about it, I wonder about this very important concern as well.
>
> Just me and my letter friends over here in our little corner --
>
> Jim Green
> mailto:JMGreen@sisna.com
> http://users.sisna.com/jmgreen