Re: ENERGY WITH Q

["John S. Denker" <jsd@MONMOUTH.COM>]

At 10:48 AM 10/25/01 -0700, kowalskil wrote:
> Do we really need the term "internal"? What is wrong with keeping only
> thermal, non-thermal and total?

That's a good question.  It made me think for a while, with the following
results.  Calling it "internal" is a bit odd.  Calling it "total" runs a
very slight risk of confusion between the total energy of this system and
the total energy of the universe.  Therefore I would present it as follows:

Let's write
        E_plain = E_nonthermal + E_thermal

The LHS is just the plain old energy. It is sometimes referred to as the
``common'' or ``ordinary'' energy, which means the same thing. It is
sometimes called the ``combined'' or ``total'' energy, referring to the
combination of thermal and nonthermal contributions. It is very often
called the ``internal'' energy, which is a slightly odd way of emphasizing
that it is the energy of the system in question, not the energy of the
whole universe. In most contexts you can just call it E, the energy, with
no adjectives at all.

> some energy inside a system can be nonthermal. Think about a system
> containing compressed springs and rotating wheels.

Yup.  Latent heat is another good example (melting, boiling, ...).