Steve's original statement of the Laws of Thermodynamics as given by
C.P. Snow are pretty succinct and an
easy way to remember them. When stated in the usual language of
physics, they do become a little less
clear to the layman. Whichever way you prefer, I would add a couple of
things as an attempt at clarification
and elaboration.
The First Law is also known as the Law of Conservation of Energy. Most
people have heard of this, but it
simply states that the total amount of energy in an isolated system is
constant. That is, energy can be
converted from one form to another, but cannot be created or destroyed.
Automobile engines operated by
converting the chemical energy stored in gasoline into heat. Engine
modifications to gain power are involved
with finding ways to convert the energy content in gasoline into heat
more rapidly. Power is the measure of
how fast energy is being converted. You can, of course, use gasoline
with more energy content (i.e. higher
octane) as well, but the principle remains - energy in = energy out.
The Second Law, also known as the Law of Entropy, concerns itself with
more practical matters. It basically
says that energy conversions involve "losses". Most of the time these
losses appear as heat, which is just
the random motion of molecules. In an automobile engine, when the
chemical energy stored in the gasoline
is converted into motion of the engine, some of the energy is also
converted to heat due to friction. This
turns out to be quite a bit of energy, so most automobile engines are
not very efficient devices. The Second
Law also explains why many processes, even though they do not violate
the First Law, are not seen to take
place. That is why many processes that can be observed in a film run
backwards seem so strange - they
represent processes which diminish the amount of Entropy (or disorder)
in a system. Put simply, things run
downhill spontaneously, not uphill. It is on the basis of this law that
perpetual motion devices are precluded.
One can get into a lot of philosophical discussions with the Law of
Entropy and the implications it has for the
direction of time, etc. One other interesting aspect of this law is
that it is not absolutely true, in the sense
that it is a statement of statistical probabilities.
Finally, these laws operate whether we wish them to or not.
Consequently, it would, indeed, be helpful if
those who determine the policies of our government with regard to energy
could take the time to understand
them. The comments of a couple of folks in this forum regarding the
conversion of corn into ethanol and the
possibility of using hydrogen power for vehicles might be better
understood in light of these laws.
Tod
B382002384LRXFE
(constantly generating entropy in my little corner of the universe)
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