68
GENERAL
MOLECULAR THEORY OF HEAT
Doc.
5
ON
THE GENERAL MOLECULAR THEORY
OF
HEAT
by
A.
Einstein
[Annalen
der
Physik 14
(1904):
354-362]
In the
following
I present
a
few
addenda to
an
article I
published
last
year.1
When
I
refer
to
the
"general
molecular
theory
of
heat,"
I
mean
a
theory
that is essentially
based
on
the
assumptions put
forth in
§1
of the article
cited. In order
to
avoid
unnecessary
repetitions,
I
assume
that the reader is
familiar
with that article
and
use
the
same
notations I
have used
there.
First, I derive
an
expression
for
the entropy
of
a
system, which
is
[2] completely analogous to
the
expression found
by
Boltzmann
for ideal
gases
and
[3] assumed
by
Planck
in
his
theory of
radiation.
Then
I
give
a
simple
derivation
of
the
second law.
After that
I examine
the
meaning
of
a
universal
constant,
[4]
which
plays
an
important
role in the
general
molecular
theory
of
heat.
I
conclude with
an
application of
the
theory to black-body
radiation,
which
yields
a
most
interesting
relationship between
the
above-mentioned
universal
[5]
constant,
which is
determined
by
the
magnitudes
of the
elementary quanta of
matter
and
electricity,
and the
order of
magnitude
of
the radiation
wave-
lengths,
without
recourse
to
special
hypotheses.
§1.
On
the
expression
for
entropy
For
a system
that
can
absorb
energy
only
in
the
form
of heat,
or,
in
other
words,
for
a
system
not
affected adiabatically
by
other
systems,
the
following equation
holds
between
the absolute
temperature
T
and
the
energy
E,
according
to
§3
and
§4,
loc.cit.:
[1]
1A.
Einstein,
Ann.
d.
Phys. 11 (1903): 170.
Previous Page Next Page