190
DOC. 4 KINETIC THEORY
LECTURE NOTES
[p. 41]
From
this
a
RT
3nr\P
Na
=
A
RT
1
A2
=
N
3nrjP
This
formula determines
Brownian
motion. Rotational motion
can
be obtained
in
an
analogous
way.[82]
Magnetism
1.
Gases
cosh
a 1
r, x
uH
-
=
F(a)
a
=
_
I sinha
a
0
0
1 For
all
attainable
fields
a
is
so
small
that
one can
set
F(a)
=
1/3a.[83]
Thus,
practically
3
r
_
1
r
_1/MV/H
3
0
3
\RTJ
T
M M
_
NnH
_
MH
0
~
T
~
RTP
U
~
RT
~
RT
2.
Solids.
Ferromagnetism.
To
explain
the
magnetic
properties
of
solids,
Weiss
assumes
that
magnetization
acts
like
a magnetizing
force
parallel
to
them.[84]
(We
shall confine ourselves to
one dimension.)
Hm =
NI.
We then
have two
equations
L
=
F(a)
a
=
-(H
+
Hm'
)
=
-(H
+ WI)'
I0
v
RTy
RTK
First
we
consider the
case
where
no
external
force
is present;
we
have
then