254
DOC.
11
LECTURE ON ELECTRICITY
&
MAGNETISM
[p. 6]
e.e x-a.
K,
=
exe
y
-bx
(1)
yi
1
e.e z-c.
/*i
r\
If
several
masses
e1
e2
....
act
simultaneously on mass
e, we
get[5]
e.e x-ax
eg x-a2
"
ex
x-a
K
=DC
=
J
-
+
-i
-2=
e
Y
-i *
xl
i
ri
"
r22
o
r2
o
r\
------------------
------------------
For
a given
distribution of the
masses
e1
etc., and a given
position
for
e,
these
force
components are proportional
to
the
e.q.
e.
But the sums
appearing on
the
right-hand
side
depend
only
on
e1
e2
...
&
the test point. These
sums
e x-a
1 1
=
X (other components
Y
Z)
1
Ti
are
called
the X-component of
the
electric
force
or
field strength.
It
is
equal
to
the
force
exerted
on
the unit of
electricity.
X
Y Z
is
a
vector
which
is
related
to
the vector of
the
force acting
upon
the
e
quantity
e
in
the
following
way:
Kx = eX Ky = eY K2 =
eZ
.....
(2)
If one
draws from every spatial
point
a
directed
straight line in the
direction of
the field
intensity,
one
gets a
picture of
the
course of
the field intensity,
of
the
vector
field
X
Y Z
that
brings
about
the (possible) actions
of
forces deriving from the
quantities
e1
e2
etc.
This field
is
determined
chiefly by
3
spatial functions (X Y and
Z).
However,
these
can
be
reduced
to
a
single spatial function.
For
we have
[p.
7]