DOC.
11
LECTURE ON ELECTRICITY & MAGNETISM
251
Doc.
11
Lecture
Notes
for Course
on Electricity
and
Magnetism
at
the
University
of
Zurich,
Winter Semester
1910/11[1]
Electrostatics
[p.
1]
If
one
rubs
glass, sealing
wax, or
other bodies
with
other
bodies,
then after
this
procedure
they
will
(temporarily)
exert forces
on
each
other that
were
not
observable
before,
without their
having
been otherwise influenced
in
a perceptible manner.
One
says
that
they
are
"electrified,"
where
by
this word
one
does not
denote
anything
but
what has
been
said.
Metals
&
many
other bodies
can
be electrified
only
if affixed to
a
prop
of
glass or sealing wax
etc.,
or
suspended
by
a
silk
body
can
be
electrified
not
only by
rubbing
but
also
by bringing
it
into
contact with
an
electrified
body.
Let
us
examine
the
laws
according
to which
electrified bodies
act
upon
one
another,
assuming
for
the
sake
of
simplicity
that the bodies
are
small
compared
with
the
distances
between them. The
forces
exerted
by
these bodies
on
each other
act in
the direction of
the
connecting
lines
(equality
of
action &
reaction,
we
can
measure
them
absolutely by
the methods of
mechanics,
for
example
in
the
following
way:
Consider
now
many
bodies,
say
small
metal
balls
suspended
by
silk
and
let
[p. 2]
us suppose
that
we
have
determined that the
forces
that
any
two
of them exert
on
each
other,
and
assume,
for the time
being,
that
they
are
at
a
distance R
that
always stays
the
same.
We
designate
attractive
forces
as negative, repulsive as positive.
If
we
combine the bodies
1
2
3
..
with
the
body a
of
our
group,
we
obtain the
forces
F1a,
F2a, F3a
....
.. If
we combine the same
bodies
1
2
3
..
with the body
b,
we
obtain
the
forces
F1b F2b F3b
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