The Electrical experimenter

844 ELECTRICAL EXPERIMENTER April, 1918
SEVERAL
years ago I happened upon
the instructive and interesting little
work entitled, "Simple Experiments
in Static Electricity," by Percival G.
Bull. Experiment No. 9, Chapter IV,
of this book, dealing with spectacular con-
denser discharges, imprest me very much
in fact, to the extent that I couldn't help
but give it the due tryout. The "bronze"
or "metal" paper referred to and needed in
the experiment seems, as I faintly remember,
to be an uncertain article on the local
market. There is something entirely wrong
with it. Either the demand for it is so
brisk that stecks are early exhausted, or
there is no call for it at all, and, consequently,
nobody bothers with it. I was for
a time inclined to think the latter way,'
until finally, after a prolonged and fruitless
search among the various stationery stores,
I was shown at some small place what
looked to be the remnant of a once glorious
pile. Whether I purchased the real, honestto-goodness
"metal" paper or not has been
an open question with me to this day, since
it was not sold to me under that somewhat
mysterious sounding name. At any rate, it
works.
I mention this little incident only as an
Lei/den Jors
;
Electro-Static Experiments
By Frederick von Lichtenow
PART II (Conclusion)
I employed in these experiments two very
finely made static Leyden jars of one pint
size each in connection with the always dependable
little "Electro" Wimshurst static
machine. According to the book in reference
the jars are to be placed one at each
end of the paper and connected with their
inner coatings to the respective poles of the
machine. I have placed them in various positions,
these latter depending on the spark
effect desired, as well as necessitated by the
nature of the paper itself.
The following illustrations
scriptions give the results
and short de-
of my tests
< Fig -
J) '
Characteristic
c
of this paper is
^
that
,
the
sparks always show a strong tendency
toward branching out over its surface,
whether the distance between the jars
be a few inches or a foot, or even more.
Their
With
color is
the jars
a beautiful
separated by
bluish-white.
only a few
inches, and up to six inches or so, the discharge
manifests itself in thousands of
bright little stars hanging together by shiny
threads. These very striking effects are
due to the relatively high conducting quality
of the metal particles covering this paper.
The paper illustrated in Fig. 2, offering a
Sap snou/a squore/y face
ff)e electroscope
Electroscope
A Novel and out-of-the-ordinary Static Experiment Which the Author Discovered. The
Insulated Electroscope Responded to the Unipolar Oscillatory Waves Set Up by a Silent
Discharge in the Spark Gap, Owing to Its Ball Being In Line With Those on the Spark Gap.
example of the handicaps, which at times
confront the experimenter even in big cities,
and which are
sponsible for the
only too frequently re-
fact that many otherwise
highly instructive and fascinating experiments
are left untried. Needless to say, I
have had several real disappointments of
this nature since, not only "close calls"
like the above.
My aim in this article is to put down the
results obtained with, and various spark
effects noted on, three different grades of
"bronze" or "metal" paper—the only number
I was able to secure—which are not
given in the aforementioned book. Following
in the order of their relative resistance
capacity they are "silver" paper, the "copper-bronze"
paper and the "brass-bronze"
paper, the latter being the poorest conductor
of the three. They measure each, as cut by
me, 19^ inches in length (the original width
of the paper) by &A inches wide, an ample
size for the accommodation of even the
largest Leyden jars ordinarily used.
somewhat higher resistance to the condenser
discharge than the former, limits the distance
between the jars to Yi, of a foot. At
or near that distance the sparks are very
pronounced and appear concentrated in the
form of miniature lightning bolts of a clear
white color. They hit around in curves and
are accompanied by a loud report. If the
jars are approached to within 4 inches or
less, as indicated in "b," the sparks will dart
in spray fashion across the intervening
space, lighting up in a vivid emerald green.
(Fig. 3.) As I have stated before, this
paper is a poor conductor, and, consequently,
permits only a separation of a few inches
between the Leyden jars. Set at that distance,
the spark effect is very similar to the
one noticed on the "copper-bronze" paper,
Fig. 2-b ; however, it is not quite so distinct.
The color shade of the sparks runs
more into a dull yellowish green, not unlike
that or oxidized brass.
The above spark-and-color effects are
those as observed in an artificially (moder-
ately) lighted room. The papers may be
placed in triple or quadruple layers, thus
insuring a better insulation for the Leyden
Spectacular Condenser Discharges Can
Be Arranged With Metalized Paper, a
Pair of Leyden Jars and a Small 3" Static
Machine. This is a "Silver Paper" Experiment.
jars, in addition to which an oilcloth covering
on the table may be advisable. Care
must be taken that the discharge balls of
the machine are first to be separated beyond
sparking distance while charging the jars,
and not set "a few inches apart," as prescribed
by the text book, which may be
misunderstood, since the small Wimshurst
machine I used
three-inch spark
condition, not to
in these tests delivers a
alone, when in a healthy
speak of the many larger
static machines with their correspondingly
greater output. After thus charging the jars
for a short while the electrodes are gradually
and slowly approached toward
other, when upon reaching the stress
each
limit'
the resulting spark will be accompanied by
the condenser discharge across the paper.
Following the above tests I was led to
another experiment, terminating in the following
discovery—if I may call it such—
which I will give here for what it is worth
In order to ascertain the conducting value
of these metal papers as a circuit link, I had
included a separate
the former set-up.
gap (spark gap) into
With the conductors
of the machine set wide apart I was testing
the spark across this new gap under various
Different Forms of Discharge Effected
Between Leyden Jars Set at Various Distances
Apart on Copper-Bronze Paper.
: