SOME ELECTRICAL EFFECTS
THE MAGIC OF MYSTERY
A PHENOMENON is always mysterious, so long as its origin remains hidden.
That is to say that any event, the causes of whose manifestation are
obscure, will be found to prompt some feeling of wonderment.
For this reason then--just as an automobile in motion will bewilder a
savage, because he has at no time seen any but living creatures moving,
and does not understand the new mechanism--so for us an electrical
effect mostly presents something of a miraculous nature. To take a
concrete example. Whereas the ringing of a church bell by the sexton
engenders no feeling of wonderment in the average listener’s breast, the
buzzing of an electric bell, which ensues upon connecting with a
battery, does have this influence to a greater or less extent, because
the electricity’s behavior is by no means so obvious as that of the
sexton pulling the rope.
Let this character of the miraculous then, which pertains with scarcely
an exception to every electrical phenomenon, stand as an excuse for the
experiments to be detailed hereafter.
Electricity may be produced by a variety of methods. For commercial
purposes, where unstinted supplies are necessary, mechanical energy is
converted into the subtle force by means of dynamos. Exceptional sources
of mechanical energy are now frequently used, as witness the Niagara
Falls, where electric current is produced on the site, and whence it is
conducted by cables to places of utility; and also the case of Nansen’s
“Farthest North” Expedition (before Cook found the Pole!), which
utilized a deck windmill for installation of electric light aboard.
Electricity is also produced when any two substances are brought into
contact, and more especially if they are placed near one another, but
not touching, in certain liquids, thereby forming “cells.” With these
arrangements, electricity finds its source in chemical action; and,
although not powerful, such cells are extensively employed, on account
of reliability, in telephone and telegraph systems. No more convenient
source of galvanic energy has yet been devised than a battery of
“cells”--_i.e._ a number of cells connected together--and the type which
we intend to use, and of whose construction the following is a
description, is among the cheapest possible to make and maintain.
The battery is to consist of eight cells, connected together, in a
manner hereafter described. For each cell procure a 1 lb. stone jar (A),
and line it inside with a sheet of tin (B), which may be cut from a
condensed milk can, and should be curved so as to press outwards against
the jar’s inner surface (Fig. 1). A 2-inch length of copper wire (C) is
soldered to its upper edge.
[Illustration: FIG. 1.--Making a cell.]
[Illustration: FIG. 2.--Copper spiral surrounded by broken coke in rag
or flannel bag.]
The next operation is to twist an 8-inch piece of copper wire for about
6 inches of its length round a pencil, thus forming a spiral (X), round
which a flannel bag (A) filled with small coke (B) is tied (Fig. 2). At
least two thicknesses of flannel are advantageous, or if this be found
rather expensive, flannel and rag combined, or odd pieces of rag alone
may be utilized.
The chief considerations are to construct a porous wall of appreciable
thickness round the coke, and to avoid colored rags if possible. The bag
is to stand upright in the middle of the jar, leaving about ¹⁄₂-inch
space all round to be packed with zinc scrap, which for convenience may
well be “granulated.” To make this, melt up as much waste zinc as can be
collected in a ladle and pour it in a thin stream into a large bowl of
cold water, moving the ladle over the surface of the water meanwhile, in
order to cool the zinc stream as suddenly as possible. The zinc which
forms in a heap at the bottom of the bowl should be breakable into very
small pieces, and is termed “granulated” (Fig. 3).
[Illustration: FIG. 3.--Granulating zinc.]
[Illustration: FIG. 4.--Section of the complete cell.]
When the cell has thus been assembled with curved tin sheet, bag of coke
and broken zinc in place, it is nearly filled with strong salt solution,
and above this, in order to prevent evaporation, a thin layer of melted
tallow may well be poured. Fig. 4 represents a section of the complete
cell, A being the flannel bag containing coke; B², wire from coke; C,
wire from tin; D, layer of tallow; E, level of solution; F, the jar; G,
the tin; H, the zinc.
[Illustration: FIG. 5.--Tray to carry battery of cells.]
[Illustration: FIG. 6.--The complete battery.]
The eight components of the battery being thus complete, nothing
necessary remains but to connect them together. However, they will prove
more portable and self contained if arranged in a shallow wood tray.
This may be either a confectionery box--if one of suitable dimensions is
obtainable--or can perhaps be constructed as indicated by the
accompanying sketch, with handles at either end (Fig. 5). It should
certainly be strong, as the set of jars is of considerable weight, and
would, if accidentally dropped, create a pretty printers’ pi. Lastly,
when the cells have been arranged in two rows of four a side, the
finishing touch is to join the copper wire ends by twisting, according
to the plan shown in Fig. 6, and the battery is complete. The end wires
A and B will be referred to hereafter as negative and positive terminals
respectively.
[Illustration: FIG. 7.--The compass test.]
_Experiment 1._--Connect one extremity of a straight wire with the
battery’s positive terminal, and place it on the table so as to lie due
north and south. Above it stand a compass, whose needle--also pointing
due north and south--will be parallel to the wire (Fig. 7). Now, when
the free end of the north-south conductor is connected to the battery’s
other terminal so that a current may flow, the needle swings round at
right angles and thus now lies east and west. Needless to add,
electricity prompts the needle’s behavior, and unless such movement does
take place, the cells are at fault somewhere.
[Illustration: FIG. 8.--Spark-producing.]
_Experiment 2._--Having decided by the compass’s behavior that the
battery is actually efficient, bring the terminal wires into contact in
the dark, and notice the slight spark (Fig. 8). Next obtain a spare
bobbin from an old electric bell (Fig. 9), and pass the current round
the coils whilst making the spark. This should now be more
distinct--thicker, and brighter, though not so frequent--owing to
induction taking place between the wire coils.
[Illustration:
AA. Bell-bobbin coils.
B. Iron base.
C. Wire from battery terminal joined with one end of coil wire.
D. Other end of coil wire.
E. Wire from other battery terminal.
FIG. 9.--Showing connections for passing current round bell-bobbin
coils.]
_Experiment 3._--Repeat the previous experiment whilst using pieces of
carbon, round which the free wire ends (D and E, Fig. 9) are twisted, to
bring into contact with one another (Fig. 10). The spark obtained is
very bright, and may possibly by careful handling be maintained for a
moment or two; if the current is more powerful, the spark does keep
constant, even though the carbons be drawn apart considerably, and thus
forms in principle such an arc lamp as floods the streets of towns with
their dazzling rays. The pieces of carbon may frequently be picked up
beneath arc light standards, after the electrician has gone on his
rounds “trimming” the lamps.
[Illustration: FIG. 10.--The principle of the arc lamp.]
_Experiment 4._--Again repeat the No. 2 experiment, but insert a rough
file in the circuit and drag the free end of a wire from the battery up
and down its surface (Fig. 11). Sparks in plenty, but apparently frail
and resembling those thrown off by squib fireworks, are produced in this
manner.
[Illustration: FIG. 11.--More spark production.]
[Illustration: FIG. 12.--Magnetic lines of force.]
_Experiment 5._--If a few iron filings (A, Fig. 12) be scattered evenly
on a sheet of paper (C, Fig. 12) and a horse-shoe magnet (B, Fig. 12)
approached from beneath, the filings arrange themselves in a curious
design, which really maps out the magnetic lines of force. Now, if this
experiment is repeated whilst using the bell-bobbin in place of the
permanent horse-shoe magnet, and a current passed round the coils, the
same disposition of the filings ensues, showing that the bobbin’s iron
cores have been magnetized. In Fig. 13, A is the filings; B, the wire
from negative terminal battery; C, the sheet of paper; and D, the wire
from positive terminal.
_Experiment 6._--“Flax” wire, whose core consists of about forty fine
copper filaments stranded together, may often be had in scrap lengths at
electricians’ shops, as it finds wide employment in lighting
installations. The silk and rubber insulation should be ignited and
allowed to burn, any residue being carefully wiped off with rag, after
which two lengths of, say, three strands apiece are separated from the
wire core. These are very flexible, so that when attached to the battery
terminals and magnet wires the bobbin, being extended as shown by a silk
strand, is able to revolve freely in any direction. As a matter of fact,
whilst the current is flowing the bobbin sets itself north and south
like any other magnet--a very ordinary performance, the reader may
remark! But, on the other hand, if the flexible wires be changed over so
that the one previously connected to the battery’s positive terminal is
now connected to the negative and _vice versa_, with the result that the
current travels round the bobbin coils in an opposite direction, the
electro-magnet swings half a turn, and comes to rest with its pole that
was towards the north now pointing south. So that the bobbin resembles a
weathercock, except in so far as it changes with the current instead of
the wind (Fig. 14).
[Illustration: FIG. 13.--The filings arrange themselves in a curious
design.]
[Illustration: FIG. 14.--An electrical weathercock.]
_Experiment 7._--The number “7” has been regarded among races of men as
peculiarly fortunate. Perhaps happily, therefore, it falls to this
experiment, which, indeed, is rather the construction of new than the
arrangement of old apparatus. The magnetic properties of a bell-bobbin
may be utilized in constructing a primitive electro-motor. Decapitate
four 1¹⁄₂-inch nails, and, having bent ¹⁄₈-inch of both ends of each at
right angles, mount them equal distances apart round the circumference
of a thread reel (Fig. 15).
[Illustration:
A. Nail ready to drive into reel.
FIG. 15.--A primitive electro-motor.]
[Illustration:
A. Square of copper or tin.
B. Brass standard.
FIG. 16.--Standard for electro-motor.]
Next plug the center hole of this reel with hard wood, and bore another
hole through of smaller diameter, so as to slide stiffly on a straight
piece of ¹⁄₈-inch brass wire. About 1 inch from the cotton reel is to be
soldered a ³⁄₈-inch square of tin or copper sheet, having a hole at its
center through which the brass spindle passes (Fig. 16). Two small brass
standards, for which straightened curtain-rod clips may well be
employed, are screwed about 3¹⁄₂ inches apart to a wooden baseboard, and
have a hole drilled near their top edges to accommodate the spindle (B,
Figs. 16 and 17). This being placed in position, should be provided near
the bearings with washers (E, Fig. 17) and beads (D, Fig. 17), the
washers being soldered in order to prevent lateral movement of the
shaft. Lastly, with a view to realistic appearance, solder a small tin
fan (C, Fig. 17) to one projecting end of the spindle, and enamel or
paint it gray. The arrangements of these fittings are made quite clear
by the diagram.
[Illustration: FIG. 17.--An electro-motor.]
[Illustration:
H. Wood strip across top of magnet.
I. Block of wood supporting bobbin at correct height.
J. Wood base board.
FIG. 18.--Bell-bobbin mounted.]
By now the most difficult part of our task has been attempted, so that
if the reel and spindle revolve “sweetly” in the bearings, no doubt need
be entertained as to whether the motor will ever reach completion.
The bell-bobbin must be mounted with its magnet faces as near the reel
circumference as possible, and with their centers the same height above
the baseboard as the spindle. A piece of wood beneath the bobbin, of
such thickness as to keep it at the right height, and another strip
across the top, through the ends of both of which screws are driven into
the baseboard, will secure the magnet firmly in position (Fig. 18). The
next operation is to bend a springy strip of brass to the shape shown in
F, Fig. 19, and fix it immovably by the screw G--round which one free
end of the bobbin wire (L) has been twisted several turns--to the
baseboard, so that its top portion misses the metal square or
contact-breaker (P) on the spindle by about ¹⁄₄ inch. Now drive a second
screw (R) carefully into the wood through another hole in the strip,
until this latter presses lightly against each point of the
contact-breaker successively as the spindle revolves.
[Illustration: FIG. 19.--The contact-breaker.]
[Illustration: FIG. 20.--Showing wire connections (X, Y, Z) and motor.]
The little motor is now complete, except, perhaps, for the addition of
two terminal screws, one of which is joined with the remaining free
bobbin wire, and the other by a short length of wire to either of the
bearings. The entire connections are shown in the accompanying sketch
(Fig. 20). Now for working! Connect the battery wires to the motor
terminals, and adjust the spindle so that one corner of the
contact-breaker is fairly touching the vertical brass strip. A current
should now be flowing round the bobbins, which consequently become
magnetized and attract the nearest iron nail fastened to the thread
reel. If the iron is not sufficiently near to be under the magnet’s
influence, turn the reel _on the shaft_ until it is in the proper
position. The motor, with a little adjustment, ought to run merrily, as
the bell-bobbin--alternately magnetized and demagnetized--attracts and
releases the short iron bars.
_Experiment 8._--Connect the battery terminals together by means of some
thin iron wire such as is used for wiring flowers, and twist it into a
spiral so that it may rest comfortably in a cup of cold water (A, Fig.
21). Stand also therein a thermometer (B, Fig. 21). The water’s
temperature will be observed to rise steadily, showing that the passage
of the electric current heats the iron wire (C, Fig. 21), which in turn
imparts some warmth to the surrounding liquid.
[Illustration: FIG. 21.--Warming water by electricity.]
[Illustration: FIG. 22.--Decomposing water into its chemical
constituents by means of an electric current.]
_Experiment 9._--The previous experiment showed that an electric current
heats a material through which it passes. If the thin iron wire be
shortened to a length of about ¹⁄₂-inch, our battery will probably bring
it to red-heat, thus demonstrating the principle of electric
incandescent lamps. The difference between theory and practice, however,
in this case consists in the use of carbon, or, very rarely, platinum,
in place of the iron filament, and of inclosing this in a glass bulb
free of air, so that combustion cannot proceed rapidly.
_Experiment 10._--Immerse two wires from the battery terminals at some
little distance apart in a glass of water, which has been _slightly_
soured with sulphuric acid or spirits of salt. The weak acid readily
conducts the electric current, which decomposes the water into its
chemical constituents, hydrogen and oxygen, the former gas coming off in
bubbles at the wire which leads from the battery tins, and the oxygen
round the other conductor (Fig. 22). The hydrogen bubbles may perhaps be
ignited as they are evolved by holding a lighted match just near the
water’s surface; or another method is to seal the wires into separate
glass tubes, so that both dip beneath the water, and light the hydrogen
gas as it escapes from the tube’s upper end (Fig. 23). In this case
great care must be taken to allow time for the expulsion of all air from
the tube, because hydrogen and air in certain proportions form a very
explosive mixture.
[Illustration: FIG. 23.--The hydrogen bubbles may be ignited by holding
a match near the free end of the hydrogen tube.]
[Illustration: FIG. 24.--Electro-plating in its infancy.]
_Experiment 11._--Repeat the foregoing experiment, using copper sulphate
solution in place of the acidified water. After the current has passed
for some time, one of the wires will be noticed to have become thicker
whilst the diameter of the other has decreased. This behavior is owing
to deposit of copper from the solution on the one conductor and
abstraction of metal from the other, whose bulk diminishes in
automatically maintaining the solution’s strength (Fig. 24). In this
reaction is seen the basis of commercial electroplating--silver and
nickel solutions being mostly employed instead of the copper bath, since
these are the metals with which those of a baser nature are more
frequently plated.
_Experiment 12._--Electrotyping is a modification of electro-plating,
where a mold of wax coated with some conducting substance like graphite
is used to deposit the metal upon. Melt some quantity of sealing-wax on
to a piece of cardboard, so that it spreads out slightly larger in
diameter than a fifty-cent piece, and when just plastic press the “head”
surface of the new coin into the wax, so that an exact replica is
obtained. Fasten a copper wire by some extra wax to the cardboard disc
(as in Fig. 25), and carefully cover the whole matrix with powdered
blacklead, working it well into the crevices and up to the copper
conductor, with a camel-hair brush. Hang this in a jar containing
saturated copper sulphate solution--the copper wire being connected to
the negative battery terminals (A, Fig. 26), whilst a sheet of copper or
coil of wire is suspended in the solution some little distance from the
sealing-wax mold, with a wire connecting to the other battery terminal
(B, Fig. 26).
[Illustration: FIG. 25.--Preparation for experiment in electrotyping.]
[Illustration: FIG. 26.--Sealing-wax mold suspended in solution of
saturated copper sulphate, near to sheet of copper or coil of wire.]
So long as the current continues flowing a reddish deposit will form on
the blacklead surface, and if the action be allowed to continue until a
fair thickness of metal is secured, the wax may be carefully melted off,
leaving an exact relief of a fifty-cent piece’s reverse side in a
copper. Any medal or seal may be used in place of the silver piece to
obtain a first mold, but the coin has been mentioned as being probably
the most suitable article near at hand.
With this example of electrotyping, our series of descriptions must
terminate. But the embryo scientist, who has traveled thus far, need not
cast his apparatus to the winds and henceforward forsake electrical
matters. He may arrange various combinations of wines and liquids--such,
for example, as passing the current through water to his motor, and
noting the decrease in speed, or insert various lengths of iron wire in
the circuit. Possibly the batteries will betray exhaustion, and they may
then be reinstated by discarding the old salt solution, rinsing and
replenishing the granulated zinc, and washing the flannel bags in
permanganate of potash solution. These batteries are, in fact, a real
asset, as they can be used--three or four together--in setting up an
electric-bell installation, and are easily replenishable, when at length
their life begins to ebb.
An endless fund of amusement--less expensive and more instructive than
many--awaits those who explore the realms of the pygmy lightning spark.