<h2><SPAN name="CHAPTER_VI" id="CHAPTER_VI"></SPAN>CHAPTER VI.</h2>
<h3>ELECTRIC CURRENTS.</h3>
<p>The simplest form of an electric machine is
one in which the operator is a prominent part
of the operation. Electricity, like magnetism,
operates in a closed circuit, even when it is
static—so-called. Take a stick of sealing-wax,
say, in your left hand, and rub it with a piece
of fur or silk with your right hand, and you
have the simplest form of electric machine—the
one that was known to the ancients, and
the one from which the science, great as it is
to-day, had its beginnings. The stick of sealing-wax
is one element of the battery, and the
piece of fur or silk is the other, while your
hands, arm and body form the conductor that
connects the two poles, and the friction is the
exciting agent and may be said to take the
place of the fluid of a battery. The electrical
conditions are not wholly static, as a slow current
is passing around through your arms and
body from one pole to the other. Even if the
conditions were wholly static there would be
polarized lines of force, in a state of strain,
reaching around in a closed circuit.<span class="pagenum"><SPAN name="Page_50" id="Page_50"></SPAN></span></p>
<p>If we rub the wax with the fur and then
take it away the wax has a charge of electricity
and will attract light objects. If we had rubbed
a piece of metal or some good conductor it
would have been warmed instead of electrified.
In both cases the particles of the substances
have been affected, and if the atomic theory is
correct—and it seems plausible—in the former
case the atoms are partly put into electrical
motion and partly into a state of electrical
strain that we call static (standing) electricity;
while in the latter case the atoms are
put into the peculiar motion that belongs to
heat. The former we call electricity, and the
latter we call heat. The electro-atomic motion
under some circumstances readily turns to
heat, which seems to be the tendency of all
forms of energy. The electric light is a result
of this tendency. All non-conductors, or electrics,
have a complex molecular structure, and,
while their atoms when subjected to friction
are put into a state of electrostatic strain, they
are not able readily to respond as a conductor
of dynamic electricity. The electric-light
filament in the incandescent lamp is a much
poorer conductor than the copper wire that
leads up to it. The copper wire is readily
responsive to the electrical influence, but the
carbon filament is not. So electrical action
that freely passes along the wire, is resisted
and becomes heat action in the filament, and<span class="pagenum"><SPAN name="Page_51" id="Page_51"></SPAN></span>
light is the attendant of intense heat. But, to
go back to the sources of electricity.</p>
<p>Frictional electric machines have been constructed
in great variety. All, however, embrace
the essentials set forth in the sealing-wax
experiment, and would be difficult to
describe without cuts. Let us, therefore, consider
another source of electricity, which was
the outgrowth of the discovery of Galvani (or
rather his wife), and reduced to concrete form
by Volta. We refer to the galvanic or voltaic
battery. If we put a bar of zinc into a glass
vessel and pour sulphuric acid and water into
it, there will be a boiling, and an evolution of
hydrogen gas, and energy is released in the
form of heat, so that the fluid and the glass vessel
become heated. Now let us put a bar of
copper or a stick of carbon into the glass, but
not in contact with the zinc; connect the ends
(that are not immersed) of the two elements—copper
and zinc—with a metal wire or any conductor,
and a new condition is set up. Heat is
no longer evolved to the same extent, but most
of the energy becomes electrical in character,
and an electrical chain of action takes place in
the circuit that has now been formed. Taking
the zinc as the starting point, the so-called
current flows from the zinc through the fluid
to the copper and from the copper through the
wire to the zinc.</p>
<p>A chain of polarized atomic activity is es<span class="pagenum"><SPAN name="Page_52" id="Page_52"></SPAN></span>tablished
in the circuit, similar to the closed
circuit of magnetic lines of force, only the
latter is static, while the former is dynamic.</p>
<p>You ask what is the difference? Well, it is
much easier to ask a question than it is to
answer it. You will remember that in the
chapter on magnetism it was stated that the
molecules of a magnet were little natural magnets,
and that their attractions were satisfied
within themselves; that when their local attachments
were broken up and all their like
poles turned in one direction they could act
upon other pieces of iron outside of the magnet.
Outside and between the poles there are
magnetic lines of force reaching out from one
pole to the other. If we put a piece of iron
across the poles these lines of force are
gathered up and pass through the iron. This
is purely a static condition. Let us go back to
the cell of battery. When the elements are in
position (the copper, the acidulated water and
the zinc), and the two wires attached to the
two metals which are the two poles of the battery
not yet connected, there is a condition induced
in these two wires that did not exist before
the acidulated water was poured in, although
the circuit is not yet established. If
we test the two wires we find a difference of potential—a
state of strain, so to speak—that did
not exist before the acid acted on the zinc and
liberated what was stored energy. It is in a<span class="pagenum"><SPAN name="Page_53" id="Page_53"></SPAN></span>
static condition, like the magnet, and electrical
lines of force are reaching out from both wires
so that the ether is in a state of strain between
the two poles. The air molecules may partake
of it, but we have to bring in the ether as a
substance, because the same conditions would
practically exist if the two wires were in a
vacuum. If now we connect the two wires, we
have established a metallic circuit between the
two poles of the battery, the static conditions
are relieved, the lines of force are gathered
up into the wire, and the phenomenon that we
call a current is established and we have dynamic
or moving electricity.</p>
<p>Having established the so-called electric current
we will now try to show you that there
really is no current. The idea of a current involves
the idea of a fluid substance flowing from
one point to another. When you were a boy did
you never set up a row of bricks on their ends,
just far enough apart so that if you pushed
one over they all fell one after another? Now,
imagine rows of molecules or atoms, and in
your imagination they may be arranged like
the bricks, so that they are affected one by the
other successively with a rapidity that is akin
to that of light-waves, and you can conceive
how a motion may be communicated from end
to end of a wire hundreds of miles in length in
a small fraction of a second, and no material
substance has been carried through the wire<span class="pagenum"><SPAN name="Page_54" id="Page_54"></SPAN></span>—only
energy. We do not mean to say that the
row of bricks illustrates the exact mode of
molecular or atomic motion that takes place in
a conductor. What we mean is, that in some
way motion is passed along from atom to atom.</p>
<p>To give you a better conception of an electric
current, let us go back of the galvanic cell
to the electric machine. If both poles of the
machine are attached to rods terminating in
round knobs we can set the machine in action
and keep up a steady stream of disruptive discharges
that will, if their frequency is great
enough, perform the function of a current, and
we have dynamic electricity from a statical
machine; when the acid of the galvanic battery
breaks down a molecule of zinc, energy is set
free, and in the battery we have what corresponds
to a disruptive discharge of infinitesimal
proportions. This discharge would have
been immediately converted into heat energy
if the copper element had been left out of the
battery, but as it is, it impresses itself on the
atomic "brick" next to it, which establishes
a chain of atomic movement throughout the
circuit. This may constitute, if you please, a
line of electrical force. But as thousands of
these disruptive discharges are taking place
simultaneously as many different lines of
force are established. You must not conceive
of these chains of atoms as simply thrown
down like the bricks and left lying there, but<span class="pagenum"><SPAN name="Page_55" id="Page_55"></SPAN></span>
that the atom is active; that it has the power
to pick itself up again in an infinitesimally
short time and is again knocked down (following
the illustration of the bricks) by the
next discharge along its line or chain of atoms.</p>
<p>If you could get a mental picture of this
action you would see that the whole conductor
is in a most violent state of atomic motion of
a peculiar kind. At the same time a part of
this electrical motion is being converted into a
heat motion of the atoms, and finally it all returns
to heat unless some of it is stored up
somewhere as potential energy. If the current
has driven a motor that has wound up a weight,
a part is stored up in the weight, which has the
ability to do work if it is allowed to run down.
If it drives machinery as it runs down, the
mechanical motion is the expression of the
stored energy. When the weight has run down
the energy will be represented by the heat
created by friction of the journals of the
wheels and pulleys and the heating of the air.
If the weight is allowed to fall suddenly it
will heat the air to some extent, but mostly the
earth and the weight itself will be heated. If
the source of energy (the battery) is great and
the pressure high and the conductor is too
small to carry the energy developed in the battery
as electricity, heat is developed, and if the
heat is sufficiently intense, light also.</p>
<p>We have seen (Vol. II) that heat motion<span class="pagenum"><SPAN name="Page_56" id="Page_56"></SPAN></span>
when it reaches a sufficiently high rate throws
the ether into a vibratory motion that we call
light. However, this vibratory motion of the
ether is set up long before it reaches the luminous
stage; in other words, there are dark rays
of the ether. We find that the electro-atomic
motions of a conductor have the power to impress
themselves upon the ether.</p>
<div class="figcenter"> <SPAN name="fig1" id="fig1"></SPAN> <span class="caption"><big>Fig. 1.</big></span> <ANTIMG src="images/fig1.jpg" width-obs="100%" alt="Fig. 1." title="Fig. 1." /> <p><b>A is the primary line; <i>a</i>, the battery: <i>b</i>, the key. B is the secondary line in which is placed the galvanometer <i>c</i>.</b></p> </div>
<p>Let us try another experiment to show that
this is the case, not only, but that the impressed
ether can transfer these impressions to
still another conductor. Suppose we stretch
two parallel wires for, say, half a mile, or any
distance, only a few feet apart, and make of
each a complete circuit by rounding the end
of the course and returning the wire to the
starting point (as shown in <SPAN href="#fig1">Fig. 1</SPAN>). Put in
one of these circuits a battery, and a circuit-breaker
(a common telegraph-key), and in the
other circuit a galvanometer (an instrument
for detecting the presence and measuring the
intensity of a galvanic current, by means of a<span class="pagenum"><SPAN name="Page_57" id="Page_57"></SPAN></span>
dial and a deflecting needle or pointer). Now
if we touch the key and close the circuit in A,
the needle of the galvanometer in B will swing
in one direction from zero on the dial; and if
we release the key, breaking the circuit in A,
the needle will swing back in the opposite
direction. In neither case will the needle stay
deflected, but will at once return to zero.</p>
<p>This shows that when the battery current
was allowed to complete its circuit through
wire A by closing its key, an electrical action
was instantly felt in wire B, although there
was no material connection between them other
than the air, which is a non-conductor.</p>
<p>The current in the second circuit is called
an induced current. Why this current? According
to one theory, when we close the primary
circuit the surrounding ether is thrown
into a peculiar state of strain that we will call
magnetic or electrical lines of force. When
the ether wave strikes the second wire there is
a molecular movement from a state of rest to a
state of static strain. During the time that
the molecules are moving from the normal to
the strained position in sympathy with the
ether we have the condition of a dynamic current,
which lasts only a moment. This state of
strain continues till the circuit is opened
(breaking the wire-line), when all the electrical
lines of force vanish and the molecular
strain of the second wire is relieved, and we<span class="pagenum"><SPAN name="Page_58" id="Page_58"></SPAN></span>
again have the conditions, momentarily, for a
current of the opposite polarity, and the needle
will swing in the opposite direction because
the molecules or atoms have, in their recoil to
the natural state, moved in an opposite direction.</p>
<p>Going back to <SPAN href="#fig1">Fig. 1</SPAN>, let us further study
the phenomena under other conditions. In
our first circuit (A) there is a battery and a
circuit-breaker, which is a common telegraph-key.
Now close the key so that a current will
be established. (Remember that "current" is
only a name for a condition of dynamic
charge.) Place a piece of soft iron across the
wire at right angles with the direction of the
wire, when of course it will be at right angles
with the direction of the current, and you will
find now that the iron is more or less magnetic,
depending upon the amount of current
passing through the wire. If we wind a number
of turns of insulated wire through which
the current is passing around the iron the
magnetism will be increased. In practice
there are a certain number of turns and a certain
sized wire that will give the best results
with a given number of cells of battery (or a
given voltage or pressure), operating in a
closed circuit of a given resistance. All these
questions are worked out mathematically in
many standard books on the subject. It is not
the intention in these talks to develop the<span class="pagenum"><SPAN name="Page_59" id="Page_59"></SPAN></span>
science mathematically but to set out the
fundamental physical facts and applications of
electricity.</p>
<p>Under the conditions above named magnetism
is developed in the soft iron bar. If we
open the key the current will cease and the
magnetism will vanish—that is to say, the
molecules will turn back to their neutral
position by their own attractions, as has been
described in a previous chapter. Magnetism
developed in this way is called electromagnetism.
(See Chap. IV.) If we use a piece
of hardened steel instead of the soft iron it
will become magnetic and remain so when the
circuit is opened, because the natural tendency
of the molecules to turn back to the neutral
position is not great enough to overcome the
coercive force, or molecular friction, of hardened
steel, as has been also described in a
previous chapter. To make the best electromagnet
we need qualities of iron just the opposite
from those of the permanent magnet.
For the former we need the purest of soft iron,
well annealed (heated to redness and slowly
cooled, making it less brittle), so that its molecules
are free to turn; while for the latter we
need hardened steel, so that when the molecules
are once wrenched into the magnetic
condition they cannot, of themselves, turn
back to the neutral state. The great value of
the electromagnet lies in its ability to readily<span class="pagenum"><SPAN name="Page_60" id="Page_60"></SPAN></span>
discharge, or go back to the neutral state,
when the current is broken.</p>
<p>Let us now go back to the beginning of our
experiment. When we closed the key and established
the current through the wire we
found that a piece of iron held at right angles
to the wire, although not touching it, became
magnetic. We have already said that when
the circuit was open, the battery being in circuit,
there were electrical lines of force established
in the ether, between the two poles
of the battery, and that they were gathered up
into the conducting wire when the circuit was
closed. We now find that there are other lines
of force of a different nature established in
the ether when the circuit is closed. These we
call magnetic lines of force, or the magnetic
field of the charged wire, and they are established
at right angles to the direction of the
current. These magnetic lines of force acting
through the ether from an electrically charged
conductor are able to break up the natural
molecular magnetic rings, referred to in Chapter
IV, and turn all their like poles in the
same direction—thus making one compound
magnet of the iron which in the neutral
state consisted of millions of little natural
magnets whose attractions were satisfied by a
joining of their unlike poles.</p>
<p>Most writers account for all of the phenomena
of induced currents in a second wire<span class="pagenum"><SPAN name="Page_61" id="Page_61"></SPAN></span>
as coming directly from these magnetic lines
of force developed upon closing the circuit.</p>
<p>So much for theory based upon a set of
facts that make the theory seem probable. If
you don't like it give us a better one. If it is
correct the writer claims no credit; it is
merely a compilation of suggestions from
many sources, including his own experience.
We are simply seeking after truth. The man
who is an earnest seeker after scientific truth
cannot afford to pursue his investigations with
any prejudice in favor of one theory more
than another, unless the facts sustain him,
and then he is not acting from prejudice, but
is led by the facts. Many people make pets of
their theories; and they become attached to
them as they do their children; and they look
upon a man who destroys them by a presentation
of the facts as an enemy. I once knew
a lady who became so attached to her family
doctor that, she said, she would rather die
under his treatment, if necessary, than to be
cured by any other doctor. There are many
people who are imbued with this kind of spirit
not only in matters scientific, but in matters
religious as well. Such people are not the
kind who contribute to the world's progress,
but are the hindrances that have to be overcome.</p>
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