THEORY OF ELECTRICITY.
In the series of chapters on Heat
(Vol. II) and in the chapter on Magnetism the
word molecule was frequently used synonymously with
atom. In chemistry a distinction is made, and
as we can better explain the theory, at least, of
electricity by keeping this distinction in mind we
will refer to it here.
It has been stated that there are
between sixty and seventy elementary substances.
An elementary substance cannot be destroyed as such.
It can be united with other elements and form chemical
compounds of almost endless variety. The smallest
particle of an elementary substance is called in chemistry
an atom. The smallest particle of a compound
substance is called a molecule. The atom is the
unit of the element, and the molecule is the unit
of the compound as such. It follows, then, that
there are as many different kinds of atoms as there
are elements, and as many different kinds of molecules
as there are compounds. If the elements have
a molecular Structure then two or more atoms of the
same kind must combine to make a molecule of an elementary
substance. Two atoms of hydrogen combine with
one of oxygen to form one molecule of water.
It cannot exist as water in any smaller quantity.
If we subdivide it, it no longer exists as water,
but as the original gases from which it was compounded.
We have shown in the series on Sound,
Heat and Light that they are all modes of motion.
Sound is transmitted in longitudinal waves through
air and other material substance as vibration.
Heat is a motion of the ultimate particles or atoms
of matter, and Light is a motion of the luminiferous
ether transmitted in waves that are transverse.
Electricity is also undoubtedly a mode of motion related
in a peculiar way to the atoms of the conductor.
Notice that there is a difference
between conduction and radiation. The former
transmits energy by a transference of motion from atom
to atom or molecule to molecule within the body, while
the latter does it by a vibration of the ether outside as
light, radiant heat, and electromagnetic lines of
force.
For the benefit of those persons who
have not read Vol. II, where the nature of ether
is discussed somewhat, let us refer to it here, as
it plays an important part in the explanation of electrical
phenomena. Ether is a tenuous and highly elastic
substance that fills all interstellar and interatomic
space. It has few of the qualities of ordinary
matter. It is continuous and has no molecular
structure. It offers no perceptible resistance,
and the closest-grained substances of ordinary matter
are more open to the ether than a coarse sieve is to
the finest flour. It fills all space, and, like
eternity, it has no limits. Some physicists suppose and
there is much plausibility in the supposition that
the ether is the one substance out of which all forms
of matter come. That the atoms of matter are vortices
or little whirlpools in the ether; and that rigidity
and other qualities of matter all arise in the ether
from different degrees or kinds of motion.
Electricity is not a fluid, or any
form of material substance, but a form of energy.
Energy is expressed in different ways, and, while as
energy it is one and the same, we call it by different
names as heat energy, chemical energy,
electrical energy, and so on. They will all do
work, and in that respect are alike. One difficulty
in explaining electrical phenomena is the nomenclature
that the science is loaded down with. All the
old names were adopted when electricity was regarded
as a fluid, hence the word “current.”
It is spoken of as “flowing” when it does
not flow any more than light flows.
If a man wants to write a treatise
on electricity outside of the mere phenomena
and applications and wants to make a large
book of it, he would better tell what he does not
know about it, for in that way he can make a volume
of almost any size. But if he wants to tell what
it really is, and what he really knows it is, a primer
will be large enough. This much we know that
it is one of many expressions of energy.
Chemistry teaches that heat is directly
related to the atoms of matter. Atoms of different
substances differ greatly in weight. For instance,
the hydrogen atom is the unit of atomic weight, because
it is the lightest of all of them. Taking the
hydrogen atom as the unit, in round numbers the iron
atom weighs as much as 56 atoms of hydrogen, copper
a little over 63, silver 108, gold 197. Heat
acts upon matter according to the number of atoms
in a given space, and not as its weight. Knowing
the relative weights of the atoms of the different
metals named, it would be possible to determine by
weight the dimensions of different pieces of metal
so that they will contain an equal number of atoms.
If we take pieces of iron, copper, silver and gold,
each of such weight as that all the pieces will contain
the same number of atoms, and subject them to heat
till all are raised to the same temperature, it will
be found that they have all absorbed practically the
same quantity of heat without regard to the different
weights of matter. It will be observed that the
piece of silver, for instance, will have to weigh nearly
twice as much as the iron in order to contain the
same number of atoms, but it will absorb the same
amount of heat as the piece of iron containing the
same number of atoms, if both are raised to the same
temperature. In view of the above fact it seems
that heat acts especially upon the atoms of matter
and is a peculiar form of atomic motion. Heat
is one kind of motion of the atoms, while electricity
may be another form of motion of the same. The
two motions may be carried on together. The earth
has a compound motion. It revolves upon its axis
once in twenty-four hours, and it also revolves around
the sun once each year. So you see that there
are different kinds of motion that may be communicated
to the same body all producing different
results.
The motion of the individual atom
as heat may be, and is, as rapid as light itself when
the temperature is sufficiently high, but it does not
travel along a conductor rapidly as the electro-atomic
motion will. If we apply heat to the end of a
metal rod it will travel slowly along the rod.
But if we make the rod a conductor of electricity it
travels from atom to atom with a speed nearer that
of the light ray through the ether. Some modern
writers have attempted to explain all the phenomena
of electricity as having their origin in a certain
play of forces upon the ether, and there is no doubt
but that the ether plays an important part in all
electrical phenomena as a medium through which energy
is transferred; but ether-waves that are set in motion
by the electrical excitation of ordinary matter are
no more electricity than the ether-waves set up by
the sun in the cold regions of space are heat.
They become heat only when they strike matter.
Heat, as such, begins and ends in matter; so
(I believe) does electricity.
Do not be discouraged with these feeble
attempts to explain the theory of electricity.
All I even hope to do is to establish in your minds
this fundamental thought, to wit, that there is really
but one Energy, and that it is always expressed by
some form of motion or the ability to create motion.
Motions differ, and hence are called by different names.
If I should set an emery-wheel to
revolving and hold a piece of steel against it the
piece of steel would become heated and incandescent
particles would fly off, making a brilliant display
of fireworks. The heat that has been developed
is the measure of the mechanical energy that I have
used against the emery-wheel. Now, let us substitute
for the emery-wheel another wheel of the same size
made of vulcanized rubber, glass or resin. I
set it to revolving at the same speed, and instead
of the piece of steel, I now hold a silk handkerchief
or a catskin against the wheel with the same force
that I did the steel. If now I provide a Leyden
jar and some points to gather up the electricity that
will be produced (instead of the heat generated in
the other case), it would be found that the energy
developed in the one case would exactly balance that
of the other, if it were all gathered up and put into
work. The electricity stored in the jar is in
a state of strain, like a bent bow, and will recoil,
when it has a chance, with a power commensurate with
the time it has been storing and the amount of energy
used in pressing against the wheel.
If now I connect my two hands, one
with the inside and the other with the outside of
the jar, this stored energy will strike me with a force
equal to all the energy I have previously expended
in pressing against the wheel, minus the loss in heat.
If I did it for a long enough time this electrical
spring would be wound up to such a tension that the
recoil would destroy life if one put himself in the
path of its discharge. If all the heat in the
first case were gathered up and made to bend a stiff
spring, and one should put himself in its way when
released, this mechanical spring would strike with
the same power that the electrical spring did when
the Leyden jar was discharged. This statement
assumes that all the energy in the second experiment
was stored as electricity in the jar. You will
be able to see from the above illustration that heat,
electrical energy, and mechanical energy are really
the same. Then you ask, how do they differ?
Simply in their phenomena their outward
manifestations.
While there is much that we cannot
know about any of the phenomena of nature, it is a
great step in advance if we can establish a close
relationship between them. It helps to free electricity
from many vagaries that exist in the minds of most
people regarding it; vagaries that in ignorant minds
amount to superstition. While it possesses wonderful
powers, they give it attributes that it does not possess.
Not long ago a favorite headline of the medical electrician’s
advertisement was “Electricity Is Life,”
and it was a common thing to see street-venders dealing
out this “life” in shocking quantities
to the innocent multitudes ten cents’
worth in as many seconds.
Science divides electricity into two
kinds static and dynamic. Static comes
from a Greek word, meaning to stand, and refers to
electricity as a stationary charge. Dynamic is
from the Greek word meaning power, and refers to electricity
in motion. When Franklin made his celebrated kite
experiment, the electricity came down the string, and
from the key on the end of the string he stored it
in a Leyden jar. While the electricity was moving
down the string it was dynamic, but as soon as it
was stored in the Leyden jar it became static.
Current electricity is dynamic. A closed telegraphic
circuit is charged dynamically, while the prime conductor
of a frictional electric machine is charged statically.
The distinction is arbitrary and in a sense a misnomer.
When we rub a piece of hard rubber with a catskin
it is statically charged because the substances are
what are called non-conductors, and the charge cannot
be conducted readily away. All substances are
divided into two classes, to wit, conductors or non-electrics,
and non-conductors or electrics, more commonly called
dielectrics. These, however, are relative terms,
as no substance is either a perfect conductor or a
perfect non-conductor.
The metals, beginning with silver
as the best, are conductors. Ebonite, paraffine,
shellac, etc., are insulators, or very poor conductors.
The best conductors offer some resistance to the passage
of the current and the best insulators conduct to
some extent. If we make a comparison of electric
conductors we find that the metals that conduct heat
best also conduct electricity best. This, it
seems to me, is a confirmation of the atomic theory
of electricity so far as it means anything. If
a good conductor, as silver, is subjected to intense
cold by putting it into liquid air, its conductivity
is greatly increased. It is well known that heating
a conductor ordinarily diminishes its power to conduct
electricity. This shows that, in order that electrical
motion of the atom may have free play, the heat motion
must be suppressed.