Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-10-26
ELECTRIC CURRENTS.
Their Nature Made Clear by the Ac-
tiOn of Heat on a Rod.
RECOGNIZED ONLY BY EFFECTS
Units Of Measurement Used in Speaking
of the Condition.
THEIR RELATION TO EACH OTHER
WRITTEN FOR THE DISPATCH!

WRITTEN FOR THE DISPATCH!
Take brass rod. say yard long, give 1t
thin coating OF wax. then place the rod on
two supports (window panes turned on edge
are good). and under one end place lighted
Bunsen burner; the coating of wax will be-
gin to melt, first directly over the flame,
then further and further away. We can see
till at last the entire bar is warm and the
wax all melted.
Ii We call that end of the bar under which
we place the burner North, and the other
end South, we would naturally say that the
heat had travelled from the north end to the
south end. and, as a matter of convenience,
such language would be perfectly
correct, but as matter of fact,
nothing has travelled from one end
OF the bar to the other, for, if there had,
this thing would, most likely, have dropped
on at the south end, or the south end would
at least have been heavier since this thing
got there, but no, nothing dropped off, and
the end is not any heavier than it was before
the heat crept over there.
THE PHILOSOPHY OF HEAT.
Heat is condition OF things and not a
material thing. Ii body OF matter is warm
Its molecules or small invisible particles, of
which it is supposed to be composed, are in
rapid motion, and this rapid motion gives
to the touch the sensation called heat Ii
one body is warmer than another its mole
cules are supposed to be in more rapid mo-
tlon than those of the other l. BODY is
warmer at one time than it is at another, its
molecules or particles are supposed to have
been in more rapid motion the first time
than the last, and this motion or condition
OF the body gives to the touch the sensation
we call heat.
Now, referring to our rod again, nothing
that We can see, weigh or hold in our
hands, has Travelled from one end of the rod
to the other. 1t is simply that the condi-
tion OF the rod has been changed, and this
change began at one end and crept over to
the other. And we naturally say in ordi.
nary conversation that "the heat crept rom
the north end to the south" and in saying
this imply both an advancing motion or
flow and direction. but as a matter of
tact, we have just seen that there is no ad-
vancing motion or flow, but there is direc-
tloD, for we can see this with our eyes and
We say it is from north to south.
KNOWN BY ITS EFFECTS.
But after all it is only the effect that we
see. Suppose that we could not see the
Bunsen burner, and we simply had a por-
tion OF the rod before us, we would still
know, by the gradual melting away
of the wax from. one end toward
the other, that heat was being applied at
one end, and not only this, we could 90 fur
oct 70 oft !
sity OF the heat by the rapidity with which
the wax melted off Or better still. if we
should grasp the rod by the hand we would
be able to form a very good idea o! what was
going on. In other words without being
able to see anything but this wax-coated rod.
we can, by observation and by noticing va
rious effects, tell great deal about what is
going on there.
Heat, therefore, is the name given to a
condition OF things, and We recognize this
condition OF things called heat by its effects
IT we see ice melting we say that there is a
little heat there, because the condition of
the lee is being changed, and in'the melting
we notice the familiar effect OF heat But
l we see iron melting we. say there is
great heat, for we know by experience
that it takes great heat to melt the metals.
Thus again, by the effect of heat we not only
recognize its presence without be able to see
it, but we also have a means OF comparison
by observing its different effects.
ANOTHER KIND OF CURRENT.
And so it is with electricity. We often
hear the expression electric current" and
electric fuid," but these are simply con-
venlent names given to certain condition
OF things. just as we say that the heat
crept along the brass rod because it had that
so we say there is a current OF
electricity in wire when we notice certain
familiar appearance or effect evidently
caused by the condition of the wire. Now,
some OF these eff cts are such that there ap-
pears to be flow or current of something in
the wire.
For example, we can start a current
of electricity in at one end of a
wire and measure the time it takes
to reach the other end. What more
natural inference then than to think
that electricity is a current or something
flowing. But as with the heat and rod,
nothing came out at the other end, so it is
with the electric current, nothing comes out
at the other end OF the wire. In lact, nobody
mas been able to weigh electricity or see it
or hold it in the hands. In other words, it
is not tangible thing, but a condition OF
things, form OF energy that we call elec-
tricity. But because it, like the heat in a
rod, acts as though it could flow or travel,
We use the convenient term electric cur
rent" and although there is no actual cur
rent, yet as with the heat and rod, so here,
there is direction, and this direction as
we'll as different amounts of electricity, and
in fact its very presence, are all known and
calculated
FROM FAMILIAR EFFECTS,
and the observations made on them. For
example, if we dip the two poles OF an cleo
trio circuit into pail of water, the cleo
tricity will decompose the water. We thus
At once recognize the presence Of an electric
current. But urther live repeat this opera
ton and find that in the second experiment
twice as much water was decomposed as in
the first, we know then by making COM
parison of the effects OF electricity that there
twice ss much current in the second
Ease as in the first, provided the time that
The current was allowed to act ON the water
was the same IN each case. Thus without |
seeing or hearing or touching anything we |
ire able to recognize the presence of cleo |
;ricity by its well-known effects, and BY |
,om pairing the effects we are enabled to /
make relative measurements.
However, in order to be able to talk about |
uch measurements and make practical use
# them we must, have standard units of |
to which we can refer all other
as in liquid measure,
or example, we must have some standard |
init OF measure, like the quart, by which we