Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-10-05
Another Simple Lesson In Electricity
From Scire Facias.
BOW DYNAMOS ARE CONSTRUCTED
Principle Upon Which the Production Of a
Current Depends.
THE POWER EXPENDED IN THE WORK
WRITTEN FOR THE DISPATCH,

resents energy because it is in q strained
condition.
We often hear the expression electric
fuid," and although it is true that nobody
knows exactly what electricity is, yet such
expressions as electric fluid" and "electrlc
current" are misleading. ior we cannot pour
electricity into pail like water, nor can we
weigh it or hold it in our hands, In other
words it is not thing, but condition OF
things, which when properly applied can
be made to do work. However, we must
use some expression and so, as matter OF
convenience, we say "electric current"
ENERGY FOR ENERGY.
But such condition of things as we are
now considering cannot be brought about
without an expenditure OF energy. A clock
cannot be wound up nor a railroad train
moved, nor can any other change be made in
the condition of material things without the
application of some outside power. Keeping
this fact we'll in mind, let us see how,
through the medium oil some outside power,
that condition of things which we call elec-
tricity may be brought about.
However, before coming right to the point,
we must have a pretty clear idea of the prop
critics of magnet. We all know what a
magnet looks like-and that it has two poles
"a north and a south, and that it will at
tract iron. But there is another very inter-
esting feature connected with a magnet, and
that is its "lines Of lorce." Radiating out
from each pole of a magnet there are lines
technically called ''lines OF torce."
THE LINES OF FORCE.
We cannot see them and we cannot touch
them; but we know that they are there and
can prove this TACT by their effect. Take for
example good bar magnet, lay it down on
table and cover it with fiat piece of glass,
such as window pane. Then if some fine
iron filings are 81 ted on to the glass, at the
same time gently tapping the glass, it will
be seen that the filings arrange themselves
in curved lines, radiating out from each
pole and curving toward each other. 1t
must not be supposed. however, that these
lines radiate only in the plane of the glass,
for, as matter of fact they radiate out in
all directions. forming, as it were, thick
bunch.
This can be readily shown by placing the
glass plate over one end of the magnet and
again sitting upon it the fine iron filings. 1t
will be noticed that the filings, INSTEAD of
spreading out, will bunch up and try to
form upright lines.
The fOUNDAT1ON
And now we are ready for the grand
principle upon which we largely depend
for the generation Of electric currents. 1t is
this: "If the lines of force OF a magnet
are cut with closed circuit of wire, cur
rent of electricity will be generated in the
wire during the time OF cutting"
Let us examine this law more closely.
Imagine spray of fine lines-then, if by
ouiok unotion of nlocad MI air
cut any or all of the fine lines in the spray,
a current of electricity will be generated in
the closed circuit. But if this closed current
be moved parallel to the fine lines, that is, in
between them, no current will be generated.
The lines must be cut to generate a current.
The greater the number OF lines cut. in
given time, the stronger will be the current
generated.
INCREASING THE CURRENT.
If we use two similar closed wires, side
by side, an equal amount of current will be
generated in each wire. If we increase the
strength and number of the magnets used
we also increase the strength of the current.
So that to generate powerful electric cur
rent we must have great many closed
wires and with those rapidly cut the lines
Of force OF one or more powerful magnets.
And this is what is done in the dynamo.
Here great many wires are wound on the
surface OF drum or 'armature," as it is
called, in such a way, that is, lengthwise of
the drum, that when the drum is rapidly
revolved in front of the powerful magnets,
the wires will cut the "lines of lorce'' of the
magnets and SO generate an electric current
in each wire.
CONNECTING THE WIRES.
If now we open all those closed wires
each end will represent pole-half of the
poles being positive and half negative-just
like the poles of 80 many batteries, aud,
like them, each wire will give certain
pressure and a certain quantity. If we
want quantity we must, as with batteries,
connect the positive poles together to make
one posting, and the negatives to make one
negative, and the total quantity will be the
sum of the individual quantities furnished
by each wire; or, if We want pressure, we
must connect the negative OF one to the
positive of the other, and the negative of
this to the positive OF the next, and so on.
The pressure between the two ends left
over will be the added pressure of the in
dlvidual wires. This first method OF con-
nection, that is, for quantity, is called
parallel" connection, tine second "series"
connection. Ii We want both pressure and
quantity we must connect sets of wires in
parallel" and then connect these sets in
"series."
OBTAINING BEST RESULTS.
The above will serve 10 explain the
action of the dynamo in its simplest form.
In practice, however, the winding Of the
armature is often very duplicated. af-
fair, the results OF which cannot we'll be
entered into here. Near the END OF the
armature shalt are two rings called "col-
lectors," one ring being connected to one
pole OF the armature, and the other ring to
the other pole of the armature Upon each
of these rings or COLLECTORS there is
pressed, by means of spring, bundle of
thin copper strips called ''brushes, 3" SO that
when the armsture, shaft aud collector
rings rotate the "brushes'' will always be in
contact with the rings
The ends of these two "brushes" then
form the two poles of the dynamo, and from
one of these poles the current is led out
out into the streets and houses to the lamps
and then back 10 the other pole, thus
closing the circuit. The armature is, of
course, put into rapid rotation by means of
a steam engine, waterfall, or other con-
venient power.
ONLY A CONDITION.
And now we are ready to understand that
electricity is a condition of things and that
1t requires power TO bring about this condl-
tion. For when the dynamo armature is at
rest, the wires on it are dead" SO to speak,
and just like any other wire. But when
power is applied to put the armature in
rapid rotation, certain condition OF things
is brought about in the wire, which we call
electricity and which magniies itself in
many well known ways. 1t is lorm o. en-
ergy, because it required power to produce
it, and it in turn will reproduce power.