Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-11-16
USING THE CURRENT.
Two Systems of Distributing Elec-
tricity for Practical Work.
VERY SIMILAR TO WATER POWER
Difference Between the Parallel and Series
Distributions.
LATE ELECTRICAL DEVELOPMENTS
WRITTEN FOB THR DIsPATcH.J

WRITTEN FOB THR DISPATCH,
There are two great systems by means OF
which the electric current can be distributed
for light and power. They are called the
parallel system" and the "series system"
In the parallel system the main current is
divided into as many separate currents as
there are lamps or motors to beoperated. The
pressure in this system is kept constant but
the quantity of current varies according to
the lamps or motors that are in operation.
In the series system the lamps or motors are
connected one after the other in the main
circuit-so that the current passes sue
cessively through each piece of electric ap-
paratus in the circuit. In this system the
the current is constant quantity while the
pressure is variable, according to the
number of lamps or motors in the circuit.
To illustrate these two great systems OF
electric distribution and present the condi-
tions of each case more vividly to the mind
of the reader it will be we'll to refer to water
power, and thus make comparisons with
power familiar to ala power that appeals
more readily to the eye, and, therefore, 70
the mind,
A SIMPLE ILLUSTRATION.
Imagine a waterfall 20 feet high and
having fall of so feet. II, now, we arrange
seven water wheels in a row, that is, across
the falls, these water wheels can be said to
be Gin parallel" In other words if the
water flowing over the falls is divided up
into seven streams, one for each wheel, these
streams will all be flowing parallel to each
other, and each will have the same pressure
or fall of 30 feet.
Or suppose that we have reservoir OF
water giving q pressure OF 90 feet, and from
this reservoir we conduct the water away
to seven water wheels through seven differ
ent pipes, this water power is then said to be
distributed under the parallel system, even
though the pipes may not be actually par
allel to each other. The water wheels are
then said to be worked sin parallel" and
under a constant pressure. Ii the water IS
turned off from one of the seven pipes the
other six will still be working as before
under the constant pressure of 90 feet. In
the same way if seven or any other number
of wires are led off from a dynamo to as
many different lamps or motors, the lamps
or motors are said to be working on the
parallel system. In this case, of course,
each wire must start out from one pole Of the
dynamo, lead to the lamp and then return
to the other pole of the dynamo to complete
the circuit.
THE PRESSURE is CONSTANT.
If the pressure at the dynamo is kept con-
slant, the lamps will all burn with a con-
slant brilliancy and one or more lamps may
be turned off at will without disturbing the
remaining ones. If all the lamps are
turned of, the pressure still remains in the
wires ready to force the current through any
oil of fha lop ho Of Mt Ic
turned on. However, in practice it is not
necessary to run q separate wire from the
dynamos to each lamp. There is another
and simple way of working the lamps in
parallel.
To explain the method of parallel distri-
button in practical use, let us once more re-
fer to the reservoir of water power. The
comparison that will now be made may re-
quire little stretch of the imagination on
the part of the reader. for, although the
comparison is a good one, few people think
of the distribution of water power as it will
now be represented. Let us imagine large
| pipe, a mile long and having its end closed,
leading out from a large reservoir OF water;
we will thus have water pressure In the pipe
| but no flow, the end being closed. But if
we make a suitable hole in the pipe, say a
quarter of mile away from the reservoir,
water will gush out with force correspond
| ing to the pressure in the reservoir. This
gush of water can then be made to do work,
say turn a water wheel, then after its work
is done this water will be evaporated by the
heat energy of the sun, and will next be
seen high in the air in the shape of clouds.
COMPLETING THE CIRCUIT.
Now, if we imagine that this same water,
which has come from the reservoirs, done
work and is now in the shape and condition
of cloud, should turn into rain and fall into
the same reservoir from which we have
taken it, it will have made "closed cir
| cult" SO to speak-and the water will again
be in condition to do work. We can now
| imagine this water going through this same
cycle process over and over again, just like
| a belt going round and round, transmitting
power from the driving to the driven pully.
| With the belt the engine is the motive
power-with the water the sun is the motive
| power. The sun is evaporating water all
the time, thus changing its heat energy into
energy called water power In this way
water is kept circulating constantly, trans
mitting solar energy each time it goes around.
We may thus speak of the water as hav-
ing ''closed circuit, at least it Will be
! convenient to do so, for that expression is
used with electric circuits, and the processes
| in each case are similar. We can now fur
ther imagine that the water, after it had
| gushed from the large pipe and done its
work, could, instead of flowing into the
ocean and from there being eyaporated, as is
actually the case, pass up a comparatively
| small pipe into the air above and then going
into a large pipe with tine one leading out
| from the reservoir. Then if this second
large pipe be connected with the reservoir
we shall have closed the circuit and OBJ
tanned the conditions existing in the electric
circuit under consideration.
A CLOSER ANALOGY.
The water will now flow from the reser-
volr through the main, out of the hole, turn
the water wheel and then be sucked up, by
the heat energy of the sun, through our
imaginary smaller tube to the second main,
or better say return main. From the return
main it will pass once more into the reser-
voir and again be ready to do work. If we
call the starting point of the water the
north or positive pole and the returning
point the south or negative pole, we can say
that the water flows from north to south or
from the positive pole to the negative pole.
Let us now punch three more holes in our
first main, one half mile away, another
three-quarters of mile from the reservoir
and the last at the end of the main. At
each hole let us place water wheel and for
each wheel a pipe as before leading the wa
ter back to the return main and so again
into the reservoir. It will now be easy to
understand why the waterwheels will
be working in parallel without having a
separate pipe from the reservoir to each
wheel. If we plug up one of these holes we
will stop its corresponding wheel, save the
water and at the same time leave the others
| dict,1 had : Il al lass