Los Angeles herald., 1908-03-01
tCOpyright by James Elversonl

IlM electricity that everybody needs to
k@k q know something about it. | do not
sATNS01 intend to give scientific discussion.
t35Yegl but l want to tell the boys some
of the main principles that cleo
tricians work on, so that they may be aDie
to reason out their own electric bells ana pat
teries. -
fists saw that it is form of motion, like
heat and light; but we. do not want to be TOO
scientific now, and if we compare it to How
ing water it will suit our purpose best.
The water comparison is very handy IT
many ways. 1t is customary to speak OF
electric currents, and this makes one think OF
something as flowing, and so many people
want to see the wire that is carrying an
electric current move, as though the operator
pushed it at one end and the push came
out at the other. This is not so. Nothing
moves-at least, that we can see; but some
thing happens and it has been found that, II
we suppose that the current flowed like water,
we reason about it all right. Hence the
comparison to water.
Now, if you had a large pipe, water would
flow through it easily; but, if you had very
small pipe, the same water would flow
through, but only in very, small stream.
Likewise an electric current flows through
large wire with very little trouble, but In
smaller wire there is more resistance and the
wire uses up more of the current. =,
Some substances conduct electricity readily,
while others do not. The first kind are cali
ed conductors. and the second kind non-con-
ductors, or insulators Silver is the best con-
ductor, but copper is so nearly as good that,
because of the cost of silver, copper is near
ly always used when the best conductor is
wanted
All metals are good conductors Even what
are called insulators conduct some, but SO
very little that, for all practical purposes we
say that they do not conduct at all. Glass
and hard rubber are samples of commonly
used insulators.
In order to keep the current in one wire
from flowing to another close to it, it is ne
cessary to cover it in some way, and SO wire
is sold under the name of insulated wire, hav-
ing one or more wrappings of silk or cotton
thread cotton being cheaper and silk the bet
ter insulator), OF sometimes with gutta percha
or other insulating combinations.
One of the principal rules of electric sci
ence is that, if you want to have a current,
you must have a circuit-that is you must
have a complete path for the electricity to
go in at one end and come out of at the
other.
Taking our water pipe comparison, if you
want the water to flow you must have an
opening all the way If you stop up the
pipe in any part the water will not flow, un-
less the pressure Is SO great as to break an
opening through somehow.
We have an example of this great pressure
in lightning. In telegraph Offices they general
ly have an instrument called lightning ar
rester. If lightning strikes wire and comes
along it to the telegraph office, when it gets
to the arrester it jumps across a short dis
tance of air and so on to the ground, in
preference to going through long, fine wire
of great resistance in the telegraph instru
ments.
The ground is a fairly good conductor, on
account of the water in it, and SO a circuit is
very often completed by running the current
through the ground thus saving one line
wire, which, on long lines, is a very big
item.
The best way to do this is to fasten the
ends of the wire, that would otherwise be
joined to a line wire, to gas or water pipe,
which is pretty sure to have a good ground
connection.
We can connect our wires in various ways.
The first method is called series or tandem
connection. 1t corresponds. in our water com