Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1916-09-16

many collufnhs. q second 81 - y - ,.s
fortunately we have a special name
for this rate of flow of electricity of
one coulpmb q second, which Is called
the ampere. This way of giving The
rate OF flow d special name relieves as
Of. the. necessity Of saying "a second
each time, as would be the case Il We
we're 70 speak or the current asa 80
many co0I0fnbs q second. Thus cnr-
rent or rate OF now Of ten coulombs q
second Is just ten amperes: fifty c0u-
lombs second fifty amperes, etc. In
the majority OF cases we are not inter-
ested m the quantity of electricity.
alone. but In the rate Of flow the am
pere, and for this reason the coulomb
Is very little used.
electrical Pressure
The numbers of gallons second OF
water flowing through a. pipe depends
III a.large measure upon the pressure
causing 1t to flow. This pressure In
the water circuit is measured as so
many pounds to the square inch or so
many pounds to the square foot. In a
similar manner the current Of cleo
tricity, in amperes. in q wire de-
ponds In part upon the pressure un0er
which the electricity flows.
The electrical pressure Is measured
IN unit called. the volt. The volt
means exactly the same thing In
speaking Of an electrical circuit as the
pound pressure does In speaking OF
the water circuit.
A higher pressure will be required to
force the same current Of water
through q small than through large
pine, and higher electrical pressure
win be required to force the same cur.
rent Of electricity through a small
wire than through q large one. Simil-
arly, higher pressures win be required
in both the water and electrical cir
cults II the length Of the circuits be
increased-that is. II the length OF
the pipe and wire be increased
The pressure produced by the pump
might be called the water moving
force. while the pressure produced by
the battery may be called the cleo
tricity moving force, or eiectfo-motiye
force. The electro-motive force Is
usually represented by the abbrevia-
ton d m. T.
II pfessure gauges be connected at
various points along the water pipe
they will indicate the pressure at the
different points, There wiz be- dif-
ference In the pressure as indicated by
the various gauges If there is q cur
rent In the pipe, and their indications
will be less and less as you pass along
the pipe In the direction in which the
water Ii flowing. The difference In the
volume OF the pressure as indicated by
any two of the gauges connected to
the pipe will represent the pressure
acting on the portion of the pipe be-
tween the two points where the gauges
are attached. The difference in pres
sure between two points on q pipe Is
called the drop in pressure or merely
the drop between the two points. The
pressure between two points along q
stream Of water Is often spoken of as
the difference in level, the drop in
level, or merely the drop between two
points.
Voltage 10 Difference in Pressure
In the case OF the electrical circuit
there is difference in the electrical
pressure between two different points
along the circuit. This difference in
pressure between any two points is
measured in volts. Just as the total
pressure produced by the battery is
measured in volts.
The pressure at any point in an
electrical circuit cannot be. measured
by attaching q suitable instrument to
the circuit at that point alone similar
to the attachment OF the pressure
gauge to the water pine. but the in
strument must be attached to two
r1infe and then n does. not read the