Evening star., 1922-04-11
ELECTRICAL POWER.

ELECTRICAL POWER.
When water flows through a pipe it
encounters the resisting effect caused
| by friction between itself and the in
| ner wall of the pipe. Some of the
mechanical energy of the water is
used up in overcoming this friction
and Is changed into heat energy. Eric
ton between two blocks OF wood will
also cause some of the mechanical
energy exerted to be transformed into
heat. and the blocks get warm. In
| fact, friction anywhere causes heat TO
a greater or lesser extent.
1t is not hard, then, to imagine that
electrical energy may be transformed
| into heat when a current OF electricity
encounters resistance in its path of
| fow. which we call circuit There is
no circuit possible which has abso-
| lutely no resistance; therefore, when
ever an electric current flows there
must be some work done in overcom-
| ing the resistance of the circuit. That
| is some energy must be converted
| into heat. however little it may be. 1t
| is quite possible. however. to create
| such a high temperature in wire as
| to melt it.
| The amount of heat created is pro-
| portioned to the resistance being over
come. the length of time the current
| is flowing and the current strength
times itself. Expressed in a simple
algebraic equation, this is:
Energy expended - Resistance Nn
ohms) X Time dn seconds) Current
(amperes) Current (amperes).
Any quantity multiplied by Itself
N "rnrrenf'
EQUALS current squared"
Now. the rate at which this energy
is expended, or the rate at which the
work is accomplished is called the
power" And since we are speaking
OF electricity we may called 1t "elec-
trical power" The electrical power is.
then. of course. the total energy ex-
pended in certain length of time i'll
seconds. In other words. it is the
amount Of energy expended every sec
ond. The unit of electrical power is
the watt" named after James Watt,
earliest steam engines Expressed
alphabetically electric power, or we
may say simply power is as follows:
Power Gn watts) - Current (am
peres) squared \ Resistance (ohmsl;;
The watt is at times rather a small
unit to use. SO unit called "kilo
watt" which means 1000 watts. is
often used.
THE ELECTRICAL CONDENSER.
When gas is pumped through a
pipe into a tank certain pressure
is exerted by the pump to force the
gas into the tank. The gas is COM
pressible, and the gas within the tank
eXerts a back pressure upon the gas
flowing into the tank. The back
ing the flow of more gas into the
tank. Finally. when the pressure of
gas within the tanks equals the pres
pressure is at every instant oppos-
gas flows into the tank. The gas
which is then inside of the tank is
condensed" and stored. If valve
in the pipe is closed the pump may
be stopped and the gas will not leak
out of the tank until wanted, provid-
ing the tank is gas tight
A somewhat similar tank Tor
electricity can be made by coating a
sheet of glass with tinfon on each
side. If the condenser" which is
then formed, is connected to bat
terry, an electrical pressure is exert
ed, which causes electricity to How
into the condenser until the back
pressure of the electricity equals the
pressure exerted by the battery. The
current then ceases to flow, and the
condenser is charged" The glass is
called the "dielectric," and it must be
very poor conductor of electricity
or the "charge" will leak off very
quickly No dielectric is an absolute
non conductor of electricity, however,
so no matter how good it is. the cleo
trio charge will leak out in time.
When the battery is connected to
the condenser plates (the tinfoil
coatings in this case), that plate
which is connected to the positive
terminal of the battery receives
positive charge of electricity. The
plate connected to the negative bat
terry terminal receives negative
charge. When the battery is remov-
ed there is then an electromotive
force present between the two metal
coatings, and current Of electricity
would Immediately flow if the two
plates were connected together by a
copper wire. If this were allowed to
happen the electricity stored in the
condenser would escape. and the con-
denser would become discharged.