The silver state news. [volume] (Winnemucca, Nev.) 1907-1909, 1909-01-12
THE ELECTRIC CURRENT AND SOME Ut
ITS HOUSEHOLD APPLICATIONS


ed only by the expenditure OF energy
The two kinds Of energy which are
most generally used for this purposs
are az chemical energy which is utii
lied in the various forms Of voltaic OF
~galvanic cells, and (2J mechanical en-.
ergy, which 10 the source of current in
the dynamo.
Every source Of current must nave
a complete conducting circuit. If the
circuit 10 broken at any point, the eur
rent leases.
A voltaic cell consists Of two plates
that are partially immersed in an eIee-
trolytic conductor Cor e~lectrolyte) and
that are externally connected by a wire
or other electrical conductor. The eiee-
tro- motive-force furnished by such a
cell il not dependent upon the size of
the cell but merely upon what sub
stances are used for the plates and the
cleetrolyte. Zine is almost exclusively
used for one of the plates and either
carbon or copper for the other. Sui
phuric acid is generally used for an
e~leetrolyte but ammonium chloride tsal
ammoniae) is used as the eleetrolyte in
the Leehlance cell.
The zine plate is called the positive
sIeetrode or cathode. The copper o.
carbon plate forms the negative elee.
trode or anode. The ends Of the uneon-
neeted wires leading from each eleo-
trode are called poles. The pole (oppo-
site end) of the positive eleetrode is
negative while the pole Of the negative
eleetrode Is positive.
When the positive electrode is com
posed of chemically pure zine, it is not
acted upon by the ~sulphurie acid until
the poles of the two plates are
ed, but as soon as this is done, chemi-
action at once takes place. The zine
10 partially Dissolved with the formation
Of zinc sulphate, and hydrogen gas is
evolved from the carbon plate but it is
found that the carbon plate itself is not
chemically acted upon. The wire con
Meeting the two plates becomes warm
and deveIopes a magnetic field of force
about it which shows that an electric
current is passing through it. If the
circuit is opened by cutting the wire,
tie evolution of hydrogen ceases; AMI
if the chemical action is stopped, the
current ceases to flow. There is thus a
relation of cause and effect between tn.
chemical action and the electric current
The energy of the chemical reaction
between zine and sulphuric acid which,
under ordinary circumstances. would be
given out as heat, is converted into an
electro-motive-force which causes the
current to flow through the circuit
A cell is therefore a sort of electro
chemical furnace in which zinc is the
fuel burned.
A good cell should furnish a uniform
current, whenever wanted and with as
little waste of Zinc as possible. One
defect to be avoided is local action.
Commercial zinc contains small partl-
eles of iron and carbon as Impurities.
Local action between these particles
and the zine sets up internal currents
even when the poles of the cell are not
connected. This waste Of zinc may be
quite effectually prevented by ANAL
gamating the zine plate.
Another source of a great deal OF
trouble are the hydrogen bubbles which
collect on the carbon plate. They OBJ
struet the direct contact of the carbon
plate with the acid and thus reduce the
effective area of the plate. This great
ly increases the internal resistance of
the cell, thereby consuming energy use
lessly. Again the film of hydrogen
bubbles make the part of the carbon
plate that is covered by them cease to
act like a carbon plate, but to set a
current opposite in direction to that
furnished by the cell The cell is thea
said to be polarized and it's effective
ness is greatly diminished.
To prevent polarization, a second
liquid, or sometimes a solid, is use.l
called a depolarizer which gives M
oxygen readily. This oxygen unites
with the hydrogen film. In dry cells,
which are now very largely used for
electric bell work, the depolarizer is
manganese dioxide. In the dry cell the
jar is composed of zine and this forms
one electrode. The carbon electrode is
suspended in the center of the zine
vessel and the space about it is filled
with a mixture of carbon, manganese
dioxide and sawdust and the mixture
saturated with a solution of sal m
lac which, in this ease, forms the cleo.
trolyte. The top is sealed with wax
and the whole cell is enclosed with a
pasteboard cover.
When local action and polarizafion