The Washington herald., 1922-04-27
Dry Cell Battery
Used IN Radio Set
Construction Of Units Elk.
plained-Low Current and
High Voltage Sought.

In, the discussion yesterday II was
explained that the storage cell was
secondary cell meaning II first.
derived its electrical properties
from a primary or direct current
source. The filament or A battery
Is usually'a storage cell because II
Is the most convenient unit for Sc
curing small voltage and high cur
rent. The battery may be q stor-
age battery but is often of the dry
cell or primary type, because low
current and high voltage Is de-
sired.
The construction of a sample pri-
mary cell includes a carbon elec-
trode, which forms the positive
terminal; the zinc casing of the
cell, forming the negative electrode;
an electrolyts, Sal Ammoniac
(water solution): and a depolarizer,
manganese, dioxide. When the
positive and negative terminals OF
the cell are Joined. chemical action
within the cell. from zinc, through
the electrolyte to the carbon. re-
suits in electrical action throughout
the circuit. It Is possible that Inn
pure materials within the cell may
cause this action to take place
without any outside connection.
This Is evident when you hear a
grating noise through your phones.
To avoid this, an absorbent mate
rial is placed along the inner lining
OF the zinc to separate the manga
nese dioxide and impurities from
the zinc A dry cell is useless when
II is dry. In other words when the
sal ammoniac has thoroughly dried
out no chemical action takes place.
This has led to many ingenious
ways of boring holes In dry cells
and filling them with water or
placing them in solution of sal am
moniac to "recharge" the cells.
Some degree of success is possible,
but dry. cells are so reasonable IN
price today and are made In such
convenient units that the trouble OF
recharging Is hardly worth while
and has no permanent advantage.
The B battery as sold today Is
made in a variety of ways The
average voltage of Individual cells
Is Is. The necessary plate voltage
In the radiophone set Is 22h. There
fore. fifteen dry cells in series
would supply the necessary emf
But fifteen dry cells Joined together
are very inconvenient to handle.
Hence the market Is supplied with
many kinds of B battery units,
small, compact and serviceable.
These units are often box-like in
shape. Some concerns manufacture
the latter in such form that the
battery cover may be removed and
one or more cells removed and re-
placed. AS the current drawn from
these cells for use as B battery
is very small the cells are long
lived. For ordinary use some manu-
facturers claim three or four
months service. One indication that
the cells are getting weak or de-
teriorating is the sputtering noises
heard in the phones Except when
this may be static). Bad B bat
teries are very troublesome.
The purpose OF the A and B bat
teries in the radiophone set may
now be briefly described, The
whole action of the vacuum tube
Is dependent on the passage Of
electrons between ilament and
plate. together with the regulating
action Of the grid. The A battery
current lights the filament, brings
1t to incandescence. When the fila-
ment Is so lighted millions OF
electrons negative particles Of
electricity are discharged from IT,.
The rate at which these electrons
are received on the plate of the tube
depends upon the field OF force
(voItage) existing between plate
and filament. This field of force is
determined by the strength of the B
battery. II Is possible to increase
the plate voltage or potential untid
all the electrons are received on the
plate. The grid, however, checks
this passage and tends to regulate
the rate OF flow of electrons by
forcing some of them to discharge
through the grid condenser, often
called the trapping condenser.
The A or flament battery. there
fore, causes the discharge of cleo
irons across the vacuum tube. while
the B or plate voltage battery
regulates the rate Of this discharge
Of electrons.