The silver state news. [volume] (Winnemucca, Nev.) 1907-1909, 1909-01-23
THE ELECTRIC CURRENT AND
sOaGE OF ITS HOUSEHOLD
APPLICATIONS
CONTINUED from Page IL

oto ~
ever, is when the lamp is new. A
gradual decrease in the candle power
goes on, at whatever efficiency the
lamp is worked. caused by the disinte-
grafton of the carbon filament, which,
becoming thinner, offers greater re-
sistance and hence allows less current
to pass, and partly by the carbon
particles from the flament darkenine
the glass.
7 have stated that the efficiency Of
a lamps i S increased as the tempera-
ture at which it is worked is increased.
Let us see why that is so. If a metal
ball be heated, say to the temperature
of boiling water, we can ascertain that
it radiates heat but not light. If its
temperature be gradually raised, It
becomes successfully dull red, bright
red. and dazzling white. As its tenn
perature rises. not only does its radi
ant energy increase, but of this
radiant energy a larger proportion is
eye-affecting. Of the total radiation
from a black-hot spiral, 0 per cent Is
light and 100 per cent is heat.
OF the total radiation from 4
white-hote spiral, 4.6 per cent IS
light and 95.4 per cent is heat. This
latter statement is a surprise to most
of us as we are apt to think of the
radiation from a white-hot spiral as
nearly all light. The total radiation
is proportional to the watts consumed
in the lamp. When a larger and larg-
er proportion of this radiation becomes
eye-affecting (light) the lamp becomes
more and more efficient as a source
an illumination.
A substance becomes red-hot at a
temperature of about 700 degrees O..
and white-hot at a temperature of 1909
degrees G. Many substances either
burn or melt before they become red
hot and very few are so refractory as
to become white hot before they melt.
Tin melts at 235 degrees c, lead at
1927 degrees G, aluminium at $40 de-
grees C, silver at 900 degrees c and
copper at 1854 degrees c. 1t is evil
dent that none of these could be used
as lamp flaments.
Carbon does not melt, and if ex-
Guided from the air, does not burn but
it rapidly d~isintegrates if raised
much above 1890 degrees C. Until
about the year 1905, the carbon fila
ment was still the most efficient on
the market, but in that year the
osmium and tantalum lamps began 10
appear in use. The tantalum lamp
has come into extensive commercial
use. Tantalum is a dense, extremely
hard metal with a very high melting
point. For use in lamps it is drawn
down to a wire $1,000 of an inch in
diameter and of this, a little over two
feet are used in the 110-volt lamp of
% candle power. The great length
of flament required makes it neces-
sary to string it in loops on support
ing spiders. The melting point of
tantalum is about 1900 degrees cent?
grade. Because the tantalum can be
heated to a higher Temperature than
the carbon filament it has a higher
efficiency. With a life of $50 hours
it has an efficiency of 2 watts per can
die power.
Even more wonderful is the tung
stem lamp which is just coming into
use in this country. AS in the tanta
lum lamp, the tungsten flament is so
long that it mus be eanchored in 5 to
7 loops. Furthermore the flament is
extremely fragile and is very apt To
be broken inshipment. But as tung
stem is fusible only at the highest
attainable temperature $1,000 de-
grees CO. it is possible to
operate its flament at a temperature
at which other flaments would dis.
~integrate and hence at a higher
efficiency. The efficiency of the
tungsten lamp is 1.25 watts per candle
power with a life of 800 hours. While
the high efficiency of the tungsten
lamp greatly reduces the cost of illu-
%mination, this point is lost sight of in
appreciation of the quality of its
light. So pure and white is its light
that it is comparable with sunlight.
Colors can be matched with it almost
as well as by daylight.
Whatever the lamp used, to be en-
tirely satisfactory, its light must be
steady. The inability of the power
company to maintain a constant volt
age (upon which a steady light de
Dnrl.N 70 0aoaa.a, e. rnnra aonrIo.n+.