Characteristics of Incandescent Lamps
as a Function of Various Voltages

Table of Contents

Amps, lumens and color temp. of 120V 100 watt 750 hour A19 lamp
Amps at various voltages of 120V 25 watt 2500 hour A19 lamp (gas filled)
Amps at various voltages of 120V 25 watt 750 hour T10 lamp (vacuum)
Explanation of how data was obtained

Lamp:  100 watt A19, 120V, clear, Sylvania, filament CC-8, lamp vertical
Updated 1/16/2011.
------------------------------------------------------------------------
Volts      .5    1    1.5   2    3   4.5   6    9   12   15   18   24   30   36   42   48   60   72   84   96   108  120  132   144   160

Amps      .047 .083  .108 .126 .152 .177 .196 .227 .254 .280 .304 .350 .394 .433 .470 .505 .571 .631 .688 .740 .788 .834 .878  .921  .976

% Volts  .4167 .8333 1.25 1.667 2.5  3.75  5   7.5  10  12.5  15   20   25   30   35   40   50   60   70   80    90  100  110   120  133.3

% Amps   5.63  9.95 12.95 15.1 18.2 21.2 23.5 27.2 30.5 33.6 36.5 42.0 47.2 51.9 56.4 60.6 68.5 75.7 82.5 88.7 94.5  100 105.3 110.4  117

log(i/I)/ .525 .482  .466 .461 .462 .472 .483 .502 .516 .525 .532 .539 .541 .544 .546 .547 .547 .546 .540 .536 .538  --- .539  .544   .547
log(v/120)

color temp. K                            ~800 ~977 1125 1245 1355 1528 1672 1800 1913 2015 2195 2360 2500 2635  2760 2875 2985  3085  3210

log(ct/CT)/                              .43  .418 .408 .403 .397 .393 .391 .389 .388 .388 .388 .388 ~.39 ~.39  ~.39 ---- ~.39  .388  .383
log(v/120)
                                            ~1.25E-4
lumens (approximately!)                 ~8 E-7   ~.0033~.025 ~.12 ~.96 ~3.7 ~10.6  24   46  125  268  483  798  1218 1750 2405  3160  4310

log(lu/LU)/                              7.18 6.35 5.72  5.35 5.05 4.66 4.44 4.24 4.09 3.97 3.8 3.68  3.61 3.52 3.44 ---- 3.33  3.24  3.13
log(v/120) (approximately!)

Lamp:  25 watt A19, 120V, clear, GE, filament CC-6, lamp vertical
------------------------------------------------------------------------
Volts      .5    1    1.5    2    3    4.5   6     9   12    15   18   24    30    36   42   48   60    72    84    96  108   120   132   144    160

Amps      .011 .0205 .0285 .035 .0455 .056 .0635 .073 .0795 .085 .090 .0995 .1075 .116 .124 .131 .146 .1595 .1725 .1845 .1955 .2065 .217 .2275   .240

% Volts  .4167 .8333 1.25  1.667 2.5  3.75   5    7.5  10   12.5  15   20    25    30   35   40   50    60    70    80   90   100   110   120    133.3

% Amps   5.33  9.93  13.8 16.95 22.0  27.1 30.75 35.35 38.5 41.1 43.6 48.2  52.1  56.2 60.0 63.4  70.7 77.2  83.5  89.3  94.7  100  105.1 110.2  116.2

log(i/I)/ .535 .482  .452 .434 .410  .398  .394  .401 .415 .428 .438  .453  .470  .479 .487 .497 .500  .507  .51  .51  .51-.52 ---  .52  .52-.53 .52-.53
log(v/120)

color temp. K                                                                                                                 2550

Lumens (approximately!)                                                                                                        210


Lamp:  25 watt T10, 120V, clear, GE, filament C-8, lamp vertical
------------------------------------------------------------------------
Volts      .5    1    1.5   2    3   4.5   6     9    12   15   18   24    30    36    42    48   60    72    84    96   108  120   132   144   160

Amps      .008 .012  .015 .018 .023 .029 .0345 .0445 .053 .061 .068 .0815 .0935 .1045 .1145 .124 .1425 .1585 .1735 .188 .201 .214  .226  .238  .252

% Volts  .4167 .8333 1.25 1.667 2.5  3.75  5    7.5   10  12.5  15   20    25    30    35    40   50    60    70    80    90  100   110   120  133.3

% Amps    3.74  5.61 7.00 8.41 10.75 13.6 16.1  20.8 24.8 28.5 31.8  38.1  43.7  48.8  53.5 57.9  66.6  74.1  81.1  87.9 93.9 100  105.6 111.2 117.8

log(i/I)/ .600 .602  .607 .605 .605 .608 .610  .606  .605 .604 .604 .600  .597  .596  .596  .596 .586  .587  .587 ~.58 .58-.59 --- ~.58   .58  .57
log(v/120)

color temp. K                                                                                                                 2550

Lumens (approximately!)                                                                                                        260

Explanations of How Color Temp. and Lumen Data Were Determined:

Color temperature:

This was done with the "Properties of Tungsten" table in the "Handbook of Chemistry and Physics", published by the Chemical Rubber Publishing Co.

In addition, plenty of interpolation was done.

Color temperature at full voltage for 100 watt 120V 750 hour A19 was assumed to be 2875 K because of mention of around 2875-2880 K in the IES Handbook. Kodak mentions 2865 K, but that dates back to when Standard Illuminant A was 2848 K, since redefined to 2854 K as a result of updating a constant in the blackbody formula.

Color temperature of coiled-coil filament in gas-filled bulb was assumed to be halfway between the actual temperature and the color temperature of a straight tungsten wire in vacuum at the same actual temperature according to the table.
Actual temperature at voltages other than full voltage were worked from filament resistance as a function of actual temperature according to the above "Properties of Tungsten" table.
Color temperature of other lamps at full voltage largely come from color matching them to a 100 watt 120V A19 that is powered by an adjustable voltage power supply and use of my data for the above 100 watt lamp.

It is to be noted that the temperature is not completely uniform throughout the filament. It is also to be noted that the temperature profile of the filament varies with temperature since heat loss from radiation and conduction vary differently with temperature. As a result, color temperature and lumen figures are only roughly approximate, especially at more extreme voltages.

Lumens:

Color temperature was plugged into a homebrew BASIC program that has the blackbody function and the photopic function. "Color emissivity" (ratio of brightness of a given incandescent surface to a blackbody surface at the same color temperature) for a coiled-coil filament in a gas-filled bulb was assumed to be the square root of that shown in the "Properties of Tungsten" table for a straight wire in vacuum, for a given actual temperature. Color emissivity varies slightly inversely with temperature. This permits working of lumens at various filament temperature given color and assumed actual temperature and manufacturer's stated lumens at full voltage.
Brightness according to the brightness column in the "Properties of Tungsten" table varies even slightly more drastically with temperature than according to my homebrew BASIC program.


Copyright (C) 2006, 2009 Donald L. Klipstein (Jr.)

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