336 
IOWA academy of science 
; TJie 'decimals are the O. P. ’s at the specified voltages as coin- 
pared with the !C. P. ’s at IIG volts which are taken as unity. 
• Volts 
lOO watt Carbon 
40 O. P. 
fl 
o 
.O 
Is 
O rH 
a 
o 
-g ■ 
(S • 
O . 
to 
20 watt Carbon | 
4 C. P. 1 
Si*’ 
aAh 
^ * 
gl 
iH 
60 watt Tungs- 
ten', 48 O. P. 
40 Watt Tungs- 
ten, 32 C. P. 
110 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
T.O 
105 . 
0.765 
0.766 
0.757 
0 . 716 , 
0.840 
0.853 
0.860 
100 
0.583 
0.566 
0.559 
0.490 
0.712 
0.706 
0.698 
95 ____________ 
0.437 
0.422 • 
0.413 
0.338 
0.583 
0.600 
0.587 
; 90 ' 
0.321 
0.301 
0.282 
0.218 
0.475 
0.480 ^ 
0.474 
,80 
0.156 
0.138 
0.133 
0.096 
0.302 
0.305 
0.317 
Volts 
r •' ■ ' : ” ‘ , 
25 watt Tungs- 
■ ten, 20 C. P. 
100 watt nitrogen 
filled 
200 watt nitrogen 
filled 
300 watt nitrogen 
filled 
110 - ::i 
1 .0 
1.0 
1.0 
1.0 ■ 
105 •_ _ __ 
0.842 
0.820 
0.834 
. 0.825 - 
100 
0.701 
0.673 
0.686 
0.670 
.95 
0.592 
0.522 
0.570 
0.561 
90 ____. 
0.475 
0.41 
0.464 
0.456 
80 
0.302 
0.246 , 
0.279 
0.291 
- If the voltage changes came in very quick succession, (say 
at half second intervals) the changes in illumination would 
make themselves felt much more for the small sized lamps than 
for the big ones, because the filaments are thinner and hence 
cool off much more quickly. This, however, has no detrimental 
effects upon the results herein given. 
Physics Laboratory, 
- Iowa State College. 
