UTAH ACADEMY OF SCIENCES 175 
suggested certain non-uniform variations in these character- 
istics in the region of high voltages. It was thought that 
these variations might be traced back to more fundamental 
relations, viz. pressure-watt characteristics. In order to 
determine this, three lamps of the tungsten type were 
selected and this characteristic studied. The lamps selected 
were 25, 40 and 60 watt. 
The curves in figure 1 show the volt ampere charac- 
teristic of each lamp. It will be observed that the rate of 
increase of the current diminishes slightly as the voltage 
increases. The cause of this is revealed in fig. 2 showing 
the relation between volts and resistance. The similarity 
of the two sets of curves is evident with the exception of the 
25 watt lamp. Here the rate of increase of resistance in- 
creases slightly causing the curve to bend downward in- 
stead of upward as in the curves of the other lamps. But 
the greater slope of the resistance curves as compared with 
that of the current curves indicates that the rate at which 
the increasing resistance diminishes is less than that at 
which the increasing current diminishes, and since by 
Ohm’s law current is inversely proportional to resistance 
it undergoes less variation than it otherwise would. This 
has a direct bearing upon the power consumed since watts 
equals volts times amperes, and explains at once why tung- 
sten lamps consume less power at the same voltage than 
carbon lamps whose resistance diminishes with increased 
voltage. 
The curves represented in fig. 3 are the pressure-watt 
characteristics. They show a constantly increasing value 
of power throughout the entire range. There are no ap- 
parent anomalous characteristics either in these or in the 
previous curves, therefore they should submit themselves 
readily to rather simple mathematical treatment. By their 
shape we recognizze them as belonging to the parabolic 
family and hence may be represented by the equation 
Pe RL Pk tA Si ok ny Se Naa YC Ul eats. rebelde (1) 
where w is the watts, e the volts, and a and n physical 
constants. By eliminating a we may solve for n which is 
found to give an average value of 1.6 for all the lamps. 
