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BELL SYSTEM TECHNICAL JOURNAL 



from those shown. Note that one curve can be superposed on any other 

 curve by a shift along a constant power Hne. 



Figure 12 shows a family of log V versus log / curves for eight different 

 values of B while C, Ra , and To are kept constant. In contrast to the curves 

 in Figs. 10 and 11 in which any curve could be obtained from any other 

 curve by a shift along an appropriate axis, the curves in Fig. 12 are each 

 distinct. For each curve there exists a limiting ohmic resistance for low 



C=5X10"'^WATTS/DEG. 



Ro-SQPOO OHMS 



T = 300 K 



1000 



o-* 



10- 



10- 



10- 



10 



10-2 



CURRENT IN AMPERES 



Fig. 12. — Logarithmic plots of voltage versus current for eight values of B in equation 

 (1). These carves are calculated for the constants given in the upper part of the figure. 



currents and another for high currents. For B = these two are identical. 

 As B becomes larger the log of the ratio of the two limiting resistances in- 

 creases proportional to B. Note also that for B > 1200 A'°, the curves have 

 a maximum. For large B values this maximum occurs at low powers and 

 hence at low values of T — To . This follows since W = C{T — To). 

 As B decreases, Vm occurs at increasingly higher powers or temperatures. 

 For B < 1200 K°, no maximum exists. 



The curves in Figs. 10 to 12 have been drawn for the ideal case in which 

 the resistance in series with the thermistor is zero and in which no tempera- 

 ture limitations have been considered. In any actual case there is always 



