ELECTRIC CIRCUITS 



79 



In this table and in wire tables generally the conductivity is 

 assumed as 100 per cent. If the conductivity of a given wire is 

 less than this the specific resistance must be changed accord- 

 ingly; thus the resistance of one circular mil foot of copper of 



98 per cent conductivity at 25 C. is 



10.55 



0.98 



= 10.76 ohms; the 



resistance of one circular mil foot of aluminium of 60 per cent 



conductivity at 25 C. is 



10.55 

 0.60 



= 17.58 ohms. 



WIRE TABLE 



57. Drop of Voltage and Loss of Power in a Distributing 

 Circuit. The distributing circuit in Fig. 63 delivers 20 kilowatts 

 at 220 volts to a receiver circuit 1000 feet distant; if the size of 

 the conductors is No. 1 B. & S. determine the voltage required at 

 the generating end of the line and the power lost in the line. 



