CHAPTER XIII. 



CAPACITY OF SINGLE-PHASE LINE. 



Capacity of Two Round Wires. The conductors of a 

 transmission line form a condenser, the electrostatic capac- 

 ity of which can be calculated from the dimensions of the 

 line. The simplest line to calculate is a single-phase line 

 consisting of two round wires, and this case will be in- 

 vestigated first. 



| --->!<- 



Fig. 19. 



k I- 



Fig. 20. 



Suppose that A and B (Fig. 19) are two long parallel 

 wires of infinitesimal section and that they are spaced a 

 distance / centimeters apart. Let A carry a charge of -f- q 

 electrostatic units of electricity per centimeter, and let B 

 carry q units per centimeter. 



First, find the force exerted on a unit charge near the 

 wire A . 



From the symmetry of the arrangement it is evident that 

 the resultant force on a unit charge at P (Fig. 20) will be a 

 repulsion away from the wire at right angles to it, since the 

 total effect of the right half of the wire must be equal to 

 the total effect of the left half. The force at right angles 



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