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BELL SYSTEM TECHNICAL JOURNAL 



show this effect. (Incidentally, this effect tends to reduce the magni- 

 tude of C and D, at the higher frequencies.) 



It is also apparent that the conductance of this simplified circuit is 

 zero at zero frequency and a maximum at very high frequencies. In 

 the intervening range the conductance at first rises nearly as the square 

 of the frequency, then the relation becomes more nearly linear and 

 finally tapers off to a final constant maximum value. 



Fig. 22 — Calculated and measured value of (G) for C. P. insulator. 



If the distributed capacitance of an insulator were accurately known, 

 as well as the resistivity of the surface film, the magnitude of G could 

 be calculated. Unfortunately, both factors are difficult to determine 

 with precision. 



However, it is useful to carry out such a calculation, even though the 

 factors be not accurately known. 



Fig. 22 shows the variation of G with frequency, as calculated for 

 the assumptions indicated on the drawing. The assumed distributed 

 capacitance and surface resistivity are intended to represent those of the 

 insulator of Fig. 6. A measured value of G for this insulator is shown 

 by the dotted curve. The agreement is not very good, being no more 



