52 ANALOGIES 



Equation 4.7 may be written 



e = -^ fidt = jr 4.8 



where q = charge on the capacitance, in abcoulombs. 



Equation 4.8 states that the charge on a condenser is proportional to the 

 capacitance and the apphed electromotive force. 



B. Mechanical Compliance. — Compliance is the mechanical element 

 which opposes a change of the applied force. Compliance may be de- 

 fined as 



X 



fM = -7r 4.9 



where Cm = compliance, in centimeters per dyne, 

 X = displacement, in centimeters, and 

 /m = applied force, in dynes. 

 Equation 4.9 states that the displacement of a compliance is proportional 

 to the compliance and the applied force. 



C. Acoustical Capacitance. — Acoustical capacitance is the acoustic 

 element which opposes a change in the applied pressure. The pressure, in 

 dynes per square centimeter, in terms of the condensation, from equation 

 1.21 is 



p = c^ps 4.10 



where c = velocity, in centimeters per second, 



p = density, in grams per cubic centimeter, and 

 s = condensation. 

 The condensation in a volume F due to a change of volume dF is 



s-f 



The change in volume is 



dF = Sx 4.12 



where x = displacement, in centimeters, over the area ^S*, In square centi- 

 meters. 

 The volume displacement, in cubic centimeters, is, 



X= Sx 4.13 



