56 • ANALOGIES 



The potential energy, in ergs, stored in the capacitance of the acoustical 

 system is 



Vp^ = i — 4.22 



2 Ca 



where X = volume displacement, in cubic centimeters, 



V 

 Ca = — , acoustical capacitance, 



V = volume of the cavity, in cubic centimeters, 

 p = density of air, in grams per cubic centimeter, and 

 c = velocity of sound, in centimeters per second. 

 The total energy, in ergs, stored in the three systems may be written, 



^E = Tke + VpE = T^LP +:,& 4.23 



Wm = Tkm + VpM = - mx" + - ^ 4.24 



Z Z L,M 



Wa = Tka + VpA - \mX'' + ^ ^ 4.25 



Z Z Li A 



The rate of change of energy, in ergs per second, in the three systems 

 may be written 



^^ = Li— + -^ = L •" + — 4 26 



dt dt Ce Ce 



dWu ... , y^x . ^- 



— - — = mxx + — 4.27 



at L.A 



C. 'Dissipation. — The rate at which electromagnetic energy, in ergs per 

 second, is converted into heat is. 



Be = rEi"" 4.29 



where Te = resistance, in abohms, and 

 / = current, in abamperes. 



