Table 6. --The relationship between total applied voltage, 

 current density, and electric field 



Whereas with aholehole, the optimum response 

 was obtained with 1 to 2 volts at 10 c.p.s. 



The power dissipation per unit volume of 

 water for the tests of the third yellowfin, cited 

 above, was calculated to be as follows: 



where R is the resistance between electrodes 

 and is given by R = p a where p is the re- 

 sistivity of the water, L is the distance between 

 electrodes, and A is the cross-sectional area. 



Thus P = — Y A is the power dissipated in the 



D l-" 

 tank. "^ 



153 microwatts/cm. 

 131 

 92 



at 12 c. p. s. 

 " 16 

 " 20 



We shall now approximate the condition in 

 the open sea by two spheres of radius (a), half 

 submerged, spaced a distance (L) apart. In 



These values are plotted in figure 6. The curve 

 drawn is only one of many possible curves 

 through the three points, but it seems highly 

 improbable that the point at 20 c.p.s. could be 

 at or near the minimum of the curve. The most 

 likely possibility is that a minimum point in the 

 curve occurs somewhere above 20 c.p.s. This 

 question can be settled only by investigating the 

 response of tuna at frequencies greater than 

 20 c. p. s. 



It is interesting to look ahead to the 

 possibility of testing this equipment in the open 

 sea. Under these conditions and maintaining a 

 similar spacing between electrodes, the total 

 current would increase and hence the total power 

 dissipation would also increase. This is a direct 

 result of the tremendously greater cross- 

 sectional area exposed between the electrodes 

 when in the open sea. 



In order to make an exact comparison of 

 the power dissipated in each case one should go 

 through a procedure similar to that in Appendix 

 I, calculating the net resistance between two 

 plane parallel electrodes in an infinite expanse 

 of water. A useful approximation can be ob- 

 tained simply by making use of the results as 

 found in Appendix I for spherical electrodes. 



Considering first the situation in the tank, 

 the power dissipated by a d.c. voltage, V, 



< 

 o 



IT 

 O 





5 



o 



0- 



connected to the electrodes would be P = 



V2 



10 15 20 25 30 



PULSE FREQUENCY, CYCLES/SEC 



Figure 6. --Power dissipation per unit volume of 

 water vs. pulse frequency for satisfactory 

 response in tuna. 



13 



