ELEMENTARY THEORY OF ELECTROMAGNETISM. 57 



di 



that -r must be negative, that 

 dt 



is - - is the rate of decrease of 

 at 



the velocity of the boat. 



that -j must be negative, that 



is is the rate of decrease of 



at 



the current in the circuit. 



hundredths of a second 



Fig. 436. 



The general solution of equa- 

 tion (i) which satisfies the 

 necessary condition that the 

 ( velocity of the boat is equal to 

 / at the beginning (i = I 

 when / = o), is: 



i = /<-<*<*>' (3) 



where R is the proportionality 

 factor in equation (i), L is 

 the mass of the boat, / is the 

 velocity of the boat when the 

 propelling force ceases to act, 

 and i is the velocity of the 

 boat / seconds after the pro- 

 pelling force ceases to act. 



The general solution of equa- 

 tion (2) which satisfies the 

 necessary condition that the 

 current in the circuit is equal to 

 / at the beginning (i = / 

 when / = o), is: 



where R is the resistance of 

 the circuit, L is the inductance 

 of the circuit, I is the current 

 in the circuit when the pro- 

 pelling electromotive force 

 ceases to act, and i is the value 

 of the current t seconds after 

 the propelling electromotive 

 force ceases to act. 



