-. ii U 



E e . 

 When work is being dune ., , it thus appears that 



when work is being done the current ia lew than that given 

 Ohm's law. It follows from this that tl:.- t. -union 

 imlu.-.-.l liy t!i.- nn>ti'>ii t at andacU 



in the contrary din-en.. n to that of the line. Hut tin- 

 current from tin- line is producing th- motion, li- 

 the induced tension tend* to stop the motion. 

 Thin is a proposition of great importance, since it gives 

 a means of determining the direction of the indm-<l 

 tension under all circumstances. We see that it is simply 

 one way of expressing the energy equation for the 

 circuit us laid down ly the I Yinciple of the ( 'onservnt i<>n 



This truth may be establ^h.-d in another way. T 

 the case of a generator where the cum -nt Hows in the 

 direction of the induced tension. The current in the 

 armature produces a tortjn--. -n ..f \%iii<-h d.-jM-ntN 



u|n that of the current, and of th.- MM fi.-ld. If 



the torque du>- t.. t li>- ctirn-nt assisted the motion we should 

 have arrived at a condition of perpetual motion, the 

 Principle of the Conservation of Kiierv'\ herefore demands 

 that the torque due to the current should op|>o8e the 

 motion, hence the induced curnMit muxt How in the 

 armature in such a direction as to oppose the motion. 



We here assume that the circuit is closed, and 



current passing in the armature in the direction of th- 

 induced tension, but as it is evident that the phenomenon 



ndnction will be present, even if the circuit be l.r.-K 

 and no current be permitted to pass, we are led to this 

 general law : Any displacement of the relative positions 

 of a closed circuit and of a magnetic system induces 



