INORGANIC RESPONSE 



107 



recovery is delayed, as the effect of overstrain. Curve 

 (a) is for a single stimulus due to a vibration of 

 amplitude 20, and curve (b) for a stimulus of 40 

 amplitude of vibration. It will be noticed how rela- 

 tively prolonged is the recovery in the latter case. 



Molecular Model. We have seen that the electric 

 response is an outward expression of the molecular 

 disturbance produced 

 by the action of the 

 stimulus. The rising 

 part of the response- 

 curve thus exhibits the 

 effect of molecular upset, 

 and the falling part, or 

 recovery, the restoration 

 to equilibrium. The me- 

 chanical model (fig. 62) 

 will help us to visualise 

 many complex response 

 phenomena. The mo- 

 lecular model consists 



a 



Ac d e 



FIG. 62. MODEL SHOWING THE EFFECT OF FRICTION 



of a torsional pendulum a wire with a dependent 

 sphere. By the stimulus of a blow there is produced 

 a torsional vibration a response followed by recovery. 

 The writing lever attached to the pendulum records 



