THE NATURE OF ELECTRICITY 131 



154. Electrical Effects. The effects produced by 

 electrical energy may be divided into four classes, 

 electrolytic, physiological, thermal, and magnetic effects. 



Briefly, the electrolytic effect is that, when an elec- 

 tric current is passed through certain compound sub- 

 stances, it will break up the compound into the simpler 

 substances that compose it. This process is useful 

 in chemistry ; it is used also in electroplating and elec- 

 trotyping. 



The physiological effects are those produced by elec- 

 tric action upon living bodies usually animals. Heavy 

 currents of electricity may kill animal life ; weaker cur- 

 rents are sometimes used in treating certain diseases. 



Thermal effects are those in which electricity causes 

 heat. The wire through which a strong current is pass- 

 ing may become very hot, as seen in small electric lamps. 

 Electric heaters and furnaces also depend upon this 

 effect. 



Perhaps most important of all is the magnetic effect. 

 Wherever electrical energy is used to cause motion 

 in motors, cars, elevators, call bells, telegraph and tele- 

 phone systems, signals, etc. force is applied by means 

 of magnets ; and these, of course, make use of the 

 magnetic effect of electricity. 



155. Potential. In describing the electrical condi- 

 tion of a body the word potential is used in somewhat 

 the same way as the word temperature is used to de- 

 scribe its condition of heat. As a body may have a high 

 or low temperature, so the potential of a body is said 

 to be high or low ; and as heat passes from a body of 



