CHAPTER VL 



ELECTRIC CURRENTS. 



The simplest form of an electric machine is 

 one in which the operator is a prominent part 

 of the operation. Electricity, like magnetism, 

 operates in a closed circuit, even when it is 

 static so-called. Take a stick of sealing-wax, 

 say, in your left hand, and rub it with a piece 

 of fur or silk with your right hand, and you 

 have the simplest form of electric machine 

 the one that was known to the ancients, and 

 the one from which the science, great as it is 

 to-day, had its beginnings. The stick of seal- 

 ing-wax is one element of the battery, and the 

 piece of fur or silk is the other, while your 

 hands, arm and body form the conductor that 

 connects the two poles, and the friction is the 

 exciting agent and may be said to take the 

 place of the fluid of a battery. The electrical 

 conditions are not wholly static, as a slow cur- 

 rent is passing around through your arms and 

 body from one pole to the other. Even if the 

 conditions were wholly static there would be 

 polarised lim-s of force, in a state of strain, 

 reaching around in a closed circuit. 

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