ELECTRIC CONDENSERS. 217 



354. Charging the Leycleii Jar. To charge the 

 jar, hold it in the hand as shown in Fig. 153, and bring 

 the knob near or into contact with the prime conductor of 

 an electrical machine which is in action. 



(a.) The prime conductor being positively charged -attracts the 

 from the inner coat and replaces it with its own + . This + charge 

 of the inner coat acting inductively through the glass polarizes the 



I i; 



FIG. 153. 



outer coat, repelling the + which escapes through the hand to the 

 earth, and binding its to the surface in contact with the glass. 

 This bound negative electricity of the outer coat, in turn, binds the 

 positive of the inner coat, and so on. If, instead of holding the 

 outer coat in the hand, the jar be supported upon a pane of glass so 

 that the repelled electricity of the outer coat cannot escape, the jar 

 cannot be very intensely charged. 



355. Discharging the Leyden Jar. The jar 

 might be discharged by touching the knob with the finger, 

 the separated electricities coming together through the 

 person of the experimenter and the earth. In this case the 

 experimenter will feel a " shock." If the charge bo intense, 



the shock will be painful or 

 even dangerous. It is better 

 to use a "discharger," two 

 forms of which are represented 

 in Fig. 154. This consists 

 of two metal arms hinged 

 FIG. 154. together, carrying knobs at 



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