A SIMPLE ELECTRIC CELL 45 



Hold the pendulum in your hand for a second or two, to dis- 

 charge it; then hold near the uncharged pendulum the rubbed 

 silk pad. Give all the results. 



c. Rub a stick of sealing wax, or a rubber ruler or comb, with 

 a piece of woolen goods, such as flannel. Bring the sealing wax 

 (or rubber) near an uncharged pendulum, and compare the 

 results with those that took place when glass was used. Also 

 try the action between the rubbed part of the flannel and the 

 uncharged cork. Give all the results. 



d. Charge two electric pendulums from a rubbed glass rod, 

 and hold them near each other, as in Fig. 119, 143, of the text. 

 What happens? 



e. On a cold, dry evening put on some heelless slippers, 

 and shuffle your feet vigorously, several times, across a rug or 

 carpet. In this way your body becomes charged; so does the 

 rug or carpet. Now hold your finger near a metallic object, 

 such as a door knob or a chandelier. Describe what takes 

 place. 



On the same kind of a night comb your hair vigorously with 

 a rubber comb, and prove that the comb becomes charged. 

 Do the combed hairs show any sign of repelling one another? 

 Why should they? 



/. With a silk handkerchief, a flannel cloth, or a fur muff, rub 

 a sheet of smooth paper, and hold the paper near the wall. 

 Tell what happens, and why? 



EXERCISE 44 

 A SIMPLE ELECTRIC CELL 



Apparatus and Materials. Strips of sheet zinc and sheet copper, 

 pieces of copper wire, block of wood, tacks, drinking glass or jelly 

 glass, compass or floating magnet, dilute sulphuric acid, saturated 

 solution of potassium dichromate. 



