SOME WAYS OF PRODUCING ELECTRICITY 179 



In the dry cell, the zinc used is placed on the outside 

 of the cell, making a container for the other materials, 

 while the carbon is a large rod in the center. Between 

 these are the chemicals, a paste of ammonium chloride 

 being placed next the zinc and a layer of manganese 

 dioxide around the carbon. The carbon pole is called 

 the positive (+) pole, while the zinc is called the negative 

 ( ) pole. A current of electricity will flow through a 

 wire which connects these poles. Dry cells have come 

 to replace the wet cells in our homes to a large extent 

 because they are more convenient to handle. 



What Produces the Light in a Flashlight? When an 

 electric cell has been used for a long time, it may fail to 

 produce any more current. In the case of the wet cell, 

 you will very likely find that one of the plates in it has 

 been used up. This suggests that some vigorous chemical 

 action has taken place in the cell between the solution 

 and the plates. This is true. The cell is really a device 

 by which energy resulting from this chemical action in 

 the cell changed into electrical energy. This electrical 

 energy can be changed to heat energy and light energy 

 as it passes through the tiny bulb of the flashlight. 



SELF-TESTING EXERCISE 



Select from the following list those words which best fit the blank spaces 

 in the sentences below and arrange them in proper numerical order. A 

 word may be used more than once. 



attract neutral ammonium conduction 



silver brass nickel chemical 



repel negative electrons insulators 



nucleus silk line conductor 



attracts friction gold metal 



repels contact protons charge 



positive induction wool current 



copper electricity sodium cotton 



Every (1) body contains equal amounts of (2) and 



(3) electricity. (4) between two unlike substances as 



