ELECTRICITY IN THE HOME 159 



door bells. Set up the cell, noting the different parts. Make a 

 drawing of a longitudinal section through the cell. 



3. Sometimes dry cells are used to operate the electric bells. 

 Make a drawing of a dry cell cut in two lengthwise. Label the 

 parts and explain the use of each part. 



HOME PROJECT 16 



Purpose. To study the parts of an electric door bell outfit, 

 and to fix it if it gets out of order. 



Directions. I . If you have an electric door bell in your home, 

 study it to see how the different parts are connected. Make a 

 drawing showing the bell, push button, wires, and cell. Notice 

 the kind and number of cells. If more than one is used, show 

 in your drawing how they are connected. 



2. If your door bell is out of order, see if you can fix it. First 

 test the bell by connecting it directly with the battery. Then 

 look at the cells. They may need either a new zinc, more sal 

 ammoniac, or simply more water to take the place of that which 

 has evaporated. Look at the binding posts and see if the con- 

 tacts are tight. Scrape all contacts to free them of non-con- 

 ducting materials that may have accumulated. If the trouble 

 is not with the cell, look at the push button to see if the contact 

 here is all right. Examine the bell to see if the connections 

 with the binding posts are secure, and if the vibrator makes 

 proper contact. Very rarely it might happen that the wire 

 was broken somewhere. 



SUPPLEMENTARY QUESTIONS FOR CLASS DISCUSSION 



1. What is the principle involved in the various instruments 

 used for cooking by electricity ? 



2. What are the advantages of using electricity in the 

 home? 



3. What uses can be made of the motor in the homef 



4. Explain how the electric bell works. 



5. How do cells generate electricity? 



