OTHER USES FOE ELECTRICITY 405 



and that the solution remains at boiling temperature. As soon as the tarnish 

 has been removed, remove the silver, rinse in clean water and wipe with a 

 soft cloth. 



Aluminum corrodes in a cleaning solution of this type so that 

 the aluminum ware should not be used unless kept for this par- 

 ticular purpose. Zinc may be used, but it becomes corroded and 

 inactive in a short time unless treated with a strong muriatic acid. 

 It is, however, less satisfactory than aluminum. 



QUESTIONS 



1. Why is it necessary for lights to have high resistance? 



2. Why do you have fuses in your home? 



3. Why is the telephone wire fused? 



4. Find the resistance in ohms of the lights about your home, 

 of the vacuum cleaner, or electric flatiron. 



5. If your home is wired for electricity, find out what size of 

 wire was used. 



6. Why are fuses enclosed in a barrel or fireproof casing? 



7. Examine a cartridge fuse. 



8. Cut one open which has not been " burned out." 



9. Cut one open which has been " burned out." 



10. Look in a screw-enclosed fuse. 



11. What do we mean when we say 15 ampere fuse or 60 ampere 

 fuse? 



12. What would be the difference in the comparative size of the 

 wire used for each? 



13. Why is it not safe to put a 30 ampere fuse on a wire which 

 is supposed to carry only 15 amperes? 



14. Why is bell wire unsafe to use on electrical apuliances which 

 are attached to the supply current? 



15. Find the resistance of some of your lights at home. 



16. What kind of light seems to have the greatest number of 

 ohms of resistance? 



17. What is the difference between the resistance of the high 

 candle power lights and the low candle power lights? 



