246 Common Science 



of the nail plug, screw the lamp into the socket. Do not 

 turn on the switch that lets the electricity flow through the 

 resistance wire, but turn on the electricity so that the lamp 

 will glow. Does the zinc shaving work satisfactorily as a 

 fuse wire? Now turn the electricity on through the re- 

 sistance wire. What happens ? 



When are the greater number of amperes of electricity 

 flowing through the zinc shaving? (NOTE. "Amperes" 

 means the amount of current flowing.) Can the zinc shav- 

 ing stand as many amperes as the fuse wire you ordinarily 

 use? Which lets more electricity pass through it, the lamp 

 or the resistance wire? Why do electric irons and toasters 

 often blow out fuses? If this happens at your home, ex- 

 amine the fuse and see how many amperes (how much cur- 

 rent) it will allow to flow through it. It will say 6 A if it 

 allows 6 amperes to pass through it; 25 A if it allows 25 

 amperes to pass through it, etc. The fuse wire across the 

 fuse gap allows about 8 amperes to pass through before it 

 melts. The zinc shaving allows only about 2. Read the 

 marks on the cartridge and plug fuses. How many amperes 

 will they stand? 



Application 60. A family had just secured an electric 

 heater. The first night it was used, the fuse blew out. 



The boy said: " Let's put a piece of copper wire across 

 the fuse socket ; then there can't be any more trouble." 



The father said that they had better get a new fuse to 

 replace the old one. The old fuse was marked loA. 



Was the boy or was the father right? If the father was 

 right, should they have got a fuse marked 6 A, one marked 

 io;l, or one marked 15 A ? 



Application 61. The family were putting up an extension 

 light. They wanted the cord held firmly up out of the way. 

 One suggested that they drive a nail through both parts of 

 the cord and into the wall. Another thought it would be 

 better to put a loop of string around the cord and fasten 

 the loop to the wall. A third suggested the use of a double- 



