240 Common Science 



1 1 . How can a wire be safely spliced ? 



12. Why is an electric arc in a circuit dangerous? 



Inference Exercise 

 Explain the following : 



351. White objects look blue when seen through a blue glass. 



352. When you pull the plug out of an electric iron, the iron cools. 



353. People who do not hear well sometimes use speaking trum- 



pets. 



354. The sounding board of a piano is roughly triangular; the 



longest strings are the extreme left, and those to the right 

 get shorter and shorter. 



355. Birds can sit on live wires without getting a shock. 



356. Deaf people can sometimes identify musical selections by 



holding their hands on the piano. 



357. An electric toaster gets hot when a current passes through it. 



358. The cord of an electric iron sometimes catches fire while the 



iron is in use, especially if the cord is old. 



359. If a live wire touches the earth or anything connected with 



it, the current rushes into the earth. 



360. When you stub your toe, you have to run forward to keep 



from falling. 



SECTION 39. Short circuits and fuses. 

 Why does a fuse blow out ? 



Sometimes during the evening when the lights are 

 all on in your home, some one tinkers with a part of the 

 electric circuit or turns on an electric heater or iron, 

 and suddenly all the lights in that part of the house go 

 out. A fuse has blown out. If you have no extra fuses 

 on hand, it may be necessary to wait till the next day 

 to replace the one that is blown out. It is always a 

 good idea to keep a couple of extra fuses; they cost 

 only 10 cents each. And if you do not happen to know 

 how fuses work or how to replace them when they blow 

 out, it will cost a dollar or so to get an electrician to put 



