8 9 



By means of a thermometer, deter- 

 mine the increase in the temperature 

 of the water. Calculate what the 

 temperature increase would have been 

 if only a pint of water had been used. 

 (Remember that the smaller the quan- 

 tity of water used, the higher will be 

 the temperature.) Calculate also what 

 the increase of temperature would have 

 been if the bulb had been in the pint 

 of water for one minute instead of for 

 five or six minutes. 



What practical use is made of the 

 heating power of electricity ? 



Which would yield more heat, a 16 

 candle power bulb or a 20 candle power bulb ? 



FIG. 66. The electric 

 buib heats the water. 



FIG. 67. 

 Coil and 

 soft iron 

 rod. 



EXPERIMENT 86. ELECTRICITY AS A MAGNET 



1. Dip a nail or an iron rod into iron filings, 

 and notice that the filings do not adhere to the 

 nail or rod. 



Wind wire around the nail, or slip the nail 

 into the coil of wire furnished by your instructor, 

 and notice that this too fails to attract iron fil- 

 ings. But connect the ends of the coiled wire 

 with an electric cell, and then test with iron fil- 

 ings. What is the result ? 



Place some small tacks on the table and see 

 whether you can lift them by bringing the coil 

 near them. Current makes a coil attract iron. 



2. Slip the nail out of the coil, connect the 



