ELECTRIC DEVICES FOR THE HOME 211 



resistance to the flow of water than a large pipe ; less water can 

 be forced through a small pipe than through a large pipe, but 

 the friction of the water against the sides of the small pipe is 

 much greater than in the large one. 



So it is with the electric current. In- fine wires the resist- 

 ance to the current is large and the energy of the battery is 

 expended in heat rather than in current. If the heat thus 

 produced is very great, serious consequences may arise; for 

 example, the contact of a hot wire with wall paper or dry 

 beams may cause fire. Insurance companies demand that 

 the wires used in wiring a building for electric lights be of a 

 size suitable to the current to be carried, otherwise they will 

 not take the risk of insurance. The 

 greater the current to be carried, the 

 coarser is the wire required for safety. 



Electric devices for the home. 

 It is often desirable to utilize the 

 electric current for the production of 

 heat. For example, trolley cars are 

 heated by coils of wire under the seats. 

 The coils offer so much resistance to ,., 



FiG. 76. An electric iron. 



the passage of a strong current 



through them that they become heated and warm the cars. 



Some modern houses are so built that electricity is received 

 into them from the great plants where it is generated, and by 

 merely turning a switch or inserting a plug, electricity is con- 

 stantly available. In consequence, many practical applications 

 of electricity are possible, among which are flatiron and toaster. 



Within the flatiron (Fig. 76) is a mass of fine wire coiled 

 as shown in Figure 77. As soon as the iron is connected with 

 the house supply of electricity, current flows through the fine 

 wire, which becomes strongly heated and gives off heat to the 

 iron. The iron, when once heated, retains an even temperature 



CLARK INTRO. TO SC. 14 



