ELECTRICITY IN THE HOME 149 



ordinary electric light socket by unscrewing the lamp and 

 inserting a plug with a wire fastened to it, or a special socket 

 may be installed in the side wall. 



In these various appliances electricity is made to produce 

 heat. In order to do this, elements are used which give off 

 heat without much light and thus transfer the heat to the 

 apparatus. These elements are made of substances which 

 are not good conductors ; and when electricity passes through 

 them they offer great resistance and so convert the electricity 

 into heat. Wires are very commonly used ; and the smaller 

 and longer the wire, the greater the resistance and heat. 

 Long coils of small wire are wound in a small compass and 

 placed near the object to be heated. The amount of heat 

 also depends on the strength of the current. By using 

 different combinations of lengths and diameters, different 

 temperatures can be obtained. A wire of nickel alloy is 

 very frequently used. Wires of iron and german silver 

 have also been tried. In some appliances these wires are 

 visible, as in the toaster; in others they are covered, as in 

 the percolator. In other elements, instead of wires, thin 

 coatings of certain metals, such as gold and platinum, which 

 have been deposited on a piece of mica are used. These 

 various elements are made into the shapes which will most 

 conveniently fit the appliance for which they are intended. 



Toaster. Some advantages of the electric toaster are 

 that it may be kept on the dining table and the toast can 

 be kept hot. The heating element is composed of a series 

 of coils of wire exposed to view. In some toasters the coils 

 are placed horizontally ; in other toasters they are placed 

 vertically. 



Coffee percolator. The top portion of these percolators 

 is made on the same principle as other percolators, but 

 at the bottom is a heating element that boils the water. 

 This lower part is a disk stove over which the upper part 

 fits closely. The heating element is a long wire in the form 



