352 



MAGNIFICATION OF DRAWINGS 



[Cn. X 



FIG. 197. DRAWING OUTFIT FOR THE HOUSE LIGHTING SYSTEM, USING 

 AN INDUCTOR INSTEAD OF A RHEOSTAT (fig. 193). 



Commencing at the left : 



The supply wires to the lamp socket, and the supply wires from the separable 

 attachment plug to the arc lamp. 



One of the supply wires is connected directly with the arc lamp and one is 

 cut and the two cut ends connected with the two poles of the inductor exactly 

 as with a rheostat (fig. 188), and from the inductor the wire is continued to one 

 of the binding posts of the arc lamp. 



The inductor is only for alternating current ( 736). The amperage can be 

 varied by sliding the soft iron core in and out of the coil. The more the core 

 is inserted the greater the inductance and hence the less the amount of current 

 that is allowed to flow. 



As shown in the picture, the core is only partly inserted and a medium 

 current is allowed to flow. 



If one uses alternating current this is a much more economical method of 

 controlling the current than a rheostat (see 736 + ) and a steadier light is 

 produced. 



The two most common changes are: (i) Using a higher or 

 lower objective; and (2) Changing the distance of the drawing 

 surface. 



