206 APPLIED SCIENCE 



of electrical work, as there are some specialized occupations, 

 such as power house work, which have been omitted. 



253. Requirements of the Trade. A very considerable 

 3 noun t of trade and technical knowledge is required by an 

 electrician. The following are some of the details upon 

 which an inside wireman must have ready and definite 

 knowledge: (1) the methods of installation of electric wires 

 and conduits; (2) the making of electrical connections 

 (fixture wiring) ; (3) the installation of electrical appliances ; 

 (4) the testing of circuits; (5) the methods of computing 

 the sizes of wires; (6) connections and fuses required for 

 specific electrical currents; and (7) the methods of estimat- 

 ing the amount of current required for the specified work. 

 This work presupposes a thorough knowledge of the electrical 

 requirements of the trade as set up by experts, and called the 

 code, together with some knowledge of the theory of electri- 

 city, with emphasis on the definition of terms and electrical 

 measurements. Some knowledge of building construction 

 is also necessary. 



Electric wiring demands careful insulation from all sur- 

 rounding material which might under any circumstances 

 become a conductor of electricity. This need for special care 

 in insulating has caused the establishment of definite and 

 fixed rules. It is important that these rules (the electrical 

 code) be understood and observed by the worker, since not 

 only his business integrity and reputation are affected by 

 poor or slipshod work, but the safety of property and even 

 the lives of many people are dependent upon the proper 

 installation of electric wires arid appliances. 



254. Switchboards. The output from generators and 

 dynamos is regulated by means of switches on a switchboard 



