WORK AND MACHINES 169 



nature. As a result of the painstaking researches of scien- 

 tists from the days of Michael Faraday down, and of the 

 genius of many inventors, the dynamo uses solar energy 

 stored in the water-fall, or in the coal that was formed long 

 ages ago, and places at man's disposal in the most convenient 

 form an increase in power for doing the work of the world 

 that is amazing. Through the study of Physics one's 

 knowledge of electricity which otherwise might be more or 

 less fragmentary, becomes more comprehensive and better 

 organized. This grouping and organizing of knowledge 

 characterizes the study of science. 



As a machine the dynamo cannot create any energy. 

 It can only return in the form of electricity a portion of the 

 energy used in its operation. The fact that it does yield as 

 a product a very large per cent (90 per cent and upwards) 

 of what is transformed makes the dynamo highly efficient as 

 a machine. The steam engine on the other hand is highly 

 wasteful of the heat energy it consumes, its efficiency often 

 being less than 15 per cent. Essentially the dynamo consists 

 of a number of closed circuits each having many turns of wire 

 that is very carefully insulated. These coils are made to 

 rotate at an exceedingly high rate of speed into and out of a 

 succession of powerful electromagnetic "fields" arranged 

 around the circumference of the rotating group of coils 

 (armatures). So long as these conditions are maintained 

 there exists within these closed coils an electric pressure. 

 Special devices have been invented whereby connection is 

 maintained between the wires of these coils and an outside 

 or external circuit so that a continuous outflow of electricity 

 from the dynamo when in operation becomes available to 

 furnish, light, power, and heat. 



It is scarcely more than a generation since schools were 

 giving much time to teaching the phenomena of frictional 

 electricity typified in the experiment where a dry glass rod 



