THE PRINCIPLES OF ENERGY 41 



Or use the entire power of the current to work a series of 

 electric fires, and estimate the quantity of heat generated by the 

 latter; it is very much less than the quantity of heat originally 

 generated by the burning of the coal that raised the steam, that 

 worked the engine, that drove the dynamo, that produced the 

 current, that generated the heat of the electric fire; or, again, 

 estimate the h.p. required to drive the dynamo, use the current 

 given by the latter to drive a motor, and then estimate the h.p. 

 developed by the latter; it is about 5 to 10 per cent, less than 

 that required to drive the dynamo. 



Finally, estimate the number of kilowatts of current required 

 to work a motor, and then employ the latter to drive a dynamo, 

 and measure the current generated by the latter; it is less (5 to 

 10 per cent.) than the current originally used to drive the motor. 



That means that there is waste incurred whenever there is an 

 , energy transformation, and it is quite easy to see how this waste 

 occurs. "When coal is burned in the furnace of a steam boiler, a 

 quantity of heat is lost by radiation from the boiler and furnace 

 doors, and another fraction is carried away through the flues into 

 the atmosphere ; there is radiation from the steam pipes and hot 

 cylinders, and still another fraction of heat is given up to warm 

 the condenser water. Thus all the heat generated by the com- 

 bustion of the coal does not transform into the mechanical energy 

 of the engine; in fact, only about 10 to 20 per cent, does so. 

 Further, there is friction in the bearings, slides, etc., of the engine, 

 and so mechanical energy is lost. In communicating the engine 

 power to the dynamo more friction is incurred. In the dynamo 

 itself there is friction, and some of the current developed is wasted 

 on heating the parts of the mechanism, while more is lost by 

 imperfect insulation. These latter sources of loss also exist in 

 the means whereby the current is transmitted and then converted 

 into radiant energy, or heat, or mechanical energy. When the 

 current is used to generate light there is great loss, for heat must 

 first be generated until the intensely hot filaments, or arc, or 

 vapour, glow. If light could be generated directly from chemical 

 action — as it is by a glow-worm — there would be great economy. 



Thus there are a host of ways in which available energy is lost 

 in the course of its transformations. There is friction, imperfect 

 heat conduction and insulation, imperfect electric conduction 

 and insulation, materials which are not perfectly elastic or per- 

 fectly rigid, etc. In all cases this lost energy reappears as low- 



