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lectively is 1 ton 7 cwt., and that of 

 copper in the armature and field-coils 

 collectively is 930 lbs. The armature 

 resistance is 1.038 ohm, and that of the 

 field coils is 3.24 ohms ; exciting current, 

 28.7 amperes. The loss of energy in the 

 armature is thus 2.08 per cent., and that 

 in the field 3.33 per cent, of the output. 

 Some experiments were made with this 

 machine to determine the loss due to 

 windage, mechanical friction, and mag- 

 netic friction. For this purpose the 

 machine was driven by a belt from an 

 electromotor, the efficiency of which had 

 previously been determined. For the 

 first experiment, the field of the alterna- 

 tor was not excited, and the power 

 required to drive it, at its normal speed 

 of 360 revolutions j)er minute, was found 

 to be 4.07 HP. In the next experiment 

 the field was excited so as to produce a 

 terminal pressure of 2,000 volts ; but no 

 current was allowed to flow through the 

 armature, and the power required was 

 found to be 9.81 HP. From these 

 experiments it appears that the loss 



