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Our Surroundings 



The commutator is an attachment which changes this alternat- 

 ing current into a direct current which flows in one direction. 



The brushes are metal or carbon blocks which, by contact with 

 the armature, take the current from the dynamo and carry it to 

 the wires in the outside circuit. 



It will be helpful to study a dynamo in some electric power 

 station, or to examine the parts of the generator in an automobile. 



Niagara Falls Power Co. 



GIANT DYNAMOS AT NIAGARA FALLS 

 They transform the energy of the falling water into electric energy. 



Source of Energy of the Dynamo. It should not be for- 

 gotten that the dynamo does not make energy. It only trans- 

 forms the energy of motion into electrical energy. It illustrates 

 well the principle of the transformation of energy. A steam 

 engine or a gas engine or a turbine is necessary to drive the 

 dynamo, and each of these is dependent on some source for its 

 energy. In every case it is possible to trace the original source 

 of energy back to the sun. 



