18 



Our Surroundings 





Experiment to Illustrate the Transformation of Energy. 



That heat is readily transformed into motion is easily demon- 

 strated by an experiment with a radiometer and a match. Place 

 an unlighted match near the glass globe of a radiometer and 

 observe that it has no effect on the instrument. Then light the 

 match and hold it near the globe. Observe what happens. Heat, 

 which is one form of energy, has been transformed, or changed, 

 into another form, that of motion. 



In order to prove that the motion is not caused by the light 

 from the burning match, heat a piece of iron 

 and hold it near the bulb of the radio- 

 meter. 



Other Illustrations. In a locomotive 

 engine, the energy stored in the fuel is changed 

 by burning into heat energy. This heat energy 

 is transferred to the water in the boiler and 

 changes it into steam. The energy freed by 

 the expansion of the steam in the cylinder is 

 transformed into the energy of motion. The 

 steam causes the piston to move back and forth. 

 The piston rod carries this motion to a crank, 

 which turns the driving wheel. The result is 

 that the engine moves. 



In a power plant, such as may be seen 

 at Niagara Falls, potential energy already 

 exists in the mass of water at the crest of 

 the falls. The water falling onto the wheels of the power plant 

 below causes them to revolve, and potential energy is transformed 

 into the kinetic energy of motion. In turn, these wheels drive 

 dynamos in which the energy of motion is transformed into the 

 energy of electric currents. These currents are carried by wire 

 cables to various cities, where they are employed in running trolley 

 cars and in providing motor power for many industries. Electric 

 energy is thus changed back to the energy of motion. According 

 to the principle of the conservation of energy, the work which 

 gravity accomplished in causing the water to fall upon the wheels 

 is precisely equal to the work accomplished by all the electric cur- 



A RADIOMETER 



The energy of heat is 



transformed into the 



energy of motion. 



