. The principles of physics. ts E andF, the cord of each being so arranged that each weight, infalling, rotated the axle in the same direction. By turningthe crank above A the weights are raised to any desired hightmeasured on the scales G and H. The resistance offered by the water to the motion of thepaddles was the means by which the mechanical energy ofthe weights was converted into heat, which raised the tem- JOULE S EXPERIMENT. 305 perature of the water. Taking two bodies whose combinedmass was, , 80 K, he raised them a measured distance, high; by so doing 4240kgm of work were
. The principles of physics. ts E andF, the cord of each being so arranged that each weight, infalling, rotated the axle in the same direction. By turningthe crank above A the weights are raised to any desired hightmeasured on the scales G and H. The resistance offered by the water to the motion of thepaddles was the means by which the mechanical energy ofthe weights was converted into heat, which raised the tem- JOULE S EXPERIMENT. 305 perature of the water. Taking two bodies whose combinedmass was, , 80 K, he raised them a measured distance, high; by so doing 4240kgm of work were performed uponthem, and consequently an equivalent amount of energy wasstored up in them, ready to be converted, first into that ofmechanical motion, then into heat. He took a definite massof water to be agitated, 2K, at a temperature of 0° the descent of the weights, the water was found to havea temperature of 5° C. ; consequently the 2 K of water musthave received 10 calories of heat (careful allowance being. Fig. 221. made for all losses of heat), which is the number of caloriesthat is equivalent to 4240 kgm of mechanical energy ; or onecalorie is equivalent to 4^4 kgm (commonly taken as X 10ergs) of mechanical energy. In other words, to ?produce the quantity of heat required toraise 1 kilogram of water through 1° C, 4^4 Ttilogrammeters ofmechanical energy must be consumed. What the experimentreally shows is that whenever a certain quantity of mechanicalenergy is converted into heat, the number of thermal unitsproduced is always proportional to the mechanical energyconsumed, or to the work done. This is embodied in the 306 MOLECULAR DYNAMICS. first law of thermo-dynamics, which is expressed as follows: When eqical quantities of mechanical effect are produced byany means whatever from purely thermal sources, or lost inpurely thermal effects, equal quantities of heat are put out ofexistence, or are generated. It is apparent that heat, being aform of energy,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
