Thermodynamics part ii Second Law of Thermodynamics Heat

Thermodynamics part ii

Second Law of Thermodynamics Heat flows in Heat can be made to flow the other way, but i. e. air conditioners

Change completely into is ! i. e. rub hands, push object across floor Changing heat Converting some into work is is possible

Heat Engine Any device that changes Heat flows from into to w/ some of this transforming into Absorb from hi temp area (inc energy) Convert into remaining energy to

Heat Engines & the Second Law When is done by a heat engine running between two temperatures, Thot and Tcold, only some of the at Thot can be converted to , and the rest is as at Tcold Undesirable heat expulsion =

Carnot Efficiency Upper fraction of heat that can be converted to useful work depends on Ideal efficiency = Depends only on temperature difference between Temperature is expressed in

For example… If a hot reservoir in a jet engine is 500 K and the sink is 250 K, the ideal efficiency is 500 – 250 0. 5 500 This means that only 50% of the internal energy of the jet fuel can be converted into work, while the remaining 50% is expelled as waste

In order to determine the for all heat engines, use THE OPERATING OF ANY HEAT ENGINE, THE HIGHER THE OF THAT ENGINE presence makes it so that than ideal is

Order Tends to Disorder Rewording the laws of thermodynamics 1 st Law: 2 nd Law: whenever energy transforms, (which is unavailable and lost) • OR…

Quality of energy is lowered with each Rewording the 2 nd law (AGAIN)… e. g. molecules energy can be changed to energy only at the expense of some

Entropy The measure of the amount of Entropy w/ in normal physical systems • Humans us/ take from the environment to increase internal organization (decrease of entropy) • Life forms + waste products = net increase in entropy

In Class (finish for homework) RQ#21, 23 -25 P/C#2, 4 T/E#2, 4, 5, 8 -10 CD 23 -1, 23 -2, 24 -1