Today, the purpose of this class is to identify the different thermodynamic processes They are adiabatic, isothermic, isobaric, and isochoric systems.
The first thing we did today is to find the state variables of Thermodynamic states. and there are four vectors that can influence: pressure, volume, temperature and No. of moles or atoms.
in this photo, we answered three questions in lab manual and draw three graphs for the state variables and ideal gas law. The first one is Isobaric processes, the P and N are constant, we know T/V=constant. The second one is Isochoric processes, the V and N are constant, we find that P/T=constant. The third one is Isothermal processes, the T and N are constant, we find P*V=constant.
in this photo, we did the quesion #4-6 in lab manual, using Isobaric, isochoric and isothermal processes to find the volume, pressure of gas.
in this photo, these for graphs represent four processes: isochoric, isobaric, isothermal and adiabatic poesses. and the reason why we can identity graph #3 and #4 because graph #3 is gradual change of volume,but graph #4 is sudden change of volume.
then we look a video about heating rubber band. After watching the video, we know when we heat the rubber band , it will shrink rather than elongates.
then in the photo, the professor let us describe the can lifter-cycle. First, we move the can onto filler conveyor belt. Then we heat the rubber band, and it shrinks. Finally, it unload the cans. Then repeat the whole process.
in this photo, we answered some questions from the lab manual. First, the heat energy is transferred in the part of No.2 (heat) and it is from heat gun to rubber band. The word is done in the part No.3(unload) the rubber band does the work and the work is done on can. Second, on a very hot day, the engine doesn't work. Third, some heat energy goes to environment.
these two photos show us that the relationship about E,Q and W . in the second photo, we figure out the efficiency .
in this photo, we begin to analyze the cycle. We get 4 points of different states. Then we use the equation:E_int=(3/2)P*V to find the internal energy of these 4 points. And find the △E between process 1-2,2-3,3-4,4-1. And in the graph, the blue area is the work done by the air, the red one is the work done on the air.
in this photo, we calculate the W by using the equation:W=P△V, and find the Q=△E+W. Then we find W_net=460J and Q_net=460J ,△E=0. We find that the work done in a cycle=Area enclosed by that cycle.
in these photos, we did the experiment about The Lncredible Mass Lifter Engine. we have 4 positions of different volume and know their pressure. Then we use the equation:E=(3/2)PV to find the internal energy. and we find the energy of every process.
Conclusion:
In this class, We figure outeach process in thermodynamic system is dependent upon its state variables. And we can derive different equations under the first law of thermodynamics. In addition, we did the mass lifter heat engine and the rubber band experiment. And we know the work is equal to the heat of hot minus the heat of the cold. At the end of the class, we look at the efficiency of the system. And if we want to increase the efficiency, we should lower the ratio between the heat hot over heat cold which will increase the amount of energy.
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