Download - Applications of First Law of Thermodynamics
![Page 1: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/1.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
1
![Page 2: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/2.jpg)
Applications ofFirst Law of
Thermodynamics
Sajjad Ahmed Memon
Senior Scientist
NIMRA
![Page 3: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/3.jpg)
Heat can be supplied to a thermodynamic system under the following conditions:
Isobaric Process
Isochoric Process
Isothermal Process
Adiabatic ProcessSajjad Ahmed Memon S.S./
Health Physicist NIMRA
![Page 4: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/4.jpg)
Isobaric Process
A thermodynamic process in which pressure of the system remains constant during the supply of heat.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 5: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/5.jpg)
Consider a cylinder fitted with a frictionless piston. The piston is free to move in the cylinder. An ideal gas is enclosed in the cylinder.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 6: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/6.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 7: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/7.jpg)
Q = U + W
But W = PV
Thus
QP = U + PV
As V = (V2 - V1)
QP = U + P (V2 - V1)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 8: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/8.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 9: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/9.jpg)
Isochoric Process
A thermodynamic process in which the volume of the system remains constant during the supply of heat.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 10: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/10.jpg)
Consider a cylinder fitted with a frictionless piston. An ideal gas is enclosed in the cylinder. The piston is fixed at a particular position so that the volume of cylinder remains constant during the supply of heat.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 11: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/11.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 12: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/12.jpg)
Let Q amount of heat is added to the system. Addition of heat causes the following changes in the system:
Q = U + W But W = PVThus Q = U + PV As V = 0Q = U + P (0) = U
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 13: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/13.jpg)
This expression indicates that the heat supplied under isochoric process is consumed in increasing the internal energy of the system but no work is performed.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 14: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/14.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 15: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/15.jpg)
Isothermal Process
A thermodynamic process in which the temperature of the system remains constant during the supply of heat.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 16: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/16.jpg)
Isothermal Compression
Consider a cylinder of non-conducting walls and good heat conducting base. The cylinder is fitted with a frictionless piston. An ideal gas is enclosed in the cylinder. In the first stage pressure on the piston is increased and the cylinder is placed on a cold body. Due to compression, the temperature of the system increases but at the same time Q amount of heat is removed from the system and the temperature of the system is maintained.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 17: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/17.jpg)
Q = U + W
Since temperature is constant, therefore, there is no change in internal energy of the system. i.e. U = 0
As the work is done on the system, therefore, W is negative
Q = 0 + (-W)Q = -W
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 18: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/18.jpg)
Isothermal Expansion
In another situation the cylinder is placed over a hot body and the pressure on the system is decreased. Due to expansion, the temperature of the system is decreased but at the same time Q amount of heat is absorbed from the hot body and the temperature of the system is again maintained.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 19: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/19.jpg)
Q = U + W
Since temperature is constant, therefore, there is no change in internal energy of the system. i.e. U = 0
As the work is done by the system, therefore, W is positive
Q = 0 + (W)Q = +W
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 20: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/20.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 21: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/21.jpg)
Adiabatic Process
A thermodynamic process in which there is no heat transfer into or out of the system takes place. In other words Q = 0.
An adiabatic process is generally obtained by surrounding the entire system with a strongly insulating material or by carrying out the process so quickly that there is no time for a significant heat transfer to take place.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 22: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/22.jpg)
Q = U + W
Since there is no heat transfer into or out of the system. i.e. Q = 0.
0 = U + WU = - W
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 23: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/23.jpg)
Since U is the change in internal energy and W is the work done by the system, therefore the possible outcomes:
1. A system that expands under adiabatic conditions does positive work, so the internal energy decreases.
2. A system that contracts under adiabatic conditions does negative work, so the internal energy increases.
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA
![Page 24: Applications of First Law of Thermodynamics](https://reader035.vdocuments.us/reader035/viewer/2022081415/56813248550346895d98bb0a/html5/thumbnails/24.jpg)
Sajjad Ahmed Memon S.S./ Health Physicist NIMRA