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From the data above, you can find what process happens to the system. Just follow this way:
Plot graphic from the given data, Pressure as Y-axis and Volume as X- axis
Based on the graphic you have made, what process happens to the system?
Based on your simple investigation, now you consider what are the Thermodynamics Process happens to the system. Just write them here,
also the characteristics.
CASE SOLVED Thanks for your help..
Reading Room
1. Isothermal Process
Isothermal process is a constant-temperature process. It means ∆T =
0. From the equation ∆U =
n R ∆T, we know that
∆U = 0 So the first law of thermodynamics become
Q = ∆U + W
Q = W And the work done by Isothermal system is stated in this equation.
W =
∫
By substituting to equation P = we get
14
W
= ∫
P P
2
T
1
= T
2
W = nRT
∫
P
1
V W = nRT ln
V
1
V
1
P-V diagram of an isothermal process
2. Isobaric Processes
A constant-pressure process is called isobaric process. On a P-V diagram, an isobaric process is represented by a horizontal line called
isobar. When heat is added to system, the volume will increase. It means system doing work. So
W = P ∆V
W = P V
2
– V
1
We can write the internal energy as Q =
∆U + W Q =
∆U + P V
2
– V
1
Because of P is constant,
P
P
1
= P
2
V
1
V
2
V
You have to endure
caterpillars if you want
to see butterflies
15
Diagram above is a P-V diagram for Isobaric process. Now you are invited to go to balcony and thinking about a match.
Balcony
VS
Let’s o side a at h et ee Isothe s a d Iso a s. Ea h of the a t to be the greatest process by doing the largest work. So they use two
moles of an ideal gas, initially at 0°C and 1 atm. The gases are expanded to twice their original volume using two different processes. First they are
expanded isothermally, and then starting Isobarically from the same initial state.
During which process does the gas do more work and be the winner? isothermal process, isobaric process, or both process do the same work?
Explain.
Conceptual Reasoning
Based on a P-V diagram, the curve of isobaric process is horizontal line, a d the isote ’s is h pe ola. So, the gas doing more work during
isobaric process because there is more area under the curve.
Follow-Up Exercise
Now try to determine the work done by the gas in each process. Hint : for isothermal process W = 3.14 x 10
3
J for isobaric process W = 4.53 x 10
3
J
Library
3. Isochoric Process
An isochoric process is a volume-constant process. As illustrated in figurebla the process path on a P-V diagram is vertical line.
P
Isotherms Isobars
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P
2
P
1
V
1
= V
2
V No work is done, because the area under curve is zero. Because the gas
can not do work, if heat is added, it is completely used to increase internal energy of the system.
W = 0 In term of first law of thermodynamics,
Q = ∆U + W
Q = ∆U + 0
Q = ∆U
4. Adiabatic Process
