Thermodynamics Problem

In summary, a cylinder with 2 moles of gas initially at state A (volume = 1*10^-2m^3, pressure = 4*10^5) is brought isobarically to state B (new volume = 2*10^-2) and then at a constant volume to state C (same temperature as A). It is then brought isothermally back to state A. The net work done during the complete cycle is positive because the work done by the gas going from A to B is greater than the work done on the gas going from C to A, with no work done from B to C. This device is a heat engine because the heat of the system increases and the work done during
  • #1
groundhog92
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0

Homework Statement


A cylinder contains 2 moles of gas initially at state A it has a volume of 1*10^-2m^3 and a pressure of 4*10^5. It the is brought isobarically to state B where the new volume is 2*10^-2. It is then brought at a constant volume to state C where the temperature is the same as in step A. It is then finally brought isothermally back to state A.
a)Is the net work done during the complete cycle positive, negative, or zero?
b)Is this device a heat engine or a refrigerator?


Homework Equations


Work=p(V2-V1)



The Attempt at a Solution


I've already got answers but I'm not positive.

Part a
Positive b/c the work done by the gas going from A to B is greater than the work done on the gas going from C to A. This is seen through A bring at a higher pressure than C while they have the same differential in volume. No work is done from B to C.

Part b
I said it is a heat engine for two reasons. First the heat of the system increases and second b/c the work done during the cycle is positive. In a refrigerator work more work must be done on the system for the cold air to move to the hot region.
 
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  • #2
Everything seems to check out here.

You should probably make a P-V graph if you want to show your answers better.
 
  • #3


Your attempt at a solution seems correct. The net work done during the cycle is positive because the work done from A to B is greater than the work done from C to A. This means that the system is able to perform work on its surroundings during the cycle.

As for part b, you are correct in saying that it is a heat engine. In a refrigerator, work is done on the system to move heat from a cold region to a hot region. In this problem, work is done by the system to move heat from a hot region to a cold region, which is the definition of a heat engine. Additionally, the fact that the heat of the system increases during the cycle also supports this conclusion.
 

1. What is thermodynamics and why is it important?

Thermodynamics is the branch of science that deals with the study of heat and its transformation into other forms of energy. It is important because it helps us understand how energy is transferred and transformed in various systems, such as engines, refrigerators, and chemical reactions.

2. What are the three laws of thermodynamics?

The three laws of thermodynamics are the first law, which states that energy cannot be created or destroyed, only transferred or converted; the second law, which states that the total entropy of a closed system always increases over time; and the third law, which states that the entropy of a pure crystalline substance at absolute zero temperature is zero.

3. What is the difference between heat and temperature?

Heat is the transfer of thermal energy from one object to another due to a difference in temperature. Temperature is a measure of the average kinetic energy of the particles in a substance.

4. How does thermodynamics relate to everyday life?

Thermodynamics is essential for understanding many common processes and devices in our daily lives. It explains how our cars and refrigerators work, how our bodies convert food into energy, and how the Earth's climate is regulated.

5. What are some common applications of thermodynamics in industry?

Thermodynamics is used in industries such as power generation, chemical manufacturing, and refrigeration. It is also applied in the design and optimization of engines, turbines, and other energy conversion systems.

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