PV Graph Question: Internal Energy Not Zero?

Thread starter bluesteels
Start date Feb 2, 2022
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Graph Physcis

In summary, "PV Graph Question: Internal Energy Not Zero" refers to a type of thermodynamics question where a graph shows the relationship between pressure, volume, and internal energy. The internal energy is represented by the area under the curve and can change depending on the system and process being studied. It is important to consider internal energy in these questions as it represents the total energy of the system and helps us understand its behavior. Internal energy can be non-zero due to initial energy or changes during the process, and examples include adiabatic and isothermal processes, as well as more complex systems involving heat transfer and chemical reactions.

Feb 2, 2022

bluesteels

Homework Statement: The idealized cycle shown is known as the Otto cycle. (Figure 1)Suppose an engine is executing this Otto cycle, using a gas (not necessarily ideal) as its working substance. From state A to state B, the gas is allowed to expand adiabatically. (An adiabatic process is one in which no heat is added to, or given off by, the working gas.) The gas is then cooled at constant volume until it reaches state C, at which point it is adiabatically compressed to state D. Finally, it is heated at constant volume until it returns to state A.

Relevant Equations: adiabactic delta u = -w

isothermal Q=W

Figure 1:

Screen Shot 2022-02-03 at 12.04.03 AM.png

im so confused on why is the internal energy not zero for the 2nd picture because i thought if the gas returning to its original states so it zero

Screen Shot 2022-02-03 at 12.02.43 AM.png

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Feb 2, 2022

haruspex

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bluesteels said:

i thought if the gas returning to its original states so it zero

The question only asks about process ##a\rightarrow b##.

1. What is a PV graph?

A PV graph, also known as a pressure-volume graph, is a graphical representation of the relationship between pressure and volume of a system. It is commonly used in thermodynamics to visualize changes in state variables of a gas or other fluid.

2. What does it mean when the internal energy is not zero on a PV graph?

When the internal energy is not zero on a PV graph, it means that there is a change in the internal energy of the system. This could be due to a change in temperature, pressure, or volume.

3. How is internal energy represented on a PV graph?

Internal energy is typically represented by the slope of the line on a PV graph. A steeper slope indicates a higher internal energy, while a flatter slope indicates a lower internal energy.

4. What factors can cause the internal energy to not be zero on a PV graph?

The internal energy can be affected by various factors, such as changes in temperature, pressure, or volume of the system. It can also be influenced by the type of gas or fluid being studied, as well as any external work or heat being added or removed from the system.

5. How is the internal energy related to the first law of thermodynamics?

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another. The internal energy on a PV graph represents the total energy of the system, including both the kinetic and potential energy. Therefore, the internal energy is directly related to the first law of thermodynamics as it represents the conservation of energy within the system.