What is internal energy? Am I right?

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SUMMARY

Internal energy in engineering is defined as the sum of the random kinetic energies of molecules and their potential energies of interaction within a thermodynamic system. It is influenced solely by heat input and work done on or by the system, excluding the kinetic and potential energy of the system as a whole. The first law of thermodynamics is expressed as ΔE = ΔU + Δ(PE) + Δ(KE) = Q - W, where U represents the internal energy. This definition is crucial for understanding energy conservation in closed systems.

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  • Understanding of thermodynamics principles
  • Familiarity with the first law of thermodynamics
  • Knowledge of kinetic and potential energy concepts
  • Basic grasp of heat transfer and work in thermodynamic systems
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lee123456789
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Am i right
Is internal energy for engineering just the sum of energy stored with a system of a substance. which is only affect by heat and work coming out of the system
 
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What do you think and why? On this forum, you don't get help until you show some effort.
 
It is a physical property of the material comprising the system, and is equal to the sum of the random kinetic energies of the molecules and their potential energies of interaction.
 
phinds said:
What do you think and why? On this forum, you don't get help until you show some effort.
Chestermiller said:
It is a physical property of the material comprising the system, and is equal to the sum of the random kinetic energies of the molecules and their potential energies of interaction.
OK, I was wrong. You DON'T have to show any work yourself
 
phinds said:
OK, I was wrong. You DON'T have to show any work yourself
well
i thought it was, the sum of energy stored with a thermodynatic system of a substance. which is only affect by heat input and work coming out of the system.
 
lee123456789 said:
well
i thought it was, the sum of energy stored with a thermodynatic system of a substance. which is only affect by heat input and work coming out of the system.
That is correct, but it is the short version. I though you wanted more detail.
 
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Chestermiller said:
That is correct, but it is the short version. I though you wanted more detail.
Sorry i was getting confused. Was reading in some engine÷ng websites that it excluded potention and kinetic energy and on overs that it included.
 
Chestermiller said:
That is correct, but it is the short version. I though you wanted more detail.
Is that the engineering defination. Some websites say excluding sum potenital and kinetic energy if motion for the system.
 
Yes. That is how it is done in engineering. The more complete version of the 1st law is $$\Delta E=\Delta U+\Delta (PE)+ \Delta (KE)=Q-W$$ so that U is strictly the random kinetic energy and potential energy of interactions of the molecules (and is a fundamental physical property of the gas).
 
  • #10
Chestermiller said:
Yes. That is how it is done in engineering. The more complete version of the 1st law is $$\Delta E=\Delta U+\Delta (PE)+ \Delta (KE)=Q-W$$ so that U is strictly the random kinetic energy and potential energy of interactions of the molecules (and is a fundamental physical property of the gas).
Thank u
Is it true that it can only be affect by heat or heat and work
 
  • #11
lee123456789 said:
Thank u
Is it true that it can only be affect by heat or heat and work
Yes, as far as I know.
 
  • #12
Chestermiller said:
Yes, as far as I know.
this is the statement i found. which confused me.
The internal energy of a thermodynamic system is the energy contained within it. It is the energy necessary to create or prepare the system in any given internal state. It does not include the kinetic energy of motion of the system as a whole, nor the potential energy of the system as a whole due to external force fields, including the energy of displacement of the surroundings of the system.also wouldn't matter as well help dtermine the internal energy. eg in a open flow system
 
  • #13
lee123456789 said:
this is the statement i found. which confused me.
The internal energy of a thermodynamic system is the energy contained within it. It is the energy necessary to create or prepare the system in any given internal state. It does not include the kinetic energy of motion of the system as a whole, nor the potential energy of the system as a whole due to external force fields, including the energy of displacement of the surroundings of the system.also wouldn't matter as well help dtermine the internal energy. eg in a open flow system
Well, the 1st sentence is confusing. But the 2nd sentence makes some sense, at least up to the comma.

Your statement about matter is a little confusing. The first law, as you have written it applies exclusively to a closed system.
 
  • #14
Chestermiller said:
Well, the 1st sentence is confusing. But the 2nd sentence makes some sense, at least up to the comma.

Your statement about matter is a little confusing. The first law, as you have written it applies exclusively to a closed system.
ow ok.
So the internal energy is the sum of energy the resides with the thermodynatic system. It is affected by work and heat. the potential and kinetic energy is minimial in the system so it is excluded. the internal energy keeps account of the energy input and output so the overall internal energy change is balanced so equals zero.
 
  • #15
lee123456789 said:
ow ok.
So the internal energy is the sum of energy the resides with the thermodynatic system. It is affected by work and heat. the potential and kinetic energy is minimial in the system so it is excluded. the internal energy keeps account of the energy input and output so the overall internal energy change is balanced so equals zero.
If you mean that the total amount of energy is conserved, then, yes.
 

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