What is internal energy? Am I right?

In summary, internal energy for engineering is the sum of energy stored within a system of a substance, which is only affected by heat and work coming out of the system. 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. In engineering, the first law states that the change in internal energy is equal to the sum of heat and work, and does not include the kinetic energy of motion or the potential energy of the system as a whole. The internal energy is also affected by the matter within the system, such as in an open flow system. Overall, the internal energy change must be balanced, resulting in an overall change of zero.
  • #1
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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  • #2
What do you think and why? On this forum, you don't get help until you show some effort.
 
  • #3
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.
 
  • #4
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
 
  • #5
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.
 
  • #6
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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  • #7
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.
 
  • #8
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.
 
  • #9
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.
 

Related to What is internal energy? Am I right?

1. What is internal energy?

Internal energy is the total energy contained within a system, including the kinetic and potential energy of all its particles.

2. How is internal energy different from thermal energy?

Thermal energy is a type of internal energy that specifically refers to the kinetic energy of a system's particles due to their temperature. Internal energy, on the other hand, includes both kinetic and potential energy.

3. What factors affect the internal energy of a system?

The internal energy of a system is affected by its temperature, pressure, and the number and type of particles it contains. It can also be influenced by external factors such as heat transfer and work done on or by the system.

4. Can internal energy be measured directly?

No, internal energy cannot be measured directly. However, changes in internal energy can be measured by observing changes in temperature, pressure, or other properties of the system.

5. How is 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. Internal energy is a part of this overall energy conservation principle, as it represents the total energy of a system that can be transferred or converted into other forms of energy.

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