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What is internal energy
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mlm1234
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#1
what is internal energy in engineering terms
ive found several definations. some say it includes the kinetic energy and potential energy of the system and some say that it excludes them.
ive found several definations. some say it includes the kinetic energy and potential energy of the system and some say that it excludes them.
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EmberPlayer
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#2
(Original post by mlm1234)
what is internal energy in engineering terms
ive found several definations. some say it includes the kinetic energy and potential energy of the system and some say that it excludes them.
what is internal energy in engineering terms
ive found several definations. some say it includes the kinetic energy and potential energy of the system and some say that it excludes them.
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mlm1234
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#3
so a defination of would
The sum of the energy located with the thermodynamic system due to its motion, excluding the potential and kinetic energy due to minimial effect of it on the system.
am i right the the internal energy keeps account of the total energy and that the sum of the input and out put of energy equals the internal energy. so that the overal energy change would be zero.
The sum of the energy located with the thermodynamic system due to its motion, excluding the potential and kinetic energy due to minimial effect of it on the system.
am i right the the internal energy keeps account of the total energy and that the sum of the input and out put of energy equals the internal energy. so that the overal energy change would be zero.
(Original post by EmberPlayer)
Generally, you exclude the change in KE and PE as it’s negligible, however, technically, they are,part of the internal energy
Generally, you exclude the change in KE and PE as it’s negligible, however, technically, they are,part of the internal energy
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#4
(Original post by mlm1234)
so a defination of would
The sum of the energy located with the thermodynamic system due to its motion, excluding the potential and kinetic energy due to minimial effect of it on the system.
am i right the the internal energy keeps account of the total energy and that the sum of the input and out put of energy equals the internal energy. so that the overal energy change would be zero.
so a defination of would
The sum of the energy located with the thermodynamic system due to its motion, excluding the potential and kinetic energy due to minimial effect of it on the system.
am i right the the internal energy keeps account of the total energy and that the sum of the input and out put of energy equals the internal energy. so that the overal energy change would be zero.
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EmberPlayer
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#5
To give an example: let’s say you had a balloon (the ballon along with the air particles inside it consist of the system). You do 3 actions to the ballon - you heat it, you move the entire balloon around, and you place the balloon at an elevated position.
Now to calculate the total change in energy of the system (the balloon):
1. the change in internal energy (the particles in the balloon move faster due to being heated, ie particles of air gain KE),
2. the change in KE of the entire system (the balloon is being moved around, hence the balloon is gaining KE)
3. The change in PE energy (the balloon is elevated, hence it gains gravitational potential energy)
So now if you calculate each individually using reasonable assumptions, eg. say the balloon is heated by 20K, it is being moved around at 100m/s and it has been raised by 10m. You’ll realise that the majority of the contribution to the total change in energy is due to heating the balloon (increasing the internal energy). Therefore, it’s generally a reasonable assumption to neglect the effects of the change of KE /PE of the system in regards to the change of total energy of the system.
Now to calculate the total change in energy of the system (the balloon):
1. the change in internal energy (the particles in the balloon move faster due to being heated, ie particles of air gain KE),
2. the change in KE of the entire system (the balloon is being moved around, hence the balloon is gaining KE)
3. The change in PE energy (the balloon is elevated, hence it gains gravitational potential energy)
So now if you calculate each individually using reasonable assumptions, eg. say the balloon is heated by 20K, it is being moved around at 100m/s and it has been raised by 10m. You’ll realise that the majority of the contribution to the total change in energy is due to heating the balloon (increasing the internal energy). Therefore, it’s generally a reasonable assumption to neglect the effects of the change of KE /PE of the system in regards to the change of total energy of the system.
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mlm1234
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#6
(Original post by EmberPlayer)
To give an example: let’s say you had a balloon (the ballon along with the air particles inside it consist of the system). You do 3 actions to the ballon - you heat it, you move the entire balloon around, and you place the balloon at an elevated position.
Now to calculate the total change in energy of the system (the balloon):
1. the change in internal energy (the particles in the balloon move faster due to being heated, ie particles of air gain KE),
2. the change in KE of the entire system (the balloon is being moved around, hence the balloon is gaining KE)
3. The change in PE energy (the balloon is elevated, hence it gains gravitational potential energy)
So now if you calculate each individually using reasonable assumptions, eg. say the balloon is heated by 20K, it is being moved around at 100m/s and it has been raised by 10m. You’ll realise that the majority of the contribution to the total change in energy is due to heating the balloon (increasing the internal energy). Therefore, it’s generally a reasonable assumption to neglect the effects of the change of KE /PE of the system in regards to the change of total energy of the system.
To give an example: let’s say you had a balloon (the ballon along with the air particles inside it consist of the system). You do 3 actions to the ballon - you heat it, you move the entire balloon around, and you place the balloon at an elevated position.
Now to calculate the total change in energy of the system (the balloon):
1. the change in internal energy (the particles in the balloon move faster due to being heated, ie particles of air gain KE),
2. the change in KE of the entire system (the balloon is being moved around, hence the balloon is gaining KE)
3. The change in PE energy (the balloon is elevated, hence it gains gravitational potential energy)
So now if you calculate each individually using reasonable assumptions, eg. say the balloon is heated by 20K, it is being moved around at 100m/s and it has been raised by 10m. You’ll realise that the majority of the contribution to the total change in energy is due to heating the balloon (increasing the internal energy). Therefore, it’s generally a reasonable assumption to neglect the effects of the change of KE /PE of the system in regards to the change of total energy of the system.
Intenral energy is the sum on energy that resides within the thermodynatic system. due to the minimial effect that KE and PE energy have on the system they are excluded. only heat can work can effect the internal energy of the system.
sorry just started mechanical engineering thermodynatics and trying to get head around it. so what would be simple defination of what it is then.
Last edited by mlm1234; 1 year ago
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EmberPlayer
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#8
(Original post by mlm1234)
See if i got this right
Intenral energy is the sum on energy that resides within the thermodynatic system. due to the minimial effect that KE and PE energy have on the system they are excluded. only heat can work can effect the internal energy of the system.
sorry just started mechanical engineering thermodynatics and trying to get head around it. so what would be simple defination of what it is then.
See if i got this right
Intenral energy is the sum on energy that resides within the thermodynatic system. due to the minimial effect that KE and PE energy have on the system they are excluded. only heat can work can effect the internal energy of the system.
sorry just started mechanical engineering thermodynatics and trying to get head around it. so what would be simple defination of what it is then.
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mlm1234
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#9
(Original post by EmberPlayer)
Heat transferred into/out of the system and also work done on/by the system affect the change in internal energy (first law of thermodynamics). Yeah, thermo is pretty confusing at first. Don’t worry it’ll make more sense as you go
Heat transferred into/out of the system and also work done on/by the system affect the change in internal energy (first law of thermodynamics). Yeah, thermo is pretty confusing at first. Don’t worry it’ll make more sense as you go
it was the kinetic and potential that throw me.
was that defintion right
Think i may exclude the potential and kinetic bit when writing about it, saves confusing and only need broad understanding off it.
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EmberPlayer
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#10
(Original post by mlm1234)
thanks for that you are life saver.
it was the kinetic and potential that throw me.
was that defintion right
Think i may exclude the potential and kinetic bit when writing about it, saves confusing and only need broad understanding off it.
thanks for that you are life saver.
it was the kinetic and potential that throw me.
was that defintion right
Think i may exclude the potential and kinetic bit when writing about it, saves confusing and only need broad understanding off it.
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reply
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