- #1
scorpion990
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I have a few extremely simple questions about thermodynamics... I'm trying to self study it, but a few things just don't add up... I'm currently working on the first law =/
1. My book defines work as an indefinite integral:
[tex]w = -\int p_{ext}dV[/tex]
However, it then states that, if the external pressure remains constant:
[tex]w = -\int p_{ext}dV = -p_{ext}\int dV = -p_{ext}v^{v_{f}}_{v_{i}} = -p_{ext}\Delta V[/tex]
It might sound like a stupid question, but I can't quite figure out why the author defined work as an indefinite integral instead of a definite integral. Is this just bad notation or a typo?
2. The books mentions that work = 0 for free expansion. However, under what circumstances would you actually have free expansion? If a gas expanded into a container with p = 0 atm, the pressure inside the container would rise as the rest of the gas is expanding into it =/
3. w = work, U = internal energy.
[tex]\int dw = w,
but
\int dU = \Delta U[/tex]
Why are these two treated differently thermodynamically and mathematically? Am I missing something, or is this just, once again, bad notation?
That's it for now. Thanks!
1. My book defines work as an indefinite integral:
[tex]w = -\int p_{ext}dV[/tex]
However, it then states that, if the external pressure remains constant:
[tex]w = -\int p_{ext}dV = -p_{ext}\int dV = -p_{ext}v^{v_{f}}_{v_{i}} = -p_{ext}\Delta V[/tex]
It might sound like a stupid question, but I can't quite figure out why the author defined work as an indefinite integral instead of a definite integral. Is this just bad notation or a typo?
2. The books mentions that work = 0 for free expansion. However, under what circumstances would you actually have free expansion? If a gas expanded into a container with p = 0 atm, the pressure inside the container would rise as the rest of the gas is expanding into it =/
3. w = work, U = internal energy.
[tex]\int dw = w,
but
\int dU = \Delta U[/tex]
Why are these two treated differently thermodynamically and mathematically? Am I missing something, or is this just, once again, bad notation?
That's it for now. Thanks!
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