Superman illustrates adiabatic cooling brought about by the rapid expansion fuel tank to the point of explosion. Thank you Superman. You've saved us. [magnify]
Recall from the previous section …
| ΔU = Q + W | ||
| Q > 0 | system absorbs heat | |
| Q < 0 | system releases heat | |
| W > 0 | work done on the system by the environment | |
| W < 0 | work done by the system on the environment | |
A system can be described by three thermodynamic variables. — pressure, volume, and temperature. Well, maybe it's only two variables. With everything tied together by the ideal gas law, one variable can always be described as dependent on the other two.
| ⎧ ⎪ ⎪ ⎨ ⎪ ⎪ ⎩ |
P = | nRT | ||
| V | ||||
| PV = nRT | ⇒ | V = | nRT | |
| V | ||||
| T = | PV | |||
| nR |
Temperature is the slave of pressure and volume on a pressure-volume graph (PV graph).
Function of State
| ΔU = | 3 | nRΔT |
| 2 |
Function of Path: Work
W = ∫ F · ds = ∫ P dV = − area on PV graph
Function of Path: Heat
| Q = ΔU + W = ncΔT | |
| cP | specific heat at constant pressure |
| cV | specific heat at constant temperature |
| W = −PΔV | ⇒ | ΔU = Q − PΔV |
| W = 0 | ⇒ | ΔU = Q |
| ΔU = 0 | ⇒ | Q = −W |
| Q = 0 | ⇒ | ΔU = W |
| = | ⎧ ⎪ ⎨ ⎪ ⎩ |
3/2 + 1 | = | 5 | monatomic | |||||||
| PVγ = constant | ⇒ | γ = | cP | = | α + 1 | 3/2 | 2 | |||||
| cV | α | 5/2 + 1 | = | 7 | diatomic | |||||||
| 5/2 | 5 | |||||||||||
Superman illustrates adiabatic cooling brought about by the rapid expansion fuel tank to the point of explosion. Thank you Superman. You've saved us. [magnify]
liquids
solids
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The Physics Hypertextbook © 1998–2013 Glenn Elert |
No condition is permanent.