Timeline for When a gas is compressed by a piston, where is the heat added to the gas?
Current License: CC BY-SA 3.0
5 events
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| Jan 6, 2016 at 23:25 | comment | added | BowlOfRed | The disk can simply be imagined as the dividing line between half the gas (or any other fraction of it). It does not matter that no physical object divides them. As long as that fraction of the gas takes up less space, then something did work on it. Without a physical disk, that would be the rest of the gas, but that does not matter. | |
| Jan 6, 2016 at 23:18 | comment | added | kitt91 | Also, in the disc scenario you mention, I'm assuming your disc forms a gas tight seal against the cylinder wall. In this case work will be done by the disc as there is a physical force on the disc due to the pressure difference upon it. However, if the disc is not sealed, the disc may move as the piston is compressed but it will do no work as there is no force on the disc due to the pressure on both sides of it being equal. No work done would means no temperature change of the gas either side of the disc (maybe). | |
| Jan 6, 2016 at 23:06 | comment | added | BowlOfRed | True, but I don't know how that helps you. The volume is only interesting in letting us know how the gas occupies it. As all parcels of gas are compressed simultaneously, work is done on each parcel simultaneously (assuming equilibrium pressure). | |
| Jan 6, 2016 at 22:49 | comment | added | kitt91 | Ahh right thanks. I like your analogy of a disk in the cylinder that does make more sense. Yes the volume occupied by each mole of gas decreases as the piston compresses, but physically the volume doesn't change surely. If a fixed point is considered which has 1cm3 of volume, it will still be 1cm3 no matter what the pressure inside the cylinder. | |
| Jan 6, 2016 at 22:33 | history | answered | BowlOfRed | CC BY-SA 3.0 |