Pressure, temperature, and volume relation in liquids | Physics Forums
Pressure, temperature, and volume relation in liquids Water temperature is 20 degrees celsius (room temp) in the pipe originally, and a. Calculating water pressure from tank volume depends on whether the Pi, or?, is the constant ratio of the circumference to the diameter in all. The water velocity into a region with atmospheric pressure goes as the . A where Q is the volume flow, V is the velocity of the flow and A is the.
By static pressure I do not mean hydrostatic - I mean static as in the other pressure factor of water not sure what it is called. Your water company decides, whelp, let's increase the city water pressure! Say originally we had a horizontal copper pipe full of water.
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At the one end of the pipe is a tap that is closed. At the other end of the pipe is the incoming city water company city pressure.
Water temperature is 20 degrees celsius room temp in the pipe originally, and a pressure of "1". Then the city increases water pressure to "2". The units do not matter, just say the pressure doubled.
Pressure, temperature, and volume relation in liquids
The water did not move, because the tap was shut. Yet the static pressure doubled. Would the temperature rise, twice as much to 40 degrees celsius due to the pressure increase?
For simplicity, let's say the copper pipe never expanded and none of the taps can leak. Liquids transmit pressure - but, when they are not moving, AFAIK they hold a static pressure, almost like a "charge". I wonder if since liquids are virtually incompressible, an increase in static pressure causes the liquid to heat up ideally.
We could think of a liquid under pressure like a gas under pressure which cannot change volume, due to its special container that doesn't let it change volume the liquid itself!
Pressure and the Gas Laws
The upper boundary of the air column that gives rise to atmospheric pressure is the vacuum of space. Being rather light, the mass of a column of air with a 1 cm2 cross section is almost exactly 1 kg.
If a much heavier liquid substance is used to balance this air column, only a relatively small length would be needed. In addition, because the density of liquids does not change with height most liquids are incompressiblesuch an equivalent liquid column has a well defined upper boundary below a vacuumOne of the heaviest liquids at room temperature is mercury Hg and the height of the Hg-column that is equivalent to normal pressure mb is only mm long For this reason, columns of mercury, "hanging" in an inverted vacuum tube, can be used as practical instruments to measure atmospheric pressure see FigureLutgens and Tarbuck, If water were used instead of mercury, the height of the column equivalent to normal pressure would be The Gas Laws The example of the gas-filled balloon can also be used to explore the basic gas laws see also Appendix D, p.
In the following, lets assume that the balloon is tight, so that the amount or mass of air in it stays the same: With density being the ratio of mass per volume, the gas density of the balloon thus varies only with its volume when mass is held constant. If we squeeze the balloon, we compress the air and two things will happen: