Jonahan
Classically pV/T = constant.. So to keep it simple if you increase T by
100 (starting at 273K) then the pressure does only increase about 1/3.
373/273 about 4/3.
Further gas internal energy is defined by the Gibbs equation that
includes the entropy. Pressure is not a linear function of added energy
only T absolute follows p.
The ideal gas law only matches real physics for a certain band of T.
Never for T below evaporation point that also is defined as an
equilibrium. So a gas must have enough internal energy to overcome the
Van der Waals attractive forces to finally behave "ideal".
J.W.
On 17.06.2024 09:07, Jonathan Berry wrote:
Jürg, the problem with that is if that is so then the thermal
capacity of the gas would need to increase as temp increases but
with say Helium it's pretty flat.
Every time I look into the math for increasing temp it is the same, if
you heat it up twice as much it needs twice as much energy not 4 times
as much!
So if you aren't disputing the temp that is created with a given
energy input, then you are disputing the pressure, but the pressure is
predicted by the Ideal gas law.
So unless you are saying that either the ideal gas law or thermal
energy goes up at the square and not in a linear manner (feels it
might have been noticed) you can't be right.
On Sun, 16 Jun 2024 at 22:06, Jürg Wyttenbach <ju...@datamart.ch> wrote:
The energy of a gas is the sum over all kinetic energies. So you
need 4x energy input to get 2x average speed = pressure. (comes
from momentum exchange!)
J.W.
On 16.06.2024 10:27, Jonathan Berry wrote:
Hooke's law states that if you compress a spring the increase in
pressure is linear, if you compress it 1 cm you might have 1 lb
of force, if you compress it 2cm you get 2 lb of force.
As that is double the force over double the distance it also
involved 4 times more work to compress it and 4 times more work out.
Reference:
http://labman.phys.utk.edu/phys135core/modules/m6/Hooke's%20law.html
<http://labman.phys.utk.edu/phys135core/modules/m6/Hooke's%20law.html>
"If we double the displacement, we do 4 times as much work"
Ok, but this seems problematic when the thermal capacity of a gas
is not just changed by making it hotter so if you put in 100
Joules and increase the temp 100 Kelvin you get about 5 PSI of
pressure increase, but if you input 200 Joules you get about a
200 Kelvin increase and a 10 PSI increase and to compensate for
this greater pressure change the piston moves about twice as far,
so twice as far with twice the pressure again is 4 times the energy.
At 10 times more input you get 100 times more out, at 100 times
more in you get 10,000 time more energy out!
The energy increase is exponential with linear increase of temp!
If this is not so please explain why not?
If the ideal gas law wrong about pressure increase being linear
with temp?
Does the thermal capacity of a gas change more with temp than I'm
finding out when I research it?
It sure does seem the gas will like the spring with twice the
pressure move about twice as much before the piston isn't
motivated, and as such it seems some laws of physics are wrong.
Jonathan
--
Jürg Wyttenbach
Bifangstr. 22
8910 Affoltern am Albis
+41 44 760 14 18
+41 79 246 36 06
--
Jürg Wyttenbach
Bifangstr. 22
8910 Affoltern am Albis
+41 44 760 14 18
+41 79 246 36 06
