Consider that an ideal gas (n moles) is expanding in a process given by P = f (V), which passes through a point (V0, P0). Show that the gas is absorbing heat at (P0, V0) if the slope of the curve P = f (V) is larger than the slope of the adiabatic passing through (P0, V0).
If an adiabatic process is passing through the point P0, V0 we can write its equation as
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As ![]()
Slope at P0, V0= ![]()
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Now, coming to the process given,
P = f (V)
We can write the equation,
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Since, ![]()
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Now, as we know PV=nRT by rearranging it we get,
T=
and P = f (V)
T=![]()
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Now,
dQ=ncv![]()
we know,
=![]()
and ![]()
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And P=f(V)
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Now, the volume is increasing.
dV=+ve
dQ should also be +ve if heat is given to the system.
at point (P0, V0) for heat to be absorbed.
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Since, ![]()
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Hence proved.
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