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Why the entropy change is not zero in the irreversible adiabatic process?

Although entropy change is defined in terms of a reversible differential transfer of heat divided by the temperature at which the heat is transferred, you can have entropy change without heat transfer....
• 75.9k

Why isn't the free expansion of a gas in an adiabatic container isentropic?

The free expansion isn’t reversible because the gas flows down a pressure gradient (that arises when you remove the piston). Any energy flow down a gradient generates entropy. In contrast, during the (...
• 27.1k
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Entropy change in the free expansion of a gas

What am I missing ? Entropy can be generated without there being heat transfer, i.e., when $Q=0$. That's the case for a free expansion into a vacuum. The classic example given is an ideal gas located ...
• 75.9k

How is ideal gas law applicable to real gas?

Ideal gas law works best for monatomic gasses at low pressures and high temperatures. It doesn't take into account molecular size and intermolucular interactions, so when the effects of those are ...
• 15.3k

How is ideal gas law applicable to real gas?

The speed of sound is defined as $c^2 = \frac{\partial p}{\partial \rho}$, which for an ideal gas becomes $c^2 = \gamma \frac{p}{\rho}$. For a real gas, the relationship to an ideal gas can be found ...
• 16.7k

Is there a generalization of the adiabatic theorem into a degenerate Hamiltonian?

Yes there is. Naturally these degeneracies should be motivated by symmetry considerations or else they would typically destroyed by perturbations. In particular, to have non trivial irreducible ...
• 13.5k

Adiabatic Quantum Computing: why not just set the system in its problem Hamiltonian $H_{P}$ immediately?

Most NP-complete problems can be formulated as finding the ground state of some Hamiltonian. If you create a physical system that has such a Hamiltonian, it will be a "frustrated system". It will ...
• 11.4k
Accepted

Rigorous Laughlin pumping argument

I solved the issue. I will explain in detail how the existence of an operator conserved by the adiabatic evolution allows us to make sense of the spectral flow argument. Let's start with the problem ...
• 781

Why the entropy change is not zero in the irreversible adiabatic process?

If you have an irreversible adiabatic process between two thermodynamic equilibrium end states of a system, there exists no possible reversible adiabatic process between these same two end states. So ...
• 34.3k

Why isn't the free expansion of a gas in an adiabatic container isentropic?

If you expand a gas adiabatically using a piston, the process is isoentropic. An adiabatic process is not isentropic unless it is also reversible. To be reversible, it must be carried out quasi ...
• 75.9k
Accepted

In an adiabatic process, that is a process in which mathematically $dQ=0$, $PV^γ=\text{constant}$. First of all, the equation only applies to an ideal gas undergoing a reversible adiabatic process. ...
• 75.9k