# What is quasistatic: Definition and 20 Discussions

Quasistatic approximation(s) refers to different domains and different meanings. In the most common acceptance, quasistatic approximation refers to equations that keep a static form (do not involve time derivatives) even if some quantities are allowed to vary slowly with time. In electromagnetism it refers to mathematical models that can be used to describe devices that do not produce significant amounts of electromagnetic waves. For instance the capacitor and the coil in electrical networks.

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I was unable show that ##PV^k## must indeed equal some function of the entropy, ##g(S)##; maybe doing so would make things easier? I proceeded as below. If we assume (as is almost surely intended by Callen) that in the given adiabatic (##d Q = 0##) process we are taking ##N## as constant and...
2. ### Assumed value of pressure during quasistatic compression

My text (Ian Ford - Statistical physics) describes an ideal gas system in a piston being quasistatically compressed by a piston head of area A under external force f. It assumes the system has a uniform pressure p. All good so far. Then it says: "the force pA equals the applied external force f"...
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### Correctness of the quasistatic EMFT approximation

Hello! I'm just trying to make sure I understand Maxwell, Biot-Savart, Faraday, etc well enough. What I'm wondering about is when the quasistatic treatment is indeed approximate, and when it is, assuming an equal if time-varying current, correct. Suppose, first, that we have a steadily...
4. ### Change in entropy, quasistatic, isothermal expansion

Homework Statement I am to show that ΔS=Q/T for the isothermal expansion of a monoatomic ideal gas, when the expansion is so slow that the gas is always in equilibrium. Homework Equations 1. law: ΔU=Q+W (We mustn't use dQ and dW - our teacher hates that :( ). Ideal gas law: PV=NkT We need the...
5. ### Irreversible Quasistatic PV Work

Hi 1) I am reading Pippard's Classical Thermodynamics and was confused by one of his examples in the attachment. What I do not understand is the concept of using P' (I am thinking P' as = P_fric + P_interface) for work calculations. If I take the system as composed of just the gas inside...
6. ### Can Ampere's Law Be Applied to Time-Varying Currents in Quasistatic Conditions?

I'd rather not post the exact problem since it's homework, I don't think my instructor in E&M would want me posting full problems but I will just ask relevant conceptual question... Let's say we I have a long cylinder with time-defendant surface current density \vec K(t)=K_of(t). So if I want...
7. ### Charge distribution and potential in a 1-dimensional quasistatic syste

Homework Statement suppose you have an 1-dimensional system with a charge distribution ##\rho(x)## (not given) moving with an speed ##v(x)##, calculate the potential ##\phi(x)## and the charge distribution ##\rho(x)## in the quasistatic limit ##\frac{d}{dt}=0##. Homework Equations...
8. ### Is Slow Compression Speed Sufficient for Quasistatic Gas Compression?

Have already received excellent help in understanding this but might need a bit more. Suppose we have a gas inside a cylinder with a piston in it. Now my teacher said that to compress the gas quasistatically we would need to press in the piston with a speed, that is slow compared to the speed...
9. ### Quasistatic Process Explained: What is dH=δQ+Vdp?

What is Quasistatic process? the first law of thermodynamics for a quasitatic process: dH = δQ + Vdp ------> A if it is quasi static dp should be very small which can be ignored and hence dH = δQ so how come the equation "A" holds true for a quasi static process.
10. ### Energy Conservation in Quasistatic process

Alright, this might sound stupid, but let us imagine a scenario. I bring an object from height 10 m to 4 m such that the velocity of the object remains constant. Due to this the potential energy of the object decreases. Now my question is, where does this energy go?
11. ### Finding the change in pressure and entropy of a quasistatic adiabatic process

Homework Statement Suppose that one mole of an ideal gas expands in a quasi-static adiabatic process from P1 = 1 Pa and V1 = 1m3 to V2 = 8m3. What is the change in the pressure and the entropy of the gas? Homework Equations PV\gamma=constant The Attempt at a Solution I can't come...
12. ### Adiabatic and Quasistatic Compression

In "Introduction to Thermal Physics" - Schroeder, the derivation for adiabatic compression: V^\gamma P = \mbox{constant} is derived by assuming the compression is still slow enough to be quasistatic. However, I'm still a bit confused with how slow is 'slow'. Quasistatic compression needs...
13. ### Process such as isobaric, isochoric, quasistatic, adiabatic

Just say an ideal gas goes through process such as isobaric, isochoric, quasistatic, adiabatic etc, is there any special cases where entropy is conserved, or am i thinking enthalpy. Also how is enthalpy found in adiabatic processes?
14. ### Calculating Pressure & Temp for NH3 Quasistatic Adiabatic Expansion

(a) For a quasistatic adiabatic process involving an ideal gas the temperature and volume are related by: TV^(a-1) = const . By substituting the ideal gas equation into this expression, derive a similar relationship between pressure and volume for an ideal gas in an quasistatic adiabatic...
15. ### Only quasistatic process can be a polytropic process

We may say a process is adiabatic if it occurs fast enough such that no heat is exchanged from the system.But we also say a process is quasi-static when it occurs very slow. Then how can PV^gamma = c hold for a fast occurring adiabatic process because a polytropic process should be...
16. ### Finding the heat transferred in an ininitesimal quasistatic process

For an ideal gas PV=nRT where n is the number of moles show that the heat transferred can be written as: dQ = \frac{C_V}{nR}VdP + \frac{C_P}{nR}PdV Really not sure where to start with this... I have used dQ = dU + PdV But it hasn't really lead anywhere.
17. ### Adiabatic & Quasistatic Expansion of Photon & Fermion Gases

Homework Statement 1.Show that PV^Y is a constant for adiabatic,quassistatic expansion of a photongas and determine Y 2. Show the same for full degenerate gas of fermions at T=0 Homework Equations The Attempt at a Solution Plz help thx
18. ### Work done in adiabatic quasistatic compression

Hey! "Calculate the work done on 1 mole of a perfect gas in an adiabatic quasistatic compression from volume V1 to V2." The work done on the gas in this compression is: -\int_{V1}^{V2} P dV Because we are talking about an ideal gas the ideal gas law applies so...
19. ### Quasistatic processes are reversible?

It's probably a silly question. I know definitions of quasistatic and reversible process. How can we proove that each quasistatic process is reversible? Before it went for me without saying. But now I noticed that I can't proove it. In books that I have this conclusion is made after both...
20. ### Quasistatic isothermal expansion

How would I show that during quastatic isothermal expansion of a monatomic ideal gas, the change in entropy is related to the heat input Q by the simple formula: delta S=Q/T Show that it is not valid for the free expansion process described. Answer: Putting heat into a system always...