What is Equilibrium: Definition and 1000 Discussions

Thermodynamic equilibrium is an axiomatic concept of thermodynamics. It is an internal state of a single thermodynamic system, or a relation between several thermodynamic systems connected by more or less permeable or impermeable walls. In thermodynamic equilibrium there are no net macroscopic flows of matter or of energy, either within a system or between systems.
In a system that is in its own state of internal thermodynamic equilibrium, no macroscopic change occurs.
Systems in mutual thermodynamic equilibrium are simultaneously in mutual thermal, mechanical, chemical, and radiative equilibria. Systems can be in one kind of mutual equilibrium, though not in others. In thermodynamic equilibrium, all kinds of equilibrium hold at once and indefinitely, until disturbed by a thermodynamic operation. In a macroscopic equilibrium, perfectly or almost perfectly balanced microscopic exchanges occur; this is the physical explanation of the notion of macroscopic equilibrium.
A thermodynamic system in a state of internal thermodynamic equilibrium has a spatially uniform temperature. Its intensive properties, other than temperature, may be driven to spatial inhomogeneity by an unchanging long-range force field imposed on it by its surroundings.
In systems that are at a state of non-equilibrium there are, by contrast, net flows of matter or energy. If such changes can be triggered to occur in a system in which they are not already occurring, the system is said to be in a meta-stable equilibrium.
Though not a widely named "law," it is an axiom of thermodynamics that there exist states of thermodynamic equilibrium. The second law of thermodynamics states that when a body of material starts from an equilibrium state, in which, portions of it are held at different states by more or less permeable or impermeable partitions, and a thermodynamic operation removes or makes the partitions more permeable and it is isolated, then it spontaneously reaches its own, new state of internal thermodynamic equilibrium, and this is accompanied by an increase in the sum of the entropies of the portions.

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  1. Ander99

    Engineering Calculating Equilibrium Points in OVA-Opamp Circuit with Ideal Diodes

    Hi everyone, I need help with this exercise becouse I don't know how to calculate the equilibrium points of a circuit. The original exersice is the following: Assume that the open loop dynamic response of the OVA-opamp gets captured by Fig. 1(a) and consider the circuit of Fig. 1(b). Consider...
  2. Justin_Lahey

    Particle in equilibrium (balancing forces on an object on an incline)

    Hi, I’m wondering if someone can help me understand this question. I can find a resultant force/vector when given an initial angle but I’m stuck here when the only information is the two magnitudes. I think I’m solving for the unknowns but a little lost on how or what equation I should be using...
  3. Butterfly41398

    Equilibrium of coplanar forces

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  4. Butterfly41398

    Equilibrium of concurrent forces -- 3 Pulleys and 2 Weights

    Help, this one is completely different, the weird pulley is making it hard for me and I don't even know what to do with it and where to start. The answer is 185N but I want to know how.
  5. Y

    Equilibrium for a rotation lab

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  6. lakuzamalakuzam

    Problem on Equilibrium ( STATICS )

    so i was wondering what assumptions needed to make this solvable and ' support at both thrust collars can totally support the moments of 400 Nm before they slip' means which axis of moment
  7. C

    Help finding the equilibrium position of an electric field

    I seem completely lost at this. I barely know where to begin. I know that the forces will sum to 0 but the vectoral nature of the question is really confusing me. Best I have is that the distance between e and q2 has to be sqrt(2) times the distance between e and q1. I don't know where to go...
  8. I

    Calculate Equilibrium Constant for Polyprotic Acid Reaction

    The principal equilibrium in a solution of NaHCO3 is HCO3-(aq) + HCO3-(aq) <-> H2CO3(aq) + CO32-(aq) Calculate the value of the equilibrium constant for this reaction. My solution: This overall reaction is the same as the sum of the following reactions: HCO3-(aq) <-> H2CO3(aq) + OH-(aq)...
  9. goodOrBad

    Block A Reaches Equilibrium: 92N Force

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  10. LCSphysicist

    Interesting exercise: Torque, radiation, momentum and equilibrium

    t is Torque I is the inertia moment P is the power c is the constant light speed r is the spot distance to the fiber p is the torsional constant theta is what we want In the equilibrium $$t = 0$$ $$ F\Delta T = \frac{E}{c} = \frac{P\Delta T}{c} => *F* = \frac{P}{c} (1) $$ This will be the...
  11. mcrooster

    Help finding the vertical component of the reaction at C

    Hello everyone, For this equation, I have found Ay as 0.677kN by using Ma = 1.5kN(7m)-Ay(15.5m). To find Cy, would I be using the sum of forces to find the answer? For example Fy = Ay - F2 - F1sin55 + Cy = 0 This would then get Cy answer as 2.05kN
  12. mcrooster

    How to find Tb and Moments 3D equilibrium of rigid bodies

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  13. Traced

    Chemistry Equilibrium K Values: Problem Solving Tips

    I know what K does, what can change K, and I know about the equilibrium equation. I don't know how to use that to answer this problem. I'm not given any chemical reactions or their K values. How should I start this problem?
  14. I

    Activity - Equilibrium Expressions

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  15. S

    Chemistry Can anyone check my answers for these equilibrium problems?

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  16. il postino

    Chemistry Calculate DeltaH between 700K and 800K

    Hi all Knowing that ##kp## is: ##k_p=\frac{pO_2.(pNO)^2}{(pNO_2)^2}## And knowing these relationships between the partial pressures, I obtained: At 700 K: ##pNO = 0.872.pNO2## ##k_p=pO_2.(0.872)^2## At 800 K: ##pNO = 2.5.pNO2## ##k_p=pO_2.(2.5)^2## Furthermore it is known that ##pNO + pNO +...
  17. D

    Phase Equilibrium of Liquid and Vapor Under External Pressure

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  18. M

    Engineering Solve Value of R: Moment & Equilibrium

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  19. B

    Pressure generated by a force on a pump with a lever

  20. S

    Why Does Torque Equilibrium Not Solve for Fcy in Static Equilibrium Problems?

    I have two questions regarding this problem 1. The following is my attempt to solve Fcy using the fact that the addition of torque = 0. I considered force mg and Fcy and their lever arms to set up the equilibrium. But this method seems not to work? Why? 2.At the bottom of the question, it...
  21. halleff

    Diffusion current and carrier concentration equilibrium (unbiased)

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  22. T

    Exploring the Grand Partition Function for an Einstein Solid

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  23. LCSphysicist

    Measuring Blocks Equilibrium Displacements

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  24. il postino

    Chemistry Chemistry equilibrium - Remove H2

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  25. D

    (Check solution) Conceptual problem about the equilibrium of a rigid body

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  26. D

    Conceptual Problem - Static Equilibrium

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  27. R

    Trouble with Static Equilibrium

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  28. T

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  29. T

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  30. S

    Think of a body which is at rest but not in equilibrium

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  31. Dman0500

    Dynamic Equilibrium -- Acceleration of a rock thrown from a bridge

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  32. K

    What does it mean that a rigid body is in equilibrium?

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  33. K

    Help with understanding this rigid-body equilibrium problem

    So here are two problems I have been working with lately: I have solved both, so I don't need the help to find the answers. The thing that confusses me is which object one should choose to apply the equations above. When it comes to the first problem, we apply the equations to the pole, but...
  34. K

    Understanding rigid-body equilibrium problem

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  35. J

    Static equilibrium: mass on beam

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  36. S

    Equilibrium value for carbonation level in beer

    Abs Pressure: Gauge press: 1 bar G = 100,000 Pa = 0.987 atm 0.1 bar G = 0.0987 atm Atm press = 101.3 kPa = 1 atm Hydrostatic press: average CO2 occurs 2.5m up the vessel (9.81 ms-2)(1010kgm-3)(5/2) = 24,770.25 Pa 1 Pa = 9.869x10^-6 atm 24,770.25 Pa = 0.2445 atm Abs press= 0.0987 atm + 1 atm...
  37. Jose18

    Static equilibrium, forces and toques

  38. archaic

    Static equilibrium problem: Finding tension

    The diagonal component of the boom's weight is ##R=w\cos\frac{\pi}{6}=\frac{\sqrt 3}{2}w##, and, considering ##R## as a "reaction", we have ##R_x=R\cos\frac{\pi}{3}=\frac{\sqrt 3}{4}w## and ##R_y=R\sin\frac{\pi}{3}=\frac 34w##. I will also have...
  39. archaic

    Static equilibrium: Placing a fulcrum

    I don't understand the question; they're telling me that the fulcrum is just under the center of gravity of the bar, but that I also need to find its position. In any case, I suppose that the fulcrum's position is ##x##. Let the weight at the left end be ##w_1##, at the right end be ##w_2##...
  40. archaic

    Static equilibrium and a diving board

    I take the left end as reference for torques: $$\sum\tau=F_\text{support}+\frac 32\times280+3\times500=0\Leftrightarrow F_\text{support}=-192.\times10^1\,N$$ It's facing up. I take the right end as reference for torques: $$\sum\tau=-192.\times10^1\times2+\frac 32\times280+3F=0\Leftrightarrow...
  41. E

    Does pressure affect equilibrium vapor pressure (or RH)?

    I'm wondering if I'm on the right track and if anyone is willing to steer me on if not: Equilibrium vapor pressure (EVP—also referred to as saturation vapor pressure) is dependent only on temperature. Outside pressure has no bearing. Now, of course, with lower external pressure (atmospheric)...
  42. gaurav_samanta

    Can heat transfer break an equilibrium?

    Here is one scenario: I have placed a metal in my room which is at room temperature. Air has little much heat capacity and metals don't like to store heat. Would heat transfer occur? Whatif I set the temperature of both to a certain degree where it crosses heat capacity of metal but not of air?
  43. S

    Static Equilibrium Problem (concept question)

    (figure)I was able to solve the problem and get the right answer. However, I solved it more with intuition, and I do not get how the force of the person pulling down on the rope makes the force to the left of the backpack equal to force to the right of the backpack.
  44. il postino

    Chemistry Equilibrium temperature of a water and ice system

    Equal masses of ice at –10ºC and water at 80ºC are placed in an insulated container and allowed to reach thermal equilibrium. Calculate the equilibrium temperature Data: Water(ice): 37,65 J/mol.K Agua (l): 75,29 J/mol.K ## Lf = 6011 J/mol ## I solved it this way: ## -Q_{l} = Q_{ice} ## ##...
  45. Eggue

    Missing factor of 2 in an equilibrium problem

    I honestly have no idea where I'm going wrong i've checked my differentiation using a derivative calculator but the answer is the same. The answer from the book is \frac{L}{2} + \frac{h^2}{L} Working:
  46. cs44167

    Why Is My Calculation of Electrostatic Equilibrium Incorrect?

    I set the electrostatic force exerted by the object at (0,0) and (3,0) equal to each other, dividing out k and q2. I was left with q1/d^2 for both terms and substituted in the given charges for each object. I then replaced d^2 for the object at (0,0) with “x^2” and d^2 for the object at (3,0)...
  47. Adesh

    Three doubts in a paragraph on the equilibrium of Incompressible fluids

    These are the images from Sommerfeld’s Lectures on Theoretical Physics, Vol 2 chapter 2, section 6, Equilibrium of Incompressible Fluids. Image 1 Image 2 Doubt 1 : What does it mean for a force to act on a fluid volume? Force acts on a point, force may act on a surface but I’m unable to...
  48. S

    Equilibrium concentration of co2 in beer

    Absolute pressure is gauge pressure + atmos press Guage press = 1.29 bar G 1 bar = 10^5 Pa 1.29 bar = 129,000 Pa Atmos Pres = 1.01x10^5 Pa Absolute pressure = 230,000 Pa Henrys law: P=KhC 230000Pa = (116x10^3Pa)C 1.98 mole fraction =C 70% CO2 = 1.387 mole fraction 44g Co2 in 1 mole 61.07g...
  49. tanaygupta2000

    Statistical Mechanics: Two systems reaching an equilibrium temperature

    First I found partition functions of both the systems and hence total energies of them using above formulas. Z(A) = (1 - e-ε/kT)-1 and Z(B) = (1 + e-ε/kT) Then I equated these values to the given values of total energies. I got: For System A, T(A) = ε/kln(2) > 0 For System B, T(B) =...
  50. S

    Calculate the equilibrium concentration of CO2 in beer in grams/liter

    Absolute pressure = Gauge press + Atmos press Atmos press = 105 Pa Co2 press = 0.1 bar g = 10000Pa Abs press = 10,105 Pa Hydrostatic pressure = absolute press + (density)(grav)(height at midpoint) = 10,105 + (1008)(9.81)(10) 10,8989.8 Pa Calc CO2 conc by henrys law P=KHC C=P/KH =...
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