Equilibrium Definition and 1000 Threads

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.

View More On Wikipedia.org
Recent contents Top users
  1. A

    Equilibrium and principle of moments

    Homework Statement Homework Equations Torque = F x D Manticlockwise = Mclockwise The Attempt at a Solution From what I understand, the moment on left hand side of the pivot point needs to be equal to the moment on right hand side, therefore... (Fx.2)+(5x.14) = (7xd) My initial...
  2. K

    Equilibrium velocity of a propeller-driven aircraft

    Hi - I just want to know if I'm approaching this correctly. I'm trying to calculate the equilibrium velocity of a propeller-driven aircraft when supplied a given amount of power. I'm iterating: min_velocity = 0.01 max_velocity= 200 aircraft_velocity = 5 for i in range(steps): force = 0.5 *...
  3. RoboNerd

    Question about static equilibrium

    1. Homework Statement problem is above Homework Equations sum of torques = I * angular acceleration = 0 for rotational equilibrium The Attempt at a Solution OK, here's what I tried to do. I wrote sigma Fy = Fleft pier up + F secondleftpierup - Fg,beam = 0 I assumed that the two piers have...
  4. V

    Stable equilibrium of a 4 mass, 6 spring system

    Homework Statement I am making a physics engine for my computer science class and couldn't figure out how to get the spring/mass system to come to equilibrium into a box-like shape such as the one on the left. I can understand why the one on the right is in equilibrium but I don't know how to...
  5. U

    A simple static equilibrium problem

    Homework Statement Suppose we have a folding ladder, so that when its legs are spread it makes an isosceles triangle. Suppose it has a support that runs parallel to the ground. There is a bucket of paint that rests on top of the ladder, and the mass of the ladder is negligible. Data: The legs...
  6. V

    A Question about Chemical Equilibrium

    say we have a reaction: N2O4 <====> 2NO2 for this reaction,if initial number of moles of N2O4 is 'a' can we write t = 0 a - at equilbrium a-x...
  7. chmergatroyd

    Finding weight of a beam using torque & equilibrium?

    Homework Statement A uniform beam at equilibrium is suspended by a cord at X which is 2m from one end of the beam and and 3m from the other end. There is a mass of 28N attached to the 2m end and a mass of 10N on the 3m end. Determine the weight force of the beam Homework Equations...
  8. TheSodesa

    Precipitation of lead hydroxide in the presence of EDTA

    Homework Statement 1. The question EthyleneDiamineTetra-acetate(##EDTA^{4-}##) is used in chemical analysis as a complex-former. ##EDTA^{4-}## is also used to treat heavy metal poisoning, as it forms water soluble complexes with them which can then be easily removed by the body. The reaction...
  9. F

    Equilibrium of NOCL Change w/ Added NO & Cl2

    Homework Statement 2NOCl(g) <--> 2NO(g) +Cl2(g)[/B] What will be the effect on equilibrium concentration of NOCL when equal moles of NOCL and NO are introduced in the mixture at constant temperature? Homework Equations Kconcentration = [NO]2[Cl2] / [NOCl]2 The Attempt at a Solution In my...
  10. Dietrichw

    Static equilibrium, tension and compression

    Homework Statement The figure below shows a light truss formed from three struts lying in a plane and joined by three smooth hinge pins at their ends. The truss supports a downward force of = 1 330 N applied at the point B. The truss has negligible weight. The piers at A and C are smooth. The...
  11. STEM_STRUGGLES

    Analyzing Forces in a Diving Board System

    Homework Statement There is a diving board held up by two pillars A and B, and there is a diver standing on it's edge. What are the directions of the forces exerted at points A and B? Picture Below: Homework Equations F_NET = 0 T_NET =0 The Attempt at a Solution I thought both A and B were...
  12. RoboNerd

    Question on entropy in adiabatic phase change

    Homework Statement Consider a closed, adiabatic system consisting of a mixture of liquid and solid substance Z at equilibrium at its melting point. Z (solid) <---------> Z (liquid) Which of the following statements is true regarding the system? A) The entropy of the system is at a maximum...
  13. RodriRego

    Finding Static Equilibrium: Solving a Rod and Cable System

    Homework Statement Homework Equations Fr (resultante force) = 0 Sum of all forces aplied at the strut = 0 Sum of the torque of all forces = 0 The Attempt at a Solution I started by analysing the torque, since the strut is on static equilibrium and I ended up having C (tension on the cable)...
  14. terryds

    How Does Adding NO2 Affect N2 Concentration in Equilibrium?

    Homework Statement At certain pressure and temperature in a 2 L closed flask, equilibrium reaction undergoes such as : N2 (g) + O2 (g) ↔ 2NO (g) Each concentration of the substances in equilibrium is 0.8 M. If we add 2 mole of NO2 gas into the flask, then the concentration of N2 gas in the...
  15. Blockade

    How to find if equilibrium points of a force is un/stable?

    Homework Statement U = Ax2 - Bx3 Homework Equations du/dx = 2Ax - 3Bx2 The Attempt at a Solution If I was given a potential energy function U = Ax2 - Bx3 and am asked to find: 1) The expression for the force as a function of x. 2) The equilibrium points and determine if are they stable or...
  16. E

    Is ΔH Dependent on Temperature in CaCO3 Dissociation Equilibrium?

    Homework Statement The thermal dissociation equilibrium of CaCO3 (s) is studied under different conditions. CaCO3 ⇔ CaO (s) + CO2 (g) For this equilibrium, the correct statement(s) is (are) (A) ΔH is dependent on T (B) Keq is independent of the initial amount of CaCO3 (C) Keq is dependent on...
  17. D

    How Should I Approach These Thermodynamics Exam Prep Problems?

    THIS WAS MOVED FROM ANOTHER FORUM, SO THERE IS NO TEMPLATE. HOWEVER, THE OP DID SHOW SOME EFFORT Hello, I have been having troubles beginning these two problems given for exam prep. Was wondering if anyone could give guidance on where to begin. Problem 1: A cylinder with adiabatically...
  18. RJLiberator

    Thermal Equilibrium Temperature Question Sodium and Water

    Homework Statement Expose the error: When sodium is placed in water, a violent reaction always occurs; therefore sodium and water can never be at the same temperature. Homework Equations Thermal equilibrium and temperature. Zeroth law. Isotherms. The Attempt at a Solution My Answer: The...
  19. S

    Rotation of a block when not in equilibrium

    Homework Statement Consider a block placed on a surface, in two different configuration, a and b. Explain the condition for which the mass is in equilibrium and describe qualitatively the rotation it follows when it falls. Homework Equations Center of mass theorem \sum F = M a_{cm} The...
  20. E

    I Pn junction to reach thermal equilibrium

    Hello! Some of the processes caused by a pn junction are not clear for me. Just after the contact between the p and the n region, a migration of charges happens in a semiconductor junction in order to reach an equilibrium condition. A valence band and a conduction band are present in both...
  21. terryds

    Solving Equilibrium Problem: Determine tan θ

    Homework Statement The system is on static equilibrium. Determine tan θ ! Homework Equations ΣF = 0 Στ = 0 The Attempt at a Solution ∑Fx = 0 Ta sin θ = Tb ΣFy = 0 Ta cos θ = mg Then, I got stuck.. I want to continue to Στ = 0 but I don't know which one to pick as fulcrum, the...
  22. UMath1

    Ka vs Kb Weak Acids: Acetic Acid Low Ka, Lower Kb?

    Since Acetic Acid is a weak acid, it has a low Ka which means that the forward reaction is not favored as much as the reverse reaction. However, the Kb is even lower than the Ka...how is this possible? Shouldn't the Kb be higher to indicate that the reverse reaction is favored?
  23. Z

    Find the displacement from the equilibrium position

    Homework Statement Find the displacement from the equilibrium position of the particle that is in the distance x=£/12 from the wave source, for the moment t=T/4. The amplitude of the wave is A=0.2 m Homework Equations x=A*cos(wt)=A*cos2*pi/T* t The Attempt at a Solution x=£/12...
  24. S

    Static Equilibrium: holding a sign

    Homework Statement You are holding a sign as shown below. The sign (including the horizontal bar it hangs from) has a mass of 2.20 kg and is 40.5 cm wide. The sign is hanging from a 1.03 m tall, 4.46 kg vertical post. The sign is symmetric with a uniform mass distribution as implied by the...
  25. M

    Mechanical equilibrium of the system in gravitational field

    Consider a system contained in a very tall adiabatically isolating vessel with rigid walls initially containing a thermally heterogeneous distribution of material, left for a long time under the influence of a steady gravitational field, along its tall dimension, due to an outside body such as...
  26. A

    Holding a block of mass in equilibrium on a slope

    Homework Statement A block of mass is held in equilibrium on an incline of angle 30 degrees by the horizontal force 500N. Determine the blocks's weight, ignore friction. Homework Equations F = MA Normal Force y = Fg*sin(theta) Normal Force x = Fg*cos(theta) The Attempt at a Solution I'm...
  27. Nasbah BM

    Has anyone studied Equilibrium thermodynamics by CJ Adkin?

    I was hoping if anyone has studied it ,I might get help especially regarding its exercise.
  28. heartshapedbox

    Determining equilibrium position between two springs

    Homework Statement see attachment ***indicates correct answer Homework Equations F=ks The Attempt at a Solution I do not understand how this works, and I haven't been able to find any examples of this.
  29. UMath1

    Solids and Liquids in Kinetics and Equilibrium

    I just now read in my textbook that solids and liquids are not included in equilibrium expressions, are they included in rate laws? If not, why? Would a greater molar amount of solid or liquid increase the rate of reaction? And why isn't surface area included in Rate Laws? Also, for the...
  30. Nader AbdlGhani

    What Does an Equilibrium Constant Value of 1 Mean and When is it Expected?

    When does the value of the "Equilibrium Constant (K)" equal one ? and what does that mean ?
  31. hackhard

    B Can body start spinning without ext cause

    suppose a platform "P" is rotating about the z-axis wrt x-axis . another platform "Q" rotating about z-axis below "P" with same angular velocity wrt x-axis standing on Q , P is at rest wrt Q, After some time rotational inertia of P about z-axis starts changing with time standing on Q , P will...
  32. S

    Virtual work principle: equilibrium state of a system

    Homework Statement We have a system (see attached graphics) of two rods with length ##l## and mass ##m## and some external force ##F##. The coefficients ##k## of the two springs are given. The springs have no deformation when ##\varphi =0##. a) Find generalized force of the system. b) Determine...
  33. K

    A Equilibrium liquid-gas ratio in a binary mixture

    Hi all. I'm in need of a formula to calculate (roughly) the percentage of an ammonia-water mixture (arbitrary ratio of ammonia to water) that will boil off under different pressure/temperature conditions, in the ballpark range of 0.2-1.3 bar and 220K-350K. I don't necessarily need to know the...
  34. A

    B Learn About Moments & Equilibriums: What Does a Moment Mean?

    Hi, I'm currently learning about moments and equilibriums. I'm able to solve the problems quite properly, like determining different forces, distances and etc. what intrigued me is that when we say that an object has a moment of 1700 Nm about point o. Does it mean that the object will provide...
  35. E

    Dielectric in a capacitor in equilibrium

    Homework Statement Consider the situation shown in the figure. The width of each plate is b. the capacitor plates are rigidly clamped in the lab and connected to a battery of emf E. All surfaces are frictionless. Calculate the value of M for which the dielectric will stay in equilibrium...
  36. T

    How does an Op-Amp "find" equilibrium (w/ Negative Feedback)?

    Hi everyone, I've been seeking the answer to this question for a long time. I've looked at posts like... https://www.physicsforums.com/threads/op-amp-transient-state.855512/ and https://www.physicsforums.com/threads/how-does-negative-feedback-in-an-op-amp-work-conceptually.584881/ ...but I...
  37. K

    How to Find Angles in a Static Equilibrium System with Pulleys?

    Homework Statement I have 3 masses (Fα, Fβ & Fg) with 2 pulleys, and a wind variable which is in static equilibrium. I have already calculated the appropriate forces for the 3 masses by multiplying it with 9.81m/s² (gravity). Fwind = 60N Fα = 313.9N Fβ = 619N Fg = 882.9N I'm required to find...
  38. slymme

    Swinging, equilibrium, kinetic energy problem

    Homework Statement This is a more than one part question that depends on answers from the previous parts, which I have so I will not rewrite those questions. I will write the question I am facing difficulty with: Answers from previous parts: Length = 1.95 m (From top of chains to center, its...
  39. slymme

    Mass hangs in equilibrium on a spring (oscillation)(MCQ)

    Homework Statement A mass M hangs in equilibrium on a spring. M is made to oscillate about the equilibrium position by pulling it down 10 cm and releasing it. The time for M to travel back to the equilibrium position for the first time is 0.5s. Which line, A to D, is correct for these...
  40. jfizzix

    Heat Equilibrium in elliptical cavities, and the second Law

    I read this what-if XKCD article recently: (Fire from Moonlight) http://what-if.xkcd.com/145/ ..so here's a nice little brain-teaser about radiating bodies in thermal equilibrium! Let's say you have a large, perfectly reflecting elliptical cavity (a prolate ellipsoid). At one focus, you...
  41. F

    Trouble with elasticity and torque on a body in equilibrium

    Supose we have a ¨U-shaped" metal bar, stuck in the ground, and I aply a force on the top of the part on the right, trying to make it wider. If I were to avaliate the forces acting on a specific part of the bar that includes the point that I´m applying the force, let`s say the portion from that...
  42. RoboNerd

    Why is Pure Water Most Soluble for AgCl?

    Homework Statement In which one of the following solutions is silver chloride the most soluble? A) 0.181 M HCl B) 0.0176 M NH3 C) 0.744 M LiNO3 D) pure water E) 0.181 M NaCl Homework Equations the Ksp expression for the dissolution of AgCl is: Ksp = [Ag+][Cl-]The Attempt at a Solution...
  43. E

    Object in equilibrium between 2 fluids

    Homework Statement if an object is in equilibrium at the interface of 2 fluids in an open tank, why do both provide upthrust? Homework Equations P=P' +dgh The Attempt at a Solution The upper fluid is not in contact with the lower part of the object, so why would the fluid provide an upward...
  44. Raptor112

    Bose Equilibrium Distribution and Atomic Units

    Homework Statement For my project I need to compute the average the number of photons given by the expression: ##\bar{n}= \frac{e^{-\bar{h}\omega/\kappa T}}{1-e^{-\bar{h} \omega / \kappa T}}## where ##\kappa## is the Boltzmann constant and ##\omega## is the oscillator frequency. For the...
  45. K

    Physical Chemistry Homework: Equilibrium Constant and Gas Properties

    Homework Statement I have the following task: A chemical reaction 2 A(g) <-> B(g) + C(g) has an equilibrium constant defined by: ln=0.8+ 1050/T−1,3.105/T² a) What is K at 400K? Calculate ΔrG0 In a volume of 5L you get 2 moles of A and 0.5 moles of B. Reaction still proceeds at 400K. Consider...
  46. R

    Virtual Work to find equilibrium condition

    Homework Statement Find the tension T needed to hold the cart shown (pic included) in equilibrium, no friction. Using virtual work, and force components. (I don't care about signs, just looking for the magnitude of tension with quick reasoning) (not homework, just studying virtual work)...
  47. J

    Black Body radiation and thermal equilibrium

    Wikipedia writes: "Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment". Why does it write "thermodynamic equilibrium"? If it is not in a thermodynamic equilibrium, then what changes as far as the absorption...
  48. kini.Amith

    Basic problem in equilibrium thermodynamics

    I was reading Thermodynamics by Herbert Callen. In the first chapter he makes the following statement. 'The basic problem of thermodynamics is the determination of the equilibrium state that eventually results after the removal of internal constraints in closed composite system.' Then he...
  49. E

    What Determines Equilibrium in a Liquid-Vapor System?

    Homework Statement A liquid is in equilibrium with its vapor at its boiling point. On an average, the molecules in the two phases have equal: (A) inter-molecular forces (B) potential energy (C) total energy (D) kinetic energy Homework EquationsThe Attempt at a Solution I know (A) is wrong as...
  50. T

    Frequency problem (static equilibrium)

    Homework Statement The lower end of a uniform beam is attached to a vertical wall by a frictionless pivot. The beam extends away from the wall and upward, making a 62° angle with the wall, and it is held in place by a horizontal wire attached from its upper end to the wall. The wire's length...
Back
Top