Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [equilibrium]

The tag has no usage guidance.

9
votes
3answers
428 views

Maximum entropy at equilibrium for closed system: Local maximum or global maximum?

For a closed system at equilibrium the entropy is maximum. Is this a local maximum or is it a global maximum? I am an undergraduate physics student and it seems that the possibility of entropy ...
0
votes
3answers
71 views

Electrostatics fundamentals

Suppose a charge is kept at the centre of a square frame and the vertices of the frame have four more charges fixed to the frame which are identical to each other but not necessary that these four are ...
2
votes
1answer
63 views

Definition of equilibrium for thermodynamics and statistical mechanics

Is the definition of equilibrium for thermodynamics and statistical mechanics the same? From my understanding, a system is in thermodynamic equilibrium if its macroscopic variables are not changing. ...
0
votes
1answer
39 views

Local equilibrium of slow time varying thermal system

I'm trying to differentiate a thermal system in local equilibrium (and slow time varying) v/s a non-equilibrium system. For a thermal system which is slowly time varying, how does one define local ...
0
votes
1answer
78 views

Proving that $c_V$ is positive

On my professor's lecture notes he claims that $c_V>0$. Intuitively, this would have been my guess as well but he mentions how you can prove this by constructing a setup: "Construct an isolated ...
0
votes
1answer
79 views

Can body of one temperature ever cause higher temperature in another body?

If you have one body that radiates heat at a constant rate and, forgive my simple assumption, thus constant temperature, and a body that may absorb this heat, may the temperature of second body ever ...
1
vote
1answer
47 views

2 body problem question

I am taking a classical mechanics course and i am struggling to determine the equilinrium points for this potential $$Q= -(k/r) + ar + (L^2/mr^2).$$ The problem is that i have to solve a cubic ...
3
votes
4answers
71 views

Thermodynamic process

"During this process, the system is always in thermal equilibrium with the surroundings." Does this statement means the process is adiabatic? Since the temperature of both systems is the same, there ...
2
votes
1answer
75 views

Why particles of thermodynamic systems have a preference for low energy levels?

While reading Ken Dill's Molecular Driving Force, I noticed this paragraph when the author is trying to explain the Boltzmann distribution. Particles don’t have an intrinsic preference for lower ...
1
vote
1answer
16 views

Overconstrained equilibrium binary mixture phase seggregation

Assume a binary mixture, with the component $A$ in concentration $c$ and the component $B$ in concentration $1-c$. The total energy $E(c)$ is thus given by a function of one variable $c$ (if we do not ...
3
votes
1answer
72 views

Thermodynamics ($dE<0, dH<0, dG<0$ )

I didn't understand the derivation of why Gibbs free energy becomes negative when change is spontaneous. Our chemistry teacher's derivation was like this. $$dE = TdS - PdV \leq TdS - P_{ext} \cdot ...
1
vote
1answer
74 views

Equilibria and conserved quantities in a superposition of central potentials

I have a Lagrangian made up of a superposition of $k$ central repulsive potentials centered at $(a_k,b_k)$. Each potential is somewhat strange - they take the form $V(r)=-\ln\left(r\right)$. The whole ...
0
votes
1answer
65 views

Why does a system assume ground state at absolute zero temperature?

I am going through Huang, Statistical Mechanics. He says at 0 kelvin, a quantum system assumes ground state so that $S=k_B ln(G)$ holds where $G$ is the degeneracy of the ground state . My question ...
1
vote
1answer
68 views

Earnshaw's theorem and stability of charge inside a hollowed cavity of conductor

When a positive charge q is placed in the center of a spherical cavity of a spherical neutral conductor, it induces a negative charge $q$ to line the inner wall of the conductor, and a positive charge ...
1
vote
4answers
129 views

Work done but no change in velocity

I’m taking an introductory course in thermodynamics right now and I have learned that in a quasi static process, one way to increase internal energy is to do work on a system or supply heat to it. But ...
3
votes
1answer
62 views

Laplace's heat equation equilibrium functions

I simulated the Laplace's heat equation on a grid (200x200) with boundary conditions of 0 (a cold source) on the top and left and 1 (of hot source) on the bottom and right. (see gif) I stopped ...
0
votes
0answers
27 views

Why are the electrodes in thermodynamic equilibrium for a working solar cell?

I was reading a paper that performed simulation of a solar cell under illuminated conditions. Obviously, in these conditions, the device is out of thermodynamic equilibrium. For example the ...
2
votes
1answer
46 views

Is temperature equilibrium actually reached in a mixer tap, or is it merely a jumbling of hot/cold droplets?

Most kitchen and bathroom sink faucets have a mixer tap which blends the hot and cold inflows into a warm, uniform outflow stream. It's difficult to believe that complete heat transfer and ...
0
votes
1answer
64 views

Relationship between binding energy of atoms in a solid and compressibility defined by bulk modulus

Consider an atom which has η nearest neighbours. The equilibrium binding energy $L_0$ of $N$ atoms is: $$ L_0 = \frac{Nηϵ}{2} $$ The bulk modulus $K$ of a solid of volume $V$ compressed under pressure ...
1
vote
1answer
48 views

Why does the thermal equilibrium change so quickly?

I performed an experiment recently where I tested the specific heat capacity of different metals in water. Once the metals were removed from a beaker and placed into calorimeter with water, thermal ...
1
vote
1answer
146 views

What is the difference between non-equilibrium and equilibrium phase transitions?

My question is about the distinction between certain kinds of phase transitions. I understand what the difference between first and second order ones are. What is the difference between non ...
6
votes
0answers
82 views

Entropy and equilibrium concepts at astronomic scales

I am always puzzled to read here and there discussions dealing with thermodynamic concepts applied to astronomic scales where gravity matters. To my opinion, there is a certain carelessness to go into ...
0
votes
2answers
172 views

Phase transitions and Helmholtz vs Gibbs Free Energy

Gibbs phase rule for Gibbs free energy says that phases during a phase transition must be in mechanical, chemical, and thermal equilibrium, e.g. $T_1=T_2$,$G_1=G_2$, and $P_1=P_2$, where the ...
0
votes
2answers
63 views

Is the method of joints only applicable to trusses?

I am confused as to whether the method of joints is only restrained to pin-jointed trusses or it can be applied to other statics problem, for example the one shown in the picture, and why?.
2
votes
2answers
140 views

How would I draw the forces on two identical ladders propped up against each other, connected by a rope?

Two ladders of uniform density and equal mass m are propped up against each other at angles $\theta$ from the frictionless ground. A rope of tension $T$ connects the two horizontally a distance $\...
0
votes
1answer
109 views

What is the law of mass action?

What is the law of mass action? This is a question which covers the area of chemistry. But unfortunately I don't know any sites which can clear my chemistry doubts. So kindly I request anyone to ...
1
vote
0answers
33 views

To which all factors chemical equilibrium is directly proportional to? [closed]

The equilibrium constant is directly proportional to the concentration. why it is so? Is chemical equilibrium dependent on temperature and other such factors? Then why we only focus on concentration?
0
votes
1answer
88 views

What does blackbody radiation look like for negative-temperature systems?

Using the thermodynamic definition of temperature, $$\frac{1}{T}=\frac{\partial S}{\partial U}\bigg|_{V,N}$$ negative temperatures are possible, in systems where the entropy decreases when energy is ...
0
votes
1answer
98 views

What is the (quantum) definition of thermal equilibrium?

What is the necessary condition for a quantum system to be in thermal equilibrium? The quantum systems I have in mind are a bunch of cold atoms, of photons in a cavity. Does a system need to obey a ...
10
votes
1answer
1k views

Earth as a perfect sphere and an object trying to stand still

I have imagined the Earth as a perfect sphere with uniform mass density and I put an object somewhere between the equator and the north pole at rest with respect to earth. And also in my imaginary ...
0
votes
2answers
156 views

How do you calculate the change in entropy for a non quasistatic process

I understand that Entropy is a state function, but the change in entropy does in fact depend on the process from a-->b. I understand the derivation for entropy where $$S_2-S_1=Ncv\ln\frac{T_2}{T_1}+...
-2
votes
1answer
193 views

Forces acting on an orange placed on a table in equilibrium [closed]

An orange sits on a table in equilibrium. What forces are acting on it? What is the reaction force to each of the forces acting on it? What are the action and reaction pair?
0
votes
1answer
137 views

How “Eyeball Glide Ball” toy works?

How this toy works? As you roll the ball on the table, the eye always point up: (original video source: https://youtu.be/_3kAjWaxM30) As far I am aware, no magnets are involved in the construction ...
1
vote
3answers
163 views

Why is boiling a non-equilibrium process? [closed]

Boiling is a non-equilibrium process. Which equilibrium (mechanical, chemical and thermal) are not maintained during boiling and why?
6
votes
4answers
552 views

Can a positively charged conductor have negative surface charge density somewhere?

This is a simple question that occurred to me while thinking about electrostatics. Let's consider a positively charged isolated conductor in equilibrium. In general, the surface charge density varies ...
0
votes
2answers
309 views

Why is the restoring force not zero at the equilibrium position of simple harmonic motion?

The restoring force is applied in order to take the body it's equilibrium. Then in a SHM why in the mean position restoring force maximum rather than being zero as it has reached equilibrium. (After ...
2
votes
2answers
514 views

Beam attached to a wall

Suppose I have a rigid beam attached to a wall, how can the reaction force on the point the beam is attached to generate a static equilibrium on the beam? ...
7
votes
0answers
432 views

Can a substance have zero vapour pressure above absolute zero?

According to this Reddit thread, the answer is no, vapor pressure can't be zero when temperature is above absolute zero. I suspect the answer might actually be yes according to a precise definition I ...
2
votes
1answer
55 views

Lagrange points and gravity

I have just found an article talking about the L1 to L5 equilibrium positions of gravitation around stars, planets, etc. As far as I could learn from this website and other research I have done the ...
3
votes
0answers
42 views

Is there an open quantum system analogue of the equilibration time bounds for classical ergodic Markov chains?

Background For classical ergodic discrete Markov chains, we can bound the time taken to reach the stationary distribution to the spectral properties of the transition matrix. I will outline this ...
2
votes
1answer
115 views

Why does the gas in Sun's outer layer not expand?

Since in the outer part of sun it consists gases. Why don't the gases expand due to heat? This was asked by my friend. And he said that the gases are attracted by the plasma layer by a force. So the ...
0
votes
1answer
105 views

What happend to the tension? [closed]

If crane with uniform arm raised by shortening cable,what is the effect to the tension of the cable?I know the tension will increase but what cause? Bcs of increasing in angle?Or got thing with torque?...
3
votes
2answers
964 views

Can a body be in equilibrium when only one force acts on the body? [duplicate]

I think that when we throw a body in air, at top point the body is in equilibrium but gravitational force is still acting. Is this correct?
0
votes
1answer
53 views

Defining a 'small disturbance which dampens in time' while identifying stable points in a nonlinear system

I'm reading the book "Nonlinear dynamics and Chaos" by S Strogatz. In section 2.2, titled "Fixed points and stability", he defines equilibrium points as solutions where ...all sufficiently small ...
1
vote
0answers
27 views

In terms of the greenhouse effect, what is the Earth's heat capacity?

Has the earth’s atmosphere reached an equilibrium at which the input radiation energy roughly equals its output, or is the output significantly lower than the input because the energy is being used to ...
-1
votes
2answers
89 views

Electric charge and net force [closed]

Consider two point charges $+Q$ and $-Q$, which are fixed a distance $d$ apart. Can you find a location where a third positive charge $Q$ could be placed so that the net electric force on this third ...
0
votes
0answers
35 views

Diffusion: equilibrium concentration at some distance from source

Say I have a point source producing molecules X at a rate of R moles/s. X diffuses away from the point source in 3D. The diffusion coefficient of X is D m2/s. By common sense, I expect the ...
0
votes
1answer
47 views

free stress boundary condition

I would like to understand better the free stress boundary condition. Indeed, force equilibrium writes $\nabla.\sigma=0$, and not $\sigma=0$, so which basic physical principle (such as force ...
1
vote
0answers
59 views

Demonstration that electric current at equilibrium is zero

As it is well known, electrons at equilibrium (no external field) do not conduct electric current, i.e. $\int_{BZ} dk\,v_{k}\,f(\epsilon_k)=0$ where $f(\epsilon_k)$ is the Fermi-Dirac distribution $...
0
votes
2answers
292 views

Thermal equilibrium vs steady state

According to Kirchhoff's law, when two objects are in thermal equilibrium, both objects have the same temperature and each object emits as much energy as it absorbs. Also, the energy absorbed at each ...