What is Phase: Definition and 1000 Discussions

In the physical sciences, a phase is a region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase. (See state of matter § Glass)
The term phase is sometimes used as a synonym for state of matter, but there can be several immiscible phases of the same state of matter. Also, the term phase is sometimes used to refer to a set of equilibrium states demarcated in terms of state variables such as pressure and temperature by a phase boundary on a phase diagram. Because phase boundaries relate to changes in the organization of matter, such as a change from liquid to solid or a more subtle change from one crystal structure to another, this latter usage is similar to the use of "phase" as a synonym for state of matter. However, the state of matter and phase diagram usages are not commensurate with the formal definition given above and the intended meaning must be determined in part from the context in which the term is used.

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  1. Kaguro

    A Meaning of density of microstates in phase space

    Hello all. I am studying stat mech from Pathria's book. It says a system is completely described by all positions and momenta of all the N particles. This maybe represented by a single point in 6N-D gamma space. So, each point is a (micro)state. Now if we restrict the system (N,V,E to E+ΔE)...
  2. Y

    Does wire length difference create phase shift?

    When wiring a 240 volt AC circuit, I've always assumed that it's important for L1 and L2 wires to be the exact same length, in order to avoid introducing a phase shift that would reduce peak voltage. Length differences can accumulate when the wires enter a panel and need to go slightly...
  3. Iwanttolearnphysics

    What exactly happens during a phase change?

    What will happen if say, I have both ice and water inside the refrigerator and I set the fridge to exactly 0 degrees Celsius? Since both melting and freezing happen at 0 degrees, what will happen to my water? what about to my ice? Will they stay the same? I know this is an ignorant question, but...
  4. P

    I Notation of the approximation in quantum phase estimation algorithm

    I'am interested in the notation of the approximation in quantum phase estimation algorithm. In the literature there are different definitions, which I divide into two cases here. Both different in their definition of the ##\delta##. In both cases I start with a quote of the source and show an...
  5. ergospherical

    I How to Find the Berry Phase in Slowly Varying Systems

    I was trying to follow this page: https://phyx.readthedocs.io/en/latest/TI/Lecture notes/2.html With ##|n(\mathbf{R})\rangle## being the eigenstates of ##H|\mathbf{R} \rangle## of eigenvalue ##E_n(\mathbf{R})##, the task is to solve the Schroedinger equation ##i | \dot{\psi}(t) \rangle =...
  6. Butterfly41398

    Three phase total power consumed

    Summary:: I don't seem to see any problem with my work. But my final answer does not match the correct answer. (In number 3) Here's my work
  7. Shreya

    Phase factor in quantum mechanics

    Please be kind to help.I would be grateful
  8. P

    I Quantum phase estimation - Question regarding rewriting the state

    In Nielsen and Chuang p.223 we have the following situation: $$\frac{1}{2^t} \sum\limits_{k,l=0}^{2^t-1} e^{\frac{-2\pi i k l}{2^t}} e^{2 \pi i \varphi k} |l\rangle$$ Which results from applying the inverse quantum Fourier transform to state ##\frac{1}{2^{t/2}} \sum\limits_{k=0}^{2^t-1}...
  9. M

    A HHL quantum algorithm and the phase estimation

    In HHL algorithm, does the controlled unitary (Hamiltonian simulation part of Quantum phase estimation) depend on Hermitian matrix coefficients and how?
  10. casualguitar

    Modelling of two phase flow in packed bed using conservation equations

    Previously, I have seen the derivation of the energy conservation equations for simulation of single phase flow in a porous media (a packed bed). These are the energy equations for the solid and fluid respectively: I understand the derivation, however, these equations will only work when the...
  11. dRic2

    Time dependent perturbation theory (Berry phase)

    If I plug the solution into the Schrodinger equation I get $$(i \hbar \partial_t - H)\ket{\psi} = 0$$ Since I know that the zeroth-order expansion is lambda is already a solution I think this is equal to $$(i \hbar \partial_t - H)e^{i\phi} e^{-i\gamma}\ket{\delta n} = 0$$ If now I carry on with...
  12. S

    Mathematica Adapting Unwrapping Techniques for Plotting Phase Values

    This discussion https://community.wolfram.com/groups/-/m/t/1340126 includes some ideas to unwrap a list of wrapped-around values such as phase (e.g. Arg[ f[N] ] ). You can use this to ListPlot a jump-free graph. I'm trying to adapt this to work in Plot rather than ListPlot. The idea is to plot...
  13. P

    I Measurement of a qubit in the computational basis - Phase estimation

    Hello, I have a question about the measurement of a qubit in the computational basis. I would like to first state what I know so far and then ask my actual question at the end.What I know: Let's say we have a qubit in the general state of ##|\psi\rangle = \alpha|0\rangle + \beta|1\rangle##. Now...
  14. D

    I Physical interpretation of phase in solutions to Schrodinger's Eqn?

    Hello all, So I've been working through the solutions to some simple introductory problems for the Schrodinger Equation like the infinite square well, and I'm trying to make sense of how to think about the phase component. For simplicity's sake, let's start off by assuming we've measured an...
  15. U

    I Phase Speed of Wave in non-relativistic Doppler Shift Derivation

    Consider the situation where an observer at rest on the ground measures the frequency of a siren which is moving away from the observer at speed ##v_{Ex}##. Let ##v_w## be the speed of the sound wave. Let ##\lambda_0##, ##f_0##, ##\lambda_D##, and ##f_D## be the wavelengths and frequencies...
  16. S

    C/C++ How can phase singularities be implemented in C++?

    hello i would like to ask how to implement phase singularities in C++. thanks very much.
  17. S

    Adding two sinusoidal waves of same frequency but out of phase

    Asin(wt)}+Bsin(wt+a) Asin(wt) +B sin(wt)cos(a) +Bcos(wt)sin(a) Asin(wt) + ksin(wt) + Lcos( wt) (A+K) sin(wt) + Lcos(wt) Fsin(wt) + Lcos(wt)
  18. N

    A What are the methods for calculating quantum phase transition?

    Trying to understand what the math methods are exist to determine quantum phase transition and how I can calculate it, by what methods.
  19. P

    A Phase diagram of Carbon at large electric fields.

    I am wondering if the phase diagram of Carbon has been explored at very large electric fields. Can one make any theoretical guesses ? In specific I am interested in Pressure Vs Electric field and Electric field vs Temperature at fixed temperature and pressure respectively.
  20. raisins

    I Phase space integral in noninteracting dipole system

    Hi all, Consider a system of ##N## noninteracting, identical electric point dipoles (dipole moment ##\vec{\mu}##) subjected to an external field ##\vec{E}=E\hat{z}##. The Lagrangian for this system is...
  21. D

    AntiNoise Amplitude and Phase

    Summary:: AmbientNoise + AntiNoise combined calculation I am having trouble with this question: Noise cancelling headphones use both passive (insulated earphones) and active (electronic “anti-noise”) methods to nullify ambient noise. One task of a sound engineer is to design low-energy...
  22. S

    I Explaining Quantum States: Global Phase

    I was teaching the basics of quantum states and was showing the students that an arbitrary state in a quantum two-level system could be written as ##|\psi\rangle = C_1 |+\rangle + C_2 |-\rangle = R_1 |+\rangle + R_2 e^{i \alpha} |-\rangle##, with {##C_i##} complex and {##R_i##} real. Then...
  23. D

    I Orbital distance increase during the white dwarf phase of the Sun

    Some estimates through calculating the sun mass loss and increase in mass loss say that the white dwarf phase of the Sun will have roughly about 50% the current mass of the Sun (not sure about it). Whatever the actual mass loss is going to be, assuming that the 50% mass loss is true, where would...
  24. M

    I Dependency of phase space generator to differential distributions

    I attatched an example plot where I created the histogram for the differential distribution with respect to the energy of the d-quark produced in the scattering process. My conception is that the phase space generator can "decide" how much of the available energy it assigns to the respective...
  25. C

    Purely passive RC Phase Shift Oscillator?

    It is possible to build a purely passive RC phase shift oscillator with 2 separate (in the future) RC stages like this? Where there would be 2 RC networks that each provide 180 degrees of phase shift. Of course, there would be a buffer in between the 2 RC networks so that they behave as 2...
  26. P

    3 Phase Harmonics and Solid State Relay Issues

    I have a 3 phase problem that I think might be applicable to this forum. The setup is equipment which contains 5 resistive heaters (A through E). The unit is powered by 208V 3 phase and each of the heaters are hooked up line to line in an unbalanced configuration as follows: L1-L2: Heater D...
  27. B

    I How to recalculate Berry phase dipole moments (jumps over time)?

    Is there anyone out there who can help a newbie understand how to deal with Berry phase dipole moment data? I ran a simulation to calculate dipole moments over time using the Berry phase method. The problem is that there are jumps in my data. There is an example at the end of this post (part...
  28. S

    A Berry phase in condensed matter

    I am trying to understand how is topology used to characterize materials. So I understand that to calculate the Berry phase you will parameterize your Hamiltonian and change this parameter in some way and return to the initial value. What I do not understand is what does this changing of...
  29. baby_1

    Phase velocity in oblique Angle propagation (Plane wave)

    Hello, Regarding the wave oblique angle propagation and based on Balanis "Advanced engineering Electromagnetic" book on page 136 ( it has been attached) I need to know why the phase velocity in x direction is not important to keep in step with a constant phase plane( Just equation 4-23). I...
  30. R

    Design a linear phase low pass filter

    Design a linear phase low pass filter whose specification is:1) Maximum tolerance in the passband equal to 0.01% (linear) in the passband;2) Cutoff frequency at ω_c = 0.3π and transition band at 0.05π;3) Minimum reduction of the 0.95 rejection band.
  31. S

    I Phase Shift of a Sine Wave

    Hi, I have created a sine wave with the following options: 1.) - changing the period/length in days of the sine wave (Cycle Length in Days) 2.) - calculating the start value of the "dummy" so that the sine wave always starts with -1 (Dummy Start at Cycle Trough) when the phase shift is set...
  32. baby_1

    Attenuation and Phase constant values in wave equation

    Regarding wave equation we are faced with this form $$\nabla^2 \vec{E}=j\omega \mu \sigma \vec{E}-j\omega \mu\varepsilon \vec{E}=\gamma ^2\vec{E}$$ where $$\gamma ^2=j\omega \mu \sigma -j\omega \mu\varepsilon $$ $$\gamma =\alpha +j\beta $$ where alpha and beta are attenuation and phase...
  33. D

    B Is Mean Temp in 2 phase Heat Exchangers Higher Than Logarithmic Mean?

    Is Mean Temp in 2 phase Heat Exchangers Higher Than Logarithmic Mean? I am looking at this paper: https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1314&context=iracc Having a bit of trouble understanding all of it, but my basic question is just: If I have a heat pump where the hot...
  34. I

    Help Plotting Phase Difference using LTSpice please

    How do i plot phase difference in a Ltspice in this circuit ?
  35. RicardoMP

    A How to reduce an integral in phase space to a one-dimensional form?

    I've been trying for a very long time to show that the following integral: $$ I_D=2{\displaystyle \int} \, {\displaystyle \prod_{i=1}^3} d \Pi_i \, (2\pi )^4\delta^4(p_H-p_L-p_R) |{\cal M}({e_L}^c e_R \leftrightarrow h^*)|^2 f_{L}^0f_{R}^0(1+f_{H}^0). $$ can be reduced to one dimension: $$ I_D...
  36. C

    RC Phase Shift Oscillator not Oscillating

    Hello everyone. I am having some trouble with an RC phase shift oscillator that I built as a hobby project. I am completely stuck on this and I just cannot figure it out. My oscillator is not oscillating. Here is the circuit that I am trying to get to work. Taken from...
  37. oscarrod5

    Exploring Phase Potential Difference in 3-Phase Power

    I understand phase voltage (phase to neutral) well, but I'm still confused by what exactly the potential difference is between any 2 phases in 3 phase power. If you were to try to find the potential difference where 2 sine wave phases cross, then at that instantaneous point, the potential...
  38. M

    Standing waves between two speakers in phase

    The solution provided in the manual poses that the point halfway between the nodes at each speaker is an antinode of pressure (node of displacement) but isn't that a contradiction to the fact that the speakers are in phase? My first thought was that they must interfere constructively and have...
  39. A

    Metering a Single Phase 208 VAC Circuit

    Good day, I hope to understand how to use a 3 phase energy meter to measure single phase 208 VAC circuit. The basic idea seems simple, yet, complex meters don't seem to have this ability. Would anyone be able to describe what kind of information one would need from a digital 3 phase meter...
  40. I

    Chemistry Why does evaporating water cause some water to be cooled and form ice?

    Answer: I know that when water evaporates, it absorbs heat, that's why the process is endothermic. I don't understand why the water would be cooled and some ice would form, when the water is supposed to evaporate. What causes some water to be separately cooled instead of evaporated? Thanks.
  41. R

    180 degree phase shift of reflected light

    When light originating from a medium of lower refractive index reflects off a surface of higher refractive index, why does the phase shift by 180 degrees? Stokes relations show that reflection coefficients at the surface are equal but of opposite signs depending on direction of light (i.e...
  42. dvscrobe

    Aliasing Phase Shift: Determining Phase Shift

    How do you determine the phase shift of an aliased signal?
  43. PHYSICSKOP

    I Undamped driven oscillation — Is there a phase delay?

    I know that there is phase delay in damped driven oscillation but I want to know is there any phase delay in undamped driven oscillation when we apply sinusoidal driving force. When driving force is maximum, displacement is also maximum as well right?
  44. adamaero

    Engineering How to calculate rotor flux of the three phase squirrel cage induction motor?

    Three phase squirrel cage induction motor with given parameters (stator winding connected in delta) nominal power: Pn=22.4kW nominal stator voltage: Vsn=230V nominal stator current: Isn=39.5A nominal stator frequency: fsn=60Hz nominal speed: nn=1168min−1 number of pole pairs: 3 stator...
  45. AHSAN MUJTABA

    A Phase Portraits of a system of differential equations

    One thing that bothers me regarding the phase portraits, if I plot a phase portrait, then all my possible solutions (for different initial conditions) are included in the diagram? In other words, a phase portrait of a system of ODE's is its characteristic diagram?
  46. tworitdash

    MATLAB How to change the frequency values inside a time domain signal phase

    The problem I am having is simple. I have a Gaussian spectrum initially. Like this, Process 1: S = m0/sqrt(2*pi*sigma^2) * exp(-(vel_axis - mu).^2/(2*sigma^2)); Here, mu is the mean velocity (frequency) and sigma is the standard deviation. vel_axis is the axis on which I am calculating this...
  47. I

    Phase shift between voltage and current

    Hello ,so am trying to find a phase shift between voltage and current ,I've done what do i do after that ?and is this right ? Q A 100Ω load is connected to a power supply of 100V at 50Hz. At time, = 0, the instantaneous value for voltage across the load was zero and the current through the load...
  48. A

    Electromagnetic wave equation - phase and amplitude

    how we get "e^(ikr)"...? Plz ans me... Thanks
  49. Cosmin1337

    Single phase universal motor, variable frequency

    Summary:: How to keep the same voltage and change the frequency of a A.C. universal motor. Hello there! I need some help regarding my final project for the university. I have a universal motor, supplied by a single phase, 220V source. I need to make this motor work at the same voltage, but to...
  50. J

    Find the phase difference in terms of d, lambda, theta

    So in figure 4.8 the path difference between the two waves is d*sin(theta), then is the phase difference just (d*sin(theta)*2*pi)/lambda?
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