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. jim mcnamara

    Oral molnupiravir phase II-a of Covid RCT by Merck

    News release https://www.thepharmaletter.com/article/preliminary-phase-iia-trial-results-of-molnupiravir-in-covid-19 Molnupiravir has passed part of a phase II-a study. Caveat: this is preliminary, not peer reviewed data. Study design Earlier paper Feb 24 2021...
  2. R

    A What Are Examples of Exotic Order-Disorder Phase Transitions?

    I am looking for possible examples and a variant of Landau's theory of phase transitions for an exotic order-disorder phase transition, in which a thermodynamic system jumps into a disordered (or less orderly) state by reaching the maximum critical value of the order parameter. That is, in one...
  3. H

    Understanding Phase Change: R, L & C

    Why do we need to consider phase change? Here are my thoughts: is it because voltages are different in phase for each of the three electrical accessories, R, L and C?
  4. M

    Engineering Questions about the workings of a phase locked loop

    Hi, I had one or two questions about the operation of a PLL, which refer to the diagrams below - a control representation of the system and a diagram of the low pass filter circuit. Questions: 1) What is the point of having another (low-pass) filter ## G_f (s) ## for ## V_o ## after...
  5. H

    Where are the waves out of phase with each other by π radians?

    I know that at the antinodes, the diffrence is pi radians and i got 0.25, 0.75, 1.25, and 1.75. for the position of antinodes. but the answer is x = 0.75 m, 1.25 m. I can use drawing to obtain the answer, but my calculation gives me 0.25, 0.75, 1.25, and 1.75. Where am I doing wrong? Thanks!
  6. PhysicsTest

    Line and Phase voltages differences

    When i study the 3 phase systems, this is want i understand for a Star connection Line voltage is ##\sqrt 3 V_\phi## and leads the phase voltage by 30Degrees. ----> eq1 So, from above we can conclude that both Line voltages and phase voltages are sine waves with phase difference. But in case of...
  7. PhysicsTest

    Optimizing Phase Current Measurements with Shunt Resistors

    I have seen an application note of how to measure the phase currents using shunt resistors as shown below I am only confused with the connection when measuring the phase Ia current, it differs from the way the shunt resistor is connected for Ic and Ib, he could have done the same way like Ib...
  8. F

    I Is there an uncertainty between amplitude and phase in an EM wave?

    Is there an uncertainty between amplitude and phase in classical quasi-monochromatic light?(E(t)=a(t)cos(phi(t)-omega_0*t))If it exist, what is the relation between classical and quantum uncertainty(delta I* delta phi>=1/2)?
  9. H

    B Apparent missing negative phase oscillation energy - where is it?

    When an oscillator produces waves - let's say they are highly focused - that are damped by a second negative phase oscillator, where is the wave energy? The energy in each set of waves must still exist. Has it become hidden?
  10. G

    Using complex numbers to model 3 phase AC

    Assume a transformer as above, with 230V L-N, and I want to work out the L-L voltage. A phasor diagram will show me that the voltages are 120° out of phase. (230∠0°) + (230∠120°) = (230cos0 + j230sin0) + (230cos120 + j230sin120) = 230 + (-115 + j199.2) 115 + j199.2 = 230∠60 What I’m looking...
  11. Euan12345

    Using phase difference to find the angle of a signal

    I want to locate an infrared signal using Angle on arrival (AoA), I have elected to use Phase Interferometry to achieve this, I am however struggling to understand how the phase difference (∆ϑ) is found. Can someone explain how I could find this?
  12. A

    220 Three Phase to 220 Single Phase

    I want to convert 220vac in a Wye configuration to 220vac single phase. So now I have L1, L2, L3 and N. Where Lx-N = 127 and Lx-Lx = 225. I want to transform to Lx-N = 225 3000W. Will an isolation transformer do this?
  13. Francis

    A Conditional phase shift for Grover's algorithm

    I am trying to understand the following deduction: "The conditional phase shift can be represented by the unitary operator 2|0> <0| - I:" for eq. 4a) I was expecting to be: [2 |0><0| - I] |0> = 2 |0> <0|0> - I|0> = 2|0> - |0> = |0> as for eq. 4b I can't understand it at all. Why does the...
  14. H

    Phase lag of light in materials

    There are 5 fantastic videos in this website: http://www.alfredleitner.com/ He is a very good educator and it is also very good to see those authentic experiments and aparatus. Anyway, in the following one at exacly 8:00 minutes he says that the phase lag induced by the dipole is always 90...
  15. M

    Engineering Filter Linear Phase Property for non-integer time delays

    Hi, I just have a quick question regarding the linear phase property of filters. It might be easier to provide some context before getting to the question, but feel free to skip to the bottom. Consider a system input as a discrete sequence obtained by sampling at t = 0, T, . . . , kT from an...
  16. L

    I What happens when two waves in counter phase affect a conductive material?

    i am writing this message after a short consultation with kuruman. if there are two waves emitted by the same source then with the same direction, but these waves are in counterphase link...
  17. danielhaish

    Does ice melt faster in water because helps to change the phase

    so according to this https://en.wikipedia.org/wiki/Nucleation nucleation start faster when there is a round matter that already in the phase that the other matter is going to ,so in case of ice melting in water because it would have more Nucleation points, edit: i mafe alittle experience and it...
  18. cnh1995

    Engineering Single Phase Inverter Waveform

    The answer given is d). Seeing the problem statement, it can be concluded that the load has some inductance, and when the switches S1, S2, S3 and S4 are off, conduction takes place through the anti-parallel body diodes (freewheeling action). Seeing the triggering pulse waveforms, S1-S4 ON...
  19. J

    I Energy in the Hamiltonian formalism from phase space evolution

    The hamiltonian ´for a free falling body is $$H = \dfrac{p^2}{2m} + mgy$$ and since we are using cartesian coordinates that do not depend on time and the potential only depends on the position, we know that ##H=E##. For this hamiltonian, using the Hamilton's equations and initial conditions...
  20. S

    Deriving relations for a hard sphere phase diagram

    Ornstein-Zernike states that ##h(r_{12}) = c(r_{12}) + \rho \int d\mathbf{r}_3 c(r_{13})h(r_{32})## which after a Fourier transform becomes ##\hat{C} (\mathbf{k}) = \frac{\hat{H}(\mathbf{k})}{1+\rho \hat{H}(\mathbf{k})}## However, I don't see how to simplify this to the second equation he has...
  21. Vivek98phyboy

    Contradiction in Phase of reflected sound

    While studying the fundamentals of sound waves in organ pipe, I noted that the fact about phase of reflected waves is contradicting while referring multiple sources This book of mine describes the reflection from a rigid surface/closed end to be in phase Whereas this one describes the...
  22. GuthrieF

    Three phase systems - current magnitude

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  23. PhysicsTest

    Why is three phase power the preferred choice in power distribution?

    I saw the information of the text at different places and when i compare it is confusing. The text is In some other section If you see the red lines i have highlighted, in the first section the book refers that the B coil is behind the A coil, but in the 2nd section it refers that in the...
  24. B

    Self Excited AC Single Phase Generator

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  25. D

    Water Phase Diagram: Mathematically Modeling and Validating

    I notice that water phase diagrams provided online always seem to show a rather linear behaviour for the solid-liquid boundary (and an extremely steep slope). How is this modeled mathematically? Say we use the Clapeyron equation with ΔH and ΔV_m being constant, as online example problems (meant...
  26. F

    I Coexistence of Solid and Liquid Matter: Conditions for Existing One Phase?

    I think in solid or liquid phase, there are many molecule having a very large speed due to random character in moving.So the liquid or solid matter must co-exist with other phase because some molecules escape from surface of solid or liquid matter.Then is there any condition for existing only...
  27. Nick tringali

    I Waves and phase shifts (attempting to learn physics)

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  28. danielhaish

    Why can't two laser beams from two sources Interfere if they have a difference phase?

    I read in the internet that the reason that two laser can't Interference because they most likely have difference phase. but electromagnetic wave are just change in the electromagnetic filed that goes up and down , so mathematically they may Interference little let say that the there is...
  29. S

    I Interpretations of phase space in Dynamical Systems Theory

    In Dynamical Systems Theory, a point in phase space is interpreted as the state of some system and the system does not exist in two states simultaneously. Can some phase spaces be given an additional interpretation as describing a field of values at different locations that exist...
  30. O

    I Rosetta orbits and phase space

    I was recently working on the two body problem and what I can say about solutions without solving the differential equation. There I came across a problem: Lets consider the Kepler problem (the two body problem with potential ~1/r^2). If I use lagrangian mechanics, I get two differential...
  31. Kaushik

    Understanding the Phase Difference Between Voltage & Current in a Circuit

    Consider a circuit with a witch, capacitor and an AC voltage source. The sinusoidal AC voltage source is depicted in the following graph: We know that, ##Q = CV## ##\frac{dQ}{dt} = C \frac{dV}{dt}## ##i = C\frac{dV}{dt} \tag{1}## So from the graph, the voltage increases rapidly around ## t =...
  32. D

    Phase Equilibrium of Liquid and Vapor Under External Pressure

    Suppose you have a container of water at a given temperature T (say normal room temperature) with a vacuum above it. Presumably water will evaporate until there is sufficient vapor that the pressure of it above the water is the SVP for that temperature. Now suppose that there is air above the...
  33. Grinkle

    COVID Covid Vaccine Phase 3 significance

    Russia's vaccine news has me pondering. How often after a successful phase 2 study do phase 3 studies show that the vaccine causes harm? If I were offered a COVID-19 vaccine that had passed phase 2 trials, I'd accept it. Is that foolhardy of me? Is it possible to use existing data to model...
  34. G

    Origin of the "underpressure" or "negative phase" in a blast wave

    In the blast wave generated by an explosion, after a first violent increase in the air pressure, there is a "negative phase" in which the pressure drops below the initial atmospheric pressure (see e.g. https://en.wikipedia.org/wiki/Blast_wave ). According to wikipedia, this underpressure is the...
  35. Rahulx084

    Thermodynamics: Single/Homogeneous Phase Differences

    #Can somebody please explain what is the difference between single phase and homogeneous phase in context with thermodynamics? #Also in the fundamental relations in thermodynamics like dg=vdp-sdT , it says this is applicable to homogeneous phase of constant composition. Isn't this equation...
  36. entropy1

    Randomizing phases of harmonics

    Suppose I decompose a discrete audio signal in a set of frequency components. Now, if I would add the harmonics I got, I would get the original discrete signal. My question is: if I would randomize the phases of the harmonics first, and then add them, I would get a different signal, but would it...
  37. I

    I Phase space path integrals

    I have heard of phase space path integrals, but couldn't find anything in Wikipedia about it, so I am wondering, what does it compute ? In particular, are the endpoints points of definite position and momentum? If so, how does one convert them to quantum states ? Also, how is it related to...
  38. N

    Thermodynamics: phase change and latent heat problem

    The second question is where I'm lost. The answer to the first question is 5.39 grams. The second is 10.3 grams. Until I saw the answer I was setting the equation up as if some of the original steam had condensed. But it appears that some of the original water changed into steam. Is it necessary...
  39. M

    A Do gas-gas and/or liquid-liquid phase transitions exist?

    I'm writing a short report about thermal storage using latent heat and the topic is liquid/solid phase transitions. I would however like to systematize all phase transitions in the intro and I'm curious if gas/gas and/or liquid/liquid phase transitions exist. For gas-gas I think that the...
  40. johnboyman

    Building a three phase motor -- figuring out how many poles

    Hello. I am building a three phase motor for a science project of mine. I am trying to match my motor with an inverter so i need to count how many poles I have in this motor. The problem is that I have read about this and some people say that this...
  41. phywithAK

    Phase shifts for a localized Coulomb and harmonic potential

    I am struggling over a problem and i could really use some help in this. So it's about finding phase shifts in a localized sphere of coulomb and harmonic potential. I tried solving the radial Schrodinger equation for both of them by using power series method, but still i am having problem...
  42. Rx7man

    What Could Be Causing My 3 Phase Motor to Lack Power and Torque?

    I have a small 1hp 3 phase that really lacks torque, it was on a big lathe (12hp) and the entire rest of the machine was wired for 240V delta.. but this motor only has 3 wires coming into the connector box, so there are no options for changing the voltage, yet the nameplate says 220V Delta or...
  43. LuccaP4

    Hamiltonian mechanics: phase diagram

    The issue here is that I don't know how to operate the final equations in order to get the phase diagram. I suppose some things are held constant so I can get a known curve such as an ellipse. I attach the solved part, I don't know how to go on.
  44. sophiatev

    I What happened to the spatial degrees of freedom for the second particle?

    In Henley and Garcia's Subatomic Physics, they introduce phase space in chapter 10 by considering all the possible locations a particle can occupy in a plot of ##p_x \ vs. x##, ##p_x## being the momentum of the particle in the x direction. They next consider an area pL on this plot, and state...
  45. D

    Phase space of a harmonic oscillator and a pendulum

    Hello everybody, new here. Sorry in advance if I didn't follow a specific guideline to ask this. Anyways, I've got as a homework assignment two cannonical transformations (q,p)-->(Q,P). I have to obtain the hamiltonian of a harmonic oscillator, and then the new coordinates and the hamiltonian...
  46. PainterGuy

    I Magnitude and phase of the Fourier transform

    Hi, A rectangular pulse having unit height and lasts from -T/2 to T/2. "T" is pulse width. Let's assume T=2π. The following is Fourier transform of the above mentioned pulse. F(ω)=2sin{(ωT)/2}/ω ; since T=2π ; therefore F(ω)=2sin(ωπ)/ω Magnitude of F(ω)=|F(ω)|=√[{2sin(ωπ)/ω}^2]=|2sin(ωπ)/ω|...
  47. jk22

    I Nomenclature : global or constant phase

    Is the phase factor in : ##e^{i\phi}\Psi(x)## a constant or a global phase factor called ?
  48. F

    Construct a circuit with single phase asynchronous machine in MATLAB

    Construct the circuit above using the block shown below. The torque was gradually increased in small steps until the load torque reached the rated torque. At each step the torque, current speed, voltage and power factor was measured and the result record in Table (1). Tn = Rated torque = 1 Nm...
  49. E

    S-wave phase shift for quantum mechanical scattering

    a.) The potential is a delta function, so ##V \left( r \right) = \frac {\hbar^2} {2\mu} \gamma \delta \left(r-a \right)##, therefore ##V \left( r \right) = \frac {\hbar^2} {2\mu} \gamma ## at ##r=a##, and ##V \left( r \right) = 0## otherwise. I've tried a few different approaches: 1.) In...
  50. M

    Engineering Superheterodyne Receiver with Phase Sensitive Detection Question

    Hi, Here is the figure 2 that the question referred to: How do I go about a question like this? I have made an attempt, but am not very confident with the method. Note, I have learned about/am aware of Fourier transforms. My attempt: So first I thought that the square wave will be at the...
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