What is Coupling: Definition and 385 Discussions

A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. In a more general context, a coupling can also be a mechanical device that serves to connect the ends of adjacent parts or objects. Couplings do not normally allow disconnection of shafts during operation, however there are torque-limiting couplings which can slip or disconnect when some torque limit is exceeded. Selection, installation and maintenance of couplings can lead to reduced maintenance time and maintenance cost.

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  1. M

    I Light coupling from optical fiber to glass?

    Hey everyone, I am trying to couple light from an optical fiber connected to an LED (365nm) into a small glass capillary which is pulled on one end and should be used as a small light source. The idea is to use the glass as a light guide. Has anyone tips for efficient incoupling of the light? I...
  2. A

    I Light coupling in fiber optic cables

    Hi Everyone! I have a photonics problem that I was wondering if anyone may be able to shed some light on (no pun intended). I work for a company that is designing a fiber optic emitter/detector as a part of one of our products and we've noticed something that would appear to defy physics...
  3. E

    I Antenna inductance calculation (RFID applications, inductive coupling)

    Inductance of antenna coils of different shapes can be estimated. Some examples are: A circular coil with single turn. N turn multilayer circular coil. Spiral coil. N turn squae loop coil. etc. For plannar design (spiral, rectangular, etc) I have used this reference (from pag. 9 onwards)...
  4. E

    Engineering Photonics / Fibre Optics - (Supermodes, PBGFs, Coupling)

    Hi, Looking for a good photonics / fibre optics textbook that covers the field, while also addressing said topics in the title. Thank you!
  5. R

    B Coupling Magnetic Fields: Does Orientation Change Strength?

    Magnetic fields coupling question. I had to make a small tool holder for my drill press, it hangs on side of press using N52 cylinder magnets. The holder is 4" long x 3/4 x 3/4" AL bar. With a spacing of 3", two 1/2" holes are bored to accept the 1/2 x 1/2 N52's, which will be epoxied in. I...
  6. Viona

    Spin-Orbit Coupling in Hydrogen Atom: Understanding the Calculation

    I was reading in the Book: Introduction to Quantum Mechanics by David J. Griffiths. In chapter Time-independent Perturbation Theory, Section: Spin -Orbit Coupling. I understood that the spin–orbit coupling in Hydrogen atom arises from the interaction between the electron’s spin magnetic moment...
  7. S

    Calculation of the lateral force of a trailer coupling

    Hello, i´ve got a problem with the calculation of the forces on the hitch of a vehicle and a trailer. I do need the lateral force on the hitch for the calculation of my single track model of the vehicle and trailer. I have a longitudinal model of the vehicle and the trailer. My input signal...
  8. DaniV

    RG flow of quadrupole coupling in 6+1 dimension electrostatic problem

    I tried to do a Euler Lagrange equation to our Lagrangian: $$\frac{S_\text{eff}}{T}=\int d^6x\left[(\nabla \phi)^2+(\nabla \sigma)^2+\lambda\sigma (\nabla \phi)^2\right]+\frac{S_{p.p}}{T}$$ and then I would like to solve the equation using perturbation theory when ##Q## or somehow...
  9. O

    Connect: Coupling Light from 2 LEDs into a Single Fiber

    Hi, I am looking for a suitable method to couple light from 2 LEDs into a fiber and then join both fibers, so that I only have one fiber at the end so that both wavelengths can be emitted from a single fiber. The first coupling step from LED into fiber seems to be more easy, I already heard...
  10. C

    What's different in a transformer core when coupling high & low power?

    This is one of those 'oh, I am not sure I know the answer' kind of thoughts. The strength of magnetic flux in a transformer core is a function of volts per turn, Faraday figured that one out. So, if I have a light load on a secondary (let's say it is pure ohmic for now, let's not confuse it)...
  11. T

    Calculating Fermi Coupling Constant (muon)

    I am trying to determine the Fermi Coupling Constant which is measured to be ##1.1663787 *10^{-5}\text{Ge}V^{-2}##. The formula for Fermi is ##\frac{G_F}{(\hbar c)^3}=\sqrt{\frac{\hbar}{\tau_\mu}\cdot\frac{192\pi^3}{(m_\mu c^2)^5}},## where ##m_\mu## is the mass of a muon which is ##\approx...
  12. H

    Inductive Current Coupling Between Two Coils

    In this case, we do not know any information about the current, right? Therefore, there is no matching answer.
  13. J

    Coupling of resonant modes in a 1D Photonic Crystal

    In 1D Photonic crystals, a defect can be introduced to create a defect/resonance mode and enable transmission. At first considerations, the thickness of the single defect layer determines the transmission frequency. Moreover, if it is a half-wavelength layer it will enable a resonance condition...
  14. J

    How to Measure PCB Impedance and Component Coupling?

    I am designing a PCB with multiple capacitors on it. I would like to measure the board impedance to compare it with results from Ansys Q3D. I can connect it to an impedance analyzer and easily get the impedance. I have recently thought about other meaningful measurements that I may be able to...
  15. tomdodd4598

    I QED - running of coupling (beta function)

    Hey there, I am a little confused about the way most textbooks and notes I've read find the beta function for QED. They find it by looking at how the photon propagator varies with momentum ##q##, in particular in the context of a ##2\rightarrow2## scattering process which is proportional to...
  16. tomdodd4598

    I Renormalisation scale and running of the φ^3 coupling constant

    I am still rather new to renormalising QFT, still using the cut-off scheme with counterterms, and have only looked at the ##\varphi^4## model to one loop order (in 4D). In that case, I can renormalise with a counterterm to the one-loop four-point 1PI diagram at a certain energy scale. I can...
  17. B

    Coupling Efficiency of LED to Fiber Optic Guide

    Most surface mount types of LED’s have a very nearly cosine distribution of light intensity. If we desire to inject light from an LED to the end of a cylindrical optical guide, what is the coupling efficiency as a function of distance (x) from the end of the guide? Assume that the LED is a...
  18. V

    Tricky coupling mechanism

    Hello everyone, I’m trying to build a coupling system between two cylinders to connect them coaxially and transfer pulling force from a string on the surface of cylinder one to a string inside cylinder two. Please have a look at the sketches attached. Both of the cylinders have an outer...
  19. E

    Fiber coupling efficiency and general questions regarding ZEMAX

    Hello everyone, a friend and I are working on our master project at a university chair. The project is to set up a free space optics communication (FSO) to, eventually, transmit data. For this we want to couple our laser beam into a fiber at the receiving end, which is then plugged into our...
  20. jorgerp24601

    Interaction picture of a phonon-electron coupling

    What I have tried to do is to separate the exponential of the unitary transformation operator to the interaction picture into three different Hilbert "subspaces" like: $$e^{i\frac{H_0}{\hbar}t}=e^{i\omega_m \hat{b}^+\hat{b}}\otimes e^{-i\hbar\nu|1><1|} \otimes e^{-i\frac{g}{\omega_m}|e><e|t}$$...
  21. tomdodd4598

    I Form of the Standard Model: Higgs-Fermion Yukawa Coupling

    Hey there, I was looking at the Higgs sector of the standard model, particularly its coupling to the fermions: ##\mathscr{L}_{ yukawa }=-\sum _{ a,b=1 }^{ 3 }{ \left( { Y }_{ ab }^{ u }{ \bar { Q } }_{ a }{ \hat { \varepsilon } }_{ 2 }{ H }^{ \dagger }{ u }_{ b }+{ Y }_{ ab }^{ d }{ \bar { Q }...
  22. tomdodd4598

    I Renormalisation and running of the φ^3 and other coupling constants

    Hey there! I am still rather new to renormalising QFT, still using the cut-off scheme with counterterms, and have only looked at the φ^4 model to one loop order. In that model, we renormalise with a counterterm to the one-loop four-point 1PI diagram at a certain energy scale. Do I simply, in...
  23. K

    I Input/output coupling of a cavity

    Hello! I am reading some stuff about building optical cavities, mainly a bow-tie cavity. Is there anything special about the input/output coupling in terms of design? I understand that these are the mirrors used to send the light inside the cavity and read some signal out of the cavity, but are...
  24. K

    I Vector addition in spin orbit coupling

    Hello! I am reading about spin-orbit coupling in Griffiths book, and at a point he shows an image (section 6.4.1) of the vectors L and S coupled together to give J (figure 6.10) and he says that L and S precess rapidly around J. I am not totally sure I understand this. I know that in the...
  25. G

    I Values of the coupling constants

    I am heavily confused about the coupling constants. I primarily refer to this source https://www.physicsmasterclasses.org/exercises/keyhole/en/projects/running_alphas.html , but other sources were not able to lift my confusion either. First, in the figure, the scales appear as quite failed. The...
  26. T

    Spin Orbit Coupling + Magnetic Field

    I am pretty confused where to even start with this question, which is not a good thing less than a week before the final :(. One thing in particular that I don't get is that I thought we were using the Clebsch-Gordon coefficients for ##\vert jm \rangle ## states, not for ##\vert J, J_z \rangle...
  27. Zala Jaydevsinh

    I About L-S interaction or spin orbit coupling

    I want to understand this topic but I can not understand very well so please suggest any reading for good conceptual grasp of this topic.
  28. T

    Finding the spin-orbit coupling constants of an Alkai transition?

    The set of quantum numbers for the 4p orbital is: 4, 1, {-1,1}, +-1/2 (n,l,m,s) The set of quantum numbers for the 4d orbital: 4,2,{-2,2},+-1/2 Hence we can calculate DeltaE for the 4p sub levels for j=1+- 1/2 And for the 4d sub levels as j=2+-1/2. Giving four total values for Delta E as: C_4p...
  29. H

    I Wave function when there is coupling between spin and position

    Why can't the general state, in the presence of coupling, take the form $$\psi_-(r)\chi_++\psi_+(r)\chi_-$$ where ##\psi_+(r)## and ##\psi_-(r)## are respectively the symmetric and anti-symmetric part of the wave function, and ##\chi_+## and ##\chi_-## are respectively the spinors representing...
  30. amjad-sh

    Band structure of a 2deg including spin orbit coupling

    first of all, I tried to obtain the energy eigenvalues of the Hamiltonian, by using the equation ##det(\hat H -\lambda \hat I)=0## ##\gamma V\delta(z)(\hat z \times \mathbf{p}) \cdot \sigma=\gamma V\delta(z)(p_x\hat j-p_y\hat i)\cdot(\sigma_x\hat i + \sigma _y \hat j)=\gamma...
  31. J

    I Can You Help Me Couple 3 Spin 1/2 Particles?

    Hello, I'm trying to couple 3 spin 1/2 particles. So far, I have been able to find the coefficient for the other states but I can't get the results for ##j_{12} = 0## to ##j_3=1/2##. Here is my attempt: 1) Using CG table...
  32. Danny Boy

    Quantum synchronization in a cavity

    I am currently studying quantum synchronization. I am reviewing a https://www.researchgate.net/publication/251232415_Quantum_Synchronization_of_Two_Ensembles_of_Atoms which describes quantum synchronization of two ensembles in a cavity. As such, I have a query regarding a cavity physics related...
  33. B

    A Vector sum schemes for LS coupling & jj coupling

    The difference between light and very heavy atoms reflects itself in these two schemes. My question is why one scheme for the vector sum is necessarily the right & suitable sum model for one case, and the 2nd scheme suits the 2nd case ? In other words, why & how the relative magnitude of the...
  34. Clara Chung

    I LS coupling and spin orbit interaction

    Why do you need a weak spin orbit interactions in individual electrons in order to use the LS coupling? From what I know, we are free to combined angular momentum whenever [L1, L2]=0 and this should be true on the orbital angular momentum (and spin) of the electrons because they are...
  35. H

    I Nuclear spin coupling in molecular (protium) hydrogen

    I'm not sure where this post belongs--here, or nuclear chemistry, quantum mechanics, NMR spectroscopy, etc. Moderator--please feel free to move it to a better location. I'm wondering if a container of liquid hydrogen subjected to a strong magnetic field would have both nuclei of each atom...
  36. cosmik debris

    I Frame Dragging Effect vs Spin Orbit Coupling in GR

    I believe that GR cannot describe exchange of classical intrinsic angular momentum and orbital angular momentum. The exchange of orbital and intrinsic angular momentum requires that the momentum tensor be non-symmetric during the exchange. GR cannot accommodate a non-symmetric momentum tensor...
  37. iVenky

    I Single-mode vs multi-mode fiber coupling

    Hi, Is coupling light from a laser into a single-mode fiber (transverse electric) more difficult than coupling to a multi-mode fiber? If so, is it due to the geometry? Does the laser light have multiple modes to begin with or it can be designed to have just one mode? Thanks
  38. L

    I What does coupling mean in physics?

    I am reading Carroll’s Spacetime and Geometry, and I have seen the word “coupled” used multiple times in seemingly different ways. I have gotten the sense that it means some sort of interaction between particles, but Carroll refers to coupling between matter fields and the curvature of...
  39. A

    I What is the significance of coupling in surface plasmons and plasmon polaritons?

    Hi, I have come across the word coupling a few times looking at surface plasmons and surface plasmon polaritons. I was wondering if anyone could give me a better understanding of what it means for something like a photon to couple to a plasmons to creating a plasmon polariton. From what I'm...
  40. M

    Spin-orbit coupling and the Zeemann effect

    Homework Statement Consider an electron in a hydrogen atom in the presence of a constant magnetic field ##B##, which we take to be parallel to the ##z##-axis. Without the magnetic field and ignoring the spin-orbit coupling, the eigenfunctions are labelled by ##\vert n, l, m, m_s \rangle##...
  41. R

    A Different gauge coupling constants

    Hi all, I am sure I am missing something really elementary, but I would really appreciate someone pointing it out to me. So, if we consider the situation in abelian gauge symmetry, say for fermion matter ψ, of charge q. The transformation law for ψ is, ψ→ψ' = e[- i q θ(x)] ψ. We then have to...
  42. M

    Determining Eigenvalues and Eigenvectors in a Coupled 2-Particle System

    Homework Statement Consider a 2-particle system where the two particles have angular momentum operators ##\vec{L}_1## and ##\vec{L}_2## respectively. The Hamiltonian is given by $$H = \mu\vec{B}\cdot (\vec{L}_1+\vec{L}_2)+\gamma \vec{L}_1\cdot \vec{L}_2.$$ Determine explicitly the eigenvalues...
  43. Edge5

    I Does spin orbit coupling cause the split in the energy level of the electron?

    Hi, As far as I understand spin orbit coupling is the interaction between proton of atom and electron. Proton's motion(from the frame of electron) around electron creates magnetic field. Hence electron experiences magnetic field. Does this magnetic field produces a Zeeman effect which cause...
  44. C

    Unidirectional magnetic coupling

    Couldn't see this news posted elsewhere. Sound too good to be true?... Quote: "We have created a device that behaves like a diode for magnetic fields." https://phys.org/news/2018-11-defy-19th-century-law-physics.html I haven't read their paper yet.
  45. ohwilleke

    I Is there new LHC data on coupling constant running?

    Question Has the LHC released any papers or reports on the observed running of any of the three Standard Model coupling constants with energy scale from either Run-1 or Run-2 data (or both data sets)? Last time I looked I couldn't find any data As of January 2014, I had not locate any papers...
  46. H

    A Is there a topological insulator without Spin Orbit Coupling (SOC)?

    There are some famous materials is determined as TI induced by SOC, like graphene and so on. But from some formula, for instance, Kane-Fu formula, they just need parities to get Z2 number. So I wonder if there is a known TI with weak soc.
  47. thariya

    I The sign of coupling Hamiltonian in CQED

    Hi all, I've always regarded the coupling Hamiltonian for a bosonic cavity mode coupled to a two-level fermionic gain medium chromophore to be of the form, $$H_{coupling}=\hbar g(\sigma_{10}+\sigma_{01})(b+b^{\dagger})$$, where ##b## and ##b^{\dagger}## and annihilation and creation operators...
  48. C

    I Pauli principle and coupling term in Weizsäcker formula

    Consider the pairing term in Weizsäcker formula. Here https://en.wikipedia.org/wiki/Semi-empirical_mass_formula#Pairing_term it is claimed that: I don't understand how Pauli exclusion principle should be the cause of this. This term comes from spin-spin interaction (or "coupling"), but I do not...
  49. Phi6er

    A What is the value of the pion-nucleon coupling constant?

    Links for context: 1. https://en.wikipedia.org/wiki/Yukawa_potential 2. https://en.wikipedia.org/wiki/Yukawa_interaction#Classical_potential I'm working on my BSc right now and I'm solving the energies of 2 nucleon systems (so basically just deuteron) by treating them as non-relativistic two...