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. A

    Coupling of spin to an electric field

    Hi PF members. I have got a little worry I am familiar with the Zeeman term that always appears in the Hamiltonian of a spin chain representing the influence of an external magnetic field. I don't know if there is a similar term if the spin was rather in he presence of an electric field ( I...
  2. L

    Gravitational Coupling Constant: Answers & Derivation

    Perhaps I'm confusing two different things but I've read online (http://en.wikipedia.org/wiki/Gravitational_coupling_constant) that the gravitational coupling constant is dimensionless and proportional to Newton's constant G. However, I have also read that the gravitational coupling constant...
  3. D

    Why is j2 = 1/2 and not -1/2 in the coupled angular momenta equation?

    Hello, I have a small question about coupling of angular momenta. When you have J² with J = J1 + J2; you change it to the form (dropping the hbar in all equations): j² = j1² + j2² + j1-j2+ + j1+j2- + 2j1zj2z now it's these j1-j2+ I have a problem with. Let's say you use it on |1/2;-1/2>...
  4. I

    Can Magnetic Fields Couple and Affect Each Other?

    Can a weak alternating magnetic field from one coil have an effect on another coil that has a stronger alternating magnetic field? I ask this because I want to know if magnetic fields follow the same principal as coupling two different voltages together.
  5. L

    Coupling Capacitors: Necessity for Signal Injection

    Is adding a coupling capacitor to the generator necessary when injecting a signal for troubleshooting.
  6. JK423

    Coupling only to the center of mass degrees of freedom?

    I am interested in the following scenario. Suppose that you have a composite system, e.g. ion, atom or whatever you want. This system will have internal degrees of freedom (d.o.f.), i.e. relative positions and momenta, and also center of mass d.o.f..What i am looking for is to find an...
  7. bibo_dvd

    A problem in Coupling Transformers

    Hello Guys ! While Studing coupling transformers i found this problem i tried to solve it but i don't know if my solving is right or no ! so tell me :) The problem : My solve is : V(out)=nV(in) V(out)= 2 * 312 = 624 v PIV = V(out) = 624 v and if the diode is turned...
  8. S

    Ac coupling and offset voltage in amplifier

    Hey all, Just a question concerning the image I have provided. If I have an offset of 0.1 mV at the non inverting input, how exactly does coupling take effect in this set up? If I input an ac signal, it will pass through the cap, but will the op-amp not still experience the offset voltage?
  9. J

    Elementary particles pre-Higgs coupling

    My question relates to the very origin of the elementary particles. I understand that the Higgs field breaks the mass symmetry of the elementary particles and that the Higgs field-based mass value for each particle is dependent upon the strength of interaction between each elementary particle...
  10. K

    Coupling constants, units and measurements

    I was thinking about units and started wondering about coupling constants. In unit-independent form, the fine-structure constant is defined as \alpha = \frac{k_e e^2}{\hbar c} I don't have a deep knowledge of particle physics but I know that there are weak and strong charges which enter the...
  11. R

    Why aren't the wheels on my car/bike connected?

    In this problem, the left wheel is connected via a slot and consequently I don't see how the wheel would undergo any motion at all until such time that the rod moves all the way to the edge of the slot because before this time, the joint can just undergo rotational motion to compensate for the...
  12. P

    SU(3) and dark U(1) coupling to dark matter

    Is anyone familiar with a $$ SU\left( 3 \right) \otimes U \left( 1 \right){}_d$$ or $$SU \left( 3 \right) \otimes SU\left( 2 \right) \otimes U \left( 1 \right)_d $$ model? Kind of what I'm currently interesting in working with, but I don't have access to anything other than the arxiv.cheers.
  13. A

    Running Coupling: QF Theory, Asymptotic Freedom & RG Law

    First a little intro. The process of renormalization introduces in a QF theory a renormalization scale μ. Physical quantities do not depend on it, as a change of μ comes along with the change of the coupling g(μ) according to the RG law. But why then the physics can change so drastically...
  14. D

    Understand Coupling Coefficient k Between Two Wire Coils

    Can someone please look at this and tell me what's going on here? I'm trying to understand the coupling coefficient k between two wire coils some d distance apart. I found this but I am lost! Please help!
  15. A

    Average power to ZL coupling coefficent and mutual inductance M?

    Homework Statement In the circuit of Figure 4-2, let N1=2000 turns, N2=1000 turns, R=0, Z1=0 and ZL=300+j400 (Ω). If V1(max)=1500 V, what is the average power delivered to ZL? A. 5400 W B. 2700 W C. 337.5 W D. 675 WHomework Equations V2=(N2/N1)V1The Attempt at a Solution since turn factor is...
  16. A

    What is V(K) of inductor given coupling coefficent?

    Homework Statement Homework Equations k=1 inductor(left)=400j inductor(right)=1600j The Attempt at a Solution how to do this! help me. my caluclator can't solve 3 rectangular form mesh currents equations so i cannot solve for individual currents for all 3 loops! i just guessed...
  17. K

    How is the effective Lagrangian for the Graviton coupling to matter derived?

    Could someone point to me where they derive the follow effective Lagrangian for the Graviton coupling to matter L = \frac{1}{M_{pl{}}}h^{\mu \nu}T_{\mu \nu}
  18. C

    Callan-Symanzik equation and the running coupling.

    In these notes(at page 71) Bilal put some emphasis on that the running coupling on a certain scale ##\mu## is defined in such a way that the logarithms in the expansions of the vertex function small. Or equivalently it is defined such that running coupling on the scale in question is always a...
  19. C

    Definition of effective QED coupling.

    (PS: this post was also posted at the quantum mechanics/field theory forum, but I did not get any replies there) Often when one speaks about the effective QED coupling one defines it as $$e = \frac{Z_2 Z_3^{1/2}}{Z_1} e_0 \ \ \ \ (*)$$ when ##Z_1 = Z_2## by the Ward identity this...
  20. C

    QED running coupling definition.

    Often when one speaks about the effective QED coupling one defines it as $$e = \frac{Z_2 Z_3^{1/2}}{Z_1} e_0 \ \ \ \ (*)$$ when ##Z_1 = Z_2## by the Ward identity this turns out to be ##Z_3^{1/2}e_0## and some authors just define the coupling to be this right away. So why do some make a...
  21. C

    Conventional renormalization to order in the coupling or loops?

    In conventional renormalization one is first supposed to compute a scattering amplitude of interest in terms of bare quantities ##\lambda_0, m_0...##, then compute these bare quantities in terms of physical quantities, i.e. ##m(m_0,\lambda_0,...), \lambda(m_0, \lambda_0,...)## and substitute...
  22. Fightfish

    Spin-Orbit Coupling: A Bohr-Orbital Model?

    In most introductory discussions on spin-orbit coupling in the hydrogen atom that I've come across, the analysis is often performed on a Bohr-orbital model. The electron is treated as orbiting the nucleus in a circular orbit. They then transform to the frame of the electron, and then assert that...
  23. A

    Serial Communcation Conversion / Noise Coupling

    I have a two way radio that I'm trying to control remotely through 120 ft of 25 conductor cable at 22 gauge. The radio uses serial communication between the actual transmitter and control head unit. After I wired the pin's up accordingly, there is to much noise pickup through the cable and it...
  24. S

    EFT & change or coupling constants

    I understand that by uncertainty relations, it is possible use an EFT to a range of energy, forgotten the interactions for bigger energies. But, ¿ why change the values of coupling costants? And, ¿ how can tell that there is no intermediate particle that happens with low probability in...
  25. C

    Measuring effective (renormalized) coupling constants

    How is the effective (or renormalized) coupling constant at a given momentum scale scale measured? If one wants a definition which makes it easy to measure I would think it would be natural to use the LSZ formula which connects the measurable Feynman amplitude with the amputated greens...
  26. Y

    Tensor coupling and 6j/9j symbols

    Hi everyone, I'm reading about the Wigner-Eckhart Theorem and the coupling of spherical tensor operators in Sakurai's Advanced Quantum Mechanics. I then came across this http://cc.oulu.fi/~tf/tiedostot/pub/kvmIII/english/2004/09_tensop.pdf, which states these concepts in Theorem 1 and 3...
  27. J

    Weak force coupling to left-handed particles

    The W couples to left-handed particles only. What about the Z? Is it the same? Thanks in advance!
  28. K

    Derivation of Spin-orbit Coupling

    I was reading Griffiths's book on quantum mechanics. In chapter 6, he tried to derive the spin-orbit coupling using a classical approach. H=-\vec{\mu}\cdot \vec{B} 1. Finding the relation between \vec{μ} and \vec{S} He consider a spinning charged ring with mass m, radius r, total charge...
  29. W

    Coupling Gel in Ultrasound Imaging - Density?

    Dear all, I have a quick question about the use of coupling gel in ultrasound imaging (of an unborn child as an example). As I understand it, if coupling gel were not used, as the ultrasound waves left the transducer, they would undergo a massive amount of reflection at the air-skin (body...
  30. P

    Hg：L-S coupling or j-j coupling?

    When testing Bohr's theory by Franck-Hertz experiment, we have electrons colliding with Hg atoms. a Hg atom will absorb electron's energy when this energy can make it jumping to a higher energy level. I wonder Hg is more like L-S coupling or j-j coupling, for I want to measure its higher...
  31. atyy

    Minimal Coupling Needed for Covariant Energy Conservation?

    Thanks. I started a new thread, because I've seen what seemed to me a contradictory claim in Carroll's GR notes (Eq 5.38) - he says diff invariance is enough to get covariant energy conservation. I've never understood whether Carroll's claims and the ones in these papers are really...
  32. T

    Near end coupling coeffecient problems

    I have been given a formula Kne = \frac{1}{4Td}(CZo+\frac{L}{Zo}) I've been given C as 10pF and L as 80nH and Zo as 70.7. I have calculated Td from the formula propogation velocity = 1/\sqrt{LC} and the line capacitance and inductance are 400nH and 80pF and then divided this into 0.05m the line...
  33. M

    Superradiance and the assumption of indiscernable atom field coupling

    Hi, If we have a system on N atoms confined to dimensions much smaller than the wavelength corresponding to the transition, we see superradiant decay. Now, in these cases, we always assume that the excitation is symmetrically or antisymmetrically distributed. For instance, if we have one...
  34. C

    LS coupling and calculating the total angular momentum

    hi all, these days i m going through Arther Beiser's modern physics book where i read about the total angular momentum in many electron atoms..now i could understand the LS coupling and spin orbit effect how they combine to form total angular momentum but if i m given the magnitude of L=2...
  35. H

    Is coupling G actually a constant of nature or it can vary?

    is coupling G (graviational coupling) actually a constant of nature or it can vary?
  36. A

    Spin orbit coupling and hydrogen problem

    I don't know if you are familiar with it, but in pertubationt theory for hydrogen it is handy to look for eigenstates of J = L + S since this commutes with the hamiltonian (L and S are not separately conserved). My book then says that the good quantum numbers are: n,l, j, mj I must admit I'm...
  37. A

    Understanding Spin Orbit Coupling: Deriving the Hamiltonian

    I have a question about how my book derives a formula. It starts with: We have an electron free too move on a cylinder and from the cylinder there is an electric field pointing radially outwards. Now for an electron moving in an electric field it sees local magnetic field given by: B =...
  38. 1

    Inductive coupling and EM Power Chargers

    Recently saw the invention on PhysOrg for a device the recharges a AA battery using "waste" EM radiation from the ambient environment. In the photos, the author was placing an array of them near a power sub-station. This brings up two questions: 1) Does this create an inductive load on the...
  39. H

    Spin-orbit coupling for s-orbital states

    In standard QM textbooks, when calculating the spin-orbit interaction term as a relativistic perturbation for hydrogenic atoms, it is said that the term gives 0 contribution for the s-orbitals (l = 0). This is apparently because the term has the form of S*L and L=0 for the s-orbitals. However...
  40. T

    Construction of coupling and maximal coupling (probability theory)

    Homework Statement Let U, V be random variables on [0,+\infty) with probability density functions f_U(x)=2e^{-2x} and f_V(x)=e^{-x}. 1. Give a coupling of U and V under which \{U\geq V\} with probability 1. 2. Give a maximal coupling of U and V. Homework Equations Cumulative distribution...
  41. D

    AC/Capacitive Coupling: Voltage Ranges & Average Output Signal

    In the attached picture R1 and R2 are assumed to be equal so that they form a voltage divider. Without any signal into C1, the voltage of the base of the NPN BJT is (1/2)Vcc. If a square wave with Vhigh = (1/2)Vcc and Vlow = 0V, and a duty cycle of 80% is fed into C1, what would be the...
  42. alemsalem

    Where does the magnetic field in spin-orbit coupling come from?

    the proton is stationary, and we're assuming there is no magnetic field in the rest frame of the proton. I know if we move to the rest frame of the electron there will be a magnetic field. but shouldn't we be able to analyze it in the rest frame of the proton?
  43. C

    Explain Spin-Orbit Coupling for d Orbital l=2

    Can someone explain to me how to get the states for an electron in a given orbital (lets say... d orbital l=2) and how to calculate the Clebsch-Gordan Coefficients for this system? I tried reading my book but I'd like someone to explain in simpler language.
  44. R

    Is the Fermi Coupling Constant Calculation from Oxygen Beta Decay Accurate?

    i'm reading through halzen and martin's chapter 12 on the weak interaction which they calculate the fermi coupling constant form oxygen beta decay using \Gamma = 1/\tau = G^2E_0^5/30\pi^3 with E_0 = 1.81MeV and \tau log 2 = 71 sec. they get G\approx 10^{-5}/m^2_N. where m_N is the nucleon mass...
  45. U

    Atomic Physics - L-S and J-J coupling

    Homework Statement 2 valence electron atom. n, l, s are : 5, 0, 1/2 n, l, s are : 4, 1, 1/2 Assume LS coupling and find the possible values of L and then J. Homework Equations None The Attempt at a Solution I am not really sure. All I know is there's something like, take...
  46. F

    Spin Orbit Coupling leading to topological insulator behaviour

    Hi I am studying how the spin orbit interaction in certain materials can lead to topological insulator effects and realize it has something to do with the effects of the SOC on the band structure of the material (Bi2Se3), possibly due to the inversion of the valence and conduction band but I...
  47. E

    Conduction band splitting under spin/orbit coupling

    Hi, Does anyone have an intuitive idea of why it is always the valence bands split under spin/orbit coupling, but not conduction band? (or a much smaller splitting than valence band) I know through tight-binding calculations, if I plug in numbers correctly, conduction bands always have...
  48. R

    Linear transformer and coupling coefficient

    Homework Statement The coupoing coefficient of K' of a linear transformer is adjusted so that Zab is purely reissitive when ω= 25k rad/s. What is Zab? Homework Equations Not sure The Attempt at a Solution I'm not sure how to being this problem. For one, from what I've been...
  49. N

    What is the difference between inductive coupling and magnetic coupling?

    Hi I was learning about wireless power transfer. It is stated that inductive coupling can be use to transfer large amount of power. But efficiency is poor if distance is large. The reccomended solution for this problem is energy transfer through magnetic coupling. May I know what is the...
  50. T

    F(R) gravity with non-minimal carvature-matter coupling

    hi guys , can someone help me with references about this case ? thx
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