What is Pair: Definition and 399 Discussions

An au pair (; plural: au pairs) is a helper from a foreign country working for, and living as part of, a host family. Typically, au pairs take on a share of the family's responsibility for childcare, and receive a monetary allowance for personal use. Au pair arrangements are often subject to government restrictions which specify an age range usually from 18 - 26 years of age, both male (BroPair) and female AuPairs are avaliable. The au pair program is considered a form of cultural exchange that gives the family and the au pairs a chance to experience and learn new cultures.
Arrangements differ between Europe, where the concept originated, and North America. In Europe, au pairs are only supposed to work part-time, and they often also study part-time, generally focusing on the language of the host country. In the United States, they may provide full-time childcare. In 1969, the European Agreement on Au Pair Placement was signed, and it came into force in 1971. Au pair companies in the United States have significant non-refundable fees once the au pair arrives in the country. The contract does not guarantee childcare, despite many families' reliance on the program.
Unlike many other types of domestic assistants, the au pair is considered a part of the host family and not merely an employee. In some countries the au pair wears a uniform, but more commonly the au pair only follows the host family's dress code and wears attire appropriate for the work description, typically including a protective apron.

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  1. M

    How successful is pair production?

    when a photon interacts with a nucleus, a positron and an electron are created, provided the photo has enough energy. But what is the probabilty of this occurring? If i fire 100 photons at a nucleus, how many electron-positron pairs will i create? Also, has anyone ever succeeded in...
  2. C

    Friction force pair between two stacked blocks on a frictionless surface

    Good afternoon! 1. The Setup One block of Mass M2 is resting on top of a frictionless surface. Another block, M1, is resting on top of the of the first block. There does exist a coefficient between these two blocks, μ. 2. What happens to the bottom block when a force less than μN is...
  3. C

    Example of encryption key pair algorithm?

    Greetings, I know that when encrypting something with the public key of a key pair, the encrypted data can only be decrypted with the private key of the pair. And it can not be decrypted with the public key that was just used. I do not understand how it is possible to perform a mathematical...
  4. V

    Electron-hole pair damping of vibration, thin film resistivity

    Hello, I'm reading something about adsorbate induced surface resistivity changes in thin metal films and there is often mentioning of electron-hole pair damping, as for example: "electron-hole pair damping of the parallel(to the surface of thin film) frustrated vibration of the...
  5. S

    Regarding pair production and annihilation

    Hi, i have a few questions about these two processes. Now, I am only 16 years old, in my last year of school, so I am not so familiar with physics, if you could put terms simple enough for an average 16 year old to understand, i'd much appreciate it :) my question is: If e‾ + e+ → γ + γ and γ →...
  6. M

    Reporting the results of a wilcoxon matched pair test

    I've done 3 wilcoxon matched pair tests and was wondering if someone could give me some advise on the most logical / correct way to report the results. test 1: pre post 1.98 1.56 1.09 2.49 2.18 2.94 1.13 1.29 1.23 2.38 result: Z = -1.438, two tail p = 0.138 So I was...
  7. S

    Solving Gamma-Ray Photon Energy: 285 keV Electron-Positron Pair

    Homework Statement A gamma-ray photon produces an electron-positron pair, each with a kinetic energy of 285 keV. What was the energy of the photon? Homework Equations E = mc2 hf = KEmax +W0 The Attempt at a Solution E = 2(9.11*10^-31 kg)(3.0*10^8 m/s)^2 = 1.64*10^-13 J = 1.02 MeV This...
  8. B

    Electron positron pair density in charge renormalization

    I am trying to find out the density of electron positron pairs around a bare electron charge. In most texts, I saw that the treatment relates to the observed charge vs. the bare charge. I wanted to know if there is a formula that describes the density of electron positron pairs that surround...
  9. J

    Probability of being dealt one pair from a 52-card deck

    Homework Statement Since no one wants to answer my heat conductor problem (*hint hint*), here's a more interesting one. If it is assumed that all (52 choose 5) poker hands are equally likely, what is the probability of being deal one pair? (This occurs when the cards have denominations a, a...
  10. Q

    Constructing a pair of sequences such that

    Homework Statement The question asks me to construct a pair of sequences {a_n} from n=1 to inf and {b_n} from n=1 to inf such that a_n and b_n are both greater than or equal to zero for all integers n, both sequences are decreasing, and both series of these sequences diverge, but also such...
  11. Z

    Circle becomes a pair of parallel lines

    Does anyone know if there is a non-Euclidean geometry(or something like that) where the circle becomes a line or a pair of parallel lines? ...or even where the circle becomes a set of parallel lines? ...i'm doing some work in Guitar Theory and this situation appears... Thanks The...
  12. Tibriel

    Can We Pair Composition of Velocities with an Expanding Universe?

    Hi All, I get that one object can't travel faster than light with respect to another object because of SR and length and time contraction. What I don't get is how this meshes up with expanding universe. If the space between 2 objects is expanding then wouldn't two objects be accelerating...
  13. Z

    Neutron-Antineutron pair production

    I think its true that you cannot use a bubble chamber to identify the pair production of a neutron-antineutron pair, but how (maybe if) is that studied? Is that reaction common in a proton collider?
  14. V

    How much energy is required to produce the electron-positron pair

    Homework Statement How much energy is required to produce the electron-positron pair in the filed of nucleus (Z=20) if electron is captured to the ground 1s state of the system. The Attempt at a Solution I can calculate the energy of the captured electron from E = - εZ2/(2n2) where...
  15. K

    Photon-photon collision - electron-anti electron pair creation

    Homework Statement two photons collide head-on and create an electron and an anti electron. The energy of photon 1 is given, but not for photon 2. Find the velocity β of the systems rest frame (where the total momentum is zero.) Homework Equations β=v/c γ=1/√1-β^2) β=pc/E The...
  16. U

    Angular momentum of pair of particles

    Homework Statement There are two noninteracting, spinless, distinguishable particles an isotropic oscillator potential. One particle is in the state |1\rangle =\frac{1}{\sqrt{2}}(|1,1,-1\rangle + |1,1,0\rangle ) and the other is in the state |2\rangle = \frac{1}{\sqrt{2}}(|1,1,0\rangle -...
  17. Z

    Pair of moving charged particles

    A positron and an electron are simultaneously fired from paralle particle accelerators a distance d apart, with equal velocity v. One calculation says that each one will, being a moving charged particle, induce a magnetic field B=\frac{\mu_0 q v}{4\pi d^2} and since the other is moving in...
  18. N

    How reasonable to assume a prime gap of at least 10 before a pair of Twin Primes?

    If we assume that the Twin Prime Conjecture is true (and thus there are infinite number of primes that are 2 apart), how reasonable is it to assume that there will be an infinite number of Twin Primes that are preceded by a prime that is at least 10 lower than the first of the Twin Primes? (I...
  19. I

    Exploring Entanglement in Quantum Collisions

    Hi, I was reading some novice stuff about quantum entanglement and I was wondering if entanglement occurs in either of these two scenarios: 1. electron and positron entangled as a result of being created by a photon passing over a heavy nucleus 2. two free electrons entangled with...
  20. C

    Ion Pair Reagents: Partitioning into Non-Polar Phases

    I'm reading about ion chromatography at the moment and read that one method is to use an ion-pair reagent which pairs with the ionic analyte, forming a neutral compound which can then partition into the non polar stationary phase. If an anionic analyte pairs with a cationic ion-pair reagent to...
  21. S

    Question about momentum of pair production

    I am learing the particle physics bit of my physics course and don't understand how momentum is conserved when a photon produces an electron/positron pair. In the bubble chamber chamber picture here...
  22. A

    Magdeburg hemispheres(action and reaction pair)

    My friend said that two horses pull the Magdeburg hemispheres with same force is as same as a horse pulls the Magdeburg hemispheres which is tell on a tree(I may forget the details about the assumption) Why? Another Q. about action and reaction i don't know why the reading isn't 2Mg,but is...
  23. J

    Understanding the Singlet State of Cooper Pairs in Conventional Superconductors

    Can anyone help me, I am some what unclear on the reason why "conventional" superconductors have cooper pairs only in the singlet state. Is it something to do with the expectation values given for the separate states calculated from their spatial and spin wave functions? For example does the...
  24. jegues

    Min. Common Mode Input MOS Diff Pair with Current Mirror

    Homework Statement See first figure attached for problem statement. Homework Equations The Attempt at a Solution I've solved everything in this circuit, I just have some confusion about solving V_{CMmin} when I have a current mirror acting as my current source connected to the...
  25. jegues

    BJT Differential Pair Amplifier Design

    Homework Statement See first figure attached. Homework Equations The Attempt at a Solution See 2nd figure attached for my work so far at attempting the design. The last figure is what my textbook gives as the small signal analysis of a BJT differential amplifier with emitter...
  26. andrewkirk

    How is momentum conserved when a particle/antiparticle pair is created?

    My understanding is that when a particle-antiparticle pair is created, they will have opposite spins and momenta. So the net momentum will be zero. But doesn't the momentum depend on the frame of reference? Say the particles both have mass m and velocities +v and -v. Then the net momentum is...
  27. F

    Prediction of pair production via WIMP decay? (Layman question)

    Hello, This may sound silly, don't be afraid to let me know just how silly though! I've read that predictions are made using the standard model. I do not know the details of this process. I understand pair production occurs randomly in a vacuum, but I wondered if there was an underlying...
  28. F

    Why Does Tighter Twisting in Twisted Pair Cable Increase Transmission Rate?

    Why is that in twisted pair cable, the tighter the twisting, the higher the supported transmission rate? Thankyou
  29. B

    Why are some nuclei more resistant to pair production?

    I've gotten interested in this pair production stuff, and I'm wondering: Why is it that some nuclei can absorb more energy than the energy needed for pair production, while other nuclei result with the incoming energy creating pair production? Is it because heavier nuclei can distribute the...
  30. B

    Electron Capture in Pair Production

    During electron-positron pair production, does electron capture always happen? Gracias
  31. J

    1 MV electrode limited by vacuum pair production?

    Hi, Someone told me that a potential of 10^6 volts is not stable because it would cause spontaneous electron-positron creation from the vacuum. Is this true? I thought one could reach higher potentials than 1000000 volts.
  32. L

    Pair Production and Mass Energy Equivalence

    Hello, In a previous discussion of Pair production I was shocked by what I heard and I have some questions from the general explanation of the subject. So you can make fermions out of bosons? You can make rest mass out of energy? Does this mean that not just relativistic mass, but...
  33. D

    Pair production: Has it been observed experimentally?

    I was reading about electron-positron annihilation and I got to the part where it says that this is a reversible process, meaning that an electron and a positron could be created from photons. About this reverse process the article says "In nuclear physics, this occurs when a high-energy photon...
  34. A

    Delay of virtual particle pair annihilation

    My grasp of physics is limited, however, I am an engineer, thus I am asking for other's assistance in understanding how to delay the annihilation of a virtual particle pair. Most literature I've read, indicates a virtual particle pair is "real" if only briefly. QUESTION: How long is...
  35. D

    Stuck on inverse fourier transform pair

    I have been trying to solve the inverse Fourier transform: \int_{-\infty}^{\infty}\left[e^{-j2\pi ft_0}e^{j\theta}\right]e^{j2\pi ft}df I know that the Fourier transform pair says e^{-j2\pi ft_0}e^{j\theta} \leftrightarrow \delta(t-t_0) but the extra phase term e^{j\theta} makes...
  36. J

    Vector XY: Possible Coordinates for X & Y

    The ordered pair <-3,2> represents vector XY. Give possible coordinates for X and Y? Homework Equations The Attempt at a Solution I really have no clue how to even attempt this problem since I haven't ever been given such a problem. Could I get any help please?
  37. L

    Darlington Pair/ Darlington Transistor

    Hey guys, I just found out about these darlington transistors, and I read that the purpose of these transistors are to "amplify WEAK signals". After taking a look at the circuit diagram for the darlington pairs, it seems to me that it is just 2 npn bjts with one of the bjt's emitter...
  38. S

    Possible Particle Pairs in Gravitational Pair Production: A Speculative Inquiry

    Although there is no experimental evidence or QG theory, it is not unreasonable that very strong gravitational fields or very high energy gravitons would cause pair production of real particles. In view of the spin-2 nature of gravity, what might these pairs be? One electron, one positron and...
  39. M

    Pair production in boson-boson collision

    Homework Statement I'm given this interaction Lagrangian: L_I (x) = -g \overline{\psi}(x) \psi (x) \phi (x) where g is the coupling constant, \psi is an electron and \phi is a neutral scalar field. I have to calculate the amplitude for process \psi + \psi \rightarrow e^- + e^+ that...
  40. 1

    Understanding DNA Base Pair Alterations: C-G to U-G Mutation and Its Effects

    If in a given DNA molecule a C-G base pair is changed to a U-G base pair the following mutational change in the DNA will result a. C-G to G-C b. C-G to T-A c. C-G to A-T d. C-G to A-U Can someone elaborate on this for me?
  41. V

    SR: Gamma rays creating election-positron pair

    Homework Statement This is a special relativity question: Two gamma rays of identical energies E collide with an angle \theta between their velocities. Show that positron-electron pair creation is impossible in the limiting case \theta=0. Find the minimum \theta value for p-e creation to...
  42. C

    One issue about Kuratowski definition of an ordered pair.

    Hello. I have understood the Kuratowski definition of the ordered pair and appreciate it's usefulness but have a nagging difficulty about it. Consider an ordered pair which is (a,a). according to Kuratowski definition it is defined as {{a},{a,a}} . Now consider an ordered triplet (a,a,a) it...
  43. F

    Building a Pair of Helmholtz Coils - Questions & Tips

    Hi, I'm building a pair of helmholtz coils to do a variety of magnetism-related experiments. I've borrowed an old Avo Douglas coil winder and plan to do a couple of thousand turns on two sections of 50mm or 60mm diameter pipe. Some nylon threaded rod will pass through the middle of each coil...
  44. E

    Proton/Antiproton collision to produce top/anti-top quark pair:

    Consider a proton and antiproton collision. The goal is to produce a top quark and anti-top quark pair. If a top quark has a mass of 174 GeV/c2, how much energy is required in the center of mass frame to produce the combination? I'm somewhat utterly stumped. Obviously, the problem deals with...
  45. J

    Is it possible to create a Positron - Electron cooper pair?

    Hello, Would it be possible for an electron and positron to form a cooper pair if an electron is brought into the neighborhood of the positron who is anchored in a penning trap (or in some other fashion)? If normal cooper pairs form by using the the attractive force of the lattice...
  46. P

    Question about a Pair of Forces - Newton's Third Law

    I was looking at a picture (attachment) in a physics website and the following doubt arose: I previously thought that the weight of the block (gravitational pull of the Earth on the block) caused a reaction force of the table, but now, from what I understand and, please correct me if I am...
  47. M

    Mutual Inductance for a Pair of Coils

    Homework Statement http://nplq1.phyast.pitt.edu/res/csm/csmphyslib/type66_inductance/PairOfCoils.jpg Coil A is a large 400 turn circular coil of radius 91.0 cm. Circular coil B has 160 turns, a radius of 2.0 cm and is located L = 92.0 cm from coil A along the same axis. The planes of the two...
  48. B

    Pair production minimal wavelength

    Homework Statement what is the minimal wavelength of electromagnetic radiation to pair-produce an electron-positron pair? Homework Equations ~ = wavelength hc/~ = 2MeC^2 + K The Attempt at a Solution hc/~ = 2MeC^2 = 2(9.11x10^-31)(3x10^8)^2 ~ = 8.24x10^-11m is tis correct?
  49. R

    Can someone explain how spin allows elctrons to pair

    I never understood this how do 2 like charges stay together, the electro is it like eddy currents or something
  50. F

    Potential Energy of a pair of charges question

    Homework Statement Two point charges of magnitude 4.79 nC and −1.11 nC are separated by 39.4 cm. The acceleration of gravity is 9.8 m/s^2 The Coulomb constant is 8.98755×10^9 N · m^2 /C^2. What is the potential energy of the pair of charges? Answer in units of V. Homework Equations...
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