# Tag Info

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In answer to the main question, matter does, in fact, "pass" through other matter. Starting from the macro scale (stars , galaxies), down to the micro scale (atoms), it happens all the time. The "free" movement of matter starts to get impeded, as the atoms start making latices (solids, crystals). But even at this scale, as Rutherford demonstrated, matter ...

4

What are phonons? Phonons aren't particles like electrons or protons are, phonons are quasi particles, these type of particles are just used to describe excitations of a field: in phonons case, phonons are used to describe elementary lattice vibrations which have certain frequency. Electron-Phonon Interaction: Basically Cooper pairs are just pairs of ...

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it depends on the situation, if 1)the copper is in a circuit as a conductor or 2)you are really separating the electrons from the whole solid or making them bounded to the atoms(by adding some impurities for example) or 3) some other processes takes place. if you mean the first case: the answer is that as a conductor in a circuit the separated electrons are ...

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This analogy might aid some insight: Think of cell in the circuit as a water pump that is constantly pumping water from a tank at the ground to the tank at any higher height, (say first floor). Now, put a tap on the tank at first floor and let the water flow continuously out of there into the tank at the ground, in between you may use use the flowing water ...

3

In order for a current to flow steadily, you have to connect the conductor (copper in your case) to positive and negative poles of a battery. Then the electrons go from the copper to the positive pole of the battery - but - they are replaced by the electrons which come from the negative pole of the battery. Thus, the free electrons in copper are only needed ...

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The number of electrons in a chunk of metal is very large, however, one can only remove (or add) relatively few, before the metal becomes so highly charged, that its potential exceeds the limits of any practical isolation. If we could remove all the electrons in the conduction band, the metal would probably disintegrate.

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The "new" electrons - i dont know what you mean by that Why does copper never run out of electrons - In Metallic bonds , the metal atoms give away the outermost shell(free) electron and become positive ions and the electrons join the "electron cloud" . When you apply an electric field the electrons are responsible for the conductivity of the material. The ...

1

Your instincts are spot on. While it’s still common for people to refer to electricity and magnetism as different phenomena, they’ve been formally unified since Maxwell’s 1873 paper on the subject, and they were known to be intimately related for decades before that through Faraday’s work among others. “Electromagnetism” covers all of the behavior of ...

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All magnetism originates from movement of charge not movement of current as you mention. Whether it is arising from flow of charge positive or negative ( current ). Spin alignment's as in a ferromagnetic. Spin is again charge in motion that is rotation.

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Even in an intrinsic material, $\tau$ is different for electrons and holes. This is because in the equation for $\mu$, the value of $\tau$ is not lifetime but rather the average time between scattering events. Since holes aren’t an actual particle, the movement of holes is really the movement of electrons in the valence band. Because there are many more ...

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Given two like charges -- two electrons for example -- does moving them farther apart release a photon? Photons are released when charged particles are accelerated. . Moving them apart may generate photons if there is acceleration. If the velocity is constant, no radiation. Electrons in conduction bands of metals are in a quantum mechanical state and ...

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Consider two models: A wave packet of a free electron with $m_e$ with negligible mean energy relative to rest state A wave packet with same parameters of an electron in crystal with $m^*$ with negligible mean energy relative to band edge Assuming that wave packet is large enough for the effective mass approximation to hold (i.e. its uncertainty of ...

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The concept of photon exchange comes from Feynman diagrams and the exchange is of a virtual photon, a four vector carrying the quantum numbers of the photon ( or whatever the off mass shell particle is) but the mass is not on the mass shell, and has a different value according to the calculation of the process under study. This is a simple description of ...

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The frequencies are the same but they are 180 degrees out of phase with each other.

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Second derivative of kinetic energy with respect to momentum equals inverse mass of a particle. In a metal, you have a band structure defined through the dispersion relation of the form E(k) where k is wave vector of electron. Second derivative of this expression can be also taken to be some sort of inertia of a particle, as you can see by analogy with a ...

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It implies that the band in question would have a narrower bandwidth than would be expected from an electron with free electron mass. In turn, this also means that the electron finds it harder to hop from site to site meaning that the electron is more localized that would be an electron with free electron mass.

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Maybe a beginning of answer to your question could be found in Lindhard theory. Considere a fermionic field $$\Psi(\textbf{x},t)=\frac{1}{\Omega}\sum_{\textbf{k}_1,\textbf{k}_2}e^{\mathrm{i}(\textbf{k}_\alpha-\textbf{k}_\beta)\cdot\textbf{x}+\mathrm{i}(E_{\textbf{k}_\alpha}-E_{\textbf{k}_\beta})t/\hbar}a_{\textbf{k}_\alpha}^\dagger a_{\textbf{k}_\beta}$$ ...

2

The electrons in a metal can be described surprisingly well as a gas of free electrons. So let me rephrase your question as: If I take a container with a gas in and rapidly partition it into two, will the pressure be the same on both side? If we look at a gas on the atomic scale it's a mass of atoms/molecules whizzing around at random. So on the large ...

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In presence of external electric fields, If you cut it fast enough (at a speed faster than the conduction speed, you can have the two alved ending up with different charges. This is because the external field redistributes the charges on the conductor' surface to annulate the field there. so the charges will not be uniformly distributed. In absence of ...

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Note that Sommerfeld's model simply generalizes Drude's theory of metals by taking into account the fact that electrons are fermions, so Pauli exclusion becomes a very important factor. In Sommerfeld's model, there's no effective mass to talk about, as one basically ignores the atoms(nuclei) in the system and considers free moving fermions. So there, your ...

12

I assume your question was asked with the implicit "and everything else is kept the same" (still GR + standard model, just with one parameter tweaked). This would have a large effect, because now the neutron would be much more stable! The neutron is already quite stable (~ 10 minute half life), due to the tight energy constraints in the reaction decaying ...

1

Not at all. Space is expanding, as in space is constantly being added. Although space might be added between the electron and nucleus, that does not effect the atom to significant degree. Its like having an atom in flatland and turning the flatland into a ball. the atom is not going to know much of a difference. If the sphere is returned to flat land the ...

4

Javier, brings up some interesting points. However, protons and neutrons get most their mass from relativistic quarks. If the quarks could be slowed down they would weigh a few electron masses. So what ever is responsible for giving the electrons mass its value seems to be giving the quarks their rest mass. I just checked the up and down,they are around 4 ...

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Electron is not like a ball, as it has no volume at all. So it can not spin like a ball. Magnetic moment comes "as is" from quantum mechanics, which do not explain its nature.

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Yes, the direction matters. Take a look at this electronic band structure diagram for gold. Atomic and electronic structure of gold clusters: understanding flakes, cages and superatoms from simple concepts If there was only one spatial dimension (like a wire), the diagram would just have energy vs momentum. In higher dimensions, instead the momentum ...

1

The fast electrons slow down in the cathode, mostly due to interactions with atomic electrons. But hard X-rays are produced mostly due to deflection to large angles in the field of atomic nuclei. Roughly speaking, an atomic electron can stop the projectile electron in a head-on collision, but a nucleus can "reflect" the projectile back, so here the ...

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The change in velocity of the electron give rise to emission of X-rays. The electrons arrive at the anode with very high velocity and end up at thermal velocities - which must mean they slowed down. Both statements are therefore true.

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When a charged particle comes into the vicinity of another, it's path is deflected. It decelerates in one direction, and accelerates in another. All charged particles that are accelerated/decelerated by another charged particle, or a magnetic field, emit radiation. See: Bremsstrahlung. Synchrotron radiation. Cyclotron radiation.

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The electron does not move - it has no well-defined position in the orbital state, and hence no well-defined momentum. Neither does it "teleport" around - as long as it is not interacting with something that forces it to be at a definite position, its state is "smeared" all over the electron as an electron cloud. Yes, this is essentially the Bohr model, ...

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Once the gammas are produced, they do not carry particular information. There is just a certain probability, measured by a differential cross section, that, if they scatter again, they produce $e^+,\,e^-$ as in the initial pair.

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Suppose a conductor with cross sectional area $A$ has $n$ mobile charge carriers per unit volume, each carrying a charge $q$, which moves through the conductor at an average drift velocity of $v_d$. Now the total charge in a segment $\Delta x$ is: $\Delta Q = (nA\Delta x)q$ Now, the charge carriers moving at an average drift velocity of $v_d$ will move a ...

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Edit after rereading the quesiton. Agree that it is (all else being equal) easier for electrons to travel down a wire with a greater cross sectional area. (Not sure why this is not intuitive - for me it is easier to walk down a wide pavement than a narrow passage between two buildings - particularly if other people are about to provide some 'resistance' - ...

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